HYDRO -ELECTRI c VON SCHON LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class HYDRO-ELECTRIC PRACTICE A PRACTICAL MANUAL OF THE DEVELOPMENT OF WATER POWER, ITS CONVERSION TO ELECTRIC ENERGY, AND ITS DISTANT TRANSMISSION BY H. A. E. C. VON SCHON It CIVIL AND HYDRAULIC ENGINEER; MEMBER OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS PHILADELPHIA &f LONDON J. B. LIPPINCOTT COMPANY 1908 08\ S3 COPYRIGPT, 1908 BY J. B. LIPPINCOTT COMPANY Printed by J. B. Lippincoll Company The Washington Square Press, Philadelphia, U. S, A. PREFACE THE economical transmission of electric energy to distances great and small, the rapidly increasing utilization of electro-motive power in industrial establishments, and the advent of the electric interurban rail- roads are responsible for the marked movement of impressing water- powers to the service of generating electric current; and now water- power, which had been almost relegated to obscurity by the perfection of the steam-engine, is not only regaining but even exceeding its former importance as an economical prime power source. It is entirely within the facts to state that a normally conditioned hydro-electric power plant can successfully compete with the most refined steam-power plant and the lowest priced fuel, natural gas. No wonder then that water-powers are to-day being sought after with feverish activity, and that some remarkable successes have been achieved, but also that many disastrous failures must be recorded. Hydro-electric power development is a much more complex under- taking than a large majority of the promoters of such enterprises realize when the subject is first approached, but which is most forcibly impressed upon them when the carrying out of the project is seriously attempted. Unfortunately, the most dangerous pitfalls are encountered at the beginning of the undertaking, and unless these are properly guarded against the finished work may disclose some incurable defects. Developments of the important natural resources of mines, of forests, and of manufacturing and transportation projects are rarely undertaken except upon the findings of recognized authorities on these respective subjects; not so, however, with hydro-electric power propositions, which are most frequently begun in a hap-hazard sort of fashion, with the stream and a fall as assumed assets, while the market, constancy of output, cost of product, riparian rights, and numerous other controlling features remain undetermined until some later day. Hence promoters of hydro-electric projects have not found the investing public at all eager to take their securities, because of the general and well-grounded impression that their presentations are not entitled to the same degree 174385 iv PREFACE of confidence as other undertakings command, nor can there be any hope for a tide in their favor until such confidence be inspired. Publicity of the realities of a subject will always carry conviction of merit, if such there be; and much of the reluctance of capital to recognize the indubitable value of investments in hydro-electric power plants is no doubt due to the paucity of the proper sort of educating literature on this subject. This at least is the judgment of the author, born of the experience gained by some fifteen years of exclusive hydro-electric power practice, and this is the reason and purpose of this volume, to place within reach of the promoter, investor, and practitioner an analytical treat- ment of hydro-electric practice in all its phases from inception to realization. This subject is treated in two parts; the first is entitled " Analysis of a Hydro-electric Project," and is written for the layman, being devoid of technical treatment, and may therefore be characterized as the com- mercial essence of the subject. The author believes that an intelligent perusal of this first part will insure the reader against those errors of commission and omission which cause most of the failures in these proj- ects. No engineering training or experience is required clearly to follow and fully to appreciate and understand the presentation of the analysis, which covers the topic as completely as can be done without the intro- duction of the technic. CHAPTER I. treats of the market of electric current, where it may be found and how its value is readily determined. This is purely a commercial subject and ranks first in importance in the analysis. CHAPTER II. discusses the power opportunity, how the available flow can be ascertained and the fall, and from these the power output on which the project may be safely based. CHAPTER III. relates to the feasibility and practicability of the development. It treats of questions of riparian rights, Federal and State control of streams, economical limitations and of the investment balance. CHAPTER IV. gives a non-technical synopsis of the cost of such a project, with general reference to the separate features of the required works and equipment; and CHAPTER V., which closes the analysis, reviews the value of the project as an investment and suggests its proper presentation. PREFACE v In this part are incorporated sixteen diagrams, from which the reciprocals of hydraulic, mechanical, and electrical power, horse-power and kilowatts, the flow over spillways and from reservoirs, fixed charges of and revenues from hydro-electric plants, and the approximate quan- tities for dams, foundations, power houses, embankments, bulkheads, and transmission lines may be readily ascertained. Other subjects, such as drainage areas, precipitation belts, and report and plans, are suitably illustrated. PART II., "Designing and Equipping the Plant," is written for the student and practitioner. The arrangement is in the logical sequence of the pursuance of the plan. The aim of the author has been to render the treatment complete in all its phases, with the exception of presup- posing a knowledge of the principles of surveying and the rudiments of hydraulics, hydrostatics, and dynamics. Each subject involving static or dynamic principles is analyzed from its basic functions, and all formulas are developed in elementary progression; wherever practicable without complexity of methods or deductions, the useful constants are reduced to diagrammatical forms, which become available for ready reference in application. All features of importance are illustrated by sketches or views from existing plants, chiefly such as have been designed and constructed by the author, and the quantities of materials for all structures are given, for useful units, in tables or diagrams. CHAPTER VI. treats of the surveys, embracing examination of maps, reconnaissance, topographic, stadia and photo-topographic operations, triangulation and levelling, flow measurements by different methods and deductions of run-off from precipitation and evaporation. CHAPTER VII. deals with development programmes. This discussion covers the many possibilities presented by various conditions, with illustrated examples of the most important and frequent occurrences. CHAPTER VIII. embraces structural types, beginning with definition of terms and methods, including the theory and constants of concrete-steel construction, methods of coffering preparatory to dam and power-house construction, with tables of quantities for dikes, cribs, sheet pile and wall curtains, and the various types of cut-off structures. The treatment of dams and spillways is introduced by an exhaustive analysis of the basic theories of pressure and resistance and of all the underlying principles, with original determinations of practical constants vi PREFACE for a variety of designs, and their detailed parts, such as foundation, substructures and superstructures, and appurtenant features. The vari- ous phenomena influencing the design of dams, such as overflow, back- swell, and the control of flood discharge, are fully analyzed. Especial attention has been given to this topic of dam designs; it is rudimentary from start to finish, with some original conclusions, it is believed. The concrete-steel gravity dam design is fully detailed as to theory and practical execution; so are several types of the open spillway, flashboards, sluices, gates, fishways, and log chutes. Timber spillways are likewise treated, with stability discussion and quantity tables. The retaining wall theory is presented in connection with abutments, as are embankments, bulkheads, and reservoir structures of various forms. Diversion works embrace open channels, flumes, pipe lines of con- crete, steel plate and wood stave, with theories of flow, slope, and velocities fully analyzed and development of practical constants tabu- lated for all the different ranges entering this subject. Power station follows, with all the practicable variations fully illustrated and described and with tabulated quantities. This subject is treated also in detail of foundation, pits, penstocks, and operating floor, and considerable space is devoted to their full description and to illustration of existing plants. The submerged power station, which represents the most recent developments in hydro-electric practice, that is, the location of all power equipment in the interior of a hollow concrete-steel spillway, is described and profusely illustrated by views of the first of this kind of plant recently completed. CHAPTER IX. treats of the power equipment, with theory of turbine designs and efficiencies, dimensions and output constants, the latter being reduced to diagrams. This treatment of turbines has been compiled with especial care, for the purpose of conveying a clear conception of this most important topic of hydro-electric practice. Hydraulic gov- ernors are also described and illustrated. Electric equipment follows, with a brief treatment of the magneto- electric theories, current symptoms, design and efficiencies of dynamos and their regulation. Dimensions and output of generators are reduced to diagrams. Transmission of electric current is introduced by an ana- lytical theory of current transformation and conversion, determination of- line capacity, and the designs of line supports, wire fastenings, and insulators. PREFACE vii CHAPTER X. closes Part II. with a brief generalization on the prepa- ration of plans, estimates, specifications, and of the engineering control of constructions. The author fully realizes that many features relating to hydro- electric practice are herein treated on the surface only, and he hopes to present them in exhaustive detail in a future work. This refers princi- pally to the maintenance and operation of hydro-electric power plants and such detail subjects as the operation of the generating, transmis- sion, and distributing plants, with chapters on underwashing of founda- tions, embankments, and retaining walls, and repair methods; flood rises, head fluctuations, anchor and slush ice formation and practical safeguards; trash-rack functions, gate operations, pipe-line defects, maintenance and repairs; turbine regulation and management; electric generating plant phenomena and their practical solution; transmission accidents and remedies; substation practice for lighting, industrial, and traction power and electric heating service; commercial rates and business management; valuations of various electric properties, such as light plants and railroads, and statistical facts of operating costs and earnings compiled from existing plants located in various sections and of different capacities. The author has drawn freely upon standard works for the various topics covered by this subject, especially Hydraulics and Water Supply, by J. T. Fanning, C.E., Hydraulics, by M. Merriman, C.E., Hydraulics and Hydraulic Motors, by Julius Weisbach, Ph.D., Hydraulic Motors, by G. R. Bodmer, A.M., Electric Motors, by S. P. Thompson, D.S.C., and Electric Transmission, by Louis Bell, Ph.D. In closing, the author wishes to give expression of his full apprecia- tion of the services rendered by Mr. K. Asker, C.E., who prepared all the drawings. H. A. E. C. VON SCHON. DETROIT, MICH., June, 1908. TABLE OF CONTENTS PART I. ANALYSIS OF A HYDRO-ELECTRIC PROJECT CHAPTER I. PAGE THE MARKET 1 Article 1. Lighting Service 1 Article 2. Industrial Service 2 Article 3. Special Service 4 Article 4. Traction Service 4 Article 5. Highest Remunerative Service 4 Article 6. Current Market Analysis 4 CHAPTER II. POWER OPPORTUNITY 8 Article 7. The Flow 8 Article 8. Drainage Area 9 Article 9. Drainage Area, Topography 26 Article 10. Drainage Area, Geology 27 Article 1 1 . Drainage Area, Flora and Culture 28 Article 12. Precipitation 29 Article 13. Stream Flow, Determination 30 Article 14. Evaporation 32 Article 15. Flow Deduction 36 Article 16. Flow Measurements 37 Article 17. Fall, Available 40 Article 18. Power Output 40 CHAPTER III. FEASIBILITY AND PRACTICABILITY 47 Article 19. Government Control 47 Article 20. Riparian Titles 53 Article 21. Practicability of Development 54 Article 22. Investment Balance 55 CHAPTER IV. COST OF DEVELOPMENT 61 Article 23. Cost of Dam 61 Article 24. Cost of Diversion Works 67 Article 25. Cost of Power House 67 Article 26. Cost of Reservoir Embankments 68 Article 27. Cost of Power Equipment 70 Article 28. Cost of Transmission Line 70 Article 29. Cost of Development 74 ix x TABLE OF CONTENTS CHAPTER V. PAGB VALUE OF PROJECT AND PRESENTATION 75 Article 30. Report on a Hydro-electric Project 75 Article 31. Value of a Hydro-electric Opportunity 88 PART II. DESIGNING AND CONSTRUCTING THE DEVELOPMENT CHAPTER VI. THE SURVEY 90 Article 32. Examination of Maps 90 Article 33. Reconnaissance 91 Article 34. Triangulation 92 Article 35. Elevations 93 Article 36. Topography 94 Article 37. Phototopography 94 Article 38. Detail Surveys 99 Article 39. Borings 100 Article 40. Stream Gaugings 100 Article 41. Stream Gaugings, Reductions 103 Article 42. Stream Discharge Curve 103 Article 43. Weir Measurement 107 Article 44. Flow Deduced from Precipitation and Evaporation 108 Article 45. A Typical Case of Flow Determination 109 Article 46. Reservoir Sites 115 Article 47. Floating Timber 115 CHAPTER VII. DEVELOPMENT PROGRAMME 116 Article 48. The Direct Development 116 Article 49. The Short Diversion Programme 117 Article 50. The Distant Diversion Programme 117 Article 51. Development Scope 129 CHAPTER VIII. STRUCTURAL TYPES 131 Article 52. Foundation Function 131 Article 53. Terms, Materials, and Methods 135 Article 54. Coffering 143 Article 55. Foundation Design 144 Article 56. Foundation Construction 147 Article 57. Superstructure 148 Article 58. The Length of Spillway 159 Article 59. Pressure and Resistance 160 Article 60. Sliding of Spillway 169 Article 61. Overturning of Spillway 170 Article 62. Crushing or Rupturing of Spillway 170 Article 63. Safety Factor in Spillway Design 174 Article 64. Spillway Design, Theoretical 176 Article 65. Spillway Design, Practical 180 TABLE OF CONTENTS XI Article 66. Spillway Crest, Shape of 185 Article 67. Gravity Spillways 186 Article 68. Open Spillway 194 Article 69. Determining the Spillway Type 202 Article 70. Timber Spillways 205 Article 71. Spillway to Part Height 209 Article 72. Abutments of Spillway 209 Article 73. Reservoir Dams 221 Article 74. Appurtenances of Spillways and Dams 227 Article 75. Diversion Works 235 Article 76. Power House 254 Article 77. Appurtenances to the Power House 264 Article 78. Submerged Power-House Design 266 CHAPTER IX. EQUIPMENT 276 Article 79. Hydraulic Equipment, Theory 276 Article 80. Classification of Turbines 285 Article 81. Mixed Flow Reaction Turbine, Description 287 Article 82. Central Discharge Reaction Turbine, Description 294 Article 83. American Impulse Turbine, Description 296 Article 84. Draft Tube Theory 296 Article 85. Turbine Efficiency, Theory of Deduction 298 Article 86. Typical Turbine Installations 300 Article 87. Reaction Turbine Output 314 Article 88. Reaction Turbine Design 318 Article 89. Output of Tangential Impulse Turbine 320 Article 90. Turbine Output Constants, Summary of 322 Article 91. Turbine Equipment, Determining Same 322 Article 92. Turbine Governors 326 Article 93. Electric Equipment, Magneto-dynamic Theory 330 Article 94. Some Current Symptoms 333 Article 95. Dynamo Parts, their Purpose and Design 337 Article 96. Current Reorganization 342 Article 97. Current Transformation 343 Article 98. Current Transmission 345 Article 99. Current Regulation 348 Article 100. Electric Generating Plant 350 Article 101. Transmission Plant, Equipment 358 Article 102. Auxiliary Power Plant 364 CHAPTER X. CONSTRUCTING THE PLANT ., 368 Article 103. Plans 368 Article 104. Estimates 369 Article 105. Specifications 369 Article 106, Engineering Control 371 xii TABLE OF CONTENTS TABLES. PAGE 1 . Drainage Areas and Low Monthly Flow 10 2. Evaporation from Water Surface 33 3. Watercourses under Government Control 50 4. Concrete Characteristics 140 5. Reinforcing Steel Characteristics ; 141 6. Concrete-Steel Beams 141 7. Values for Concrete-Steel Beam Designs 141 8. Coffer Structures, Quantities 144 9. Cut-off Walls, Quantities 147 10. Characteristics of Normal Solid Spillway Section 185 11. Gravity Spillway, Bending Moments 191 12. Gravity Spillway, Dimensions 192 13. Gravity Spillway, Material Bill 192 14. Gravity Spillway, Characteristics of Design 194 15. Timber Spillway, Quantities 208 16-24. Flow in Open Channels, Characteristics 238-241 25-29. Flow in Pipes, Characteristics 249-251 30. Permeability of Field Magnet Metal 339 31. Copper Wire Characteristics 340 32. Standard Generators, Characteristics 355 33. Aluminum Wire, Characteristics 359 LIST OF ILLUSTRATIONS CHARTS PAGE 1. Drainage Area of Green River, Ky., above Glenmore 11 2. Cumberland River Drainage Area above Nashville, Tenn 29 3. General Distribution of Precipitation 30 DIAGRAMS 1. Horse-power and Kilowatts ' 3 2. Discharge over Flat-crested Spillway 39 3. Water-power and Electric Power 43 4. Continuous Flow from Reservoirs 45 5. Fixed Charges for Plants of 500-1000 H. P 57 6. Fixed Charges for Plants of 1000-5000 H. P 58 7. Fixed Charges for Plants of 5000-10,000 H. P 59 8. Current Rates for Horse-power and Kilowatt 60 9. Masonry Dams, Dimensions and Quantities 63 10. Concrete-steel Dams, Quantities 64 11. Cost of Concrete 65 12. Dam Foundation and Abutment Quantities 66 13. Power House, Quantities 69 14. Earth Embankment, Quantities 71 15. Reservoir Bulkhead, Quantities 72 16. Transmission Line, Weight of Line Wire 73 17. Surface to Mean Velocity > 104 18. Rod to Mean Velocity 105 19. Typical Discharge Curve 106 20-25. Backswell, Slope 152-157 26-29. Pressure Moment, Solid Spillway 165-168. 30. Comparative Cost of Timber and Concrete Spillway 211 31-33. Retaining Wall, Pressure Moments , 215-217 34. Vertical Turbines, Cased; Dimensions of 303 35. Horizontal Turbines, Drowned, Dimensions of 307 36. Single Horizontal Turbines, Drowned, Dimensions of 311 37. Horizontal Turbines, Cased, Dimensions of 317 38. Reaction Turbines, Maximum Efficiency Output 319 39. Tangential Impulse Turbine, Maximum Efficiency Output 323 40. Generator Dimensions 357 FIGURES 1. Base Benches; Base Supporting Brackets 92 2. Tripod and Target 93 3-6. Phototopography 94 7. Detail Surveys ; . . . . 99 8. Borings to ascertain Character of Soil at Sites of Dam, Diversion Works, etc 100 9-11. Stream Gaugings 101 xiii xiv LIST OF ILLUSTRATIONS FIG - PAGE 12- Dike 135 13. Timber Sheet 136 14. Steel Piling 13g 15. 16. Log Crib and Timber Crib 137 17. Concrete Piles 138 18. Triple-lap Sheet Pile 139 19. Sheet Pile Dike 143 20^1. Spillway Sections 161-183 42. Solid Spillway, Crest and Toe 187 43-45. Diagrams illustrating Pressure and Resistance Factor 189, 190 46. Gravity Spillway 193 47-49, 55. Overflow and Underflow Sluices 195 } 197 f 200 50-54. Stop-logs, Needles, Valves, Gates, and Shutters 197-200 56. Movable Wier 202 57. Timber Spillways 207 58-61. Spillway Abutments (Diagrams) 210-212 62. Retaining Crib 213 63. Gravity Retaining Wall 21e 64. 65. Concrete Steel Retaining Wail 219 220 66. Reservoir Embankment 223 67. Reservoir Bulkhead 225 68-71. Discharge through Submerged Orifices 227-229 72. Fish-ladders 232 73. Flashboards 233 74. Wells and Galleries in Solid Spillways 235 75-77. Diversion Canals 236 245 78. Canal Headgate 247 79. Flumes and Trestles 249 80. Pipe Line and Details 253 81. Intake Gate Valve and Trash Rack 254 82. Power-house Substructure 256 83. Power-house Turbine Bays 257 84. Power-house, Low Head, Vertical Turbines, Drowned . 259 85. Power-house, Low Head, Horizontal Turbines, Drowned in Forebay 261 86. Power House for Low Head and Horizontal Turbines, Drowned 262 87. Power House, Fluctuating Head, Serial Turbines 263 88. Power House for Low Head and Double Vertical Turbines, Drowned 265 89. Power House, Medium Head, Horizontal Turbines, Cased ; . . . 267 90. Trash Rack and Details 268 91. Power Spillway 271 92-101. Hydro-dynamic Energy (Diagrams) 281-285 102-106. Reaction Turbine Runner 288 107. Wicket-Gate Guide-Wheel 288 108. Sections of Guide-Vanes and Shutters 289 109. Reaction Turbine, Wicket Gate 291 110. Reaction Turbine, Cylinder Gate 293 111. Double Turbine Draft-Chest 294 112. Assembled Twin Turbines 294 113. Reaction Turbine for High Head 295 114. Impulse Wheel 297 115. Vertical Turbines, Paired and Drowned, Geared Connections 302 116. Vertical Turbines, Paired and Cased, Geared Connections 305 117. Horizontal Turbines, Paired and Drowned 306 LIST OF ILLUSTRATIONS xv FIG. PAGE 118. Horizontal Turbines, Three in Line, Drowned 309 119. Horizontal Turbines, Four in Line, Drowned 312 120. Horizontal Turbines, Paired, Cased, with Top or Side Supply 313 121. Horizontal Turbine, Cased, with End Supply 315 122. Lombard Governor 326 123. Sturgess Governor 327 124. Woodward Governor 328 125. Lombard-Replogle Governor 329 126. 127. Field of a Magnet 330, 331 128, 129. Generating Current by Revolving Loop 334 130. Two- and Three-phase Current Waves 335 131. Watt-less Current (Diagram) 337 132. Alternate Current (Diagram) 337 133. Alternate Current Transformation 343 134. Transmission Line Towers and Poles 363 135. Transmission Line Insulators and Pins 365 136. 137. Sectional Armature and Revolving Field of a Three-phase, Thirty-cycle Alternator 366 138. Continuous-current Dynamo coupled to the Turbine Shaft 366 139, 140. General View of Partial Generator Installation; Rotary Converter 367 PLANS 1-6. Sandusky River, Ohio, Drainage Basin and Topography 77-83 8, 9. Direct Development in Alluvial Location 118, 119 10, 11. Short Diversion Development 120, 122 12, 13. Direct Development in Rock Gorge 123, 124 14-16. Distant Diversion Development 125-127 17. Divided Development 128 18. Foundation Design 145 19. Upper Pool, with Contour Lines showing Elevations of Banks 151 PROFILES 1. Precipitation and Run-off, Green River, Ky 35 2. Ground-flow Diagrams 113 VIEWS 1. Breakwater 142 2. Timber Crib 142 3. Log Crib Coffer 143 4. Sheet Pile Dike 143 5. Steel Pile Coffer (U. S. Steel Pile) 144 6. Steel Pile Coffer (Friestedt Channel Bar) 145 7. Canal in Rock, Excavating and Channelling 244 8. Canal in Rock, with Channelled Sides, Completed 244 9. 10. Canal in Earth, Timber Lined 245 11. Canal in Earth, Timber Lined, Completed 246 12-14. Canal Headgates 246, 247 15. Power House Foundation .' 256 16. Power House Substructure, Upstream View 256 17. Power House Substructure, Downstream Elevation 257 18. Power House Superstructure, Upstream Elevation 257 18a. Power House, Upstream View 257 19. Power House Superstructure. Downstream Elevation 257 20. Turbine Bay 257 21-32. Submerged Power House 272-275 / inc. * ( f UNIVERSITY ) HYDRO-ELECTRIC PRACTICE PART I ANALYSIS OF A HYDRO-ELECTRIC PROJECT WHEN it is desired to examine an undeveloped water-power for the purpose of producing electric current as a commercial commodity, experi- ence has taught that it is best to ascertain first where the product will find its market, and to follow up a satisfactory showing at that end by determining the power capacity of the source, the feasibility of harness- ing the same, and the cost of accomplishing this. Observing this pro- gramme, which is really that adopted in any commercial enterprise, is found to insure a reliable conclusion. CHAPTER I THE MARKET THE MARKET of electric current is to be found in any community. The commercial unit is the product of quantity of current and time of service; the measures are one electric horse-power, or one kilowatt, and the year and hour. The horse-power-year is the basis of mill and factory power contracts, while the kilowatt-hour is most generally adopted for lighting, shop, and traction service, because of the greater fluctuations from continuous operations. Diagram I gives converted values of the horse-power and kilowatt. Electric current finds its market for lighting, industrial, and traction service. ARTICLE 1. Lighting service consists of arc and incandescent lights. Arc lights are chiefly used for street, store, and hall illumination, and they generally require 550 watts. Diagram I shows relative current and power for any number of arcs. i HYDRO-ELECTRIC PRACTICE Arc service is either of all-night or moonlight schedule, and the rates are most frequently per lamp per year, ranging from $50 up, the price depending solely upon local conditions. Occasionally arc-lighting service is per lamp-hour. This branch of current service is generally remunera- tive, and grows with the community if the service is at all satisfactory. Large stores and public halls, railroad depots, freight yards, and shipping docks are all light customers. Incandescent lights are principally of 16-candle power, requiring 55 watts, or one-tenth of the arc-lamp current. Diagram 1 serves to find relative power. The rates of incandescent lighting are either per lamp per month, being denominated the "flat rate," or per kilowatt-hour, mostly of a sliding scale, the price lowering as total monthly consumption increases; this is termed the "meter rate." In cities incandescent-light service may be estimated at 700 hours per year per lamp, representing about 38 kilowatt-hours; in rural districts it is somewhat less. Meter rates range from 8 cents per kilowatt-hour up, depending entirely upon conditions of supply. The field for this business is in every dwelling, store, shop, mill, factory, and public institution and gathering place; the number of incandescent lamps which can be placed may generally be taken as equal to one-half the population. ARTICLE 2. Industrial service comprises the motive power used in shops, mills, and factories; the current is furnished as horse-power per year or month to industries operating for regular periods and with full loads, and on kilowatt-hour measure where periods and loads fluctuate. This service reaches every industry; for instance, the laundries and printing-shops, barbers, hotels, and all places using pumps, fans, and elevators, saw-mills and turning-shops, grist- and flouring-mills, machine- shops, textile, woollen, cotton, and knitting-mills, pulp and paper indus- tries, wagon, buggy, automobile, furniture, piano, organ-factories, and, in fact, every class and kind of industry, none of which are too small to use power in some form or other. The power quantity used depends upon the character and size of the industry; a laundry may use 10 horse- power, printing-shops about 5 horse-power per press, wood-working shops 5 horse-power and metal shops 10 horse-power per machine, grist-mills one-half horse-power and flour-mills one-third horse-power per barrel capacity, ground wood-pulp mills 75 horse-power, sulphite-pulp 13 horse- power, paper-mills 18 horse-power per ton output. ARTICLE 3. There is also a special class of manufactures in which 123456784 115 / / 1 A 1 A. 14 / / 13 1 / 1 q Diagram 1. Horse Power and Kilowatts Power f&r lighting ten inc. - one arc. / / / / 12 11 10 9 8 7 6 5 I i E 3 2 1 1 / / 1 9 / / / / / ' ' / / / / / / / 1 A / / /i / / * s > / / ram. -i in- Low Area. Flow. Year. At State. Great Miami Ohio Great Pee Dee Great Pee Dee Great Pee Dee Green Colorado Green Colorado Green Colorado Green Ohio Greenbrier Greenbrier Guadalupe Gunnison Grand Gunnison Grand Gunnison Grand Gunnison Grand Haw Cape Fear Heart Hiwasscc Hiwassee Hiwassee HiwuKsee Holston Holston Holston, South Fork Hood Hoosic Hudson Hoosic Hudson Housatonie Housatonic Hudson. Hudson Hudson Hudson Hudson Humboldt Humboldt Humboldt Humboldt, North Fork Humboldt, South Fork Huron Illinois Mississippi Illinois Mississippi Illinois Mississippi Indian Creek Iowa Mississippi Iowa Mississippi James James James James Jefferson Jefferson John Day Juniata W. Susquehanna Juniata W. Susquehanna Kalamazoo Kalamazoo 5,400 498 3,399 17,000 7,450 26,620 38,200 0.76 0.45 0.075 0.026 0.042 Ohio '04 North Wilkesboro N. C. '04-'05 Salisbury N. C. , N. and S. C. '05 Greenriver Wyo. '04 Jensen Utah '05 Greenriver . ..Utah 1,575 1,344 5,100 2,298 3,844 5,233 7,868 1,675 1,250 410 1,180 2,297 2,698 3,060 3,790 828 370 579 710 1,020 1,933 1,092 2,800 4,500 8,000 13,368 5,014 10,780 13,800 1,020 1,150 775 6,480 13,250 29,013 740 3,317 12,519 2,058 3,027 6,232 9,700 8,984 9,400 7,800 3,223 3,476 847 1,471 Va. 0.15 '04-'05 Alderson W. Va. 0.102 '06 Cuero Tex. lola Colo. 0.12 '05 Cimarron Colo. 0.09 '04-'05 Cory Colo. 0.11 '04-'05 Whitewater Colo. N. C. 0.0012 '04-'05 Richardton N. Dak. 0.59 '04-'05 Murphy N. C. 0.54 '04-'05 Reliance Tenn. Charleston Term. mouth Tenn. 0.32 '05 Austins Mill Tenn. mouth Tenn. 0.27 '04-'05 Bluff City Tenn. 1.92 '06 Winans Oregon 0.370 '06 Buskirk N. Y. Mass., Vt., and N. Y. 0.484 '05 Gaylordsvillc Conn. Mass, and Conn. Hadley N. Y. 0.794 '05 Fort Edward N. Y. 0.583 '04-'05 Mechanicsville N. Y. Troy N. Y. N. Y. 0.0068 '05 Palisade Nev. 0.000025 '05 Golconda Nev. 0.00014 '05 Oreana Nev. 0.00051 '05 Elburz Nev. 0.00 '05 Elko Nev. 0.110 '06 Geddes Mich. 1.08 '04 Minooka 111. 0.50 '06 Peoria 111. 0.072 '06 Crescent Mills Cal. 0.11 '04-'05 Iowa City Iowa Iowa 0.20 '04-'05 Buchanan Va. Balcony Falls Va. 0.25 '04-'05 Cartersville Va. Va. 0.07 '04-'05 Sappington Mont. Three Forks Mont. 0.04 '06 McDonald Oregon 0.40 '04-'05 Newport Pa. below Battle Creek .... Mich. 0.405 '06 Allegan Mich. POWER OPPORTUNITY 17 River. Tributary of Drainage Area. Low Flow. Year. At State. Kalamazoo 2,064 Kankakee Illinois 5,300 Kansas Missouri 58,550 Kansas Missouri 59,750 Kaskaskia Mississippi 5,876 Kaweah 520 Kennebec .- 1,250 Kermebec 1 ,670 Kenntebec 2,570 Kennebec 2,880 Kennebec 2,900 Kennebec 3,330 Kennebec 4,030 Kennebec 4,380 Kennebec 4,410 Kennebec 5,470 Kennebec 5,770 Kennebec 6,400 Kentucky Ohio Kentucky Ohio 7,870 Kern 2,345 Kings 1,742 Kings 1,775 La Mine Missouri 2,700 Laramie North Platte 3,179 Laramie North Platte 4,076 Lehigh Delaware 1,330 Licking Ohio 696 Licking Ohio 3,870 Little Bighorn 1,276 0.07 '04-'05 0.23 0.403 0.437 0.403 '05 0.089 0.108 '05 '05 3,461 6,000 17,630 2,290 600 Little Blue Big Blue. Little Colorado Colorado. Little Colorado Colorado. Little Kanawha Ohio. . . . Little Missouri Little Missouri 1,900 Little Missouri 5,785 Little Muddy 800 Little Nemaha Missouri 990 Little Sioux Missouri 4,223 Little Tennessee 682 Little Tennessee 2,470 Little Wood Snake 1,270 Locust Fork of Black Warrior 1,020 Logan Bear 218 Loup Platte 13,540 Loup Platte 15,553 Luis Rey '. 318 North Loup 4,024 Machias, East and West 465 Machias, East and West 800 Mackinaw Illinois 1,182 Mad 290 Madison 2,085 Madison. . 2,420 0.143 0.06 0.0048 0.0044 0.0017 0.004 0.0014 0.0085 '04 '05 '05 '05 '05 '06 '05 '05 mouth Mich. 111. andlnd. Lecompton Kas. mouth Three Rivers Cal. Moosehead Lake Me. The Forks Me. below Dead River Me. North Anson Me. Carritunk Falls Me. Madison Me. Norridgewock Me. Somerset Mills Me. above Sebasticook River. .Me. Waterville Me. Augusta Me. mouth Me. Little Hickman Ky. mouth Ky. Bakersfield Cal. Sanger Cal. Red Mountain Cal. mouth Mo. Uva Wyo. Ft. Laramie Wyo. Pa. Pleasant Valley Ohio Ohio Crow Agency Mont. Woodruff Ariz. Holbrook Ariz. Alzada Mont. Camp Crook S. Dak. Medora N. Dak. Williston.. ..N. Dak. 0.66 0.73 '04-'05 '05 0.22 0.44 0.193 '04-'05 '06 '06 0.01 0.465 '06 '04 0.445 0.53 '05 '05 Mahoning Malade Snake. 2 958 2,190 0.174 '06 Minn. Judson N. C. McGhee Tenn. Toponis Ida. Palos Ala. Logan Utah Columbus Nebr. Nebr. Pala Cal. St. Paul Nebr. Whitneyville Me. mouth Me. 111. Springfield Ohio Norris Mont. Threeforks Mont. Youngstown Ohio Toponis Ida. 18 HYDRO-ELECTRIC PRACTICE Drainaare Low River. Tributary of Area. Flow. Year. At State, Malade Snake 3,550 Bliss Ida. Malheur 4,860 0.01 '06 Vale Oregon Maple 459 Maple Rapids Mich. Maple 919 mouth Mich. Marias 2,610 0.09 '04-'05 Shelby Mont. Mattawamkeag Penobscot 1,510 0.123 '05 Mattawamkeag Me. Mattawamkeag Penobscot 1,533 Me. Maumee 2.190 0.13 '05 Sherwood Ohio McCloud 608 2.27 '06 Gregory Cal. McKenzie 960 2.30 '06 Springfield Oregon Medicine Arkansas 1,300 Kiowa Kas. Meherrin Chowan 1,675 Va. and N. C. Menominee 2,415 0.77 '02-'05 Iron Mountain Mich. Menominee 4,113 Mich, and Wis. Meramee 340 0.44 '04 Meramee Mo. Meramec Mississippi 3,497 0.27 '04-'05 Eureka Mo. Meramee Mississippi 3,914 Mo. Merced 1,090 0.057 '05 Merced Falls Cal. Merrimac 1,460 0.774 '06 Franklin Junction N. H. Merrimac 4,553 0.390 '06 Lawrence Mass. Merrimac 4,916 N. H. and Mass. Methow 1,710 0.25 '06 Pateros Wash. Miami Ohio 2,450 0.140 '06 Dayton Ohio Michigamme Menominee 756 Mich. Middle Loup 6,849 St. Paul Nebr. Milk Missouri 7,300 0.0001 '06 Havre Mont. Milk Missouri 14,040 0.00036 '05 Malta Mont. Milk, North Fork 1,422 0.13 '06 Chinook Mont. Minnesota Mississippi 13,400 0.099 '05 Mankato Minn. Minnesota Mississippi 16,000 Minn. Mississippi 12,400 0.211 '05 Sauk Rapids Minn. Mississippi 36,085 St. Paul Minn. Missoula 5,960 0.14 '05 Missoula Mont. Missouri Mississippi 14,500 Townsend Mont. Missouri Mississippi 15,036 . 4 . . . . Canyon Ferry Mont. Missouri Mississippi 17,615 Craig Mont. Missouri Mississippi 18,295 0.11 '05 Cascade Mont. Missouri Mississippi 492,000 0.05 '05 Kansas City Mo. Missouri Mississippi 527,155 Mont. Mohawk Hudson 1,306 0.755 '03-'05 Little Falls N. Y. Mohawk Hudson 3,440 0.331 '06 Dunsbach Ferry Bridge, N. Y. Mohawk Hudson 3,493 N. Y. Mokelumme 642 0.30 '06 Clements Cal. Molalla 220 0.35 '06 Molalla Oregon Monongahela Ohio 2,324 Fairmont W. Va. Monongahela Ohio 2,749 Morgantown W. Va. Monongahela Ohio 4,574 Greensboro Pa. Monongahela Ohio 5,427 Lock No. 4 Pa. Monongahela Ohio 7,625 W. Va. Montreal Wis. Moose Black 349 0.624 '00-'05 Moose River t N. Y. Moose Kennebec 680 0.174 '02-'05 Rockwood Me. Mouse 8,400 0.0019 '06 Minot N. Dak. Muskegon 1,764 above Big Rapids Mich. Muskegon 2,352 0.389 '06 Newaygo Mich. Muskegon 2,663 mouth Mich. Muskingum Ohio 5,828 0.329 '06 Janesville Ohio POWER OPPORTUNITY 19 Drainage Low River. Tributary of Area. Flow. Year. At State. Muskingum Ohio 7,740 Ohio Naches 636 0.42 '06 Nile Wash. Naches 1,120 0.06 '06 North Yakima Wash. Nashua Merrimac 773 Nashua Mass. Nashua, South Branch 119 0.543 '97-'05 Clinton Mass. Neches 8,200 0.03 '04-'05 Evadale Tex. Nemaha Missouri 1 ,924 Kas. and Nebr. Neosho 3,670 lola Kas. Neosho 12,746 Kas. and I. T. Neuse 5,300 N. C. New 1,100 Oldtown Va. New 2,725 0.44 '04-'05 Radford Va. New 4,523 ab. Greenbrier River. .W. Va. New 5,600 Hinton W. Va. New 6,200 0.173 '04 Fayette W. Va. Niobrara Missouri 6,070 0.13 '05 Valentine Nebr. Niobrara Missouri 6,300 0.104 '06 Ft. Niobrara Nebr. Niobrara Missouri 13,200 Nishnabatona Missouri 3,100 Iowa Nodaway Missouri 1,886 Iowa Nolichucky 640 ab. Tenn. State line Nolichucky 817 Chucky Valley Tenn. Nolichucky 1,099 0.44 '04-'05 Greenville Tenn. Nottaway Blackwater 1,650 Va. Ocmulgee Oconee 1,500 0.22 '04-'05 Jackson Ga. Ocmulgee Oconee 2,425 0.17 '04-'05 Macon Ga. Ocmulgee Oconee 6,000 Ga. Oconee Altamaha 1,100 0.33 '05 Greensboro Ga. Oconee Altamaha 1,346 Carey Ga. Oconee Altamaha 4,182 0.19 '04-'05 Dublin '. Ga. Oconee Altamaha 5,400 mouth Ga. Oconto 1,017 mouth Wis. Ogeechee 4,720 Ga. Ohio Mississippi 23,820 0.358 '06 Wheeling W. Va. Ohio Mississippi 214,000 Ohoopee 1,280 0.06 '05 Reidsville Ga. Okoee 374 2.28 '06 McCays Tenn. Oneida Oswego 1,313 0.563 '05 Euclid N. Y. Oneida Oswego 1,421 N. Y. Oostenaula Coosa 1,614 0.51 '06 Resaca Ga. Oostenaula Coosa 2,190 Rome Ga. Osage Missouri 15,300 Mo. and Kas. Oswegatchie , . . , 1,580 50 '05 Ogdensburg N. Y. Oswego 4,916 Fulton N. Y. Oswego 4,990 0.797 '04-'05 Battle Island N. Y! Oswego 5,002 mouth N. Y. Otter Creek Lake Champlain. 615 0.68 '06 Middlebury Vt. Ottertail , 1,310 40 '06 Fergus Falls . . .Minn! Ouachita Red River 19,000 Ark! Owyhee 9,875 0.0006 '05 Owyhee Oregon Palouse 2,210 0.007 '06 Hooper Wash. Palouse 2,460 mouth Wash! Pascagoula 8,350 Mo. Passaic 360 Two Bridges Passaic 960 N J Patapsco 251 0.46 '04 Woodstock ! . . ! ! Md! Patapsco 350 mouth Md! 20 HYDRO-ELECTRIC PRACTICE Drainage Low River. Tributary of Area. Flow. Year. At State. Paw Paw St. Joseph 429 Mich. Payette 2,240 0.383 '06 Horseshoe Bend Ida. Pea 1,180 0.15 '04 Pera Ala. Pearl 3,120 0.17 '05 Jackson Miss. Pearl 8,670 Miss. Pembina 2,940 0.038 '06 Neche N. Dak. Pemigewasset Merrimac 615 0.276 '86-'04 Plymouth H. H. Penobscot 1,880 0.225 '05 Millinocket Me. Penobscot 3,160 below mouth East branch Penobscot 6,630 0.387 '05 West Enfield Me. Penobscot 7,240 Oldtown Me. Penobscot 7,910 Bangor Me. Penobscot 8,500 Me. Penobscot, East Branch 1,130 0.196 '05 Grindstone Me. Pepacton Delaware 1,919 N. Y. Peshtigo 1,123 mouth Wis. Piscataquis Penobscot 280 0.283 '05 Foxcroft Me. Piscataquis Penobscot 380 Dover Me. Piscataquis Penobscot 750 Sibec Lake Piscataquis Penobscot 1 ,500 mouth Pit Sacramento 1,500 0.004 '05 Canby Cal. Pit Sacramento 2,948 0.004 '05 Bieber Cal. Platte Missouri 2,487 Iowa and Mo. Platte Missouri 53,300 0.005 '04 Lexington Nebr. Platte Missouri 56,867 0.01 J 04-'05 Columbus Nebr. Platte Missouri 90,000 Nebr. North Platte 7,668 Sweetwater North Platte 14,255 Douglas North Platte 14,828 Orin Junction North Platte 16,240 0.028 '05 Guernsey Wyo. North Platte 16,416 Fort Laramie North Platte 20,492 below Laramie River North Platte '. 23,190 0.006 '04 Bridgeport Nebr. North Platte 24,340 Gering Nebr. North Platte 24,400 0.018 '05 Mitchell Nebr. North Platte 24,830 Camp Clarke North Platte 28,520 0.015 '05 North Platte Nebr. North Platte 36,000 Colo., Wyo. and Nebr. South Platte Platte... 1,677 Lake Cheesman Colo. South Platte Platte 2,612 0.04 '04-'05 South Platte Colo. South Platte Platte 3,840 0.021 '06 Denver Colo. South Platte Platte 9,470 0.015 '06 Kersey Colo. South Platte Platte 20,600 0.001 '06 Julesburg Colo. South Platte Platte 23,294 North Platte Nebr. South Platte Platte 24 ; 000 Colo, and Nebr. Potomac 1,487 W. Va. Potomac 2,882 N. & S. branches Potomac 3,388 Great Cacapaw Potomac 4,059 bel. Great Cacapaw Potomac 4,099 Hancock W. Va. Potomac 5,556 Williamsport Md. Potomac 6,354 Harpers Ferry W. Va. Potomac 9,397 below Harpers Ferry, incl. Shenandoah Potomac 9,654 0.13 '02-'05 Point of Rocks Md. Potomac 11,100 Edwards Ferry Potomac 11,427 Great Falls POWER OPPORTUNITY 21 Drainage Low River. Tributary of Area. Flow. Year. At State. Potomac 11,545 Chain Bridge D. C. Potomac 14,500 Potomac, North Branch 293 Bloomington Md. Potomac, North Branch 406 0.065 '04-'05 Piedmont \V . Va. Potomac, North Branch 891 Cumberland Md. Potomac, North Branch 1,365 junction, South Br. Potomac, South Fork 318 junction, North Fork Potomac, South Fork 640 below Seneca Creek Potomac, South Fork 1,198 Moorefield Potomac, South Fork 1,407 Romney W. Va. Potomac, South Fork 1.443 0.305 '06 Springfield W. Va. Potomac, South Fork 1 ,475 0.064 '03-'05 Springfield W. Va. Potomac, South Fork 1,487 Potomac, South Fork 1,580 Powder 275 0.04 '06 Salisbury Oregon Presumpscot 700 1.11 '06 Me. Quinnebaug Shetucket 725 Conn, and Mass. Raccoon Des Moines 3,329 Iowa Rapid Creek 410 0.17 '06 Rapid '....S. Dak. Rappahannock 2,700 Va. Raquette 1,169 0.518 '04-'05 Massena Springs N. Y. Raritan 490 0.422 '06 Finderne N. J. Raritan 800 0.551 '03-'05 Bound Brook N. J. Raritan 1,000 mouth N. J. Red Cedar 1,840 0.219 '05 Janesville Iowa Red Mississippi 40,200 0.075 '06 Arthur City Texas Red Mississippi 92,700 Tex. and La. Red River of the North 6,000 0.08 '05 Fargo N. Dak. Red River of the North 25,800 0.067 '04 Grand Forks N. Dak. Red Lake Red 5,525 0.151 '06 Crookston Minn. Red Lake Red 6,518 Minn. Red Water 1,015 0.14 '04-'05 Belle Fourche S. Dak. Republican Kansas 23,270 0.011 '05 Bostwick Nebr. Republican Kansas 24,600 Nebr. and Kas. Republican Kansas 25,840 0.015 '04-'05 Junction Kas. Republican, South Fork 5,910 0.001 '06 Benkelman Nebr. Republican, North Fork 1,390 Haigler Richelieu 7,750 0.849 '06 Fort Montgomery N. Y. Rio Grande 1,400 0.209 '05 Del Norte. . . . Colo. Rio Grande 7,695 0.0025 '04 Lobatos Cal.. Rio Grande 14,050 0.025 '05 San Ildefonso N. Mex.. Roanoke 388 0.255 '06 Roanoke Va. Roanoke 3,076 0.35 '04-'05 Randolph Va. Roanoke 7,344 Clarksville Roanoke 8,717 Neal Roanoke 9,200 Va. and N. C. Rock Mississippi 6,150 0.104 '06 Rockton 111. Rock Mississippi 10,973 111. Rock Big Sioux 1,660 Minn. Rocky Savannah 241 S. C. Rogue 2,020 0.65 '06 Tolo Oregon Rum Mississippi 1 ,420 0.43 '06 Anoka Minn. Sabine 2,900 0.067 '05 Longview Sabine 10,400 mouth Tex. Saco 385 0.408 '06 Center Conway N. H. Saco 856 Great Falls Saco 1,366 Highland Rips 22 HYDRO-ELECTRIC PRACTICE Drainage Low River. Tributary of Area. Flow. Year. At State. Saco 1,578 Bonny Eagle Falls Saco 1,750 Me. and N. H. Sacondaga Hudson 1,028 N.Y. Sacramento 655 Oregon Sacramento 9,134 Jellies Ferry Cal. Sacramento 9,295 0.555 '05 Red Bluff Cal. Saint Croix 500 Little Falls Me. Saint Croix 1,390 0.806 '04 Spragues Falls Me. Saint Croix 1,530 0.810 '06 Calais Me. Saint Croix 1,620 mouth Me, Saint Croix Mississippi 7,576 Minn, and Wis. Saint Francis Mississippi 8,000 Mo. and Ark. Saint John 26,000 0.203 '06 Me. and Canada Saint Joseph 863 above Three Rivers .... Mich. Saint Joseph 1,417 below Three Rivers. . . . Mich. Saint Joseph 3,616 above Niles Mich. Saint Joseph 3,898 below mouth of Dowagee Saint Joseph 3,935 0.373 '06 Buchanan Mich. Saint Joseph 4,157 above Paw Paw Mich. Saint Joseph 4,586 below Paw Paw Mich. Saint Louis 3,272 above Cloquette Wis. Saint Marys 763 0.059 '06 Fort Wayne Ind. Salinas 4,084 Salinas Cal. Saline Smoky Hill 2,730 Beverley Saline Smoky Hill 3,463 Kas. Salmon 259 0.40 '06 Pulaski N.Y. Salt Gila 2,880 above Verde River Salt Gila 5,756 0.036 '04-'05 Roosevelt Ariz. Salt Gila 6,260 0.045 '04- '05 McDowell Ariz. Salt Gila 12,260 Arizona Dam Ariz. Saluda Broad 1,056 0.51 '04-'05 Waterloo S. C. Saluda Broad 2,350 mouth S. C. Sandy Kennebec 340 Farmington , Me. Sandy Kennebec 650 0.137 '04-'05 Madison Me. San Diego 208 0.0005 '06 Lakeside Cal. San Francisco 1,800 0.021 '05 Alma N. Mex. San Gabriel 222 0.18 '06 Azusa Cal. Sangamon Illinois 5,592 111. San Joaquin 1,637 Herndon Cal. San Juan 1 ,320 Arboles Colo. San Juan 6,920 0.035 '05 Farmington N. Mex. San Pedro 2,870 Dudleyville Ariz. Santa Ana 182 0.26 '06 Mentone Cal. Santa Ynez 207 0.005 '06 Santa Barbara Cal. Santee 14,700 S. C. Santiam, North Fork 740 1.00 '06 Mehama Oregon Santiam, South Fork 640 0.47 '06 Waterloo Oregon Saranac 624 0.498 '06 Plattsburg N.Y. Sauk Mississippi 968 Savannah 2,712 Calhoun Falls S. C. Savannah 7,294 0.35 '04-'05 Augusta Ga. Savannah 10,000 S. C. and Ga. Schoharie Creek Mohawk 240 0.125 '06 Prattsville N. Y. Schoharie Creek Mohawk 684 Central Bridge Schoharie Creek Mohawk 930 Schoharie Falls Schoharie Creek Mohawk 947 Fort Hunter N. Y. Schroon.. ..Hudson.. 479 .... Schroon Lake POWER OPPORTUNITY 23 Drainage Low River. Tributary of Area. Flow. Year. At State. Schroon Hudson 502 Tumblehead Falls Schroon Hudson 556 Warrensburg N. Y. Schuylkill Delaware 1,915 0.368 '05 Philadelphia Pa. Scioto Ohio 153 Kenton Ohio Scioto Ohio 1,051 0.039 '04-'05 Columbus Ohio Scioto Ohio 1,660 Shadesville Ohio Scioto Ohio 6,400 Ohio Sebasticook Kennebec 1,070 Me. Seneca Oswego 745 Waterloo Seneca Oswego . 771 Seneca Falls Seneca Oswego 1,593 below Cayuga Lake Seneca Oswego 2,472 Monte/uma Seneca Oswego 3,101 0.605 '04-'05 Baldwinsville N. Y. Seneca Oswego 3,447 N. Y. Seneca Tubelo 646 1.07 '05 Clemson College S. C. Seneca Tubelo 908 S. C. Sevier 255 Salina Sevier 3,986 0.0063 '05 Gunnison Utah Sevier 5,595 Leamington Shell Rock Cedar 2,631 Iowa Shenandoah Potomac 2,624 Riverton Va. Shenandoah Potomac 2,850 Va. and W. Va. Shenandoah Potomac 2,995 0.19 '04-'05 Millville W. Va. Shenandoah, South Branch 1,288 Shenandoah Shenandoah, South Branch 1,491 Overall Shenandoah, South Branch 1,569 0.23 '04-'05 Front Royal Va. Shenandoah, North Branch 215 Brocks Gap Shenandoah, North Branch 511 Mt. Jackson Shenandoah, North Branch 1 ,037 0.165 '05 Riverton Va. Shetucket Yantic 396 0.558 '04-'05 Willimantic Conn. Shetucket Yantic 1,245 Norwich Conn. Sheyenne , 5,400 0-009 '06 Haggart N. Dak. Shoshone 1,480 0.12 '04-'05 Cody Wyo. Shoshone 1,718 Corbett Shoshone 2,720 Lovell Wyo, Shoshone, South Fork 500 0.212 '06 Marquette Wyo. Siletz 220 0.90 '06 Siletz ...Oregon Silver Creek 221 0.06 '06 Silver Lake Oregon Silvies 865 0.025 '06 Burns Oregon Skunk Mississippi 4,409 Iowa Smoky Hill Republican 2,255 above Ellsworth Kas. Smoky Hill Republican 7,980 0.0047 '04 Ellsworth Kas. Smoky Hill Republican 20,000 Kas. Snake Columbia 10,100 Idaho Falls .Ida. Snake Columbia 17,900 0.109 '05 Minidoka Ida. Snake Columbia 22,600 Montgomery Ferry Snake, North Fork 1,040 0.902 '06 Ora Ida. Snake, South Fork 820 0.458 '05 Moran Wyo. Snake, South Fork 5,480 0.376 '05 Lyon Ida. Solomon Smoky Hill 5,539 Beloit Solomon Smoky Hill 6,815 Niles Solomon Smoky Hill 6,939 Kas. South Shenandoah 1,050 Pt. Republic Va. South Ocmulgee 595 Ga. Spanish Fork 670 0.001 '06 Spanish Fork Utah Spearfish Creek 230 0.35 '06 Spearfish S. Dak. Spokane 4,000 0.40 '06 Spokane Wash. 24 HYDRO-ELECTRIC PRACTICE Drainage Low River. Tributary of Area. Flow. Year. At State. Spoon Illinois 1,905 111. Stanislaus 935 0.20 '06 Knights Ferry Cal. Staunton Dan 3,076 Randolph Va. Staunton Dan 3,450 Va. Staunton Dan 3,546 Clarksville Va. St. Mary 452 0.21 '06 Cardston Alberta Stony Creek 760 0.023 '06 Fruto Cal. Susquehanna 1,638 bel. mouth Unadilla Susquehanna 1,789 Nineveh Susquehanna 2,024 Susquehanna Pa. Susquehanna 2,279 Birmingham Pa. Susquehanna 2,400 0.294 '06 Binghamton N. Y. Susquehanna 4,945 ab. mouth Chemung Susquehanna 7,463 bel. mouth Chemung Susquehanna 9,810 .0.46 '04-'05 Wilkesbarre Pa. Susquehanna 11,070 0.288 '06 Danville Pa. Susquehanna 24,030 0.395 '06 Harrisburg Pa. Susquehanna 26,800 0.47 '06 McCall Ferry Pa. Susquehanna, W. Branch 5,640 0.43 '04-'05 Williamsport Pa. Susquehanna, W. Branch 6,538 Allenwood Pa. Susquehanna, W. Branch 7,027 mouth Sweetwater 2,929 mouth Wyo. Tallapoosa Coosa 2,500 0.20 '04-'05 Sturdevant Ala. Tallapoosa i Coosa 2,610 Susanne Tallapoosa Coosa 3,840 Milstead Tallapoosa Coosa 4,935 Ga. and Ak. Tar Pamlico 2,290 Tarboro Tar Pamlico 3,000 N. C. Tennessee 8,990 0.30 '04-'05 Knoxville Tenn. Tennessee 21,418 0.30 '04-'05 Chattanooga Tenn. Teton 960 0.26 '06 St. Anthony Ida. Teton 967 0.387 '05 St. Anthony Ida. Thames 1,450 Conn., R. I., Mass. Thornapple ....Grand 824 Mich. Thunder Bay 580 ab. North Branch Thunder Bay 789 ab. South Branch Thunder Bay 1,267 0.294 '05 Alpena Mich. Thunder Bay, S. Branch 454 Mich. Thunder Bay, N. Branch 199 Mich. Tieton 289 0.80 '06 Naches Wash. Tiffin Maumee 723 Mich. Tiffin Maumee 748 0.064 '04-'05 Defiance Ohio Tiger Broad 720 Tioga Susquehanna. . . . 750 Canisteo N. Y. Tioga Susquehanna 1,530 Pa., N. Y. Tioughnioga Susquehanna. . . . 428 Atselic Tioughnioga Susquehanna 735 N. Y. Tioughnioga, W. Branch 103 Tioughnioga, E. Branch 164 Tippecanoe 1,890 0.279 '06 Delphi Ind. Toe Nolichucky 438 Huntdale N. C. Tohickon Creek Delaware 102 0.560 '06 Pt. Pleasant Pa. Tombigbee Alabama 4,440 0.15 '04-'05 Columbus Miss. Tombigbee Alabama 8,830 0.190 '06 Epes Ala. Tombigbee .Alabama 21,917 Ala. Tongue 3,875 Miles City Mont. Tonto Creek Salt 1,030 Livingston Ariz. POWER OPPORTUNITY 25 Drainage Low River. Tributary of Area. Flow. Year. At State. Trinity 16,000 0.04 '04-'05 Riverside Tex. Truckee 502 0.040 '05 Tahoe Cal. Truckee 955 0.403 '05 Nev .-Cal. State line Truckee ; 991 mouth Little Truckee Truckee 1,014 Laughtono Nev. Truckee 1,519 0.167 '05 Vista Nev. Truckee '.. 2,130 0.096 '05 Wadsworth Nev. Tuckaseegee 662 0.71 '04-'05 Bryson N. C. Tugaloo 593 1.0 '04-'05 Madison Ga. Tugaloo 870 Ga. and S. C. Tule 437 0.09 '06 Portersville Cal. Tuolomne 400 Hetch Hetchy Valley Dam site Tuolomne 1,501 0.041 '05 Lagrange Cal. Tuolomne 1,635 Modesto Cal. Tygart's Valley Monongahela 1,367 Uinta 218 Whiterocks Utah Uinta 672 0.140 '04 Fort Duchesne Utah Uinta 967 0.086 '04 Ouray School Utah Umatilla Columbia 353 1.00 '06 Gibbon Oregon Umatilla 1,200 0.04 '06 Yoakum Oregon Umatilla 2,130 0.0005 '06 Umatilla Oregon Umpqua, North Fork 1,000 0.90 '06 Oakcreek Oregon Umpqua, South Fork 1,800 0.12 '06 Brockway Oregon Uncompahgre Gunnison 433 0.021 '04-'05 Colona Colo. Uncompahgre Gunnison 497 Ft. Crawford Uncompahgre Gunnison 565 0.050 '05 Montrose Colo. Uncompahgre Gunnison 565 0. 10 '06 Montrose Colo. Uncompahgre Gunnison 1,130 0.010 '04-'05 Delta Colo. Upper Iowa Mississippi 952 Minn. Verde 6,000 0.030 '04-'05 Ft. McDowell Ariz. Verdigris Arkansas 3,067 McTaggart's Mills Kas. Verdigris Arkansas 8,010 Kas. and I. T. Vermilion Missouri 2,230 Dak. Vermilion Illinois 1,413 111. Wabash Ohio 3,163 0.273 '05 Logansport Ind. Wabash Ohio 12,200 22 '06 Terre Haute Ind. Walker 2,420 0.024 '05 Wabuska Nev. Walker 306 0.26 '06 Coleville Cal. Walker, East Fork 1,100 0.09 '06 Yerington Nev. Walker, East Fork 1,103 0.052 '05 Yerington Nev. Walker, West Fork . . . . 306 0.199 '05 Coleville Cal. Walla Walla 130 1.70 '06 Milton Oregon Wallowa 510 0.53 '06 Wallowa Oregon Wallowa 870 0.42 '06 Elgin Oregon Wapsipinicon Mississippi 1,308 0.127 '06 Stone City Iowa Wapsipinicon Mississippi 2,568 Iowa Watauga 261 Butler Tenn. Watauga 408 0.475 '04-'05 Elizabethton Tenn. Weiser 1,670 0.046 '04 Weiser Ida. Wenatchee 1,190 0.90 '06 Cashmere Wash. West Gallatin 860 0.40 '04-'05 Salesville Mont. White, East Branch 4,900 0.18 '04-'05 Shoals Ind. White, West Branch 1,520 0.23 '04-'05 Indianapolis Ind. White Arkansas 27,925 Ark. and Mo. White , . Connecticut 680 0.309 '04 Sharon Vt. Willamette 4,860 0.69 '06 Albany Oregon HYDRO-ELECTRIC PRACTICE River. Tributary of Drainage Low Area. Flow. 0.10 0.60 0.015 0.018 0.695 1.10 0.834 0.97 Willamette, Coast Fork 690 Willamette, Middle Fork 1,450 Willow Creek 259 Willow Creek 455 Winooski 885 Wisconsin Mississippi 2,630 Wisconsin Mississippi 5,800 Wisconsin Mississippi 12,280 Wood 906 Wood 2,190 Yadkin 500 Yakima 1,960 Yakima 3,300 Yakima 5,230 Yamhill 290 Yampa 1,730 Yampa Green 1,730 Yampa Green 3,670 Yazoo Mississippi 8,580 Yazoo Mississippi 12,794 Yellowstone 2,635 Yellowstone 3,580 Yellowstone 11,180 Yellowstone 66,090 Youghiogheny Monongahela 295 Youghiogheny Monongahela 435 Youghiogheny Monongahela 1 ,800 Yuba 1,220 0.376 Yuba, North Fork 483 Yuba, Middle Fork 205 Year. '06 '06 '06 At State. '06 '06 '06 '06 Goshen Oregon Jasper Oregon Malheur Oregon '05 0.210 0.031 0.28 0.16 0.072 0.050 0.159 0.289 0.240 0.068 0.160 0.126 Dell Oregon Richmond Vt. Merrill Wis. Necedah Wis. mouth Wis. Hailey Ida. Toponis Ida. North Wilkesboro N. C. Selah Wash. Yakima Wash. Kiona Wash. Sheridan Oregon Craig Colo. Craig Colo. Maybell Colo. Yazoo City Miss. Miss. Harr Mont. Livingstone Mont. Billings Mont. Glendive Mont. Friendsville Md. '04-'05 Confluence Pa. Md. and Pa. '05 Smartville Cal. North San Juan Cal. North San Juan . . . . Cal. '06 '06 '06 '06 '05 '05 '04 '05 '05 '05 '04 ARTICLE 9. The topography of the drainage area represents the undulations of the surface, which exercise an important influence upon the distribution of run-off. It is self-evident that the storm run-off will be greater from a hilly country than from table-lands and that the part of precipitation remaining available for ground storage will be correspond- ingly smaller; the topography, therefore, is one of the fundamental conditions determining constancy, fluctuations, and flood characteristics of stream flow and should receive commensurate consideration. A topographical map of the United States is published by the United States Geological Survey, from which the general topography of all important drainage areas can be readily found, that is, it can be learned whether the area is generally of a hilly or flat country, whether stream channels are narrow and declivitous or broad valleys, and what, if any, is the area of lakes and swamps. It is not necessary to define these conditions as to details, but it is essential to understand the pre- vailing features as distinguished between the flat land drainage areas of streams in Iowa, Illinois, Indiana, and the middle West, and those of POWER OPPORTUNITY 27 rolling and hilly formation in Virginia, Kentucky, Vermont, or the Pacific slope; or of parts of a river, when perhaps a site on its upper reach is considered, where practically all of the area is in mountain ranges or foot-hills, or a point near the mouth of the river, where only a small part of the area is in hilly and by far the greater is in flat or roll- ing country. As an example, the Cumberland River may be cited, of which Chart 2 gives drainage areas for two important water-power sites, the upper one at Cumberland Falls, Ky., often called the Niagara of the South, the lower one near Nashville, Tenn. ; the first is almost wholly in the mountain region, while the Nashville site area is largely of flat and roll- ing country. Such general information, as has been said before, can be gleaned from the United States Geological Map or from the Map of Altitudes published by the same department. Some conclusions as to topography can frequently be drawn from location of railroads and highways, espe- cially from the former, which in hilly and broken country more generally parallel the watercourses than in flat or rolling parts. Many sections have been covered by detail topographical surveys, and the informa- tion then is conclusive. To secure a sufficient appreciation of the topography from any or all of these sources requires considerable experience in the reading of the projections. It is, of course, prohibitive in cost to make surveys for this purpose, but a horseback reconnoissance or drifting down the river, or the major portion of it, will frequently enable the investigator to form correct conclusions on this point. The author has examined several rivers by going down in a canoe, and the information thus gained proved exceedingly valuable in planning power developments. ARTICLE 10. The geology of the drainage area should be understood to the extent of influencing the degree of absorption and storm run-off. Where rock ledge is at surface or crops out in banks, the depth of over- lying drift is readily ascertained; otherwise borings should be made, if practicable to rock, and the character of the overlying material found. The percolosity of the ground determines its storage capacity. A very satisfactory conception of this latter can be obtained from the observance of conditions following heavy rainfalls, when frequent accumulations of pools of water in level fields are evidence of the prevalence of non-absorb- ent soil, while its rapid disappearance indicates sandy and gravelly for- 28 HYDRO-ELECTRIC PRACTICE mations. The stream itself gives testimony of these conditions, the water being turbid where draining clayey soils, while the run-off from porous earths shows little discoloration. No practical information, for the inves- tigation in hand, can be gained from this study beyond the formation of the immediate subsurface, and this can be obtained by a personal examination of the locality in question and a study of the farming culture. In many sections conclusive data can be obtained from records of well borings, which are generally sunk by one concern covering several coun- ties. Some of the State Geological departments publish such records. ARTICLE 11. The flora and culture in the drainage area constitute the third characteristic which influences the flow. Forests are conservers of water, protecting it from the heat of the sun and the winds, and thus retarding its evaporation as compared with cultivated fields, grazing land, or open soil, while the many obstructions to the storm run-off in timbered areas result in a greater portion finding its way into ground storage. The requirement of moisture for tree growth is considerably less than that of crops; for instance, long grass consumes six times as much water as fir trees. Wooded hill-sides, tamarack and cypress swamps are storage reservoirs; highly cultivated table-lands with tile drainage leave but little, if any, surplus during the growing season for run-off. It is important, therefore, to secure an adequate knowledge of these conditions. The degree of cultivation can be ascertained from the rural population of counties and the character and volume of produce shipped out, all of which, together with the forest area, can be obtained from the United States census publications. ARTICLE 12. As stated before, precipitation is the source of all stream flow, which latter can only be a fraction of it. Frequently a good enough preliminary estimate of flow can be made if quantity of precipi- tation in drainage area and the extent of the latter which contributes to the river at the point under examination are known, and reliable data of fluctuations of flow throughout seasons and years can be found from such information. Drainage areas, as has been seen, can be readily measured, and precipitation is ascertainable from public records. For fifty years and longer rain- and snow-fall have been measured in the United States and Canada through the agency of the Government, in this country by the United States Weather Bureau, in the Dominion of Canada by Provincial meteorological departments; points of observations are distributed over 30 HYDRO-ELECTRIC PRACTICE the country with somewhat of a uniformity, and one or more of them can always be found in a certain drainage system. The measurements are made by means of standard cups, so exposed that they receive the normal rain- and snow-fall, which is measured as to its depth in inches and fractions, the snow being melted for that purpose and therefore ex- pressed in the same quantity as the rain. Observations are made daily of the rain- or snow-fall during twenty-four hours, and the daily, monthly, and annual totals are given in public records. Such measurements require no skill and may, therefore, be accepted as a fairly accurate record of precipitation. From these data the general distribution of precipitation is well known; it is illustrated on Chart 3, on which equi-precipitation curves are projected, the precipitation being the normal annual quantity in inches. This may be used with advantage for first investigations of stream flow, exhibiting neither the wet nor dry but the normal year. Observations of this character have been carried on for a sufficiently continuous period to warrant the conclusion that precipitation is not undergoing any great changes : it does not rain more or less now than it did fifty years ago, nor does the clearing of land seem to be followed by any marked change in rainfall in that section. The ordinary fluctuations of precipitation appear to be represented in a cycle of seven years, that is, the totals of seven years of precipitation are very nearly equal; each of these seven-year periods contains one dry year, the one of least precipi- tation, and generally one or two extremely wet years. ARTICLE 13. The information to be sought in connection with determination of stream flow comprises the quantity and distribution of rain and snow during at least one complete cycle of seven years, in order to fix upon the ordinary dry year of the period. The safe method is to collect the precipitation data by monthly totals from as many observa- tion points as are obtainable in the drainage area for a period of fifteen continuous years, which are certain to contain a complete cycle. If the entire drainage area is located in the same precipitation belt as per Chart 3, the monthly means of all observations are compiled and may be taken as applying to the entire area; when the drainage area extends through different precipitation belts, the monthly means of stations in each precipitation belt are to be found, the drainage area is to be divided into parts covered by different precipitation belts, and the respective monthly means applied to each. Such precipitation records from five points in 121 119 117 115 113 111 r <>9 107 105 103 101 99 B5 83 81 79 POWER OPPORTUNITY 31 drainage area of Green River, Ky., for fifteen years by monthly means, which in the case of this system, lying in the same precipitation belt, may correctly be accepted for the whole area, are here given. PRECIPITATION IN GREEN RIVER, KY., DRAINAGE AREA FROM 1891 TO 1905, BY MONTHLY MEANS. Station. 1891 Jan. 680 Feb. 7.61 March 8.24 April 2.42 May 0.76 June 3.02 July 1.08 Aug. 6.76 Sept. 2.41 Oct. 0.96 Nov. 6.56 Dec. 4.37 Total. 50.99 52.73 45.56 52.61 44.86 51.59 50.95 51.70 35.35 39.41 37.73 44.44 40.94 40.72 46.85 45.73 47.59 41.50 39.26 43.54 53.39 48.94 51.35 58.73 54.05 48.04 52.50 50.59 48.40 43.95 Edmonton . . . . . 5.77 6.84 6.80 2.60 3.04 2.62 4.26 4.67 4.61 6.37 5.47 5 14 9.46 8.83 5.48 4.79 3.52 3.29 3.66 3.63 2.72 2.70 3.26 2.61 2.05 10.84 8.56 8.15 7.12 5.10 5.61 3.59 3.33 2.71 0.97 0.65 6.64 4.97 4.92 8.67 8.63 5.44 3.47 4.18 3.14 6.71 4.07 4.35 3.78 2.67 5.87 6.46 8.52 0.93 1.79 3.59 2.15 2.38 1.19 2.58 4.02 5.85 5.29 6.02 3.84 2.54 2.97 6.27 4.84 2.57 5.29 1.37 2.09 3.26 2.98 4.62 4.75 1.41 2.30 4.12 3.20 2.74 3.54 3.21 3.28 3.91 2.64 0.94 1.31 0.10 0.41 0.10 4.88 3.08 4.46 0.83 1.22 1.25 6.22 5.22 4.39 4.30 3.80 4.03 3.63 2.83 1.41 2.13 1.42 3.38 3.15 7.73 5.50 4.53 2.79 3.42 3.47 2.84 4.21 3 94 Grecnsburg . . . . . . 4.96 1892 Bowling Green ... 2.60 Edmonton Greensburg . .. 2.42 . . . 2.04 1893 Bowling Green . .. 0.72 Edmonton . . . 1.38 Greensburg . . . 0.64 1894 Bowling Green. . . . .. 3.09 Edmonton . .. 3.31 292 1895 Bowling Green. . . . .. 5.28 0.47 0.84 0.81 3.26 3.87 3.86 3.35 3.54 4.46 4.39 6.92 7.56 6.90 5.47 4.92 7.61 2.82 3.09 3.32 3.67 2.52 1.25 0.78 0.43 7.45 5.42 4.46 2.18 5.71 5.24 4.30 6.41 5.04 2.43 1.96 2.03 5.10 3.94 3.48 8.47 2.87 3.10 0.80 9.95 5.35 4.85 8.21 8.27 9.32 6.58 5.00 2.98 3.63 1.79 2.38 1.48 3.21 1.85 1.25 1.25 2.30 0.67 1.18 0.25 3.82 3.28 3.60 3.54 3.60 0.08 1.45 2.69 2.06 1.32 0.74 0.99 1.41 1.48 0.80 4.08 3.42 3.73 5.42 5.12 4.71 5.47 4.68 3.15 5.17 6.06 4.92 1.70 1.63 1.64 3.06 3.02 376 Edmonton . . . 5.57 Greensburg . . . 6.73 1896 Bowling Green 1.40 Edmonton . . . 0.81 Greensburg . . . 0.70 Leitchfield . .. 1.31 St John 1897 Bowling Green 3.34 4.56 Edmonton . . . 2.87 7.64 8.10 6.57 1.88 2.08 4.90 2.40 0.82 0.78 1.38 1.65 4.95 5.25 6.65 5.14 3.50 1.57 2.22 2.18 2.04 2.61 3.74 3.77 4.35 4.46 3.22 2.87 2.77 3.08 2.57 1.83 1.68 1.94 2.75 1.75 3.80 3.78 3.48 3.62 2.96 2.87 3.85 2.94 2.76 4.86 5.44 4.88 4.74 4.77 Greensburg , .. 3.62 6.10 8.22 7.16 5.04 3.21 4.90 4.00 Leitchfield 3.36 6.66 9.62 5.72 3.10 1.84 2.86 3.70 St John . .. 3.41 5.60 0.82 1.49 1.26 1.09 1.26 4.14 6.33 4.59 3.68 3.32 8.92 7.44 5.96 6.85 9.27 9.36 8.65 10.73 10.32 8.09 7.65 5.11 4.08 3.21 3.21 4.25 4.20 4.14 4.42 4.02 3.88 4.02 3.39 4.75 2.50 4.06 5.83 4.75 4.83 4.61 6.16 5.01 4.05 3.31 3.87 5.45 1.75 4.34 5.05 1.93 2.67 3.82 2.84 1.98 2.71 2.19 3.15 4.94 4.35 2.31 5.26 5.45 3.16 3.32 2.45 1.33 3.80 2.04 1.81 1.59 3.22 2.61 1.54 1.26 3.78 4.61 0.03 3.32 3.62 4.90 6.12 5.35 0.71 1.23 0.92 1.07 0.86 1898 Bowling Green ...11.99 Edmonton . . . 10.53 Greensburg . . . 9.30 Leitchfield . . . 10.73 St John .... . . . 9.72 1899 Bowling Green .. 7.51 Edmonton .... . . . 6.18 Greensburg . . . 7.34 Leitchfield . . . 7.20 St. John. . . 5.88 HYDRO-ELECTRIC PRACTICE Station. Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. Total, 1900 Bowling Green ...... 3.15 Edmonton ......... 2.26 Greensburg ......... 2.16 Leitchfield ......... 3.06 St. John ........... 2.98 1901 Bowling Green ...... 2. Edmonton ......... 2.31 Greensburg ......... 1.99 Leitchfield ......... 1.99 St. John ........... 1.57 1902 Bowling Green ...... 8.25 Edmonton ......... 7.37 Greensburg ......... 7.54 Leitchfield ......... 6.61 St. John ........... 5.65 1903 Bowling Green ...... 2.64 Edmonton ......... 2.25 Greensburg ......... 2.69 Leitchfield ......... 2.55 St. John ........... 2.44 1904 Bowling Green ...... 2.93 Edmonton ......... 3.81 Greensburg ......... 3.34 Leitchfield ......... 3.32 St. John ........... 2.99 1905 Bowling Green ...... 3.21 Edmonton ......... 2.84 Greensburg ......... 3.12 Leitchfield ......... 2.70 St. John ........... 2.60 5.30 2.74 2.60 4.78 3.97 2.71 4.85 3.63 2.68 6.48 2.09 3.33 5.59 2.37 2.56 4.01 5.67 5.72 2.66 7.14 6.27 3.44 9.94 6.43 4.58 3.79 3.32 3.25 4.46 4.45 1.67 4.41 2.65 10.94 3.17 3.73 3.01 1.22 10.05 3.09 4.31 1.66 1.23 6.85 3.21 3.21 1.34 2.91 11.06 3.21 4.57 1.37 2.25 8.81 2.79 :.13 '31 1.15 1.11 3.36 3.81 3.90 5.36 1.31 2.69 2.71 4.57 0.17 0.40 7.34 7.31 5.38 5.66 0.62 1.15 1.25 1.32 5.60 480 .99 qq 0.93 1.14 3.23 4.21 4.30 3.57 2.35 2.35 4.19 2.65 1.55 1.12 3.66 5.80 3.87 6.49 0.97 0.89 1.03 1 10 4.35 525 .57 ; ?5 1.08 1.39 4.02 6.18 2.22 2.68 2.65 3.82 3.98 3.22 1.30 0.72 3.86 2.53 4.15 4.35 0.79 2.78 1.12 4.49 4.95 9.24 .37 ' 54 1.40 0.60 7.03 4.80 2.86 2.02 2.77 2.42 2.77 3.46 3.31 4.27 1.78 2.18 4.96 4.88 2.57 3.07 4.29 5.05 9.82 882 i.61 i.65 0.89 0.85 3.91 3.67 3.31 2.14 2.94 3.73 5.51 5.16 0.89 1.17 2.15 4.04 8.25 8.26 1.04 1.36 4.45 4.67 11.97 7.19 8.37 8.65 8.48 8.19 7.94 2.61 2.45 2.05 2.34 3.13 1.96 2.53 2.05 2.23 2.31 3.10 6.67 6.01 3.78 3.64 5.00 7.27 5.52 6.85 6.09 3.53 5.15 5.59 4.67 4.66 3.23 5.35 4.22 3.93 3.16 2.46 2.62 2.78 3.67 2.98 2.16 2.46 2.99 3.33 3.55 4.95 5.95 5.46 3.69 4.28 5.63 4.27 3.84 3.02 4.65 5.43 4.33 3.86 3.94 2.30 2.32 5.50 4.09 4.17 2.35 4.26 2.50 2.47 2.84 1.37 6.03 2.49 3.50 3.25 2.75 3.39 4.22 3.65 4.31 5.59 6.53 3.81 3.69 6.03 6.65 5.52 5.32 5.74 4.85 5.93 2.03 0.76 2.63 1.21 3.57 2.19 0.35 3.01 3.89 3.02 5.25 0.35 3.11 3.39 3.08 3.95 1.35 1.48 2.97 3.38 4.50 0.30 1.57 4.45 2.54 2.41 2.24 0.05 1.40 5.40 2.92 1.48 0.30 1.34 4.98 5.48 2.66 0.16 1.06 4.67 1.28 4.33 0.20 0.40 5.14 1.12 2.49 0.21 0.57 5.46 1.19 3.00 3.34 2.23 3.55 2.58 4.45 4.92 3.52 4.72 4.04 6.13 5.33 2.94 4.68 2.00 3.90 4.16 3.53 5.22 2.16 1.90 5.80 3.19 5.13 52.03 50.89 50.39 48.38 45.45 34.92 40.49 32.42 36.56 31.69 49.65 50.93 49.11 51.92 47.89 43.90 48.91 47.71 45.99 40.64 36.41 37.95 35.53 37.42 34.54 35.43 49.62 50.40 49.23 47.82 The annual totals are plotted as shown on Profile 1, from which the fluctuations are readily appreciated, the year 1901 being unmistakably the dryest of the period. This is the year we are concerned with, and by plotting the monthly precipitation as shown on Profile 2 we see how it was distributed and which are the months of low flow. This closes the necessary precipitation investigation, the dry year has been found, the low flow months are known, and it remains to be determined what portion of this precipitation evaporates, which will leave the quantity representing the run-off and thus the flow. ARTICLE 14. Evaporation. Investigations have been carried on in this country and abroad for many years with the object of finding a POWER OPPORTUNITY 33 practical method for evaporation determination, and observations and measurements of evaporation from water surfaces, forests, uncultivated lands, and fields with growing crops of all kinds have conclusively estab- lished such a ratio. Evaporation from water surfaces is found by aid of evaporation pans which are of considerable area and water-tight, the contents of which may be found precisely at known intervals of time, the diminution being due to evaporation. For this determination from land, known areas are isolated, surrounded by ditches in which the water draining off can be accurately measured, when the difference between the quantity of a certain rainfall and that draining off by these ditches represents evaporation from that area for a given time, other climatological conditions being duly observed. These experiments have been repeated in various latitudes by different persons, and from them certain evaporation values have been determined. Table 2 gives monthly evaporation in inches from different surfaces for certain locations. TABLE 2 .* EVAPORATION FROM WATER AT EMDRUP, DENMARK. (Latitude, 55 41' N.; longitude, 12 34' E. from Greenwich.) Year. Jan. Feb. Mch. Apl. May. June. July. Aug. Sept. Oct. Nov. Dec. Total. in. in. in. in. in. in. in. in. in. in. in. in. in. 1849 . . ..1.1 0.3 1.8 2.5 4.1 5.8 4.7 4.0 2.6 1.1 0.9 0.6 29.5 1850 . . ..1.1 0.3 1.2 1.7 4.5 5.6 4.8 4.8 2.4 1.6 0.9 0.2 29.1 1851 . . ..0.5 0.4 0.7 1.7 4.2 4.8 5.7 5.1 2.7 1.5 0.6 0.5 28.4 1852 . . ..0.7 0.5 0.8 2.4 3.8 4.6 6.4 4.5 2.7 1.7 0.8 0.5 29.4 1853 . . ..0.5 0.1 0.7 1.0 4.1 6.2 5.1 4.2 2.8 1.1 0.6 0.5 26.9 1854 . . . .0.5 0.9 0.9 3.2 3.3 4.5 5.2 4.3 2.6 1.2 0.7 0.6 27.9 1855 . . ..1.0 1.1 0.5 1.2 2.6 4.1 4.7 4.1 2.8 1.4 0.9 0.7 25.1 1856 . . ..0.5 0.5 1.2 2.1 2.8 4.6 4.3 4.0 2.0 1.9 0.6 0.5 24.0 1857 . . ..0.7 0.6 0.6 1.4 4.1 6.6 5.9 4.3 3.2 1.4 0.7 0.4 29.9 1858 . . ..0.4 0.7 1.2 3.1 5.1 6.1 4.9 5.6 2.8 1.6 0.7 0.4 30.6 1859 . . ..0.3 0.5 0.7 1.9 4.3 5.8 5.3 3.8 1.8 1.0 0.7 0.3 26.4 Mean.... 0.7 0.5 0.9 2.0 3.7 5.4 5.2 4.4 2.6 1.3 0.7 0.5 27.9 Ratio... .301 .215 .387 .860 1.592 2.323 2.237 1.892 1.118 .559 .301 .215 Mean Evaporation from Short Grass, 1852 to 1859, inclusive. Mean 0.7 Mean 0.9 Mean. ... 1.5 1.2 2.6 4.1 5.5 4.7 2.8 1.3 0.7 0.5 Mean Evaporation from Long Grass, 1849 to 1856, inclusive. 0.6 1.7 1.4 2.6 4.7 6.7 9.3 7.9 5.2 2.9 Mean Rainfall at same Station, 1848 to 1859, inclusive. 1.0 1.6 1.5 2.2 2.4 2.4 2.0 2.3 1.3 1.8 0.5 1.5 30.1 44.0 21.9 * J. T. Fanning, Water-Supply Engineering. 34 HYDRO-ELECTRIC PRACTICE EVAPORATION FROM WATER-SURFACE AT BOSTON, MASS., IN INCHES FOURTEEN YEARS*, 1875-1890. 1876. 1877. 1878. 1879. 1880. '81-'84. 1885. 1886. 1887. 1888. 1889. Total. Mean. January 0.96 0.96 0.96 0.96 0.96 0.96 0.96 0.96 0.96 0.96 0.96 15.36 0.96 February 1.05 1.05 1.05 0.15 1.05 1.05 1.05 1.05 1.05 1.05 1.05 16.80 1.05 March 1.70 1.70 1.70 1.70 1.70 1.70 1.70 1.70 1.70 1.70 1.70 27.20 1.70 April 2.98 2.98 2.98 2.98 2.98 2.98 2.98 3.12 3.07 2.78 2.84 47.57 2.97 May 4.45 4.05 4.14 5.89 5.22 4.45 3.77 4.45 4.83 3.35 4.57 71.42 4.46 June 5.44 5.68 5.26 5.32 6.46 5.55 7.01 5.25 5.05 5.98 3.94 88.69 5.54 July 7.50 4.82 6.04 6.41 5.82 5.98 7.09 5.59 5.96 5.57 5.04 95.72 5.98 August 6.21 4.40 4.33 5.23 5.34 5.50 7.41 5.80 6.20 5.81 4.25 87.98 5.50 September 3.48 4.08 4.04 3.80 4.04 4.20 5.13 4.55 4.57 3.91 3.08 65.88 4.12 October 3.12 2.51 3.52 2.99 2.79 3.11 2.79 4.13 3.61 3.27 3.13 50.52 3.46 November 0.66 2.23 2.23 2.23 2.60 2.23 2.23 2.69 3.00 2.71 1.98 35.94 2.25 December 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 24.16 1.51 Total 39.06 35.97 37.76 40.07 40.47 39.22 43.63 40.80 41.51 38.60 34.05 627.24 39.20 Evaporation from an entire drainage area of a stream is readily determined if precipitation and flow for a sufficiently continuous period as, for instance, one year are known. Precipitation may be measured as already described, while the actual quantity of water passing down the stream may also be found by physical measurements. This has been done on many streams for long periods, measuring weirs have been erected and the overflow recorded by automatic gauges, and thus the continuous and total flow per day, month, or year determined; the difference between this flow and the total precipitation is chargeable to evaporation. From such data, resulting from extensive systematic investigations, rules have been evolved to find evaporation, the correct application of which will give results in harmonious agreement with those found by measurements, and these rules or formulae may be applied to any set of conditions for the purpose of finding similar results. A detailed description of the method of determining evaporation will be found in Part II.; a practical application of it, from the author's practice, will go far toward securing for its further study that degree of confidence in its value for the general investigation of stream flow which it deserves. Green River, Ky., was the subject, the development of power to be planned at a Government lock. The drainage area was delineated from a State map, as shown on Chart 1 ; precipitation data were collected as * Desmond Fitzgerald, C.E., Rainfall, Flow of Streams, and Storage. (Transactions Am. Soc. C. E., Vol. XVII.) 45 40 35 Annual Precipitation Green river, Ky. 35 3.0 3. 2.5 2.0 1.5 1.0 2.5 2.0 1.0 0.5 / IP $?F/ \\ S Monthly Run - off Measured & computed Cjr / \ \ / ^^ / "^^ \ / 1> * \ / *jl . \ x^ / fM \ X =^ ^t -v 7 i ____\_ """"**- ^-^^' ^^^ =^= ===i 0.5 H.E.P.6. H.vA 35 36 HYDRO-ELECTRIC PRACTICE given on Table 3 and on Profiles 1 and 2 ; from these evaporation and run-off were computed, the results for the latter being plotted on Profile 3, in heavy line, as monthly run-off for the dry year of the period covered by precipitation records. The overflow at the Government dam had been recorded daily for this same year, and from these the flow was computed from the weir formula, and these results are also plotted on profile in light line. Both of these operations were executed by different persons. The agreement between the two profiles is striking, the discrepancies during the winter months are accounted for by the fact that the run-off as computed was partially frozen and therefore retained until spring. The reliability of the computation method is, however, evident. Similar results can be quoted from published records, especially in New England and Eastern States, where the flow of many streams has been measured in similar manner for many years and the run-off as computed from evaporation compared with it. In fact, the system has been evolved from compara- tive results on rivers where flow has been established by physical measure- ments. The author has always used the two methods of calculation and measurements to check results whenever authentic flow measurements covering sufficient periods were available, and has found them to agree most satisfactorily. ARTICLE 15. The application of flow deductions from precipitation for preliminary investigation purposes is expressed by the following rules : Rule 1. About 30 per cent, of annual precipitation remains avail- able for flow; the other portion is evaporation. Rule 2. The low monthly flow cannot exceed one- twelfth of the total available flow. Rule 3. The monthly flow during three months, generally in the fall, in Northern latitudes is from one-half to one-third, in Southern latitudes from one-fourth to one-sixth, and in Western States from one-sixth to one-tenth of one-twelfth of the annual pre- cipitation excess over evaporation. The author has met cases where the application of this simple rule would have saved to the promoters of water-power projects thousands of dollars. One in point is recalled, where a water-power was projected on a stream with a drainage area of about 700 square miles, the avail- able fall was 30 feet, and the opportunity was credited with a power output of 3500 horse-power, which would call for an available flow of POWER OPPORTUNITY 37 about 1450 cubic second feet, requiring run-off of 2.07 cubic second feet per square mile of area, which represents monthly precipitation excess over evaporation of 2.3 inches. These facts should be sufficient to reveal a gross error in' the assumed power output, that is, if the area has been ascertained. The stream was in a Northern State where normal annual precipitation is 35 inches, annual temperature about 48, and annual evaporation therefore nearly the same as that found in the example given, or about seven-tenths, leaving a residue of precipitation for annual run-off of about three-tenths, or eleven inches for the entire year. As a matter of fact, the opportunity was good for about 1500 horse-power with a 250 horse-power auxiliary plant supplementing the three months low flow output. About 1000 acres of lands had been purchased and paid for, but no power development has yet taken place. Many similar instances could be cited. ARTICLE 16. Flow measurements are made by various methods, but, unless they extend over a sufficiently long period, especially covering the low stages, their result is not conclusive as to the available flow. As a rule, the time necessary to do this properly cannot be taken ; when water- power projects ripen to the stage of such investigations, results are expected promptly, and, unless it is then the period of low flow, measure- ments will be of little practical value. On many streams measurements have now been made for several years by the Federal Government, the results being published in annual reports of United States Geological Survey as stream measurements, and, where these have been carried on long enough to furnish a rating table for the stream, this information may be taken as conclusive for the purpose. Table 1 gives low flow for some rivers in the United States compiled from this source. The most reliable method of measuring a stream's flow is by an overflow weir, which is a type of low dam over which the entire flow passes. It is, of course, necessary that no portion of the flow passes under it or around its ends, and this is neither readily nor economically constructed, and, as a rule, is impracticable unless the stream is a very small one. If the river is already crossed by a dam, it may afford a satisfactory opportunity for measurement, provided it is free from leaks and its crest is horizontal. Old mill-dams are generally not water-tight and are more or less out of alignment, and therefore not very reliable for this purpose. The technic of weir measurements and reductions is described in 38 HYDRO-ELECTRIC PRACTICE detail in Part II., Chapter 6; for practical purposes of first investiga- tions, the following method will yield sufficient results. Ascertain the length of dam crest by stadia measurement or triangulation, and the height of overflow by differential levels between water surface some thirty feet upstream of the dam and of dam crest, and take correspond- ing flow from Diagram 2, which gives the volume passing per linear foot of overfall over a wide flat-crested dam in cubic second feet for depths of overflow in tenths of inches. Example. Overflow of 1.2 inches over dam crest 236 feet long repre- sents a flow of 4.35 cubic second feet. Mill-dams, unless in very bad condition, may furnish valuable data as to flow; millwrights know how much power is required to operate their plant, the effective head can readily be measured, and, crediting the water-wheels with an efficiency of about 65 per cent, when of old pattern, the volume passing through them can be computed. Nothing is more strongly impressed upon the miller than shortage of water and the length of time during which he has to shut down to raise the pond, and the depth below the dam crest to which the pond lowers during low seasons after running the mill a certain period; each one of these facts may be utilized in determining the low flow of the stream and its duration. The author determined the low flow on the Cannon River, Minn., in 1904 from such data collected at a mill which had operated some forty years with a water-wheel equipment representing the earliest Ameri- can turbine styles, and the result was only about two per cent, lower than was afterwards found from measurements and gaugings extending over an entire year, and this discrepancy was chargeable to leakage through mill tail-race. Where weir measurement is impracticable, a well-conditioned cross section of the stream is selected, its area found by soundings, and the velocity determined with which water passes through it by meters or floats. Part II., Chapter 6, treats the technical phases of these measure- ments and of the instruments, methods, reductions, and computations; the practical application for preliminary investigations is as follows. Select a section about one hundred feet long on a straight stretch, with shores parallel and of gentle and even slope, containing no islands, visible rocks, or other obstructions, and where the water appears to pass at a nearly uniform speed throughout the entire width. Stretch two .0 o u. 13 12 11 10 9 8 7 6 5 2.0 2.5 3.0 3.5 , 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 Diagram 2 Discharge over flat- crested Spillway H.E.P.2. H.V.S. 0-5 1.0 1.5 2.0 Overflow, in feet 39 40 HYDRO-ELECTRIC PRACTICE lines (|-inch rope) across the river, secured at shore and one hundred feet apart. Stretch a third line midway between these two and mark it off in ten-feet sections by tying on it alternately red and white bits of cotton ribbon. When the river is wider than one hundred feet, attach two guy lines to this centre line so that a boat may pass along without sagging it greatly out of straight line. Find the depth of water at each red and white marker along the centre line by differential level between water surface and river bed, by means of a levelling instrument reading on a rod held by a man, in boat, on river bottom. Collect chips of wood or pieces of lath or bark which can be recognized while floating, and have man in boat throw one at a time in the river some fifty feet above the upstream line, time the passage of float under upper and lower lines, also spot the red or white marker under which it passes; use as many floats as there are markers in the line, endeavoring to have at least one pass under each. Find the mean of the velocities observed, the product of 0.85 of this mean velocity and the cross section area represents the approximate discharge at that period for the purpose of preliminary investigation. Part II., Chapter 6, will deal with and describe measure- ments by meter, surface and rod floats, and of reductions, coefficients, etc. ARTICLE 17. The fall available for development must be found from the total fall existing in entire reach of stream to be controlled, that is, from the upper to the lower point to be affected by the develop- ment, less the fall represented by the slope in the upper pool, which may be from 0.05 to 0.5 feet per mile. The condition of river stage on which these fall determinations are based must be that which represents the flow to be utilized. If the consideration of backswell is neglected, the upper pool will extend beyond the expected limit, lands will be flooded which perhaps have not been secured, and, if there is an upper develop- ment or power site, the upper pool water will trespass on its tail waters. When available fall is thus fixed, it remains to be determined whether all or only part of it is to be utilized, which will depend upon the topo- graphical conditions as influencing location and character of develop- ment. The constancy of the fall as depending upon flow fluctuations must be carefully studied; on many streams the fall may all disappear during extreme floods. ARTICLE 18. Power Output. The unit of output of a hydro-electric development is the electrical horse-power, being representative of the power available for actual work. POWER OPPORTUNITY 41 The original energy is hydraulic power, which is converted by means of turbines into mechanical power, and this in turn into electric power; both of these transitions entail some loss of originally available energy, due to friction in one form or another. The amount of this loss from hydraulic to electric energy depends upon the type of the machines and their mode of operation, and in practice is generally considerably in excess of that which is claimed for them or even shown by tests. After the plant is in operation for a period, it is found that efficiencies of 76 per cent, for turbines and of 94 per cent, for generators may be obtained with proper equipment correctly installed. Based upon these the electric power realized is 72 per cent, of the hydraulic energy, or about 12^ cubic second feet with one foot fall represent one electric horse-power. By the aid of Diagram 3 flow and fall may be readily converted into electric horse-power, or the flow required for certain output with fixed fall determined. Example. Flow 250 c. sec. ft., fall 22 ft. Output = 440 E.H.P. Fall 30 ft., desired output 100 H.P., required flow = 417 c. sec. ft. Having found, by one method or the other, the monthly mean flow during a dry year, the volume on which maximum development may be based, which will be called the power-flotv, is to be fixed upon. The development plant, with exception of equipment, will gener- ally cost nearly as much for a small as for a large output development, and, if for no other reasons, this is sufficiently important to seek the development into useful energy of the greatest possible portion of the entire flow during the dry year: the most complete utilization of this is the best development. However, the low month flow presents undis- putably the maximum continuous volume which is available for twelve months; if any higher is taken, the deficiency must be made up, and the substance of the inquiry lies in the question, "How much can be added to the low flow, and from what source?" The source is threefold: the market conditions may, and most generally do, call for current service only during a portion of the 24 hours; in that case the plant closes at the expiration of the operating period, and the natural flow may be accumulated by pondage above the dam during the remaining portion of the 24 hours, the non-operating period. This is accomplished by temporarily raising the height of the pond a foot or more through the fixing of flashboards along the crest; the ponded flow then becomes available, together with the natural flow, 42 HYDRO-ELECTRIC PRACTICE during the succeeding operating period; the addition will not be large, but every 12^ cubic second feet represents one electrical horse-power for each foot fall. For instance, the low-month flow is 250 sec. ft., the fall 30 feet, the non-operating period is six hours, from midnight until 6 A.M.; the accumulated, or ponded, flow will be 250X21,600 = 5,400,000 cub. ft., and, deducting 10 per cent, for leakage and seepage, the quantity added during the operating period of 18 hours is 4,860,000-^64,800 = 75 sec. ft., which represents an added power output of 75^12.5x30 = 180 horse-power; the low-month flow is increased to 325 sec. ft. If the pond is two miles long and 200 feet wide its area is 10,560X200 = 2,112,000 sq. feet, and the dam crest, or pond level, must be raised by 5,400,000^-2,112,000 = 2.5 feet. The second source of increasing the low monthly flow is from storage. Some of the stream's tributaries emptying within a few miles above the power plant may present suitable reservoir sites, where the valley can be closed by an economical dam structure rising to a moderate height of 10 to 15 feet, thereby empounding a storage reservoir; such a dam would be of the earth and rock fill type, with a suitable timber waste gate, as water is not to spill over the structure. The reservoir is permitted to fill during high-flow season, when the withdrawal of this portion from the main stream is of no consequence, and the supply is drawn out dur- ing the low month as needed. Taking the last example and a reser- voir site of 250 acres of an average depth of ten feet, the volume stored is 250X43,560X10 = 108,900,000 cubic feet, the daily loss from evapora- tion and seepage of about 2.5 per cent, will be replenished by the nor- mal run-off from a drainage area tributary to the reservoir site of about 100 square miles. This stored volume represents an 18-hour flow for thirty days of about 40 cub. sec. ft. and with 30 feet fall an output of 96 horse-power. Diagram 4 gives continuous flow for stated periods from a water surface of 10 acres area and one foot deep. Pondage and storage may be combined, and in the case cited the low flow would be increased from 250 to 365 sec. ft. The third source of replenishing the low-month output is by auxiliary power. When the hydro-electric plant goes into business, some power customers may be found who are then using steam power, and arrange- ments can be made with them by which the use of their steam-power plant may be had during low-flow seasons, and, in that event, the low- flow output can be increased by the capacity of such an auxiliary plant. POWER OPPORTUNITY 43 130 120 110 100 90 80 70 60 50 40 *2 M 30 I 20 A u 10 o E 123456789 130 120 110 100 90 80 70 60 50 40 30 20 10 / / / f / / Diagram 3 Water Power and Electric Power Efficiency 72 pet. / 7 / / / > / / / / / ' / / / / ,, ^ A V A i D / s '# A* y / / / / / / / / . / / / / / . 7 / / / / ^ 1 1 F '7 / 4 y^ j^_ 7 / 123456789 E H .P. 44 HYDRO-ELECTRIC PRACTICE The entire subject of developing the opportunity in excess of the low dry-year flow is one of comparisons between cost of reservoir storage, or auxiliary plant, or both, and the returns from additional output thus secured; but in this connection it must be borne in mind that increasing the low-months output enables the plant to contract for delivery of this increase during the entire year, while the auxiliary plant will only be operated during one month. Given the reservoir project above of 250 acres, the land costing $25.00 an acre and the reservoir dam $2500.00, the increased hydraulic and electric equipment for 96 horse-power $1500.00, and the annual operating cost of reservoir gates $250.00, the annual charges will be Interest 6 per cent, on investment of $10,250.00 $615 Operation of reservoir 250 Taxes on reservoir site 200 Maintenance of reservoir dam 50 $1,115 The revenue from 96 H.P., 18 hr., at $35.00 p. year 3,360 Annual surplus $2,245 From which may be deducted for sinking fund 500 Leaving net surplus of $1,745 This amount will go far toward meeting the operating cost of the gener- ating plant, and the reservoir is therefore a profitable addition. In the case of the steam auxiliary of, say, 100 horse-power capacity, it has been pointed out that it may not be necessary to purchase the plant, as arrangements can generally be made to use an existing one; but, supposing the plant is bought outright and installed at the hydro- electric station so that one of the generators can be belted to the engine, the annual accounts would be like this: Charges: 100 H.P. steam plant $6,000 Housing 500 Investment . . . . : $6,500 Interest, 6 per cent $390 Fuel at 3 pounds per H.P. hours for 18 hours per month, 81 tons, @ $3 243 Oil and waste 25 Maintenance 125 Taxes 132 $915 (The station personnel operates the plant.) Revenue from 100 H.P. at $35 $3,500 Surplus $2,585 Charging off for sinking fund 325 Net surplus $2,260 20 15 10 o X 5 / / / / / Diagram 4 Continuous Flow from Reservoirs / j / / / / / / r < i / S- /< $ X p ) V r X <$ / < ? / / / X 1 7 / i r f / Hi iV in :v b s :C. ft h .L H. P.8 '.S. OOOOOm O^OOtx vO u . / / / / / / ^ t / / / / / / C / / / / / > \ ^ / / / / / ' / / / / / \ / / / / / / \ V f / / / /< ^, / / / / / / / / / / / / / / / / / / / / / / / S f / / / / / / / / / / / / / ^ / 7 / / / ' / / / / E P r 1 \. k i. 1 14 16 18 20 22 Dollars pr. H.F. 58 HYDRO-ELECTRIC PRACTICE 1300 1200 1100 1000 900 800 700 gi 2 s^ e S 500 400 300 200 100 Diagram 6 Fixed charges for hydro-electric plants operation / 7 * / / / / / / i / / / 1 / 600 500 c g as 8 <# - s 300 200 100 / / / k / / / 1 I ' / "S & / I'r- A Js' / / A ^ / ^ s / * / / > / / / f / s ^ / / ^ ^ V / / / y ^ ^ / / / / ' b / / / / / / / /( '\ / / / "ft / / / / ^ '/ / / / ^ *~ / / ** ^ / s *r +* .*- / t -^ *\ ) / *tf i-\ - ,-* ** ^ 1. lu . ^** *** \ r v. *** Dollars pr. H.P. 12 16 20 24 28 32 36 40 1100 1000 900 co g - 8* ^ e c -S 14 700 600 500 400 Dolls 1800 1700 1600 1500 1400 1300 1200 4-1 _ C I s * .2 i i 1000 900 800 700 600 500 400 Diagram 7 Fixed charges for hydro-electric plant's operation j~ / / 1 / / / / / / / / / / J f / / t / f / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / t / / f / / / / / / / / / / / / z 4 / / / / /i / , / / / g i C / / / & b ^ / / / / A g A, \ / / / / / /u> A V ^ / / / / /^ & r / / J / / ^ ^ v / / s / A ' / A ^ / / 1 / / / / f? ./ / / / / ,/ / s / / / 1 s / ^ / f / / 7 / '( / / / / / * ^ & . / / / / / / / ^' f / t / / ' / ^ / A ' / / / / ^ , / / / , ' / / / / f / / / / ' / / / / / / / / / / / / / / / / / / / / ' / / / / / / 7 / / / / / V / / / / / / / / / / / \ E r / / / i. V. b>. z / / s / irspr. H.P.8 10 12 14 16 18 20 22 25 59 60 HYDRO-ELECTRIC PRACTICE 50 40 30 20 / /- / 60 y / Diagram 8 Current rates H.P.&K.VV. / / 7 / / / 50 41) / / / / f / / / / / /< t^ ^ ^ A -r / ^~ 30 20 10 r c / Ai / o / 2 / / / - T3 -T/T ,./ ID te "O ' I rO "-. / t_ >< 10 X <*>- / K O K V3 u -Q. / 73 B m -ta- rt O- H 8 / a ,.di- -TV / a A- -fc- i / o. f- / ? / f / H < IV / l.Y t. -? / Hours 5 10 15 20 24 CHAPTER IV COST OF DEVELOPMENT THE COST of the development can be found correctly only from estimates based upon a well-defined programme and the plans and detail designs of the required structures, all of which is treated exhaustively in Part II. Only some general rules and guides are given here, by which an approximate first estimate of such cost may be found. ARTICLE 23. The cost of the dam, only the spillway proper being here considered, depends not only upon the type to be built but also upon the conditions of flow and character of river bed. A reasonable allowance must be made for controlling the flow during construction period, which may require erection of coffer-dams of more or less sub- stantial design and the operation of a pumping plant. Where the river is shallow and the possibilities of a material rise during construction period are remote, this item may not be very important; sheet piling often proves sufficient to exclude the flow from the area, the seepage being accumulated in one sump and thence removed by moderate pump- ing. Again well-constructed timber cribs loaded with rock may be required to guard against flooding and a large capacity pumping plant needed to perform continuous duty. Sheet piling, where gravel and boulders prevail, is best of interlocking steel material, which will cost from $1.50 to $3.00 per foot length of piles in place, depending upon the depth to which they are to be driven. In rock or hard bottoms timber cribs must be employed to coffer the desired area; these are constructed of square timber suitably framed, from 6 to 10 feet wide, filled with rock and puddling material; if water is shallow, rock diking with puddling placed on outside may answer the purpose. The characteristics of the flow, of material in river bed, and probable duration of construction under such safeguards must decide the means to be employed; at any rate, the item "control of flow" is an important one, and may be from a few hundreds to several thousands of dollars. For some dam constructions it will be less than for others, even on the same site; with a structure, for instance, consisting of piers rather than a continuous mass of masonry the completed portion can readily be utilized for water-way while the 61 62 HYDRO-ELECTRIC PRACTICE remaining is being built; like methods can be employed with concrete- steel dams. This brings us to the type of dam itself, which should be chosen because of its peculiar fitness to the conditions and purpose as well as for considerations of first cost. Part II. treats this point in all its prac- tical phases. Diagrams 9 and 10 give quantities required for masonry, concrete, and concrete-steel dams of different heights and for unit length of ten feet; the cost can be found for different values of labor and material from Diagram 11. The dam should contain waste-gates or sluices and perhaps flash- boards, which must be covered in estimate. This cost, as given on diagrams, does not cover the construction in river bed required to carry the dam, safeguard it against underwashing or the downstream area against scouring. In soft locations a pile founda- tion, cut-off walls or curtains, and apron construction will be required, the extent and cost of which depend solely upon the character of the material on which the dam is to rest. Again reference for details is invited to Part II. Diagram 12 gives quantities for foundation, cut-off, and apron construction in alluvial locations for different heights of dams and for lengths of ten feet. And, finally, the dam terminates in abutments, unless the site is a rock gorge into which the dam structure may be built; Diagram 12 also gives quantities required for two abutments of concrete-steel design for dams of different heights. Compiling the cost of the dam in alluvial river bed, with small flow and no floods during construction period, height above river bed 30 feet, length between abutments 250 feet, labor being $0.20 per hour, material for cub. yd. of xxx concrete $4.75, forming timber $25.00 per 1000 ft. b. m., and re-enforcing steel 3c. per pound. Item 1. Controlling flow: Coffer-dam or sheet piling $2,500.00 Pumping, 200 days at $5.00 1,000.00 Item 2. Preparing bed, excavation, etc 500.00 Foundation, cut-off and apron dam: Rubble masonry $36,300.00 or Cyclopean concrete 28,117.00 or Concrete-steel 22,100.00 Item 3. Abutments 2,060.00 Item 4. Waste- or sluice-ways and gates depending upon flood flow volume. 45 Height of Dam 30 35 40 45 40 35 30 25 20 15 .a Diagram 9 Masonry Dam Dimensions and Quantities V 50 ft. 7 45 40 35 30 25 20 15 10 Height of Dam 15 40 45 50 ft. 63 ^7.0 Buttresses on 14 ft.centers Diagram 10 Concrete Steel Dam Height of Dam 10 64 6.00 4.00 4.50 5.00 S.50 5.00 4.00 3.00 4.00 3.00 2.00 6.00 6.50 / X ^ / X / x X / ^ x X . x x x ' / x > ? xxx Concrete x x x / ^ x / ^ i - x x rfl c j c rt- / x ^ x^ u r ( C X x J X a - 3 tt v ^ y ^ / / / L ^ N ^ / , - 1 J i 2 \j ^v a -rf J x ^^ V/ 3 x tri u tn < x r c x >V / C 4 V-? D x Jj X V 5 / / V x / ^ x / ^ ' Diagram 11 Cost of Concrete x & xxx per c.yds. x X x ( X ,/ X x ( x / ' x ! x ,/ r x ^ / x x x / ' x ^ x / | x . X ,/ ' X ! / / [ x X / ' x ,x / ~ x X / r x x / x ( x / ^ X / x x ( /* _/ / X X ^ X X / _/ J X x / ' ^ x x s [- c T i X 1 ? / a ! f .^ vx \>^ s ? o c J U 1 ; y^ x> c^x ' c 3 : \ D ^ 0, ^ * .' 1^ ^x ex ** -f , x X ^ ( 1 X x / x Concrete (/ c J U 1 i x x > ' c c ' <: s x x* ^ \/ X / X X / x X x x x ,/ ' x x X X x x X ' / / x / H 1^ P ^ . X x x HI V S. X / / Jc st [ C -01 ? c ct i 3.00 3.50 4.00 4.50 5.00 5,50 65 300 200 : 9.0 8.5 8.0 7.5 7.0 6.5 Abutment and Foundation Quantities Height of Dam 10 66 COST OF DEVELOPMENT 67 ARTICLE 24. The diversion works, by which the water is carried from dam to the power station, are next in line. These may be canal, flume, or pipe line, depending upon the volume and distance over which the water must be conducted. If no diversion is required, these are, of course, unnecessary. These structures involve excavation of rock or loose material, timber or concrete lining, slope paving, timber framing, wood stave, steel plate, or concrete-steel conduits, pipe-line anchorages, flume supports, intake works, head-gates, culverts, waste- or sluice-ways, and gates and forebays with bulkheads, all of these being treated spe- cifically as to design and construction in Part II. Excavation cost of rock depends upon its character, and may vary from 75 cents to $1.50 per cubic yard, also that of loose material from 25 to 50 cents per cub. yd. ; timber lining of canals, with timber at $20.00 per 1000 ft. b. m., costs $4.50 per square yard, concrete lining $5.00 per sq. yd., slope paving $1.25 per sq. yd., timber framing of flumes costs $40.00 per 1000 ft. b. m. The cost of pipe line at present is 36-inch. 48-inch. 60-inch. Wood stave $4.00 $6.00 $8.00 Steel plate " 6.00 8.00 10.00 Concrete-steel 5.00 7.00 9.00 per linear foot of pipe, to which must be added cost of delivery, and putting in place, painting, etc. Cost of head-gates, waste- and sluice-ways, etc., depends upon character of design and size of conduit. The canal prism should be of an area sufficient to pass the flow at a velocity not exceeding three feet per second; the diameter of pipe conduits depends upon the ratio of head which can be economically expended in friction. The designs of all diversion works should be based upon appropriate hydraulic theorems. ARTICLE 25. The power-house is the last of the principal structures. Its location is determined by the development programme; it may be at the end of the dam or inside of the spillway, immediately below or at the terminal of diversion canal or pipe line. The design is fixed by the method of bringing the water to the turbines, the dimensions by number of power units it is to contain. Whether it is recommendable to let the water enter the power station freely or by means of feed pipes depends upon the height of fall, volume of flow, and topography at chosen power- house site. In both cases the structure consists generally of three parts, 68 HYDRO-ELECTRIC PRACTICE foundation, substructure or pit, and superstructure in which turbines and generators are housed. Foundation must adapt itself to the character of the material at the site, pit to volume of flow, height of fall and of backwater, and superstructure to power equipment. The walls and floors should be of masonry, monolithic concrete, or concrete-steel. Wherever permissible the water should be taken to turbines in conduits, as the power-house required for such an arrangement will be considerably less costly than where the water enters freely; and, for the same reason, if otherwise recommendable, the power units should be rather large than small, as the length of the power-house materially depends upon this condition. Especially is this true where water enters freely, since the structure in that event performs, in a sense, the functions of a dam, and the foundation and pit structures must in that case be designed not only for the duty of supporting vertical loads but also to resist horizontal pressures, which adds considerably to dimensions. The power-house should be readily approachable by the best available means of trans- porting the heavy equipment; ample room should be provided on the operating floor, so that each machine can be readily dismantled, repaired, or removed; a power traveller, by which parts of equipment can be handled, should be provided. There should be no stinting of light, and the roof had best be of the most substantial and fire-proof character. Diagram 13 gives quantities for power-house per power unit length and for varying heights of fall, both for structures into which water enters freely and where it is conducted to turbines by feed pipes; the same diagram shows quantities required for foundations for structures in alluvial locations. ARTICLE 26. In addition to these works there may be required reservoir embankments, in the event that a part of the stream valley must be closed; in fact, this is the most frequent condition. These embank- ments are a continuation of the spillway, but rise sufficiently higher to guard them against possible overflow, the spillway proper being designed of sufficient length to pass the greatest probable flood volume at a safe height. These structures may be of earth or concrete-steel, depending largely upon the availability of suitable material for the former type. Reservoir banks or bulkheads partake of the importance of the spillway, and require the greatest care of design and still more so of construction. This consists in preparation of surface on which they are placed by a complete removal of all vegetable growth, roots, and stones, loosening 450 400 350 325 300 ** / / 0^ ^ / $> v 7 ^ ' 3UUU Diagram 16 Transmission Line Weight of Line Wire EC o 2UUU 1 1 1 f\l\C\ H F ?1 -r. o V 'c Rl t of Li le vV ir^ 11 ill! 73 74 HYDRO-ELECTRIC PRACTICE ARTICLE 29. The probable cost of the development may be com- piled from these approximations by finding cost of dam from Diagrams 9, 10, 11, and 12, cost of diversion works from a location profile, cost of power-house from Diagrams 11 and 13, cost of reservoir structures from Diagrams 11 and 15, taking cost of power equipment at $20.00 per horse- power, cost of transmission line from Diagram 16, and cost of trans- formers and substation as stated. To these items must be added 10 per cent, for engineering and inspection, and to the total the value of lands, right of way, of charter and franchises. CHAPTER V VALUE OF PROJECT AND PRESENTATION THE SUMMING UP of findings from investigations of market, power capacity, feasibility and practicability, and cost of a hydro-electric project takes the shape of an engineer's report, with such documentary proofs and legal opinions as conditions may call for. If the funds re- quired for development are to be secured from individual investors or through the customary financial channels, by which the securities of new enterprises are underwritten and placed on the market, the make-up of the report should be of a presentable character, preferably in bound book form, with plans, profiles, and designs reduced to photographs. Such a report is here given in full. ARTICLE 30. Report on a Hydro-electric Project. FREMONT POWER AND LIGHT COMPANY, FREMONT, OHIO. GENTLEMEN: In accordance with your commission, I have secured all the needed data to report to you on the hydro-electric power development on the Sandusky River near your city. My conclusions are thus summarized: This project contemplates the consolidation of four old mill powers and the modern development of the opportunities they present. The plan is feasible, practical, and void of serious or costly problems, to the extent of developing a marketable output of twenty-two hundred electric horse-power and delivering the product for dis- tribution at Fremont, O., for about one hundred thousand ($102,600.00) dollars; the required invest- ment aggregates one hundred and seventy-five thousand dollars. Fremont, O., offers remunerative market for the output, and the investment will earn from ten to fifteen per cent net. The data, calculations, and arguments upon which these findings are based form the subject of the following report. Yours truly, (Signed) H. VON SCHON, DETROIT, MICH., October, 1905. Consulting Engineer. Hydrography. The Drainage Area. Plan 1, of the Sandusky, is of the Great Lakes system, all of it being in the State of Ohio. Head-waters are in Richland County; the river empties into Sandusky Bay of Lake Erie. The length of the river is* about one hundred and fifteen (115) miles; the drain- age area tributary to the point here considered (Fremont, Ohio) covers approximately fourteen hundred (1400) square miles. 75 76 HYDRO-ELECTRIC PRACTICE There are some lakes, of small areas, at the source of the river, which is at alti- tude of twelve hundred and eighty (1280) feet above sea level. The basin is under- laid by lime-rock and shale; the land is generally under cultivation; the wooded area is small. Precipitation, evaporation, and run-off are those normal to the lower Lake region; the annual temperature is fifty (50) degrees. The flow has not been established by authentic measurements. Precipitation has been observed for fifteen years at three (3) points in the water- shed concerned; the monthly totals from 1891 to 1905 are given on Tables 1, 2, and 3, and the monthly means for the drainage area for same period on Table 4. (Here omitted.) The fluctuations in annual precipitation are shown on Profile 1. (Omitted.) Evaporation and run-off have been computed for the two dry years 1894 and 1905 of this period, results being given on Tables 5 and 6, and Monthly flow from mean run-off of these dry years is noted on Table 7 and shown on Profile 2. (Omitted.) The ground flow factor used in these calculations is that established for water- sheds of bold relief, with light drift overlying rock, and no swamp or lake storage. TABLE 5. ORDINARY DRY-YEAR MONTHLY RUN-OFF FROM SANDUSKY RIVER WATER-SHED. (All measurements in inches.) PRECIPITATION. EVAPORATION. RUN-OFF. Ground MONTH . Monthly. Total. Monthly. Total. Monthly. Total. Storage. December '93 2.34 2.34 0.65 0.65 1.69 1.69 full January '94 .... 1.84 4.18 0.45 1.10 1.39 3.08 full February '94 2.48 6.66 0.55 1.65 1.93 5.01 full March '94 .... 1.18 7.84 0.60 2.25 1.40 6.41 0.82 April '94 .... 2.08 9.92 1.08 3.33 1.40 7.81 1.22 May '94 5.31 15.23 2.93 6.26 1.16 8.97 full June '94 3.86 19.09 3.47 9.73 1.32 10.29 0.93 July '94 .... 2.70 21.79 3.81 13.54 0.46 10.75 2.50 August '94 .... 0.69 22.48 2.79 16.33 0.28 11.03 4.88 September '94 3.26 25.74 2.28 18.61 0.22 11.25 4.12 October '94 . . . . 3.50 29.24 1.30 19.91 0.28 11.53 2.20 November '94 .... 1.81 31.05 0.84 20.75 0.40 11.93 1.63 December '94 2.31 33.36 0.65 21.40 0.68 12.61 0.65 T.=50. Ground flow for minimum capacity of storage. Computed by H. VON SCHON, Cons. Engr. TABLE 6. ORDINARY DRY-YEAR MONTHLY RUN-OFF FROM SANDUSKY RIVER WATER-SHED. (All measurements in inches.) MONTH. Monthly. December '04 3.78 January '05 1.56 February '05 1.43 March '05 0.94 April '05 2.94 ATION. EVAPORATION. RUN-OFF. Ground Total. Monthly. Total. Monthly. Total. Storage. 3.78 0.80 0.80 2.98 2.98 full 5.34 0.43 1.23 1.13 4.11 full 6.77 0.44 1.67 0.99 5.10 full 7.71 0.58 2.25 1.32 6.42 0.96 10.65 1.16 3.41 1.16 7.58 0.34 VALUE OF PROJECT AND PRESENTATION 77 78 HYDRO-ELECTRIC PRACTICE TABLE 6. ORDINARY DRY-YEAR MONTHLY RUN-OFF FROM SANDUSKY RIVER WATER-SHED. Continued. (All measurements in inches.) MONTH. May '05 PRECIF Monthly. 4.93 TTATION, Total. 15.58 19.03 23.79 25.99 28.88 31.15 33.54 35.49 EVAPORATION. Monthly. Total. 2.84 6.25 3.36 9.61 4.43 14.04 3.17 17.21 2.20 19.41 1.15 20.56 0.90 21.46 0.61 22.07 RuN-Orr Monthly. Total. 1.75 9.33 1.20 10.53 0.64 11.07 0.38 1145 0.32 11.77 0.38 12.15 0.68 12.83 1.10 13.93 Groum Storag full 1.11 1.32 2.67 2.30 1 56 0.75 0.51 June '05 3.45 July '05 4.76 August '05 2.20 September '05 2.89 October '05 2.27 November '05 2.39 December '05. . . 1.95 T. =50. Ground flow for minimum capacity of storage. Computed by H. VON SCHON, Cons. Engr. The fall of the river has been found from instrumental levels and is shown on Plan 3, The elevations (referred to sea level) of points pertinent to this discussion are: Sandusky Bay 573 feet Lower Rapids (in Fremont, O.) 580 feet River bed at Creager power-house 585 feet River bed under Ballville bridge 590 feet Roadway of Ballville bridge 613 feet River bed at Cemetery Hill 600 feet River bed at Tucker dam 609 feet Crest of Tucker dam ". 618 feet River bed at Tindall bridge 627 feet Tindall bridge roadway 643 feet Sandusky Falls, upper level 630 feet The topography of river banks and adjacent territory has been developed instrument- ally and is shown on Plans 3, 5, and 6. Development Programme. The available fall is fifty (50) feet from Upper Sandusky Falls, at elevation of 630 feet, to Lower Rapids, at elevation of 580 feet. To utilize this fall in one development requires diversion of river by a canal on south side, entailing the acquisition of the right of way and the withdrawal of prac- tically all flow during low stages from the natural river bed, by which property and legal difficulties would be encountered. Forty (40) feet of the available fall can be utilized within the flowage limits of the mill powers to be acquired, and without change of natural flow in river, by two developments, a twenty-two (22) foot development at the Cemetery Hill and an eighteen (18) foot development at the Creager power-house. The remaining fall can be utilized for purposes of a storage reservoir. The lower development to be at the Creager power-house; realizing a power head of eighteen (18) feet by deepening tail-race from Lower Rapids, at elevation of 580 feet, to river bed elevation at Creager power-house, 585 feet, and erecting .an eleven (11) foot high dam with two (2) feet high flashboards rising to elevation 598 feet. VALUE OF PROJECT AND PRESENTATION 79 80 HYDRO-ELECTRIC PRACTICE SI 82 , HYDRO-ELECTRIC PRACTICE The upper development would be at the Cemetery Hill, creating a power head of twenty-two (22) feet by erecting a twenty (20) foot high dam on river bed, elevation of 600 feet, which, with two (2) feet high flashboards, would reach an elevation of 622 feet. A storage reservoir could be created on the Tindall power property by erecting on the river bed above the bridge, at elevation 627 feet, a six (6) foot high dam, which, with two (2) feet high flashboards, would rise to elevation of 635 feet, creating a reser- voir of about six (6) million cubic feet capacity, furnishing a ten-hour flow of one hundred and sixty (160) cubic second feet, which could be increased by adding flash- boards, as flowage covers to elevation of 638 feet. TABLE 7. ORDINARY DRY-YEAR OUTPUT OF DEVELOPMENT AT FREMONT, O., ON SANDUSKY RIVER. Mean of 1894 and Month. January RUN-O Water- 1905, shed, inches e 1 : 1.26 FP FROM Square mile, ubic sec. ft. 0.896 1.12 1.61 1.21 1.14 1.30 1.12 0.49 0.29 0.24 0.29 0.48 0.79 Water- shed, square miles. 1400 1400 1400 1400 1400 1400 1400 1400 1400 1400 1400 1400 Flow, cubic sec. ft. 1568 2254 1694 1596 1820 1568 686 406 336 406 672 1106 AVAILABLE Electric Horse-Power, Fall, per ft. for 40 feet fall. feet. 40 125.44 5017 40 180.32 7212 40 135.52 5420 40 127.68 5107 40 145.60 5824 40 125.44 5017 40 54.88 2195 40 32.48 1299 40 26.88 1075 40 32.48 1299 40 53.76 2150 40 90.08 3603 February 1.80 March 1.36 April 1.28 May 1.45 June 1.26 July 0.55 .August 0.33 September 0.27 October 0.33 November 0.54 December . . . 0.89 Efficiencies: turbines, 76 per cent.; generators, Compiled by Market. 90 per cent. H. VON SCHON, Cons. Engr. The proposed development is half a mile from the city limits of Fremont, O. (This market analysis appears in Article 6.) Output. The present power consumption at Fremont, O., aggregates 2850 electric horse- power, of which 2050 ig day motor ( 10 hour), 250 is light (night), and 450 is mixed day and night load. The available power output (see Table 7) is for nine months 2200 electric H.P. for eleven months. . e 1300 electric H.P. for twelve months. . 1100 electric H.P. VALUE OF PROJECT AND PRESENTATION 84 HYDRO-ELECTRIC PRACTICE The recommendable programme appears to be to develop twenty-two hundred (2200) electric horse-power; to operate the plant during nine months with continuous flow, giving 24-hour output of 2200 electric horse-power; ' during three months of lower flow with ten-hour flow doubled by night storage, yielding a 10-hour (day) output of 2200 electric horse-power; and to supplement for night service with 250 horse-power steam plant. Underlying Values. 1. To be constructed. The proposed power works are to consist of one concrete spillway twenty-two feet high, with power-station at its end; of one concrete spillway eleven feet high, with Creager power-house arranged for station; of one concrete spillway six feet high; of embankments and waste-flumes to empound and control the entire flow of the river; of the hydraulic and electric machinery to develop the water-power and convert it into electric energy; and of the transmission line by which the current is to be delivered to the customers. The total cost of these works and this equipment is estimated to aggregate 102,620 dollars. 2. Existing properties to be acquired consist of mill powers and lands controlling the flow and fall of the river, the necessary pondage and storage, and the sites for dams and power-stations. They are (a) The Creager water-power property, of six acres of land, a partial timber dam, an obsolete race-way, and a substantial mill building, with some hydraulic machinery not now utilized (lower power site). (b) The Heim & Baum woollen mill property, of eleven acres of land and a good mill building not occupied at present (upper power site). (c) The Tucker water-power and mill property, of eleven acres of land, a timber dam now in commission, serviceable head-works and race-way, and a modern flour grist-mill now being operated by water-power (upper power site). (d) The Tindall mill power, consisting of eleven acres of land (reservoir site) ; and (e) Some twenty-seven (27) acres of bottom-land, to be flooded by upper development. The purchase price of these properties aggregates 65,000 dollars. VALUE OF PROJECT AND PRESENTATION 85 Inventory of Properties: Buildings and Equipment. 1. Creager property: Valuation. One four-story slate-roofed mill building, lately used as a power-house $3,500.00 One Samson 168 H.P. water-wheel 250.00 One Leffel 104 H.P. water-wheel 150.00 One Leffel 30 H.P. water-wheel (fair condition) 50.00 One engine-house and 100 H.P. boiler and engine 1,000.00 2. Heim & Baum property: Three-story frame woollen-mill 2,000.00 Office building 100.00 3. Tucker property: Three-story stone mill building 5,000.00 Two Leffel water-wheels, 67 and 30 H.P. respectively, in good condition . . . 150.00 Modern milling machinery of 60 barrels capacity, good condition 600.00 One 70 H.P. boiler and engine 1,500.00 Stables and sheds 100.00 Cooper-shop 100.00 Total valuation of $14,500.00 Structural Types. Lower Development. Concrete spillway, on rock, 11 feet high, 300 feet long; south end terminating in concrete-steel abutment, north end butting against masonry substructure of Creager power-house. Earth embankment, 300 feet long, connecting south abutment with natural bank at south end of Ballville bridge. Power equipment in Creager power-house. Upper Development. Concrete spillway, on rock, 20 feet high, 300 feet long; south end against rock bank, north end terminating in concrete-steel abutment. Earth embankment, 500 feet long, connecting north abutment with natural bank at Cemetery Hill. Power equipment in station constructed at end of dam. Reservoir. Concrete spillway, 6 feet high, 300 feet long; ends terminating in concrete-steel abutments. Earth embankments, 300 feet long on south and 200 feet on north end, connecting with natural banks. Estimates. Estimates are based upon following unit prices not quoted in connection with schedules. Cement, Portland, delivered, per barrel $2.50 Concrete, 1-3-6, monolithic, placed, per cub. yd 6.00 Concrete, 1-2-4, cyclopean, placed, per cub. yd 7.00 Concrete, 1-2-4, formed and placed, per cub. yd 8.00 Excavation, rock, per cub. yd , 0.75 Excavation, no rock, per cub. yd 0.30 Gravel, or broken stone, for concrete, per cub. yd 1.00 Labor, per day 1.75 86 HYDRO-ELECTRIC PRACTICE Planking, timber for forms, per M. ft. b. m $25.00 Sand for concrete, per cub. yd 0.75 Steel, re-enforcing, per Ib 0.03 Steel, structural, erected, per ton 100.00 Team and driver, per day 3.50 I. Lower Plant Cr eager Dam. Item 1. Controlling flow by diking $500.00 Item 2. Preparing dam site, clearing 200.00 $700.00 Item 3. Foundation on rock ledge. Item 4. Spillway, 11 ft. high, 300 ft. long: 810 cub. yds. cyclopean concrete, at $7.00 5,670.00 Item 5. One abutment, concrete-steel: 10 cub. yds. concrete, at $8.00 80.00 700 Ibs. re-enforc. steel, at 3 c 21.00 5,771.00 Item 6. Earth embankments, with concrete core, 20 ft. 15' h., 50 ft. 10' h., 300ft. 5' h.: core wall, 100 cub. yds. concrete, at $6.00 600.00 1370 cub. yds. earth fill, at $0.35 480.00 1,080.00 Item 7. Power station in Creager mill for two power units: 2 pits and penstocks, 16' x 20', concrete-steel: 280 cub. yds. concrete, formed, at $8.00 2,240.00 2000 Ibs. re-enforc. steel, at 3 c 600.00 Item 8. Repairing mill building 1,000.00 3,840.00 Item 9. Deepening tail-race, 2000 ft. long, 25 ft. wide, 5 ft. deep at upper end: excavating 5000 cub. yds. rock, at 75 c 3,750.00 3,750.00 Item 10. Hydraulic equipment, 18 ft. head, 400 cub. ft. flow, four 33-inch turbines with draft tubes, two per unit, at 330 H.P., 180 R.p.m., placed, at $6.00 per H.P 3,960.00 Item 11. Two turbine governors, at $300.00 600.00 4,560.00 Item 12. Electric equipment: Two 250 Kw. alternators, 2300 volts, 60 cycle 3-phase, placed, at $12.00 per Kw 6,000.00 Item 13. Three switchboards, equipped, at $275.00 825.00 Item 14. Two 1\ Kw. D. C. motors, at $250.00 500.00 7,325.00 Lower plant complete $27,026.00 II. Upper Plant Cemetery Hill Dam. Item 15. Controlling flow by diking $500.00 Item 16. Preparing spillway site, clearing 200.00 $700.00 Item 17. Foundation on ledge rock. Item 18. Spillway, 22 ft. h., 300 ft. long: 2475 cub. yds. cyclopean concrete, at $7.00 17,325.00 Item 19. One abutment, concrete-steel: 48 cub. yds. concrete, at $8.00 384.00 2100 Ibs. re-enforc. steel, at 3 c. 63.00 17,772.00 Item 20. Earth embankment with concrete core, 30 ft: 20' h., 20 ft. 15' h., 225 ft. 10' h., 225 ft. 5' h.: core wall, 242 cub. yds. concrete, at $6.00 1,452.00 3330 cub. yds. earth nil, at $0.35 1,166.00 2,618.00 VALUE OF PROJECT AND PRESENTATION 87 Item 21. Power station for 2 units, same as lower station with addition for roof and end walls $8,000.00 $8,000.00 Item 22. Tail-race in river bed (none). Item 23. Hydraulic equipment: Four 30" turbines with draft tubes, two per unit, at 400 H.P., 200 R.p.m., placed, at $6.00 per H.P 4,800.00 Item 24. Two turbine governors, at $300.00 600.00 5,400.00 Item 25. Electric equipment: Two 300 Kw. alternators, 2300 volts, 60 cycle 3-phase, placed, at $12.00 per Kw 7,200.00 Item 26. Three switchboards, equipped, at $275.00 825.00 Item 27. Two 10 Kw. D. C. motors, at $275.00 550.00 8,575.00 Upper plant complete $43,065.00 III. Reservoir Dam (Tindall). Item 28. Controlling flow $500.00 Item 29. Preparing river bed 200.00 $700.00 Item 30. Foundation ledge rock. Item 31. Spillway, 6 ft. h., 300 ft. long: 300 cub. yds. cyclopean concrete, at $7.00 2,100.00 Item 32. Two abutments, concrete-steel: 12 cub. yds. concrete, at $8.00 96.00 1000 Ibs. re-enforc., at 3 c 30.00 2,226.00 Item 33. Earth embankment with concrete core, 100 ft. 10' h., 550 ft. 5' h. : core wall, 220 cub. yds. concrete, at $6.00 1,320.00 2030 cub. yds. earth fill, at $0.35 710.00 2,030.00 Item 34. Sluice-gate 500.00 500.00 Storage plant complete $5,456.00 IV. Transmission. One mile, 2300 volts, 1500 Kw., 5 per cent, drop, 18,000 circ. mils, No. 6 wire. Item 35. 53 poles, 35 ft., set, at $5.00 $265.00 Item 36. 116 cross-arms, placed, at $0.50 53.00 Item 37. 159 insulators, placed, at $0.50 80.00 Item 38. 1280 Ibs. copper wire, at $0.26 3,228.00 Item 39. Wire strung, at $2.50 per pole 132.00 $3,758.00 V. Distribution. Item 40. Lines (poles in place), 2 miles $6,986.00 Item 41. Transformers, 1500 Kw., at $4.00 6,000.00 Item 42. Substation 1,000.00 $13,986.00 Summary. Lower plant 27,026.00 Upper plant 43,065.00 Reservoir plant 5,456.00 Transmission 3,758.00 Distribution 13,986-00 Total 93,291.00 Item 43. Engineering and inspection, 10 per cent 9,329.00 Total cost of development $102,620.00 88 Output. HYDRO-ELECTRIC PRACTICE Generated. 2200 E.H.P. Delivered 2090 E.H.P. or 1560 Kw. Cost per H.P. delivered for service $49.10 Annual Operating Cost. Generating, Day Service. One operator, supervising both plants $1,000.00 Two assistants, at $720.00 1,440.00 Two laborers, at $600.00 1,200.00 $3,600.00 For night service add operator and 2 assistants $2,440.00 Distributing, Day Service. Superintendent 1,200.00 Assistant 720.00 Two linemen, at $720.00 1,440.00 Book-keeper 720.00 Office and stationery 600.00 4,680.00 For night service add assistant and one lineman $1,440.00 Maintenance and Depreciation. Works, $60,000.00, 2 per cent 1,200.00 Equipment, $32,000.00, 5 per cent 1,600.00 2,800.00 Taxes. 2 per cent, on valuation of lands and works, $112,000.00 2,240.00 Investment Balance. Capital investment: Property, franchises, etc $65,000.00 Hydro-electric plant 102,620.00 $167,620.00 Charges. Item 1. Interest and redemption at 8 per cent, on $175,000.00 14,000.00 Item 2. Operating cost, day and night: Generating 5,080.00 Distributing 6,120.00 Maintenance and depreciation 2,800.00 Taxes 2,240.00 30,240.00 Revenue. Item 3. From 2090 H.P., 1560 Kw., 10-hour service, at 1} c. p. Kw. hr., with 75 per cent, load factor, 308 days 3080 hours 4,804,800 Kw. hours, OR 3,603,600 Kw. hours, at 1$ c 54,054.00 about $26.00 p. H.P. Surplus 23,814.00 No revenue is estimated from night service; operating cost estimate includes night operation. ARTICLE 31. Value of Hydro-electric Opportunity. The value of any commercial enterprise is deduced from the value of its product; if this is not marketable, there is no value. Given a market for the power out- put of a hydro-electric opportunity, the intrinsic value of the latter must VALUE OF PROJECT AND PRESENTATION 89 be established by comparison with other power sources from which the market could be supplied, and it becomes purely a process of balancing the comparative earning capacities of the two power plants and the conversion of the balance into the principal of which it represents the interest or cost of money. A hydro-electric plant shows on estimates an annual surplus of $5000, and a steam plant of similar output pays fixed charges and no more; it is evident that the hydro-electric opportunity is capable of earning interest on a larger investment than the steam plant; the theo- retical difference is $100,000, and the intrinsic value of the hydro-electric plant is that based upon the rate of valuation of personal property for purposes of assessment in the district in which it is located. Valuations of lands or riparian rights representing water-power opportunities, determined otherwise than from a conclusive estimate of earning capacity of the projected plant, are purely speculative values, which may be a hundred per cent., and greater, in error either way. Only one programme gives safe results, safe commercially, and that is to secure a complete and correct analysis of the project. PART II DESIGNING AND CONSTRUCTING THE DEVELOPMENT THIS PART treats of the engineering of the hydro-electric develop- ment; in it are presented methods, theories, designs, and their execution, as they have been found, in the author's practice of this specialty, to secure the desired results in a manner adapted to the commercial as well as the engineering requirements of the business. Some of these leave the trodden paths of former practice; the majority must needs follow them; only where necessary, in the author's judgment, to make clear his mean- ing, have rudimentary methods been employed; on the whole, it has been the purpose to render the treatment of this subject complete within its scope. The subheads are of five chapters dealing with surveys, development programme, structural types, equipment, plans, and estimates and speci- fications, construction, and superintendence, each of which is divided into articles covering detail topics. CHAPTER VI THE SURVEY SURVEY embraces all operations by which the hydrographic, topo- graphic, and geologic characteristics are investigated and determined. ARTICLE 32. The first preparation for the work of surveys is the examination of maps of the stream and the projected power-plant loca- tion, if such has been fixed. The best obtainable maps are the United States Geological Survey topographic sheets, which may be secured from the Director of the Survey, in Washington, D. C., or at local agencies. Several of the States provide annual appropriations for co-operative surveys with the Federal department, and the annual reports of the State Engineers, or Geologists, contain topographic county maps of similar origin. This is the available information from which the topogra- phy of a stream system, or so much as is involved in the examinations, 90 THE SURVEY 91 may be studied; it will reveal the course of the river, the contour forma- tion of its banks, its fall, by the crossing of successive contours, the locations of railroads and highways, of fords and ferries, and of settle- ments. All this furnishes ample data for the appreciation of the general conditions, which will become useful in locating dam site, estimating fall, flowage areas, and storage opportunities. An examination of the drainage area on State maps and of pre- cipitation records will throw considerable light upon the probable flow characteristics of the watercourse; note the origin of its principal sources, whether in foot-hills or flowing out of swamps or lakes, and the length of its tributaries, the import of all of which will be discussed in detail further on. Finally, much practical information as to subsurface formations in the vicinity of the projected power site can be gained from well borings; one concern frequently operates a well-boring apparatus in several coun- ties, and these may be traced through hardware merchants at the county seat or near-by town. ARTICLE 33. Reconnaissance. With the general knowledge of hy- draulic, topographic, and geologic characteristics thus gathered, a recon- naissance is the next best preparation, on horseback or preferably in a boat floating down the river, equipped with a camera, compass, hand- level, aneroid, field-glasses, sketch-book, and the plan of the river's course, showing county, township, and section lines. On such a trip many details will be revealed which are not on the maps or are given erroneously. The aneroid should be read at regular intervals of time, the location being identified on the map; the velocity of flow, and there- fore of transit, can be estimated and thus distances sufficiently deter- mined to aid in fixing the fall. Observe the character of the banks and make notes in the sketch-book of likely dam sites, estimating the river's width and finding the approximate and relative heights of the banks by aneroid and hand-level; note also the improvements on river bottom lands and the height of bridge crossings, paralleling railroads and high- ways. A few days devoted to reconnaissance will prove an exceedingly valuable investment, the benefits of which will be frequently recognized in the course of perfecting the development programme; above all, it is highly recommendable to make copious notes and sketches of whatever is worth remembering and to take photographic views of the most notable features. HYDRO-ELECTRIC PRACTICE Fig. 1 ARTICLE 34. Triangulation. With this general equipment the work of definite determinations can be approached. It is not always feasible to, foretell what the extent of the survey will be. It must cover the dam site, the flowage area, and perhaps the tracing of property lines. It is, however, always advisable first to establish some fixed references for elevations and points by a system of triangulation of one or more quad- rilaterals; this should be planned to be readily accessible and safe from interference during construction and above the highest pond level. The base should be at least twice as long as the width of the stream valley. The line is ins trumen tally projected and permanent base-point markers of stout posts or of stones are set. Measuring benches (Fig. 1) are placed at intervals of 100 feet along the line; they consist of two stout vertical stakes set twelve inches centres and a horizontal piece with two- inch flattened top face secured to them; the bench pieces of each successive 100- foot section are on same level, and where this changes two bench pieces are secured to stakes. Supporting brackets (Fig. 1), consisting of a stake with one horizontal piece at the level of the respective 100- foot section, are set 25, 50, and 75 feet from the section bench. The measurement should be made with a standardized 100- foot steel tape, which is placed on sup- porting brackets, ends on benches, and a ten-pound weight secured to each handle; the zero is marked on the permanent base point and the fractional foot to the marked centre of the bench piece is measured with a hardwood scale to one-hundredth of a foot; record of the length of each section of base is kept. This measurement should be repeated three times and the mean accepted. The selected triangulation points are permanently marked, and tripods (Fig. 2), constructed of fence- posts, are placed securely over them, the legs being set three feet in the ground; tops are covered by a two-inch wooden plate with a two-inch hole in its centre and plumbed over the base point ; the top of the tripod should be from four to four and a half feet above the ground. Triangu- H.E.P.26 H.V.S. Base Benches; Base Supporting Brackets. THE SURVEY Fig". 2 lation points are preferably marked with targets, consisting of two boards one inch thick, twelve inches wide, and three feet long, secured to each other as shown in Fig. 2, wings being painted alternately white and red; a two-inch handle, secured to the end, is set into the hole of the tripod plate. The angles should be measured with an engineer's transit reading by vernier to thirty seconds. The instrument is secured to a trivet plate with three spikes which rest on the tripod plate. Each angle should be measured five times in both direc- tions, giving ten readings; the mean is accepted. The azimuth of the base should be determined from Polaris, so that any station in the survey system may be available for the tracing of the mag- netic bearings given in the boundary descriptions. The sides of triangles are computed by trigonometrical func- tions; the location of points is deter- mined by co-ordinates. ARTICLE 35. Elevations. A refer- ence bench is selected or established, and the elevations of the triangulation points are determined by return levels from reference or line-benches and plainly marked on the station tripod. An eigh teen-inch "Y' ; level in good adjustment and rods reading to hun- dredths of a foot are used in running the level lines. Triangulation benches being established, a level line is run up and down the stream over the entire reach affected by the development. When the immediate river shore is inaccessible or the stream tortuous, the line may follow along the top of the bank, or at some distance from it along roads, and levels taken to water at accessible points. Every fifth turning-point should be a bench of permanent mark, and each section of level line between benches should be returned until an agreement between two runs within 0.001 foot is secured; where convenient the line benches should be con- nected with the triangulation benches for check. Elevations are plainly marked on all permanent benches. Tripod and Target. 94 HYDRO-ELECTRIC PRACTICE ARTICLE 36. Topography. A stadia survey is made of all the river valley to be considered in the development; it is referred to the triangu- lation system. This survey should develop the topography to one-foot contours at the probable location of the works, and in five-foot contours over the remaining territory; the bearings should be of azimuths in harmony with the triangulation system; distances are read on plumbed rods; vertical angles are measured to the height of instrument; stadia stations are marked by stakes with tack, and the instrument is plumbed. When- ever practicable, reference readings are taken to triangulation and water points. By this survey, with a rodman on each side of the river, the shore lines, property corners and boundaries, buildings, bridges, roads, and a sufficient number of contour points to project the true topography are located. Plan 7 shows the results of trian- gulation, levelling, and topographic survey. The instrument's adjustments should be checked at the beginning and close of each day's survey. ARTICLE 37. Phototopography.Ii, is not the purpose to enter upon a broad dis- cussion of the subject of photogrammetry, but to describe only the practical process by which a general projection of the topo- graphy of the stream valley and its imme- diate high banks can be obtained within contour intervals of about ten feet. In a photographic camera (Fig. 3) C is the optical centre, being the middle point of the optical axis between the two lenses of the objective; N G is the negative plane in which the sensitive plate or film rests; V V is the optical axis produced and its vertical projection called the vertical; H H' is the horizontal projection of the same axis known as the horizon; C V is the focal length which is uniform for distances beyond 100 feet; P S is the imaginary positive plane, being parallel to the negative plane and focal length from the optical centre. The image on the negative plane is the reverse of the object it repre- THE SURVEY 95 Fig. 4 sents and in true perspective, but if reflected on the positive plane it would there appear as a perfect miniature facsimile ; the points F and F' in the negative plane would be found as F and F' in the positive at like distances hor- izontally or vertically from the vertical or horizon. This is the optical and geometrical principle on which the utilization of the camera for this purpose is based. Fig. 4, A B D E, is a print of the negative laid down flat with H H', the reproduced horizon, parallel to P S, the positive plane, and at any convenient dis- tance above it; V V is the vertical produced; F is the image of a flag on top of a hill. To locate F graphically drop- a perpendicular from F to the positive plane at F' and connect this point with the optical centre C, fixed in V V produced and focal length, in natural scale, from the positive plane. The true location of F will be in the extension of the line C F', and will be fixed by a similar operation with the second view taken from the other end of the base line, as the two projections will intersect at the location of F in the plan. To find the location of F algebraically measure "y" on the print, being the distance along the horizon of the vertical projection of F to H.E.P.29 H.V.S. 96 HYDRO-ELECTRIC PRACTICE the image vertical, then tg. a = ^ (f 1 = C V focal length) angle a + b is known from azimuths of triangulation points, so is the length of the base line C C' and therefore also lines C F and C' F which are plotted in the scale of the base line. In this manner all points which appear on two views can be located. To -find the Elevation of an Object Algebraically. Fig. 5, A B D E, is the positive plane; F is the flag the elevation of which is to be deter- mined. Drop the perpendicular F L to the horizon and connect L with C, the optical centre, measure F L in natural scale from the point; then Fig. 5 H.E.P.30 H.V.S. C L (focal length in natural scale) : F L = C F' : F F' ; C F' has been found as per preceding discussion and is expressed in the scale of the base line, and F F is the elevation of the flag point above the horizon expressed in the scale of the base line. This determination can be re- peated from the other view containing F, thus affording a valuable check. For F the elevation- is above horizon and therefore to be added to H I, height of instrument or its elevation; for M, being below the horizon, the reverse is the case. To find the Elevation Graphically. Fig. 6, A B D E, is the positive print, F the image of the flag, P S the positive plane, C N the focal length ; drop a vertical from F to the positive plane in F', connect C with F' and produce to F as per previous discussion in the scale of the base line; measure x, the height of the flag point above the horizon, on the print, THE SURVEY 97 Fig. 6 draw a perpendicular to C F at F equal to x in the scale of the print, then C F' : x = C F : x', which is the height of the flag point above the horizon measured in the scale of the base line. The practical operating programme is as follows: The camera is attached to an engineer's transit by means of screw hooks fixed on the side of one of the standards, and two lugs or sleeves correspondingly spaced are secured to the side of the camera box. When the camera is thus suspended from the transit standard and the latter is levelled up, the following conditions are met: 1. The optical centre of the camera objective lies in a vertical plane over the station point occupied by the transit. 2. The optical camera axis is in a ver- tical plane parallel to the optical transit telescope axis. 3. The optical camera axis lies in a horizontal plane with the transit telescope revolving axis. 4. The negative plane is vertical. These four conditions remain rigid throughout the operations here considered that is, the more complex and broader prac- tice of photogrammetry in which the nega- tive plane may be inclined from the vertical or of curved surfaces does not here enter. H.E.P.31 H.v.S. Any commercial camera can be employed with satisfactory results, the lighter the better; a 5 x 7 is well adapted; the objective should be rectilinear and the focal length uniform for distant points. The vertical and horizon are marked on the ground glass or finder, and small arrows or pointers are fixed to the interior of the four sides of the plate or film holder at the intersections of vertical and horizon with the frame, so that each view taken bears these marks, by which the control lines can be correctly reproduced on the positive print. The apparatus is now ready for operations, that is, the survey of a stream valley, a triangulation system having been established. 5. The instrument is set over a triangulation station, the camera attached, and the transit levelled. 7 OF THE UNIVERSITY OF 98 HYDRO-ELECTRIC PRACTICE 6. A pointing is made with the transit and known azimuth to the triangulation target on the opposite side of the stream valley. 7. The plate or film is exposed, removed, and the camera is re- charged. Sweeping the horizon in the direction of the operating programme, up or down stream, one pointing is made and view taken to each visible opposite triangulation target. 8. A record is kept as in surveys, views being identified as 1 to 2, 1 to 4, 1 to 6, etc., and the same notation is made on the plate holders as they are taken from the camera. The same programme is repeated from the opposite side, that is, 2-1, 2-3, 2-5, etc. The operator needs no technical photographic knowledge or skill beyond adjusting, charging, and unloading the camera, protecting plates from being light-struck, guarding against halation, that is, exposures toward the sun, and a practical guide to the use of the proper diaphragm or stop and the length of exposure under different conditions of light and time of day. Such an exposure and diaphragm scale should be adapted to the characteristics of the objective and the sensitiveness of the plate, and the data required can readily be obtained from the photographic supply house where these are secured. Development of the exposed plates or films and the printing of the positives had best be delegated to a photographer. In practice it will be found advisable to duplicate all views, to make certain by examination of image on ground glass or in finder that the key point connecting with the previous view is in the field of view. The instrument must be exam- ined before each exposure as to its level condition, as the weight of the camera may throw it out. The prints should be strong, and in order to secure detail an orange-colored screen may be fixed in the camera imme- diately back of the objective. 9. For the projection of the plan the horizon and vertical are drawn on the prints in vermilion, and likewise all objects to be plotted are marked by small circles or dots of the same color and num- bered identically on the different prints containing them. After the principal points are projected and their elevations have been determined, the contours and topographic characteristics are plotted on the plan as indicated in the prints. As stated at the beginning of this subject, the results to be expected THE SURVEY 99 are of a general character only, and therefore the refinements of guard- ing against change of paper texture have no place here. ARTICLE 38. Detail surveys should be made of gauging sections, recommendable dam sites, and of the location of the diversion works; they are referred to bench marks by determination of land or river bed and of water surface elevations at intervals of five feet by means of " Y" level, the points in the river being taken from a boat passing across along a line held taut by means of upstream guy ropes, the line being suitably marked off in five-foot lengths. One such section suffices at the gauging point, the terminals being fixed by posts; gaugings of different days 100 HYDRO-ELECTRIC PRACTICE Fig. 8 Reference Level should be preceded by re-sectioning in order to detect changes in the river bed. At the dam locations a section of the stream, two hundred feet long, should be covered by transverse lines five feet centres; canal, flume, and pipe line locations must be cross sectioned every ten feet longitudinally for a width double that of the probable construction, the centre line being traversed and marked at 100-foot points. The power- house location site should be cross sectioned as described for the dam site. Fig. 7 shows the plan and cross-section of a dam site. ARTICLE 39. Borings should be made on sites of dam, diversion works, and power station, being carried to rock or imperme- able material, and about fifty feet centres in each direction. The elevation, depth, and character of each class of material should be ascertained. The stratifications of rock for upper ten feet of its depth must be ascertained in order to discover possible water channels, nor must the rock surface found at fifty-feet points be accepted as being uniformly level between them, but intermediate borings should be made to establish fully these conditions. Gravel, clay, and sand should be classified as to their characteristics, samples of all being preserved for future reference. These in- vestigations by borings cannot be made too exhaustively; the more thorough the knowledge of the subsurface formations, the better for the sake of safety and economy. A well-digger's outfit will prove the best for all purposes; nothing of much value can be secured with hand-boring apparatus. All borings should be instrumen- tally located and all elevations referred to bench marks. Fig. 8 shows the record of a boring station. ARTICLE 40. Stream gaugings should be made daily for as long a period as practicable, which will employ a separate force of three or four men constantly. A well-conditioned section is selected, preferably on a straight reach of the river, the best obtainable being a bridge cross- Clay & Sand Gravel & Clay travel & Boulder Rock THE SURVEY 101 ing, and in its absence a point where the perimeter is of nearly uniform elliptical shape and the flow is not influenced by islands, shoals, rocks, or other obstructions. A gauge is set at each shore point, preferably in a recess of the shore where it will be guarded against floatage ; it consists of a board graduated to feet and tenths, which is secured to a post or pile firmly set, or to a bridge pier. The gauge boards are marked to correspond with the elevation reference of the survey. The cross-section is determined as described in Art. 37. Gauges are read and a velocity measurement is made with a current meter. The programme will depend upon conveniences at hand, most readily from a flat boat passing across by aid of a ferry rope or, better, from two such boats secured together by a timber platform. The meter must be rated before and after the operation, which is most conveniently done by having two meters, one of which is used only as the standard, all the measurements being made with the other. Velocity meas- urements should be made at depth inter- vals of two feet; if the river stage fluctu- ates during measurements, they should be rejected. The meter is used from the up- stream end of the boat; three separate readings of one, one and a half, and two minutes' duration should be taken for each observation, and the mean accepted; the boat must be held firmly in a fixed position during the observations. The measurements at all the verticals of one meter station are to be made before moving to the next station in the section. The first measurement should be taken two feet below the surface; the last, two feet above the river-bed, and at least three on each vertical. In great depths, or swift currents, a sufficient weight must be suspended from the meter to main- tain it in a vertical position. Weeds and floating sand will interfere with correct measurements. The total discharge is ascertained by plotting the velocities found for each vertical as shown in Fig. 9, where S' F represents the verticals and total depth, a', b', c', d', e' the meter points 2 feet centres, and a' a, b' b, c' c, d' d, and e' e the corrected velocities for each; there- fore the discharge through section S' F is represented by the area S' S a b c d e F. 102 HYDRO-ELECTRIC PRACTICE Fig. 10 represents the entire cross-section; 1, 2, 3, 4, etc. are section points ten feet centres; the lower ordinates express the depth, the upper the mean velocities; the discharge at a section point = d x v, and the total discharge is the product of the sum of all point discharges into ten, their spacing. Meters should be run for a short time before beginning the operations, i.e., before readings are taken, as they are likely to overspeed at first. When current meters are not available, the velocity may be found by aid of floats. The gauging station is arranged as described in Art. 16; Fig. 10 H.E.P.35 H.V.S. surface floats, preferably corked bottles sufficiently weighted to project only with their necks, are placed in the water fifty feet above the up- stream gauging section limit, being the "dead run," the locus of their passage into the gauging section area is noted by line markers, and the time of such entry is taken by a stop-watch; one satisfactory run should pass under each marker; the bottles may be recovered by a boat below section. Subsurface floats, or double floats, are sometimes employed; they consist of a surface float from which a lower float is suspended, the theory being that thus the velocity of lower strata will be indicated; in practice this result is not readily realized. Rod-floats are likely to secure a much more reliable measurement of mean velocity of the stream. They are one-inch square soft wood sticks THE SURVEY 103 weighted at one end with lead strips or wire to float upright and as near the bottom of the river as practicable without striking it; they are set adrift fifty feet above the section, being located and timed as are surface floats; one should be sent under each line marker. ARTICLE 41. Reduction of Stream Gaugings. The discharge of a watercourse is the product of its area and the velocity of flow ; the former having been found from cross-section and the latter by any of the de- scribed methods. When surface floats are employed, the observed velocity is the surface velocity, which is reduced to the mean velocity and then plotted, as in Fig. 10, for the respective vertical. The ratio of surface to mean velocity is fixed by the depth and the coefficient of the perimeter rough- ness, " N," which for alluvial stream beds is .017 for a smooth channel bed without any obstructions to flow, such as boulders, snags, or large gravel in bed; .020 for smooth channels with large gravel in bed; .0225 for slightly irregular channel beds; .025 for an irregularly contoured bed with some boulders; .0275 for same as last with boulders and some weeds; .030 for rough rock channel beds ; .035 for very rough rock beds with many boulders. With these values of "N" for the respective channels, the compiled results of many experiments suggest, as an approximate ratio of mean to surface velocities, the values given on Diagram 17; when the mean velocity on a vertical has thus been found from the observed surface velocity it is plotted as shown on Fig. 10. The velocities of rod floats represent the mean velocity of a vertical section when their submerged length is 0.99 of the depth of the water; but it is impracticable to float them of such length, and their velocities are therefore in excess of the mean velocity; the necessary corrections, as established by experiments, are given on Diagram 18. ARTICLE 42. Stream Discharge Curve. When the river's discharge is known for a considerable range of its stages, a discharge curve is pro- jected, as shown on Diagram 19, by which the flow, corresponding to any gauge height, can be found; only constant repetitions of stream measurements, especially during the extreme low and high stages, will furnish the complete data for a reliable rating of its flow. Diagram 17 Flow Measurement Surface to Mean Velocity Ritio of nean to surface velocity oooo o oooooo oo o 104 5 4 3 u 8 1 u > 1 "3 tf i c / i 1 t / / /. i 1 1 i i / .7 i i / 1 / t T / 1 i / t / / / / i i 1 1 i 7 i i / / 1 / 7 i ^ i y / / / / ^ I ^. 7 f ( r J / / i L, lj y / i '/ { ( Y y / f a / & f ^ // y / / 1 / i / ^ '/ / ( / / 1 / / 1 \ ' , / t / 1 / i / / F R D Diagram 18 bw Measureme by Rod Float Rod to Mean Velocity Length of Ro< Depth of Wat I 1 1 / / nt / 1 / / / / '/ / / / / / // 1 1 / / / / / / 7 1 / / / 1 / / 1 I I / t / f er yj t / / / 1 | / / / /> / / 3 J3"7 Df H.> r;3/ ' 5 Mean ^ Velocity ^ in feet n per sec. "* (A 105 6 12 18 24 30 --^ *S Gag. ! heij rht ii i ft \ e I J ^ \ \ ~ 2? o-g " S N- ^ V- Discharge Curve for Susquehanna River at Wilkesbarre, Pa. D I to 3 \ \ \ \ \ > S V 9 \ a \ o o M d 3333: 8-3553 ? 1 3 0. 5' i \ o p- \ , P \ \ r* 1 \ \ O O ^ o* K> *^ O 00 sO 36 42 4ft \ \ \ V \ Ki \ < ? c*> r V G \ 106 THE SURVEY 107 ARTICLE 43. When the stream is small, it may be practicable to ascertain the flow by weir measurement. Fig. 1 1 shows the elevation and section of a weir, being a rectangular opening of horizontal base and vertical ends, the edges of the weir crest and ends being wedge shaped. The weir crest should be of such height that the downstream water surface is below it. The theory of measuring the volume passing over the weir is based upon the law of velocity of flow discovered by Torricelli, to wit: "the theoretic velocity of the flow of water is like that of a body^alling freely in a vacuum through a height equal to the head," - V=^2 gh, where V is velocity in feet per second, g is acceleration of gravity, 32.2 feet per second, and h is the head or height of water above the weir crest. Fig. 11 H.E.P.39 H.v.S. In Fig. 11, C is the weir crest, S the surface of the water; each film of water passes with a velocity due to the head acting upon it, i.e., of 0.1, 0.2, 0.3, etc., feet down to the lowest film, the one near the crest, the velocity of which is that due to S C = h. Were the respective film veloci- ties projected as ordinates a a', bb', c c', d d', etc., they would terminate in a parabolic line S a' b' c' d' e' P, and the volume passing in a unit of time would be represented by the parabola segment S P C. In accordance with the geometric theorem, the area of this segment is two-thirds of the rectangle of like base and altitude, orSPC = hx-y/2gh, which there- fore expresses the theoretic volume passing over the weir. This value is based upon the free falling of the water in a vacuum, and the actual volume will therefore be reduced from this theoretic by reason of the friction of water against the weir crest and ends and against the air, all of which retarding influences are expressed by coefficients 108 HYDRO-ELECTRIC PRACTICE which have been determined from results of many experiments. End contractions are expressed by J. B. Francis in a reduction of length "L" of weir = 0.1 h for each such contraction, while the other reductions from the theoretical volume are expressed by the same authority by a coefficient M = 0.622. More recent determinations by M. H. Bazin differ slightly from this. The weir formula is then Q (discharge) =Mh^2gh X (L-0.2hL). Solving, Q = 0.622 X 8.02h Vh X (L-0.2hL). When L exceeds 5 h the correction for end contractions may be omitted, and for the purposes of stream measurements Q = 3.33 \/h 3 per linear foot of weir, where "h" represents the height of water on the weir crest measured at a point upstream of the weir and above the initial depression due to the overfall. Diagram 2 is constructed from this formula. ARTICLE 44. Flow deduced from Precipitation and Evaporation. When flow measurements are insufficient to yield a rating curve, espe- cially when the low flow remains uncertain, the only method by which an approximation of it can be found is by the deduction of the run- off as the difference between the precipitation and evaporation. The general theory on which this method is based has been outlined in Art. 16, Part I. The detail operations of its practicable application are as follows: Evaporation computations are based upon the determined monthly ratios due to the requirements of vegetation, the capacity and condition of ground storage, and the temperature. The year, for this purpose, is divided into two periods, the first being from December to May, when vegetation needs but little moisture and the evaporation is only that due to the action of the sun; during these six months evaporation is small and fluctuates only with precipitation or is very similar to evaporation from water surfaces. The quantity of evaporation during this period is approximately expressed by E = 4.20 + 0.12 R, in which "E" represents THE SURVEY 109 total evaporation and "R" total precipitation during this period. The second period is from June to November, when vegetation matures and requires a large amount of moisture; this is generally expressed by E = 11.30 + 0.20 R. The monthly distribution of these quantities is given by the fol- lowing values: For December e = 0.42 + 0.10 r For January e = 0.27 + 0.10 r For February e = 0.30 + 0.10 r For March e = 0.48 + 0.10 r For April e = 0.87 + 0.10 r For May e = 1.87 + 0.20 r For June : e = 2.50 + 0.25 r For July e = 3.00 + 0.30 r For August e = 2.62 + 0.25 r For September e = 1.63 + 0.20 r For October e = 0.88 + 0.12 r For November e = 0.66 + 0.10 r "e" is monthly evaporation, "r" monthly precipitation. These values were found substantially correct for the latitude of New Jersey, while for others a temperature correction is to be applied. Five per cent, for each degree of temperature as differing from that normal in the latitude above referred to appears to correct these values for stream systems in other latitudes, and it is sufficient to apply this correction as based upon the mean annual temperature of the drainage area in question, which correction is expressed by 0.05 T 1.48, in which "T" is annual temperature; this may be termed the temperature factor, with which the values above given for monthly evaporation are to be multiplied. ARTICLE 45. A typical case of flow determination will now be taken up and argued month by month to its conclusion. The river taken is the Maitland in Ontario, emptying into Lake Huron at Goderich, which was examined by the author in 1905, the flow being measured for a suffi- cient period to prove substantial agreement between the two methods. The year taken is 1903. Monthly precipitation records were available for five well-distributed stations in the area, and, as the stream flows generally westerly and its drainage area is located in one precipitation belt, the monthly mean of all stations was adopted. The mean annual temperature was found to be 46 F. Temperature factor 0.05 X 46 - 1.48 = 0.82. 110 HYDRO-ELECTRIC PRACTICE Month. Precipitation. Evaporation. December '02 2.18 (0.42 + 0.10 r) X 0.82 = 0.52 January '03 1.36 (0.27 + 0.10 r) X 0.82 = 0.33 February '03 1.80 (0.30 + 0.10 r) X 0.82 = 0.39 March '03 1.19 (0.48 + 0.10 r) X 0.82 = 0.49 April '03 0.89 (0.87 + 0.10 r) X 0.82 = 0.79 May '03 2.74 (1.87 + 0.20 r) X 0.82 = 1.98 June '03 2.85 (2.50 + 0.25 r) X 0.82 = 2.63 July '03 2.68 (3.00 + 0.30 r) X 0.82 = 3.12 August '03 2.87 (2.62 + 0.25 r) X 0.82 = 2.74 September '03 3.54 (1.63 + 0.20 r) X 0.82 = 1.92 October '03 3.92 (0.88 + 0.12 r) X 0.82 = 1.11 November '03 0.96 (0.66 + 0.10 r) X 0.82 = 0.62 December '03 4.28 (0.42 + 0.10 r) X 0.82 = 0.69 Having found the monthly evaporation, it is evident that the excess of precipitation over evaporation represents the run-off; but an exami- nation of these two reveals the fact that during July evaporation exceeds precipitation; this generally will be the case during several months and apparently there would be no run-off under such conditions. This, how- ever, is not so, at least only rarely on western streams, which sometimes dry up entirely during seasons of drought; but there is water stored in the ground and in lakes and swamps, and whenever the evapo- ration is greater than precipitation, and in fact when the excess of precipitation becomes small, water stored in the ground feeds out into the stream. It would be well, at this stage, for the reader to retrace his steps and review the discussion of drainage area, its topography, geology, flora, and culture, as the important influences of all of these conditions are about to become more apparent. The supply from which a stream is fed during periods when precipi- tation only slightly exceeds evaporation, or when there is no such excess, which is the case on almost every system during the growing season from June to September, depends on the drainage area characteristics: if the ground contains no storage, there can be no supply ; if the storage is. large, the supply from it will be correspondingly plentiful, yielding frequently as much, and a greater flow than a normal rainfall would furnish. The rainfall is generally very small during two or three months of this growing season: a wet summer is an exception rather than the rule. From a generalization of drainage area characteristics, as repre- sented by topography and geology, the investigations in this field have THE SURVEY ill resulted in a classification of (1) An area of bold relief and in highlands with no surface storage. (2) An area of drift-covered rock with no surface storage. (3) An area of deep drift and large surface storage. Others could be added as being descriptive of conditions between these, but in practice the investigator will generally find that the area under examination is practically described by one of these three classes. It is evident that the ground storage capacity of these three will greatly differ, and, as they do, they will be capable of furnishing a comparative supply to the stream during the periods of small rainfall. In the course of the search for a practical determination, fixed values of ground flow from areas of these different classes have been found and are represented by ground-flow diagrams on Profile 2. The side nota- tions stand for monthly flow in inches from the ground storage, while those at the bottom represent the corresponding depletion of the ground storage, also in inches. Examining the projected curves, their more gradual flattening will be noted as the storage capacity of the area increases, while all finally assume almost the horizontal, indicating that storage is nearly depleted; it will also be seen that each of these begins to feed out with a flow of two inches, which means that, whenever the excess of precipitation over evaporation is less than two inches, ground storage begins to supply in accordance with the quantity of the remaining stor- age. The essence of all of this ground storage topic may be expressed by the following: The ground storage conserves the excess precipitation and from it feeds to the stream during dry seasons in accordance with its capacity. We may now go back to the finding of the flow on the Maitland River, and we note that during the very first month the excess of precipi- tation over evaporation is less than two inches, and, from what has been said before, we know that ground storage will add some supply and the storage itself will be correspondingly depleted. The ground-flow diagram arrangement shows what the depletion corresponding to a certain out- flow from ground storage is, which may be expressed as d t = depletion or condition at the end of the month preceding the one under consider- ation, when d 2 for present month = d t + e + f r, being the sum of existing depletion and present month's evaporation and flow less precipitation, 112 HYDRO-ELECTRIC PRACTICE and for the average condition of the month . Applying this to December, 1902, where r - 2.18, and e = 0.52, ^~ = 0.83, there being no previous depletion, therefore d t = and d = |- - 0.83. Zi The ground-flow diagram for Maitland River is that of a drainage area with drift-covered rock and no surface storage (No. 2) , and, exam- ining the curve, we find that the intersection of d = 0.25 and f = 2.15 fills the condition because | = 1.07 and { - 0.83 = 0.24; "f " is there- fore 2.15 inches. The difference between the sum of evaporation and flow and of precipitation must come from ground storage and d = e + f r, or in this case 0.52 + 2.15 - 2.18 = 0.49. When the next month, January, 1903, is examined, r = 1.36, e = 0.33, and ground storage is depleted by 0.49 inch. Then from A f i r - e = 2 " dl " ~2~ = | + 0.49 - 0.52 Ji -1-0.03, which is practically met by the intersection on the ground-flow diagram of 0.78 d and 1.62 f or 0.78 = 0.81-0.03, and f therefore =1.62, while depletion is again = to total evaporation and flow less total precipita- f Profile 2 Groundflow diagrams 2.0 v \ C ~\ i * V- 1.5 5 V ^ Bold relief and in 1 ft - - ^ l.O v Highlands s s~ _ _ v a v.5 ^^ ft in q in o o - -* 2ej q tn q in o ri ri rt ro ^ in j \ ^ *) ft \ Z.U \^ k V ^ 1 S ^^ _ 1.9 N and no swamp * r *> storage > i i n - - v ^^- -- . = ~- --._. ____ ~~ - - . _ t\ E - * "" i U.5 " * , -_ -- - ~~-= -c i) in O f in mom q in q in q U> j < O ^H ^H N _ * J 5* ^ ~ ~ " large swamp storage 11 - . " * 5 Z 5 v 1ft - S * s s x _ S J s V n % - x ^ Sj " t " - r.. E^l^rtr n - From report of Geol. Survey of N. J. 1894 by C. C. Vermuele C. E. 113 114 HYDRO-ELECTRIC PRACTICE tion = 0.85 + 3.76 - 3.54 = 1.07; or, in other words, the total supply represented by the total precipitation and the ground storage outflow (depletion) must always equal the total amount expended, that is total evaporation and total flow. As rainfall increases, ground storage again becomes gradually replenished, as appears at the end of the year. In this manner month by month is taken up and the run-off found in inches from the drainage area, which, for practical application, is later transposed into flow of cubic second feet. The convenient arrangement of these deductions is as follows: Column 1 gives the months, commencing with December of the previous year, because the accepted water year is from December to November. Column 2 shows monthly precipitation r Column 3 shows total precipitation R Column 4 shows monthly evaporation e Column 5 shows total evaporation E Column 6 shows monthly run-off f Column 7 shows total run-off F Column 8 shows depletion of ground storage d The computations are here given in detail in accordance with above arrangement, and Column 6 contains the resultant monthly run-off in inches per square mile of drainage area. ORDINARY DRY YEAR MONTHLY RUN-OFF FROM MAITLAND, ONT., RIVER WATER-SHED. (All measurements in inches.) 1903 Month. 1 December '02 .... PRECIP Monthly. 2 2.18 ITATION : Total. 3 2.18 3.54 5.34 6.53 7.42 10.16 13.01 15.69 18.56 22.10 26.02 26.98 31.26 EVAPORATION : Monthly. Total. 4 5 0.51 0.51 0.33 0.84 0.39 1.23 0.48 1.71 0.77 2.48 1.93 4.41 2.56 6.97 3.04 10.01 2.67 12.68 1.87 14.55 1.08 15.63 0.54 16.17 0.68 16.85 RUN-OFF : Monthly. Total. 6 7 1.67 1.67 1.03 2.70 1.41 4.11 1.44 5.55 0.76 6.31 0.60 6.91 0.60 7.51 0.40 7.91 0.33 8.24 0.44 8.68 1.71 10.39 1.32 11.71 2.70 14.41 Ground Storage. 8 full full full 0.73 1.37 1.16 1.47 2.23 2.36 1.13 full 0.90 full Remarks. T = 46 Ground flow taken as from watershed of bold relief with no swamp or lake storage and some drift overlying rock. January '03 1.36 February '03 1.80 March '03 1.19 April '03 . 089 May '03 2 74 June '03 . . . 2.85 July '03 . . 2 68 August '03 ... 2 87 September '03 . . . 3.54 October '03 . . . 3.92 November '03 . . . 0.96 December '03 . . . 4.28 THE SURVEY 115 ARTICLE 46. Reservoir sites should be looked for along the tribu- taries above the power site, and on lakes or swamps in the drainage area, and when found they should be surveyed to determine their available area and depth, location of reservoir dams, and cross-section at such. Diagram 4 gives the continuous flow capacity, for various periods of time, in cubic-second feet, from an area of one hundred acres and one foot depth, from which the area corresponding to a required flow, or vice versa, can be taken. Evaporation from reservoir surface, as per Table 4, Article 14, must not be overlooked, and some allowance should be made for water escap- ing from storage by seepage and by leakage through reservoir dam. The time required by the flow, from the storage reservoir to the power site, must also be determined. ARTICLE 47. The prevalence of timber floating down the stream, either from logging operations or trees on the banks which will be up- rooted by the raising of the water above the dam, should be investigated ; also the ice conditions during the winter periods, to what thickness it is likely to form and whether there is likelihood of its gorging in the river bends or above islands. CHAPTER VII DEVELOPMENT PROGRAMME THE data collected by the various operations described in Chapter VI. will furnish the information required to plan the best programme. ARTICLE 48. The direct development utilizes all the available fall at the dam, and the power station is located at its end or in the in- terior of the spillway. This plan is recommended because of the con- centration of the entire plant at one point and the consequential saving in the operation cost, and because of its securing the highest obtainable hydraulic efficiency of the power components, fall and flow; by any other programme losses of both of these are incurred. Any diversion sacrifices a portion of the available fall by the slope in canals and flumes or the friction-head in pipe lines, while losses of flow are represented by leakage, evaporation, and ice conditions. When the water is passed at once from the upper pool through the turbines, no such losses occur. The conditions which determine this choice are the cost of the dam and embankments as compared with that of a lower dam and of diversion works ; also the extent and cost of flowage for the upper pool and further the advantages secured by an extensive pond area; the flood flow condi- tions as affecting power house ; the rise in the lower pool and the fluctua- tions in the working head. The rapid increase of cost with the height of the dam is shown on Diagrams 9 and 10, Art. 23, and of the foundations, if in alluvial location, and of abutments, on Diagram 11, Art. 23. When the location is in a narrow rock gorge, the entire width of the river will be required for the passage of the flood flow, and then it is not permissible to occupy any portion of it by the power house; to create a location for it in the rock bluff would be a costly undertaking. The solution for such a case may be found in arranging the interior of the spillway for the power station, as will be detailed further on, and in this way a spillway of the full river width becomes available and the direct development feasible. If the river is subject to frequent high stages, when the discharge over the spillway represents large volumes, it will correspondingly raise the level in the power-house pits and may impede the efficiencies of turbines; floating timber and ice also have a bearing upon this pro- ne DEVELOPMENT PROGRAMME 117 gramme, as it may necessitate costly safeguards to prevent injury to the power house or interference with the free entrance of the water to the turbine chambers. Thus, while the direct development plan realizes the highest percentage of flow and fall and represents the greatest simplicity of works and lowest operating charges, and therefore, as a rule, the most economical, the conditions may sometimes be such that its adoption is prohibited by the first cost or by considerations of safety and of con- tinuity of operations. ARTICLE 49. The short diversion programme meets conditions where the dam location of the power house is not feasible because of contraction of the river channel or of the insufficient height of the spillway to accom- modate the power equipment in its interior. The power house is then located as close below the dam as practicable, but at a safe distance from the spillway overfall. Water is conducted from the spillway pond in accordance with the volume to be utilized, in a canal, flume, or pipe. Since this programme is adopted only to escape the excessive cost or dangerous conditions, it presents more problems requiring careful solu- tion than the former. No matter how short the diversion works, proper guards at point of intake are required, which, in combination with the spillway structure, cover a wide range of types. It may be advisable to locate the intake at some distance above the dam, in order to escape heavy rock cutting or ice gorges and to secure the most complete diver- sion of the low flow into it; to accomplish the latter object, on a wide river it may be necessary to provide a diverting dike or weir. When the rock bank continues precipitous for some distance above the dam, a partition wall may be required, or in some such cases it may be found to be most economical to arrange for diversion through a tunnel around the dam abutment. The intake entrance must be guarded by some kind of head gates, their character depending upon a number of controlling conditions which will be treated in detail later on. The diversion method will be shaped by the character and the formation of the river bank and the volume to be carried, detail considerations of which will be found under "Canals, Flumes, and Pipe Lines." The power house is placed at the most convenient point immediately below the dam; types will be described in the next chapter. ARTICLE 50. The distant diversion programme is applicable only when the concentration of the available fall at one point is not feasible or is too costly. The spillway or reservoir dam is located at the most 118 HYDRO-ELECTRIC PRACTICE DEVELOPMENT PROGRAMME 119 OF THE UNIVERSITY CF 120 HYDRO-ELECTRIC PRACTICE DEVELOPMENT PROGRAMME 121 advantageous point, and the water is conducted from there to the lower level by a canal, flume, or pipe line, and the power station is at the terminal. The features of this class are very similar to those of the short diversion programme, the difference being only the distance of diversion. The choice of development programme is, as a rule, not a difficult problem; as the existing conditions in most cases readily point to one or the other, only occasionally may some doubt exist as between the first two. When the development is on the lower reach of a river without falls or rapids, aiming to concentrate so much of its natural fall as may be feasible with the available height of its banks, and when the formation is generally alluvial, the direct programme is the solution, the power house being placed at the end of the spillway, as is shown on Plan 8, of the Mottville, Mich., development; or if this is 30 feet and higher, in the spillway's interior, as illustrated on Plan 9, of the Manistee River, Mich., plant. On such locations high flood conditions may advise the adoption of the second programme, or the peculiar formation shown in Plan 10, High Bridge, Mich., where a promontory juts out into the river, presents a favorable condition for the short diversion development. The third would be available only in case sufficient more fall could be secured by it, for instance when the river makes a long detour, doubling back to within a short distance abreast of the dam site, the diversion location being across the peninsula formed by the river's oxbow course. The fall of rivers of such characteristics rarely exceeds two feet per mile and the length of its course around the detour must be five miles or more to war- rant such a programme; in fact, its advisability must be weighed by a comparison of the earning capacity of the fall thus gained and the invest- ment represented by the. cost of the diversion works plus their mainten- ance and operation. This case is illustrated on Plan 11, of the Clinton River, Mich., Renshaw site development, where the stream departs easterly for a distance of five miles and returning approaches the dam site within 1200 feet, gaining 12 feet fall. In rivers with rock beds and palisade banks the first programme is admissible only when the spillway's interior can be utilized for the power station, as the entire width of the river channel must remain available, unobstructed, for the passage of the flood flow, and the creating of a power-house site at the spillway end involves the removal of rock and would be very costly. Such a development is shown on Plan 12, of the 122 HYDRO-ELECTRIC PRACTICE DEVELOPMENT PROGRAMME 123 UNIVERSITY 124 HYDRO-ELECTRIC PRACTICE HM fflHW^! "2. a 5' S' Kentucky River -*. 8 FT g 99 v> p to * *- DEVELOPMENT PROGRAMME 125 OF THE UNIVERSITY 126 HYDRO-ELECTRIC PRACTICE DEVELOPMENT PROGRAMME 127 /^ ff OF THE ( UNIVERSITY J V OF / 128 HYDRO-ELECTRIC PRACTICE DEVELOPMENT PROGRAMME 129 Canon Falls, Minn., plant, the river forming practically a rock gorge, the spillway 40 feet high, and the power station inside of it; this can be carried out only when the spillway is 25 feet or higher, and the only alter- native is as shown in Plan 13, at Little Hickman, Green River, Ky., where the power house is 200 feet below the dam, diversion in this case being by tunnel. When falls or rapids continue over a considerable distance, the third programme only is available, that is, if a fall exceeding the feasible accumulation at one point is to be utilized. Plan 24, of the Pennington, Ind. Ter., illustrates this, the fall in 3J miles being 135 feet; diversion is by flume and pipe line; also Plan 15, of the development at Sault Ste. Marie, Mich. The development of most of the high falls is of this type, as appears on Plan 16, of the Eugenia Falls, Ont., where a vertical drop of 78 feet is followed by continuous rapids in the stream flowing for one mile around a rock bluff; the spillway here is placed above the fall, and | mile diversion by tunnel and pipe line terminates at a point 400 feet below the spillway crest. Occasionally successive falls can only be de- veloped by separate treatment, that is, topography or right-of-way lim- itations prohibit any diversion programme. This is the case on the Sandusky River near Fremont, 0., Plan 17, where a fall of 40 feet occur- ring in half a mile can be developed only by two separate dams within a quarter of a mile of each other. Only the best market conditions will warrant such a treatment when the operating cost of the two stations creates a heavy charge against the enterprise. ARTICLE 51. Development scope i.e., what output capacity is the development to be based upon should be determined before the plant is designed. This question is be decided from the considerations of the available market for the product and of the fall and flow which can be utilized. The market topic has been discussed in Part I. In the direct development it is generally advisable to utilize all the available fall ; with distant diversion the cost of the latter corresponding to the fall gained is the criterion. If only a part of the available power is to be developed, the decision whether to use partial fall or flow rests with the cost of works adapted to one or other purpose; this, however, is rarely the case ; on the contrary, it will be almost uniformly desirable to develop the largest possible capacity, as the market for the product is sooner or later created, and the greater the output at a given site the more econom- ical will be the unit development and the operating cost. An estimate 9 130 HYDRO-ELECTRIC PRACTICE of the largest practicable development is among the first questions met while the project is being exploited, and when it is furnished it must be based upon reliable data and be conclusive. The low flow during the nine-month period will in the majority of cases be the most recommendable to adopt as the power flow; that during the remaining period of three months lower flow 'must be increased by drawing supply from reservoir storage, by ponding during non-operating hours, by auxiliary power plant, or by charging an electric storage battery with so much of the current output as is not called for because of the fluctuations of connected loads. It is only in rare cases that the available market exceeds the low- flow output from the very beginning; if such is the case, the cost of creating any or all of these supplementary flow or power sources must be provided for in the first development estimate; if, however, none such will be required at the outset, the future increase of power demand will take care of the added investment for these additional power sources. CHAPTER VIII STRUCTURAL TYPES IN this chapter are presented some practical designs for the works of a hydro-electric plant. They are preceded by the nomenclature of terms herein employed, specifications of material and of methods, fol- lowed by the development of one or more designs for each separate structure of importance, with an outline of the theory of stability and adaptability from which they are evolved, and concluded with estimates of quantities and, in some cases, of cost. This treatment of structural types is largely as developed in the author's practice and as proved practical, safe, and economical for the purpose. The dam comprises the entire structure by which the river and its valley are closed, from bank to bank, for the purpose of accumulating the water, concentrating its fall at one fixed point, and diverting the flow in the desired direction. The dam may or may not pass water over its crest; in the affirmative case it becomes a spillway, in the other a reservoir dam; generally it is a composite structure of both types, the river proper being closed by the spillway, which terminates in abut- ments and is flanked at one or both ends by reservoir embankments or bulkheads. The spillway consists of the foundation and superstructure. ARTICLE 52. The foundation's functions are to prevent the passage of water below the structure and to afford rigidity of position to the superstructure. Its design is determined by the character of the material at its site, as to hardness, strength, and porosity, the height and weight of the superstructure, the maximum height of water to be ponded, and the effect of its overflow. Foundation sites are in rock or alluvial formation. The primitive rocks, formed by original solidification, fusion, or later volcanic action, are granite and sienite; they are igneous and silicious. Granite is composed of quartz, feldspar, and mica, with talc and hornblende as impurities; its hardness and durability are increased by the proportion of contained quartz and decreased by that of feld- spar and mica; it is unstratified. Sienite closely resembles granite; it 131 132 HYDRO-ELECTRIC PRACTICE consists of feldspar and hornblende with some quartz and mica; it is as hard and durable as granite. The transition or metamorphic rocks are gneiss, sienite gneiss, green- stone, trap, and basalt; they are sedimentary, but have undergone changes due to heat, pressure, or chemical action. Gneiss or mica slate is silicious and stratified, resembling granite. Sienite gneiss is a stratified sienite. Greenstone, trap, and basalt consist of hornblende and feldspar and are unstratified. The secondary rocks are the sandstones, which are formed by the solidification of disintegrated primitive rocks, being composed of grains of silicious rocks cemented together by silica, lime, and alumina. To this class also belongs soapstone, silicate of magnesia. The physical characteristics of sandstone vary with its density and it is generally stratified. The tertiary rocks are calcareous, being formed of shells and marine animals compacted under pressure of superimposed rock or soil; to this class belong the limestones, marble, chalk, and slates. Limestone, car- bonate of lime, varies from the hardness and density of marble to the softness and porosity of chalk. Slate occurs in thin strata, of which clay forms the basis. PHYSICAL CHARACTERISTICS OF ROCKS. Rock. Granite , Weight per * Cubic Foot. 180 Ibs. Crushing Strength Stratified or per Square Foot. not. 750 tons Unstratified 750 tons Unstratified 700 tons Unstratified 700 tons Unstratified 700 tons Unstratified 700 tons Unstratified 700 tons Unstratified 600 tons Stratified 500 tons Unstratified 500 tons Unstratified 600 tons Stratified Sienite 180 Ibs. Gneiss 180 Ibs. Sienite gneiss . . . 180 Ibs. Trap 180 Ibs. Basalt 180 Ibs. Greenstone 180 Ibs. Sandstone 150 Ibs.' Marble 168 Ibs. Limestone (hard) 168 Ibs. Slate. . . 175 Ibs. Under alluvials are comprised gravel, sand, clay, loam, marl, and peat. Gravel is fragmentary rock reduced by the atmosphere and water to pebbles, chiefly of quartz and of crystalline origin. Sand is of the same origin as gravel and consists merely of smaller particles, generally inter- * For structural considerations 0.25 only of crushing strength here given should be accepted for safe load capacity. STRUCTURAL TYPES 133 mixed with gravel; it is of angular or rounded fragments as its existence is due to recent or older disintegration of the rocks. Quicksand consists of small rounded particles of calcareous materials which, under the influence of water, becomes like a fluid. Clay is decomposed crystalline rock, consisting of hydrated silica or alumina, and generally contains some sand and lime; it occurs in all colors from lightest to darkest, and, according to quantity of water contained in it, is soft or stiff. Loam is a mixture of clay and sand, the latter predominating so far that the clay loses its coherence. Soil is fine earthy material mixed with more or less organic matter; mud is moist, soft soil; silt is a fine earthy sediment. Marl is correctly classed as a tertiary formation, and is a consoli- dated mixture of clay and carbonate of lime which readily disintegrates when exposed to the atmosphere. Peat is decomposed vegetable matter, spongy and containing much water near the surface. Material. PHYSICAL CHARACTERISTICS OF ALLUVIALS. * Weight per Cubic Foot. Gravel 90-106 Ibs. Sand, dry and loose 90-106 Ibs. Sand, wet ; 118-129 Ibs. Clay, dry , 119 Ibs. Clay, in lumps 63 Ibs. Clay, damp Clay, wet Loam, dry, loose 72-80 Ibs. Loam, wet 66-68 Ibs. Mud 104-110 Ibs. Gravel and loam Gravel and sand, dry Loam on moist clay Loam on wet clay Clay on gravel Peat.., t Bearinc- per Angle of Coefficient Square Foot. Repose. of Friction. 2-3 tons 38 0.78 2-3 tons 28 0.53 2-3 tons 28' 0.53 4-6 tons 4-6 tons 45 4-6 tons 45 1.0 4-6 tons 15 0.27 4-6 tons 35 0.70 4-6 tons 35 0.70 4 r 6 tons zero 0.70 2-3 tons 38 0.78 8-10 tons 45 45 17 45 20 1.0 1.0 0.3 1.0 0.36 Having analyzed the character of the material at the foundation site, the following arguments and deductions should control the design. In rock its hardness, stratification, condition and shape of surface determine the foundation. * Compacted, f At depth beyond atmospheric influence. 134 HYDRO-ELECTRIC PRACTICE In hard unstratified rock with level surface no foundation is required; the homogeneous ledge will not permit water to pass beneath its surface and it will safely carry the superstructure which is anchored and keyed to it. In hard but stratified rock a cut-off wall must be constructed along the upstream side of the spillway structure in a trench excavated from the rock to a sufficient depth to pass below those strata which are less than two feet thick, its upper portion becoming part of the superstruc- ture. The rock ledge may be of sufficient solidity to carry safely the spillway. In soft stratified rock a cut-off wall is essential. The superstructure may be founded on the rock surface after the soft, disintegrated upper portions are completely removed, but an apron must be constructed on the downstream side of the superstructure to receive the overfall and resist its erosive force. In compact alluvial gravel and sand, defined as hardpan, with no interior sand strata to a depth of one-third of the water height on the upstream side of the spillway, a cut-off toall is required to a depth below the river bed equal to one-fourth of the maximum water head; when the aggregate weight of the superstructure and water does not exceed two tons per square foot of its base, it may be placed directly upon the levelled, cleaned hardpan surface, but when the load exceeds this limit, bearing piles must be driven to support safely the superstructure, which may be placed directly upon them, or a concrete foundation floor may be laid, the pile tops being imbedded in it. An apron is required on the downstream side. In clay with no sand strata or pockets for a depth of one-fourth of the maximum water head, upstream cut-off walls must be constructed to a depth of one-third of the maximum water head, and these must form a part of the foundation floor, which rests upon the bearing piles and is extended up- and downstream of the superstructure base as aprons. In soft alluvials of clay, gravel, sand, loam, silt, or peat, upstream cut-off walls are required to a depth penetrating into impermeable material or to rock, and a pile bearing foundation with up- and down- stream aprons, as will be later on described, must be constructed. In all alluvial locations the foundation must be specially designed to provide safety against scour or underwashing and secure ample bearing capacity. Whenever sand strata exist, even at a considerable depth, at STRUCTURAL TYPES 135 the spillway site or upstream of it, they may rise or connect with higher strata of the same material, and eventually form channels through which the water, under increased pressure head, finds a passage beneath the spillway base, which will cause leaks and in time remove some of the mass upon which the structure rests. The only reliable safeguard under such conditions lies in securely confining so much of the mass between the cut-off and intermediate foundation walls or beams that its weight exceeds the sliding force, and to penetrate through and below this body with bearing piles which will safely maintain the superstructure, even should it, so to speak, float upon the mass enclosed between the cut-off and the foundation walls. Upon this theory the depths of the cut-off walls should be based. This liability of water passing under the foundation by way of permeable strata is not confined to the river bed, but in fact is much more likely to have its origin in the banks, where the con- stant passage of the ground- water into the stream has formed permanent channels which, when the water is ponded above them, become readily connected by lateral channels; springs issuing from the river bank are evidences of the ground- water channels, which, however, are not always thus plainly marked. Of this subject more will be said under "Embankments." ARTICLE 53. Terms, Materials, and Methods. (A) Coffering com- prises the operations and structures required to control the water during construction, to exclude it from the site. (B) Dike, Fig. 12, is a loosely thrown up rock-and-earth bank; its function is to exclude water from the site it encloses; it consists of a core of loose rock of all sizes and an earth or clay and sand facing fill. Loosely piled limestone and sandstone weigh 86 pounds per cubic foot; one cubic yard solid of either yields 1.75 of loose volume. A rock bank with slopes of one-half in one, no top width, and of height equal to the depth of water in which it is placed, is safe against overturning by a Dike. 136 HYDRO-ELECTRIC PRACTICE Timber Sheet. factor of two, and can be made practically water-tight by placing alter- nate coverings of straw, hay, or manure and ashes, clay, or coarse loam against its pressure side, the water on the opposite side being maintained at a lower level while the facing is placed. The earth fill should rise 3 feet above the top of the rock core. (C) Timber sheet, Fig. 13, is a vertical curtain or wall, consisting of planks driven to overlap, of sheet piles to interlock, or of close-driven square piles for the purpose of coffering; they are effec- tive only to enclose small areas, and must be strength- ened by waling, which are timbers secured horizontally to them at differ- ent heights, against which inclined timbers, securely footed, are strutted. With five feet of pressure head against the timber sheet of three-inch planks, the struts must be spaced five feet. Such a sheet is made water-tight by canvas cover- ing and earth facing. Tim- ber sheets are driven to a depth equal to the water head against them and rise 3 feet above water surface. (D) Steel sheet consists of driven interlocking steel shapes, which are rolled of different sections from 11 to 45 pounds per foot ; they are driven like timber sheets, are capable of resisting moderate pressure heads unsupported, and can be made water-tight by filling ashes against their pressure side; they can be pulled out and used again. Fig. 14 shows some of the sections now on the market. (E) Log cribs, Fig. 15, are constructed of round logs laid upon each other in crib fashion of alternate longitudinal and transverse streaks, the Fig. 14 Steel Piling. STRUCTURAL TYPES 137 Log Crib. first from five to sixteen, the second from eight to twelve feet centres; the open rectangular spaces enclosed by the logs are the crib bays; the logs are spiked to each other at all crossings with f" round 18" wrought- iron drifts set in f" holes; logs may be gained to secure firmer connections and to bring those of the same layer, or streak, to a uniform level. Log cribs are used for coffering, confining and di- recting flow, or retaining banks and slopes; they may be framed in place, the second streak being formed into an open log floor and the bays filled with gravel or loose rock as the framing progresses, or they may be floated light into position and there loaded and sunk; they can be made water-tight by planking or boarding, or by diking. To resist overturning, with a factor of two, their interior width should equal 0.75 of the water height and their rock- filled height should rise three feet above the water surface. (F) Timber cribs, Fig. 16, are built of dimension timber in crib fashion similar to log cribs, or of solid timber walls, and are filled with rock, gravel, or sand and made water-tight by canvas cov- ering and puddle placed along their footing on the pressure side. To resist overturning, with a factor of two, the width of timber crib should be 0.66 of the water height and the filled height should equal that of the water. (G) Timber. Boards are one inch thick, and sawn; planking is two or three inches thick, sawn ; scantling is 1" x 3" or 4", sawn. Dimension comprises all sawn or hewn sticks of rectangular or square section ex- Fig. 16 H.E.P.55 H.V.S. Timber Crib. 138 HYDRO-ELECTRIC PRACTICE Fig. 17 ceeding three inches in thickness; ft. b. m. is the abbreviation for feet board measure, the unit of which is one square foot one inch thick. Round timber measure is in cubic feet = length X ; C is the circumference of the log in feet. (H) Bearing piles are straight logs 16 feet and longer, 8" in diameter at the small end under the bark; they must be of one year's cut and sound and are barked. They are driven to refusal when they do not sink more than 0.5 inch under a free 20- feet drop of a 2000-pound hammer. The theoretical bearing capacity of timber piles equals cube root of fall of hammer in feet x weight of hammer in pounds x constant 0.023, divided by constant 1 + sink- ing distance per stroke in inches, which for " driven to refusal" conditions are 4/20 X 2000 X 0.023 + 1.5 = 64 tons. The actual loading should not exceed one-half of theoretical when the pile stands in gravel, clay, and sand; one-fourth of theoreti- cal when the pile stands in clay and sand; one-tenth of theoretical when the pile stands in mud. To drive bearing piles in com- pacted sand is difficult and generally requires clearing by water jet. (I) Concrete piles are constructed by different processes. In Fig. 17 a collapsible steel core inside of a steel plate shell is driven, the core is withdrawn and the shell filled with concrete. In the other type a steel form fitted with a bucket point is driven to the required depth, some concrete is then lowered into it and the shell is pulled up two feet, by which operation the bucket point opens and permits the concrete to drop to the bottom and it is there rammed in place; lowering more concrete, I "o U H.E.P.56 H.v.S. Concrete Piles. STRUCTURAL TYPES 139 Fig. 18 pulling shell two feet, and ramming the concrete are repeated until the pile is completed. These piles can be re-enforced by imbedding steel rods in the concrete. (J) Cut-off wall intercepts flow and seepage below the surface; it may be of puddle, timber or steel curtain, or a concrete wall. (K) Core wall serves the same purpose as the cut-off in the interior of earth embankments. (L) Puddle is a plastic mass of clay, small gravel, and coarse sand in the proportions of 5 to 3 to 2, compacted in a confined space. (M) Timber curtain serves the purpose of cut-off or core wall, and consists of triple-lap sheet piles, Fig. 18, which are constructed of three planks placed on face sides, centre plank overlapping, thus form- ing tongue and groove on opposite edges; planks are secured by wrought-iron boat spikes one inch longer than thickness of pile, spikes are driven from opposite sides of pile, points are clinched. Piles up to 8 feet long are 6 inches thick; piles up to 16 feet long are 9 inches thick; piles up to 24 feet long are 12 inches thick. One end is scarf pointed so that, when driven, it crowds toward pre- ceding pile, forcing the tongue into the groove. These piles should be driven with a light hammer and a low drop and be guided all the way down; the timber for them should be pine or hem- lock, sound, of uniform thickness, and preferably edged. (N) Steel curtain is constructed of steel sheet pile sections described under D. (O) Concrete herein considered consists of true Portland cement mortar and hard broken stone or gravel ; the mortar is composed of one part of cement and two or three parts of sand by weight and of sufficient volume to fill completely the voids in the aggregate. A 1 : 3 : 6 mixture is designated as x concrete, a 1:2:5 mixture is called xx concrete. The cement and sand should conform to the standard specifications of the American Society of Civil Engineers; the aggregate is sized from one-quarter inch to two and one-half inches. Triple-lap Sheet Pile. 140 HYDRO-ELECTRIC PRACTICE The mixing is by hand or in batch mixers as follows : the cement and sand are dry mixed ; water is added and the mortar mixed, the aggregate is added, thoroughly washed and wet, and the concrete is mixed to a wet but not flowing mass, that is, water should not stand on its surface nor ooze out of it during handling or transporting. The concrete is placed in a manner to avoid disintegration of the mixture when dropped from cars, barrows, or shovels; the height of its fall should be restricted, and the inclination of chutes must not be steep. When concrete is placed on rock, the surface should be cleaned of all vegetable and earthy matter and drenched with water, and smooth rock surfaces should be scarred. Unfinished joints are to be treated in the same manner as rock faces before new concrete is added, and the maximum length of unfinished joints on the same plane should not exceed ten feet. Finished concrete should be covered, if practicable, with a layer of wet sand) or otherwise shaded from the sun and kept damp, for 48 hours. Such concrete may be expected to develop in six months the follow- ing characteristics, expressed in pounds per square inch: TABLE 4. CONCRETE CHARACTERISTICS. X Concrete. XX Concrete. Modulus of elasticity EC = 3,000,000 2,400,000 Compressive strength fc = 2,000 2,400 Tensile strength ft = 200 200 Shearing strength C = 300 300 Expansion = 0.000006 per degree F. Adhesion to rust-free steel = 600 Working stresses should be taken at 0.25 of above. Cyclopean concrete has imbedded in the concrete mass solid stones of any size, each stone being surrounded by not less than a twelve-inch wall of concrete, and no stones being placed closer to the finished sur- faces of the structure than two feet. Monolithic concrete is a solid mass of concrete. Block concrete consists of shaped concrete units laid in the manner of ashlar or coursed masonry in Portland cement mortar. Forms are shapes of boards, planking, or metal walls in which con- crete is moulded into blocks, walls, partitions, arches, or beams; the interior sides of the forms are smooth and oiled. Forms should not be removed until the concrete is fully set, generally 48 hours. Concrete steel, or reinforced concrete, is a structure in which the STRUCTURAL TYPES 141 imbedded steel increases the strength of the entire section; or in which the proportions of the steel to the concrete area, and the location of the steel with reference to the stresses, are determined to secure the action of both as a unit. The random placing of steel members in a concrete mass, or the lining or supporting of any side or face of a concrete section with steel, is not of the class herein considered. The characteristics of reinforcing steel are taken in pounds per square inch as follows: TABLE 5. REINFORCING STEEL CHARACTERISTICS. Modulus of elasticity Es = 29,000,000 Ultimate strength fs = 64,000 Elastic limit F = 50,000 Expansion = 0.0000065 per degree of F. The concrete steel designs herein used are based upon the concrete and steel characteristics given in Tables 7 and 8, and are according to formulae of Mr. A. L. Johnson, M. Am. Soc. C. E. TABLE 6. CONCRETE STEEL BEAMS. X Concrete. XX Concrete. Moment of ultimate resistance = 3620 t 2 5505 t 2 ; Area of steel in width of sec q = 0.077 t 0.132 t; t is depth of the beam. Values of t and q for beams to resist various bending moments in accordance with these formulae are given in Table 7. Many different kinds and shapes of reinforcing steel rods are used in such structures, but the above formulae apply generally and differ only with the change of concrete and steel characteristics. TABLE 7. VALUES FOR CONCRETE STEEL BEAM DESIGNS. M = ultimate bending moment of external forces in 1000 inch pounds; t = depth of beam in inches; q = square inches of steel in one toot width of beam. Steel is placed 0.9 t from compression face of the beam. X Concrete. XX Concrete. M. t q t q 100 5.27 0.408 4.27 0.562 150 6.45 0.500 5.22 0.689 200 7.45 0.576 6.02 0.795 250 8.32 0.644 6.74 0.889 300 9.12 0.706 7.38 0.975 350 9.85 0.762 7.93 1.050 400 10.52 0.816 8.52 1.125 450 11.15 0.861 9.05 1.193 500.. .11.73 0.910 9.53 1.258 142 HYDRO-ELECTRIC PRACTICE X Concrete. XX Concrete. M. t q t q 550 12.38 0.956 10.00 1.320 600 12.90 0.998 10.44 1.3SO 650 13.40 1.040 10.84 1.435 700 13.92 1.078 11.29 1.486 750 14.40 1.113 11.68 1.540 800 14.88 1.151 12.02 1.588 850 15.34 1.188 12.41 1.640 900 15 80 1.222 12.79 1.686 950 16.25 1.258 13.11 1.735 1,000 16.68 1.289 13.49 1.780 1,500 20.40 1.580 1650 2.180 2,000 23.50 1.812 19.05 2.520 2,500 26.30 2.038 21.30 2.810 3,000 28.80 2.230 23.35 3.075 3,500 31.15 2.410 25.20 3.325 4,000 33.25 2.573 26.90 3.560 4,500 35.25 2.730 28.59 3.780 5,000 37.20 2.880 30.10 3.9SO 5,500 39.10 3.025 31.60 4. ISO 6,000 40.80 3160 33.05 4.360 6,500 42.50 3.285 34.39 4.530 7,000 44.00 3.410 35.65 4.700 7,500 45.60 3.530 36.SO 4.870 8,000 47.00 3.640 38.10 5.030 8,500 48.55 3.760 39.30 5.190 9,000 49.90 3.860 40.40 5.340 9,500 50.25 3.965 41.50 5.585 10,000 52.70 4.075 42.60 5.620 (P) Breakwater consists of log cribs placed ten to sixteen feet centres, the intervening spaces being closed by planks or timbers placed in an inclined position, ends resting on the stream bed and tops against longi- tudinal logs secured to the top of cribs; its purpose is to check swiftly flowing water. (Q) Sheet pile dike, Fig. 19, is employed for coffering service; it consists of two parallel sheet pile curtains from five to fifteen feet apart, the area between them being filled with puddle, and the pressure side, or both sides, being covered with riprap and facing fill. (R) Riprap is loose rock thrown up against a bank, wall, or curtain, to break the force of flowing water or resist its pressure. (S) Steel pile dike is a structure similar to the sheet pile dike, the curtain being of steel sheet piles. (T) Paving consists of large flat stones placed by hand on faces or edges, interstices being filled with stone chips or spalls, on slopes of earth banks or surfaces, to prevent erosion. View 1 Breakwaier I I.E. P. 59 H.v.S. View 2 Timber Crib View 3 Log Crib Coffer View 4 Sheet Pile Dike STRUCTURAL TYPES 143 Water Surface Fig. 19 ARTICLE 54. Coffering is the first operation preparatory to the construction of any part of the dam, in order to exclude the water from the construction site. It requires judgment born of experience to con- fine the means employed, which will accomplish this, to devices of tem- porary character and economical cost; their failure will generally cause damages which would cover the cost of the most permanent works. Depth of water, velocity of flow, river-bed material, area to be coffered, and possibility of exposure to flood rises are the conditions to be weighed in determining the recommendable programme. In a rock bed and shallow water where the velocity does not exceed three feet per second, a dike (53, B) answers the purpose until its required section exceeds the cost of a log crib (53, E) , which latter must be chosen for swift water. In rapids a break- water (53, P) should first be constructed, such as is seen in View 1, which was erected in the Sault Rapids at the foot of Lake Superior, being 300 feet long in ten- feet-deep water with velocity of twelve feet per second. Rock is not always the most economical filling for cribs, as, for example, in the case of the location just referred to, View 2, where the construction site was coffered by a timber crib filled with sand which was pumped in. In gravel and clay beds a dike answers until its cost exceeds that of a log crib, as the one shown in View 3, which was 250 feet long, placed in ten feet of water and exposed to considerable wave action. In clay and sand and depth of water exceeding ten feet, a sheet pile dike (53, Q) will prove the most serviceable, such as is shown in View 4, which was placed by the author in twenty feet of water, was two thousand feet long, and consisted of two timber curtains, fifteen feet centres, braced and strutted, filled with puddle, riprapped and banked; it remained in service during a period of three years and developed no leaks. When water is shallow, timber or steel sheets (53, C and D) may answer; two examples of the latter, constructed of different type of steel-sheet piles, H.E.P.58 H.v.S. Sheet Pile Dike. 144 HYDRO-ELECTRIC PRACTICE are shown in Views 5 and 6. In compacted sand a steel sheet may prove the only practicable coffer up to ten feet depth of water; when deeper, a steel pile dike may be- the proper solution; timber sheets cannot be driven successfully in this class of material. In soft formations and water depth of five feet or less, timber sheets will answer; in greater depths the sheet pile dike is preferable to cribs, as it will be difficult to find firm footing for the latter. In all coffer operations it is essential to provide, and constantly maintain, ready means to add promptly filling, riprap, and facing material to the coffering structures, and further to provide and keep in commission a sufficient pumping plant to remove all water accumulating from leaks and seepage which is collected in a pump sump conveniently located. TABLE 8. QUANTITIES REQUIRED FOR DIFFERENT COFFER STRUCTURES IN 10-FEET LENGTHS, AS PER SECTIONS SHOWN IN FIGS. 12 TO 19. _ SHEETS. Depth, Water, Timber, Steel, ft. ft. b.m. Ibs. DIKE. Cub. yds. Rock. Puddle SHEET PILE DIKE. Timber, Puddle, Riprap, . ft. b.m. cub. yds. cub. yds LOG CRIB. TIMBER CRIB. Logs, Drifts, Rockfill, Timber-Drifts, Spikes.Sandfill, . lin. ft. Ibs. cub. yds. ft. b.m. Ibs. cub. yds. 5.. 1230 1430 5 45 2400 10 12 125 150 7 1750 175 5.5 6.. 1420 1650 7 54 2800 * 13.3 15 155 170 11.7 2175 200 9 7.. 1630 1870 9 64 3200 17 19 174 190 15.5 2475 225 13 8.. 1860 2090 12 75 3600 21.6 23 198 205 20 2825 250 17 9.. 1880 2310 15 88 4000 27 28 220 220 25 3150 270 21 10.. 11 2300 2530 18 22 27 31 36 42 100 113 126 141 154 171 4400 4700 5000 5450 5800 6200 6700 7100 7500 7900 8400 32 37.8 44.4 51 58.5 66.6 75 83.7 93 102.8 112.4 33 37 42 47 53 60 66 74 82 90 98 250 275 294 317 352 375 400 425 450 475 515 230 245 260 275 290 305 320 335 350 360 380 30.5 35.5 43 52 61 71 80 89 98 107 117 3600 4000 4275 4625 5150 5525 5900 6325 6700 7100 7700 290 315 335 360 380 410 430 460 480 500 530 26 31 36.5 42 48 55 65 75 85 95 105 12 13 14 15 16 17 18 19 20 ARTICLE 55. A foundation design for a thirty-feet high spillway in alluvial location, based upon the theories outlined in Art. 52, is shown in Plan 18. The structure consists of a cut-off wall, bearing piles, floor walls or beams, and floor. The cut-off may be a driven timber or steel curtain, provided the river bed material is such that these can be driven in a manner guaranteeing an unbroken, solid curtain. Timber sheet piles do not secure this result if driven through coarse gravel, or if bould- ers are encountered, as these will deflect the driving point and force the tongue out of the groove, leaving openings between sheet piles, and thus u eq II -H 08 Plan 18 Foundation design 10 H.E.P.65 H.V.S. 145 146 HYDRO-ELECTRIC PRACTICE defeat the purpose for which they are employed. Steel piles readily penetrate gravel without deflection, but not so when large boulders are struck, as their interlocking parts may then be ruptured and thus also leave openings. These defects are not readily detected during the pro- cess of driving, and therefore the decision as to adaptability of driven curtains for cut-off service must be solely based upon the correct diag- nosis of the material, as all other considerations are insignificant in importance when compared to the results expected from the foundation cut-off wall. A driven curtain presents the double advantage of economy and expedition, as it can be frequently driven before any coffering operations are started and may in part also serve to aid in coffering and, when of timber, it forms the most economical cut-off wall type. The tendency, therefore, predominates to rely upon this form; but these influences must not be permitted to outweigh the sound judgment of the engineer; when the presence of numerous and large boulders has been fully estab- lished, a driven curtain should under no conditions be relied upon. If the material favors the use of a driven curtain, the piles must be constructed and driven with the greatest care, and this operation, above all others, demands the most rigid supervision on the part of the engineer. When a timber curtain cannot be used, it is not always likely that the steel curtain solves the problem: the very conditions which prohibit a timber curtain form difficulties in the construction of a perfect steel curtain. The cost should be estimated, as it will come close to, and per- haps exceed, that of a concrete wall, as will appear in a comparative estimate of quantities for various cut-off structures at the end of this article. Steel curtains are described in 53, D, and it is just as essential to observe every detail of their construction as with timber curtains. When carefully placed they form an effective cut-off wall; but they are perishable, nor can their life be prolonged by any protective coating, as this would be more or less removed during driving. Steel which had been imbedded in wet clay and sand for six years was found reduced in section nearly one-half by corrosion when recovered by the author. When driven curtains are not adapted for cut-off wall, trenching must be resorted to and the question of cut-off type further examined. During trenching much valuable information is gained as to the exact subsurface formation, and advance borings from different levels will greatly add to this. When the required depth is reached, a close estimate STRUCTURAL TYPES 147 can be made as to which is the most economical cut-off, a timber curtain or concrete wall; both will give equally satisfactory results as cut-offs, as the timber sheet piles can now be placed with perfect interlocking, and their durability is guaranteed by their constant saturated condition. It becomes then solely a question of cost, which, with low-price concrete and high cost of timber, may be in favor of the former or, with values reversed, the latter may be more economical. The placing of timber curtains in the trench needs no further detail- ing nor that of the concrete wall. Trenches should be three feet wide to ten feet depth, four to twenty, five to thirty, and six to forty feet depth, in order to provide room for shoring and handling of material. Concrete cut-off walls may be uniformly three feet thick; the remaining trench-space is refilled with puddle (53, L). TABLE 9. QUANTITIES FOR CUT-OFF WALLS IN TEN-FEET LENGTHS. DRIVEN CURTAINS. Depth in feet. 6... 8.., Timber, ft. b. m. 600 800 10 .................. 1,000 12 .................. 1,200 14 .................. 1,400 16 .................. 1,600 18 .................. 1,800 20 .................. 2,000 22 .................. 2,200 24 .................. 2,400 26 .................. 2,600 28 .................. 2,800 30 .................. 3,000 32 .................. 3,200 34 .................. 3,400 36 .................. 3,600 38 .................. 3,800 40 ................. 4,000 Spikes, Ibs. 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 Steel, Ibs. 660 880 1,100 3,000 3,500 4,000 4,500 5,000 7,700 8,400 9,100 9,800 10,500 13,400 14,280 15,120 15,960 16,800 TRENCHED CURTAINS. Trenching, Puddle, cub. yds. cub. yds. 7 9 11 18 21 24 27 30 41 44 48 52 55 71 75 80 85 90 5 6 7 13.5 15 18 20 23 33 35 38 41 49 59 62 67 71 75 CONCRETE WALL. Concrete, Puddle, cub. yds. cub. yds. 11 13 15.5 18 20 22 24 27 29 31 33 35.5 38 40 42 45 5 5.5 6 7 8 15 17 19 21 22 35.5 37 40 43 45 ARTICLE 56. Foundation. When a sufficient area of the foundation site is safely coffered and the water removed by draining or pumping or both, the site is prepared by being levelled to a uniform plane, and all vegetable matter, roots, etc., removed; then the bearing piles are driven as per Plan 18 and, as specified in 53, H, to refusal. Piles must be driven with care; brooming of tops should be avoided; in hard driving timber followers should be used. In order to guard against the driving of piles 148 HYDRO-ELECTRIC PRACTICE which prove too short, or prevent waste by using those which are too long, advance borings should be made by which the character of the material and thus its penetrability can be determined with certainty. In very soft soils every other longitudinal pile row should be driven at a batter leading downstream, by which additional resistance to sliding of structure will be secured, since a downstream movement would have to be accompanied by a rising upward of pile tops and thus involve lifting of the foundation walls in which they are imbedded and of the super- structure. All piles should be driven before any of the concrete is placed, to avoid possible rupture caused by vibration due to pile driving. Pile tops are cut off on a uniform horizontal plane being that of the bottom of foundation floor. The trenching for floor walls should begin at the upstream cut-off wall, if it is a trenched structure, and only so much trench is opened as can be kept entirely free of water by pumping; the wall concrete is of x mixture and is compacted in the trench on both sides of the curtain top and covering the same. If the superstructure is to connect with the cut-off wall, as is generally the case, re-enforcing steel rods are imbedded in this cut-off concrete. The other floor walls or beams are placed like- wise successively, steel rods or dowels being imbedded in them two feet centres. This concrete should not be too wet, as the soil itself will con- tain more or less water, and as all of it should be given considerable ram- ming. The top surfaces of floor walls must be left as rough as possible. The foundation floor consists, as shown in Plan 18, of separate arches, longitudinal to the floor, the walls forming the skewbacks. Beginning at the upstream end, the soil between cut-off and first upstream wall is trimmed away to the arch form, and, the section being kept entirely free of water, the respective floor arch is laid of x concrete, the wall tops being first cleaned, roughened, and thoroughly wetted, and the concrete rammed into place. Along the top of each floor wall a groove is left free of concrete, one foot wide and deep, to form a connecting key for the superstructure, and, when the latter consists of transverse buttresses or partitions, similar grooves are formed in the floor transversely. In this manner the entire foundation floor is constructed. Quantities in such foundations for spillways of different heights are given on Diagram 12. ARTICLE 57. Superstructure. The subjects to be considered for the selection of a recommendable type are the height, length, section, char- acter of material in river bed, flood volume to be controlled, fluctuations STRUCTURAL TYPES 149 of fall, floatage and ice, legal requirements, location of the power station, availability of structural material and skilled labor, and of transporta- tion facilities to the site. The height is fixed, generally speaking, by the available power fall and the depth of water in the river at the site. The fall is to be based upon conditions prevailing when the volume of flow is that which is to be diverted, and is represented by the total fall in the stream over the reach to be controlled less the slope which will prevail in the upper pool, proper weight being given to the flood conditions. The slope or back- swell is the fall in the pond above the dam which creates the flow; this is most readily determined from the application and solution of the flow formula for a sufficient number of stream sections in the length which will be covered by the upper pool. For this purpose a contour plan of the stream valley, to the height to which the pond level is to be raised, must be available, and, assuming then section B B at some point above the dam site, the cross-section is plotted as on Plan 19, from which the wetted perimeter is scaled P = feet, the flow area to the future pond level is computed A = square feet, and the hydraulic radius is found from A -=- P R = Assuming the flow volume which is to be diverted when no water passes over the spillway as Q = cub. sec. ft., the velocity with which it passes through the section B B is V = f t. per sec. The flow formula best adapted to solve the problem is that of M. H. Bazin: R S = (a + ~) V 2 , in which R is the hydraulic radius, S is the slope of the water surface, a and b are constants expressive of the retarding influence of P, and V is the velocity of the flow. All the factors in this formula are known with the exception of S, and this is the value which is sought, as from it the fall in the pool's surface, which causes the flow toward the dam, is found. "S" can be taken from Diagrams 20 to 25 for the different river- bed characteristics, whether in rock, gravel and sand, or clay and sand. 150 HYDRO-ELECTRIC PRACTICE According to the length of the pond and the uniformity of its prism, S is determined for the centre section of lengths of 1000 feet or more, or of such as represent approximate similarity of channel in area and shape, and the slope found for it is credited to that reach, and thus the aggre- gate slope or swell is determined for the entire pool until its upper terminal is reached, which will be detected by the rapid increase of S. Example. Length of pond deduced from the horizontal plane of the produced spillway crest level is 12 miles; the flow to be diverted, none passing over the spillway, is 2600 cubic second feet, the height of the dam crest above the river surface with this flow is 20 feet ; the length of the spillway is 200 feet. For the first 5000 feet above the dam the pond lies between uniformly sloping banks and is of approximately uni- form cross areas, the perimeter is of gravel and sand formation; section A is therefore taken midway, or 2500 feet above the dam, where P = 243, A = 3466, R = 14.2, and V = 0.75, S = (0. \ 000122 + 7 - = 0.000007 ; 14.2 / 14.2 the total fall in this reach of 5000 feet is therefore = 0.035 ft. The next 3000 feet of the pond is of smaller flow area, the pond is nar- rower, the material the same; a section B is taken midway, or 6500 feet above the dam, where P = 161, A = 2500, R = 15.5, and V = 1.0, S = 0.000011, the fall in this reach = 0.033 ft. Then the pond widens again for the next 4000 feet, and at mid-section C, or 10,000 feet above the dam, P = 240, A = 2780, R = 11.6, and V = 1.0, S = 0.000009, the fall in this reach therefore = 0.036 ft. Thus for 12,000 feet of the pond the total fall or swell = 0.104 ft. In this manner the process is continued to the head of the pond, or about twelve miles in this case. From this point up the original stream condi- 151 152 153 Sand and Gravel Perimeter 154 Sand and Gravel Perimeter 155 156 20 20 157 158 HYDRO-ELECTRIC PRACTICE tions continue, which means that the velocity will be much greater and therefore also S; for instance, where P = 256, A = 866, R = 3.4, and V = 3.0, 8 = 0.00085, and thus the approximate head of the pond can be readily fixed. In addition to determining the backswell for the volume of the nor- mal flow, it must also be found for other river stages, especially for the high flow, in order that the full effect of ponding the water to a certain height at the dam may become clear. If the flood flow is, for instance, in this case = 9600 c. sec. feet, the volume passing over the spillway is 9600-2600 = 7000 c. sec. feet, or 35 c. sec. ft. per linear foot of spillway crest, the overfall being = 4.9 feet. At section A the volume of water will be increased approximately by a depth of five feet, and, assuming the banks to slope up uniformly, P = 257, A = 4500, R = 17.9, and V = 2.13, S = 0.000032, and the fall in first reach = 0.160; at section B, under like conditions and assumptions, P = 165, A = 3200, R = 19.4, and V = 3.0, S = 0.000073, and the fall in this second portion of pond = 0.219; at section C, again assuming uniform enlargement of area, P = 258, A = 3900, R = 15.1, and V = 2.46, S = 0.000067, and the fall in this reach = 0.264 : therefore the total fall in the 12,000 feet of pond = 0.643 as against 0.104 during the normal flow stage. Carrying this investigation to the head of the pond, assumed for normal stage, the flood rise at that location will become apparent, and this, compared with the known flood height at that point before the dam is erected, will show what increase will be caused by such a dam. It is the author's experience that this subject of backswell receives generally but scanty attention, and often is altogether ignored, in con- STRUCTURAL TYPES 159 sequence of which the first flood brings in its wake numerous damage claims for inundations of lands, highways, and railroad tracks, while bridges and buildings may be endangered, all of which might have been avoided had a proper knowledge of the extent of the backswell been secured before the dam was constructed, as considerable control of it can be secured by its proper design, as will appear later in this discus- sion. At any rate, the consideration of the height of the spillway is incomplete unless the backswell is fully determined. ARTICLE 58. The length of the spillway is primarily that which is required to pass the maximum flood flow within the limit of a certain height of overfall over the spillway crest, and this height will be largely determined by the elevations of the natural banks or of the embank- ments to be erected and by the volume of the flood flow ; aside from this consideration the spillway should be as short as possible. However, in alluvial formations it will generally be most advisable to make the spillway length equal to the width of the stream bed, as contracting this is always fraught with danger which will have to be counteracted by costly abutment and embankment structures. The flood flow is found from a rating table of the river's discharge compiled from flow measurements (Art. 41) or from flow computations (Art. 44) ; from this the volume to be diverted for the power develop- ment is deducted, the residue is to be passed over the spillway. The maximum overfall height having been determined, the weir discharge for this height per foot length is found (Diagram 2), the total volume to be passed is divided by this, and the quotient represents the required spillway length. Example. Flood flow assumed at = 9000 cub. sec. ft. Diverted flow assumed at = 1000 cub. sec. ft. Volume to be passed = 8000 cub. sec. ft. Maximum overfall height = 3.5 feet Spillway discharge per foot of length = 21.5 cub. sec. ft. Spillway length required 372 feet. As the spillway will be provided with waste flumes, by the aid of which the pond can be drawn down, their discharge capacity will be available for additional flood passage, and they therefore represent a safety factor in this respect. 160 HYDRO-ELECTRIC PRACTICE ARTICLE 59. The amount of pressure and resistance is the first sub- ject to be considered when the spillway section is to be designed. The pressure P of a column of water restrained in its natural passage is repre- sented by the product of the pressure area A' and the weight of water W; the area factors are height of water column H and the length of pressed surface. In Fig. 20 S is vertical, H = S, ordinates and abscissae represent factors of pressure area A' which intersect in pressure plane a b. A' = S (base) X ~ (half altitude) = -?-. - 2 When the water level is below the top of the pressed surface, the pres- sure area decreases in like ratio, both S and H being reduced by h u or H = S -- h t and A' = J (S - h)>. When the water stands above the pressed surface, the pressure area becomes a trapezoid. In Fig. 21 S is vertical, S = H - h, A' = H - h (base) X H J" h (altitude) H 2 -h 2 2 or expressed in S - + Sh. The same result is illustrated geometrically in Fig. 22, where tri- angle b g 1 represents area due to H h and S. Trapezoid b c f 1 is area Q2 when H = S + h = J - + S h, by which the rectangle b c k 1 = S h a which = parallelogram b c f g, is added to triangle b g 1. Or for expres- TT2 _ U2 sion in values of H, A' = - -, being the trapezoid b c f 1 which con- & TT2 Jj2 sists of half the square a e f 1 = -- - less half the square a b c d = . 2 A STRUCTURAL TYPES 161 Fig. 20 "ti.E.P.73 H.v.S. H tJ.E.P.74 H.V.S. T~ Fig. 22 H.V.S. Fig. 23 H.E.P.76 H.V.S. 11 162 HYDRO-ELECTRIC PRACTICE The same pressure area expressions apply when the pressed surface is inclined, but the values vary with the inclination of S. S H In Fig. 23 A' is a triangle, S is base, H is altitude; A' = -. tt In Fig. 24 A' is a trapezoid, S is base, ^ is altitude ; A' = S X . Z 2i The product of the pressure area and the weight of water (62.5 pounds per cubic foot) is the pressure "P" against the surface, which when the latter is vertical and H = S P = 31.25 H 2 .............................. F. 1 H = S -- h P = 31.25(8 -- hj 2 ........................ F. 2 H = S + h P = 31.25 (H 2 -- h 2 ) ....................... F. 3 When S is inclined and H = ,| P = 31.25 H S ....................... F. 4 V 2 H = S -- h, V2 P = 31.25 H (S - h t V2) ............. F. 5 H=l+ h P = 31.25 S(H + h) ................. F. 6 A 2 The intensity of the pressure of any volume is concentrated in its gravity plane passing at right angles to the pressed surface through its centre of gravity G. In a triangle lines drawn from apex to bisect opposite sides are gravity lines, and the centre of gravity lies at their intersection and one- third of the altitude above the base. In a trapezoid the centre of gravity is found as in Fig. 25 by extend- ing the base lines in opposite directions to equal their sum, connecting the ends of these extensions, d i, and connecting bisects of the base lines as b f ; the intersection of d i and b f marks the centre of gravity. The height of the centre of gravity above the base g e = X - (h' = altitude of trapezoid). ac + ge 3 When the pressure acts upon a body, its force is expressed by the product of its intensity and the lever arm through which this pressure is applied. STRUCTURAL TYPES 163 H.E.P.78 H.v.S. Fig. 27 K H--WJH.E.P.84 H.V.S. 164 HYDRO-ELECTRIC PRACTICE The lever arm L is the vertical distance from the pressure line to the turning point M of the pressed body. In Fig. 26 S is vertical, A' is triangle, S = H, G = ~, and, as the TT pressure passes through G in a direction vertical to S, I/ = , and the dynamic force M P = ^?, and of water M P = 10.417, H 3 . . .F. 7 In Fig. 27 S is vertical, H = S -- h u L' = ^~^ t MP = 10.417 (S - hj 3 ..... F. 8 In Fig. 28 S is vertical, H = S + h, L' = *L + 2h X | H + h 3 M P = 10.417 (H 3 -- 3 H h 2 + 2 h 3 ) ..... F. 9 Diagrams 26 to 29 give M P for different values of H and h. In Fig. 29 S is inclined; the pressure acts vertical to S at M through the lever arm I/, the value of which varies with inclination of S. In Fig. 30 P intersects M and L, therefore becomes zero, and as S becomes more inclined P intersects the base of the body. For the practi- cal solution of the dynamic forces acting on inclined surfaces the pres- sure is analyzed into its horizontal and vertical components, h P and v P. In Fig. 31 S is inclined 45 and = H \/2, P is the total pressure acting perpendicular to S; a b c d is a square of which P is the diagonal, andhP =, S = H V2,fromF. 4, P = 31.25 SH and hP V 2 31 25 H ? x Inserting value of S, = - ~~o~^~~ = 31.25 H 2 , which is the same as P in F. 1, when S is vertical and = H. The horizontal component of P equals P in Fs. 1, 2, and 3 as per height of water, no matter what the inclination of S is. The vertical com- ponent of P is the weight of the water area overlying the base e f. M P for inclined surfaces is the product of h P and L, and there- fore the same as expressed in Fs. 7, 8, and 9, to wit: when H =,| MP = 10.417 H 3 . ...... F. 7 V 2 H =S- h t V2 MP = 10.417(8 -- hj" ................... F. 8 H = I + h M P = 10.417 (H 3 - 3 H h 2 + 2 h 3 ) ........ F. 9 V 2 When a structure is to restrain water, P and M P must not only be counteracted but resisted by greater forces, otherwise the effect of these 21 H 19 18 17 16 ->.? /' // // 13 H 12 11 // /v Diagram 26 Solid Spillway Pressure Moment 10 MF| \a\ ^qo|o[4i|)4 o o o o o -o 'o ' ' 'o ' ' ' '6 H.1-]*^ H.vS 165 38| / / / j t / / ' / / - '//' ' 37 /' / T * // / X , / ' J ' ' J / . f / H 1C / / . t / / /' 35 7 / / / / / ' / / / 7 / ^ X 11 / / / ^/ % fy/j ^ 32 / / J * / 31 7 / . / / / // f 30 - / / 1/L 7 / / ~/~7i ' / ' / 1' / , > / // 2" f 7 71 /. / / / /, L I uJL // / / /// L L Ul Diazram 27 27 - / 1 I/A L L UL Solid Spillway Pressure Moment 26 H 1 Pllt U'l 25 i 77 / 1 III i 24 - I 1 lit 1 LI ti' 23 '/// 1 L-. * ] in 10(0 ft.bs IE 11, ;'s ! 22 o o O in o o o o o in o mo O O O in o in 166 52 f / / / / t /', // y ^ 51 / - J- J- f / ' / M I. ^ 5U H / ' / A V < 49 - / / / | / ff t 48 - / / '/ 47 - s ? if /' I f 46 - AS / T t / f / y> i ''"V /(' 1 A A 1 i / / / Li 'ft tf 44 A.1 - f r -J.-i.j-L / // Diagram 28 Solid Spillway Pressure Moment A?) - / III// / ' / ' A1 - / 7 /// / /._j /'// // ft H Af\ , / '/I 1 ! 1 //I if 39 - / 7 / lift /// 7 / / 75 7/ f A y ii 100< t it I F H El 81 i j 38 OOOOOOO o o o o o o o IO \O t^ 00 ^^ ^> '"'^ o o O o o 167 / / J // / j 1 / , / / / / / / / / / V t / / / / / / / / / i. / / t / / / / ]' H / . / / / 7 / / / / / u / 58 - / i f f \i / / z i/ / t 1 f f i / 7/ // I / // '/ / I i / / v/ 57 / > / *? l\ 1 < / /y< 'A / -, ' / / 7/ s ? I / J_ /A** 56 f t / // //'* / / / / / f) 1 1 / / 1 /I / t 1 f / i / / t 1 1 , / ' / ''/ I / / / t 1 /// / Diagram 29 KA _ / 1 1 /// /I Solid Spillway 34 H / / / ' I / / I 1 /'/ /, // / e^ _ / ' /'/ Pressure Moment 53 / ' III, // f / ' i I / ( \ \\\ r K KiO ft bi H I 1.1 .V > S ?: 52 o - o oooooooo oooooooo 168 STRUCTURAL TYPES 169 will be to displace the structure by sliding it along the base or any hori- zontal plane, by overturning it around its toe, crushing its material, or rupturing the structure. ARTICLE 60. Sliding would be caused by h P, which must be met by the effective weight W of the resisting body, being the product of its material weight, plus the vertical water pressure v P on its horizontal projection, and the friction coefficient "f " developed at the horizontal joints and at the base between the structure and the material on which it rests. When the structure is a homogeneous, impervious mass, its material weight is the product of its area A and the unit weight W of the substance composing it, which is not diminished by standing in water; if water enters under its base and remains there confined, an upward pressure is created which is equal to the product of the area of the base, the depth of its centre of gravity, and 62.5 pounds; if it freely escapes from under the base, no such upward pressure exists. The friction coefficient f is the proportion of ultimate friction between two masses to the perpendic- ular pressure, i.e., the weight of the upper. Ex.: if it requires a force of 600 pounds to move a 1000 pound stone resting upon a horizontal surface, f = T VA = 0.60; when surfaces are connected in any manner, resistance to sliding is represented by the cohesion of the bond or con- nection which is added to the frictional resistance. In the designs herein to be considered for spillways the structures are assumed to consist of a homogeneous, impervious mass; water is prevented from entering beneath the base; the foundation is connected to the underlying material and the superstructure is bonded to the foundation. 170 HYDRO-ELECTRIC PRACTICE Resistance to sliding is theoretically found in the weight of the superstructure plus the vertical water pressure; but in practice it is recommendable to ignore the latter, excepting in those designs which are specifically based upon gravity theory, that is when the pressed surface is inclined from the vertical. As a general rule, therefore, the weight of the structure is to equal the horizontal component of the water pressure, Aw = or > h P. ARTICLE 61. Overturning of structure is caused by the dynamic force of the horizontal component of the water pressure, h P L/, and is theoretically resisted by the moment of weight, M W, being the sum of the products of weight of structure into its lever arm, A w L, and of the vertical water pressure into its lever arm, v P L", or M W = A w L + v P L", provided the resultant of these two forces cuts the base of the structure. In Fig. 32 G is the centre of gravity of the structure, M its fulcrum or toe, O is the locus of the gravity plane in the base of the structure, O M = L the lever arm through which W acts. In Fig. 33 G O = L' is the lever arm of P or h P, O M = L is the lever arm of A w, N M = I/ is the lever arm of v P, G P = P or h P, G W = A w or A w + v P, G W = R, the resultant of h P and G W, O' = the locus of the resultant in the base of the structure. When the pressed surface is inclined, v P is credited to W as adding to the resistance against overturning, the structure being of a gravity design. The resultant must always fall into the middle third of the base, for reasons given in next article. Resisting sliding and overturning guarantees stability of position by AwL = or>hPL' and O' falling in middle third of the base. ARTICLE 62. The crushing or rupturing of the structure may be caused by the concentration of excessive pressures on parts of it. In Fig. 34 the weight W of the rectangular structure c d e f acts in the gravity plane on the centre of the base B and is transmitted to the material on which the structure rests. The pressure due to W is repre- sented by the reaction rectangle e f i j = W, in which the ordinates P, P', etc., represent the pressure and its distribution in magnitude as per length of ordinates. If the material beneath the structure does not yield STRUCTURAL TYPES 171 Fig. 32 ' H.E.P.89 H.V.S. Fig. 33 H.E.P.90 M' H.V.S. Fig. 35 H.E.P.92 H.V.S. 172 HYDRO-ELECTRIC PRACTICE to these pressures, they react on the structure, and the resistance therein developed must be sufficient to safeguard the material against crushing. Rigidity of foundation is herein presupposed, and therefore the pressures tend to crush the structure's mass. In Fig. 35 the structure is a trapezoid c d e f , W acts on the base B T> at some point near e = b; the pressure is represented by the t reaction trapezoid e f i j, The pressure is not uniformly distributed over the base, but is maximum at the end nearest to the gravity plane and minimum at the other, its ratio between these being proportional. The mean pressure ordinate lies in the gravity plane produced, because the sums of pressures on both sides of this plane are equal as represented by reaction diagram; the distribution of the pressures therefore depends upon the locus of the gravity plane in the base B and essentially on its distance from the centre of B. Fig. 36 represents the reaction trapezoid e f i j, the locus of the gravity plane is at O and its distance from the centre of the base B = b, which is determinable from the formula for distance of centre of gravity above the base of a trapezoid, to wit: e O = y = P + 2 P/ X ? (P and P' = Px and Py); substituting for P' its expression from p _i_ p/ ^^ - X B = W, y== r ( p + 4W_ 2p) ^ (p , 2W ^1B B B 'J3' solving for P, P = ~B~ B 2 STRUCTURAL TYPES p = w + 6W. b ? assigning to " b " a value of 0.1 B, B B 2 B = W , 173 p = and placing this in - B 2 P' = , which are the expressions for the maximum and B minimum pressure ordinates in the reaction trapezoid on the base of structure or on any horizontal plane of the structure, W representing the superposed weight. When b is a function of the locus of resultant of total pressures against the structure, P, P', etc., are expressions of total pressures due to structure's weight and of pressure moment of water column restrained by the structure. Fig. 36 i H.E.P.93 H.V.S. Fig. 37 H.E.P.94 H.V.S. From Fig. 37 it is evident that the distance between the locus of resultant and the centre of the base, "b", controls the distribution of the pressure. When b is = P = o B and P' = zero, the pressure distribution is then represented by the triangle e f j and the maximum, P, is double the mean pressure. This condition represents the limit within which the pressure strains are met by compression in the structure; any further moving of O from the centre of the base, or r> any increase of b beyond -, creates tension in the superstructure. 174 HYDRO-ELECTRIC PRACTICE Fig. 38 T> In Fig. 38 b exceeds --, the reaction forces are represented by a positive and negative triangle, the latter represents tension developed at the base of the structure, by which the pressure theories heretofore discussed undergo a complete change. T> This condition prevails, therefore, whenever b exceeds , and the 6 structure may then be ruptured in the portion where tension stresses are developed. Safety against crushing must therefore be secured by so proportioning the section that the maximum pressure P is within the limits of the strength of the material, while the pressure resultant R must fall in the middle third of any horizontal joint and of the base. Upon these theories the spillway de- sign must be based, the desideratum being the most economical section in area which meets the requirements, guar- anteeing stability of position and safety of structure, which practically resolves itself into obtaining a value for M W which exceeds M P by some margin called the safety factor, S f. ARTICLE 63. What a safety factor should be must be decided for each case from those conditions which are likely to become important factors in developing the resistance capacity of the structure and those which may tax it. The character of the foundation is one of these important elements, no matter what the spillway section is. It will be appreciated from the presentation of the stability theories that, with a foundation lacking in rigidity, several of the important theoretical deductions become unreli- able in fact, as stated; preventing water from entering beneath structure and placing it on an unyielding mass are essential in theorizing from causes to effects. When set upon a hard rock ledge and securely keyed into it, the structure may be regarded as having become a part of it, and it will develop its resistances to the fullest capacity. This cannot be expected in alluvial locations ; water penetration can be guarded against efficiently H.E.P.95 H.v.S. STRUCTURAL TYPES 175 by proper cut-off construction, and rigidity may be obtained by a cor- rectly planned pile-bearing foundation; but, after all, the responsibility is merely transferred to the substance in which the piles stand. In one case in the author's experience the underlying material, to the depth of fifty feet, consisting of clay and sand, bodily moved several inches down- stream; these conditions, therefore, when compared with rock location, call for fundamental increase of obtainable safety. The abutments may enhance the spillway's resistance; when these are natural rock banks, the structure, unless of considerable length, gains from them greater security than from abutments constructed in or against alluvial banks, not merely because there is less possibility of water finding a way around them, which should be absolutely guarded against, but because of the rigidity afforded by the natural bulwarks. The height of overflow is an important condition; though fully credited in the respective design in accord with sound theory, it is never- theless obvious that the larger the natural forces the greater the possi- bilities of failures. In general high overfalls are best avoided, but, where they must be reckoned with, the safety factor should be prudently adapted. Prevalence of trees and logs passing over spillway must be met by an increase in section over that normally required. In northern latitudes heavy ice is likely to form and subject the structure to abnormal thrust which finds no proper resistance factor in the theoretical design, or ice may gorge upstream of the spillway during the spring break-up, as occurred during the last winter in the Alleghany and Monongahela rivers and brought destruction to several dams. And finally the height of the spillway itself has a most important place in this category. High dams have been constructed a century or more; not so, however, with spillways; designing a structure a hundred feet or higher over which large volumes of water are pouring with conse- quential shocks of the leap of a Niagara is quite a problem apart from that of a dam of similar height restraining a pond of quiet water. It would be a serious fallacy to lay down a rule of designing spillways of any and all heights with a fixed safety factor of two or whatever measure. It is a good enough business axiom to apportion the insurance to the probable loss, and this has its place here; when the failure of a spill- way is likely to work great destruction to property and, perhaps, of human life, the possibility of such a happening should be considered sufficient reason for an increase of the safety factor. 176 HYDRO-ELECTRIC PRACTICE The following is suggested as a basis for determination of the safety factor: 1. For spillways founded on rock ledge with natural rock abutments S f = 2.00 2. For spillways founded on rock ledge with constructed abutments S f = 2.25 3. For spillways founded on alluvial material with constructed abutments ... S f = 2.50 4. For overfall in excess of 0.20 of spillway height add per foot of such excess to above 0.10 5. For each five feet of height of spillway in excess of 50 feet add to above 0.10 6. When failure would cause great destruction add to above 0.25 Example. For a spillway 40 feet high, founded on alluvial material, with maximum overfall of 10 feet, and not in close proximity (5 miles) to any settlement, the safety factor should be taken at 2.5 + 0.2 = 2.70, or a spillway 65 feet high, on rock bed, with constructed abutments and a maximum overfall of 8 feet, should be designed with a safety factor of 2.25 + 0.30 = 2.55. ARTICLE 64. Having determined the height of the spillway, the maximum overfall, and the safety factor, the theoretical design is worked out, and by rinding the smallest section in area in which the resultant falls in the middle third of the base and M W = M P X S f, the other stability requirements will be satisfied until certain limits of height are reached, as will appear in the further discussion. Fig. 39 represents sections of an equilateral triangle, the perpendic- ular being the upstream or pressed surface: condition 1, without water pressure, i.e., when the pond above the spillway is drawn down; condi- tion 2, when the water stands at the top, representative of the low stage, all the flow being diverted to the power station; condition 3, with normal overflow; and condition 4, with highest overflow under which the sta- bility requirements are satisfied. The sections are 15 feet high; their material weight is taken at 140 pounds per cubic foot; the areas contain 112.5 square feet; the weights are expressed in short tons, the pressure ordinates in pounds. T> Sec. I. No water pressure, W = 7.875, b = 2.5 = , max. pressure on 6 the base 2100 Ibs. at the upstream end. Sec. II. Water at the top of the section, M W = 78.75, M P = 17.5, b = 0.28; the max. pressure on the base = 1274 Ibs. Sec. III. Water stands 3.75 feet over the section, M W = 78.75, M P 31.6, b = 1.5, the max. pressure on the base = 1940 Ibs. Sec. IV. The water stands 6.5 feet over the section, M W = 78.75, M P = 40.0, b = 2.5 = ?, max. pressure on the base = 2800 Ibs. 6 MW= 78.75 MP =17.50 MW=78.75 MP= 40.00 178 HYDRO-ELECTRIC PRACTICE These are representative of the fluctuating forces to which a spill- way structure is exposed, from the dry pond to the maximum overflow condition, and the reaction diagrams illustrate the shifting of the pres- sures on the base from the upstream to the downstream end, being a forcible reminder of the necessity of rigidity in the foundation and correct analysis of the pressures for the overflow conditions; any rise above 6.5 feet will develop tension at the upstream end of the base and the structure will become unsafe. Fig. 40 presents the same triangular sections as in Fig. 39, but in this case the hypothenuse is the pressed surface. Sec. V. No water pressure, W = 7.875, max. pressure = 2100; Sec. VI. The water stands at the top of the section P = 5, h P and v P = 3.5, W is composed of AW = 7.875 + vP = 11.375 M Wis made up of A W I/ = 39.375 + v P L" = 74.375 M P is made up of H P L' = 3.5 X 5 as in sec. II = 17.5 R' resultant of P and W = 5 and 7.875 = 12 T> b = 2.5 = and max. pressure =1.6 tons. From this it is evident that this section will not meet the require- ments that R' fall in the middle third when water stands above it, as tension will be developed at the base and, though stability of position is amply safeguarded by a large safety factor, the structure will be en- dangered by reason of the tension stresses developed at the upstream end of base. Note that v P does not enter R', which represents the total pressure resultant, but that it is a component of M W, as M P contains h P only; also that the pressure on the upstream end of the base is zero, with and without water pressure, because of the influence of v P in the latter case. The maximum pressure is, of course, increased under water pressure. Sec. VII, Fig. 40, is a rectangle of the same area as the previous sections; its height is 15 ft., the base 7.5 ft. Water stands at its top, M W = 29.5, M P = 17.5, b = 2.22 and the max. pressure 3.17 tons with negative pressure of 0.77 ton at the upstream end. This section is apparently unstable for any water pressure condition. Fig. 40 MW=74.4 MP = 17.5 H.E.P.97 H.V.S. 179 180 HYDRO-ELECTRIC PRACTICE ARTICLE 65. The practical design of a solid spillway must conform to other conditions aside from those of stability considerations. The top of the structure will be exposed to shocks from waves, logs, and ice, and must be given commensurate thickness; the overflowing water will plunge vertically on the downstream face of the spillway and on the river bed below unless that side is so formed that the volume of maximum overflow follows the spillway face and is guided in a direction by which the river bed will be protected against the water's force. The shocks against the spillway top will be most frequent when the overflow is shallow, then logs and ice hit the structure before clearing it; under these conditions, however, the velocity of the approaching water is low and these shocks are comparatively light. When the river is in flood, the overflow depth is correspondingly great and most of the floatage then clears the crest without touching it ; the velocity of the water is, however, high, and if floatage then strikes the top the shock would represent great force. This would be the case when bridges, boat landings, and build- ings are carried away, or large trees are precipitated with the caving banks into the stream; or when log and ice jams break loose and are hurled in large masses against the structure. The force of such shocks cannot be estimated, nor can the probability of such occurrences be ignored, and it is proper to take account of these possibilities when designing the spillway. In practice reservoir dams are given a top width of one-tenth of their height, and that of spillways, generally speaking, should be twice this, i.e., the top width of the spillway should be two- tenths of the height of the spillway. The investigation is now confined to the designing of the minimum area section in which 1. The pressed surface is vertical; 2. The top width equals two-tenths of the section height; 3. The downstream face is inclined to receive and guide the overfall; 4. The safety factor against overturning, with maximum overflow, exceeds two; 5. The locus of the resultant of pressures falls into the middle third of the section base; and 6. The maximum pressures do not exceed the safe strength of the material, which will be taken at ten tons per square foot. STRUCTURAL TYPES 181 A trapezoid represents this section, which will hereafter be referred to as "the normal solid spillway section," and its proportions of design are: Crest width equals two-tenths of height; Base length equals eight-tenths of height; Upstream face is vertical; Downstream side is inclined one vertical in 0.6 horizontal; : Structure is of cyclopean, monolithic, or block concrete. Fig. 41. Spillway height S = 15 feet Crest width C = 3 feet Base length B = 12 feet Spillway area, section A = 112.5 square feet. In sec. I the upper pool is dry; stability against crushing is the only requirement to be met. The pressures are represented by the weight of the structure, which is taken at 140 pounds per cubic foot; AW = 112.5 X 140 = 15,750 Ibs. The locus of the pressure line in the base, b, is found from the height of the horizontal gravity plane G C = ^4,- X | = 0.4 S = 6 feet, and the length of the horizontal gravity plane g p = x + c = o.; then T) __ T> "D -* c\ c\ C\ Maximum pressure p ^ .R 6_Rb_ . 15750 , 170100 _ LQQ -L X. ~~~ _ "T" ~T -. ~~~~ ^ AyO IDfe* B B- 12 182 HYDRO-ELECTRIC PRACTICE In sec. II, Fig. 41, the water stands level with the spillway crest; all characteristics are as in sec. I, and H = 15 feet. Water pressure P = 31.25 H 2 7031 Ibs. q Its lever arm I/ = - 5 ft. o Pressure moment M P = 7031 X 5 = 35,155 ft. Ibs. Spillway weight W = 112.5 X 140 = 15,750 Ibs. Its lever arm L = B g P = 7.8 ft. 2 Weight moment M W = 15,750 X 7.8 = 122,850 ft. Ibs. Sliding safety factor S s f = 15,750 *- 7031 = 2.24 Overturning safety factor Osf = 122,850 -*- 35,155 = 3.5 Pressure resultant R = J3.5* + 7.875* = 8.6 tons. Locus of R in base b = 0.5 g p + O R - 0.5 B = 0.43 Resultant falls in the middle third. Maximum pressure P x = 1790 Ibs. Minimum pressure P y = 1070 Ibs. In sec. Ill, Fig. 41, the water stands 3 feet above the spillway crest; characteristics are as in sec. 2 excepting H and h H = 18 feet h = 3 feet P = 9,843 Ibs., L' = 5.713 M P = 56,243 ft. Ibs. W = 15,750 Ibs., L = 7.8 M W = 122,859 ft. Ibs. Ssf=1.6 Osf = 2.18 R = 9.27 tons b = 1.77 P x = 2,905 Ibs. All the requirements are met by this section for a spillway of any height up to one hundred feet, provided the following conditions are complied with: (a) the structure is properly founded and supported; (b) protection against underwash is effective; (c) the spillway consists of a homogeneous mass of concrete; (d) the maximum overflow does not exceed two-tenths of the height of the spillway. The normal section may be adapted to abnormal overflow by adding, for each foot of overflow in excess of the normal, a rectangular section half a foot wide to the normal section; and by reducing the normal section by a similar rectangle for each foot decrease of overfall from the normal. Normal Solid Spillway Section 184 HYDRO-ELECTRIC PRACTICE The overturning safety factor may be increased, from the normal, by the addition of a rectangle half a foot wide for each one-tenth increase of such safety factor. Deductions and Tabulation of Dimensions, Weights, and Characteristics of the NORMAL SOLID SPILLWAY SECTION. These expressions are to serve for the designing of CONCRETE spillways to the limit of 100 feet height; they have been equated for the two fundamental values, height of spill- way and of overflow, which must be fixed before the work of designing can be approached; the expressions of weights are in specific gravity = 140 -f- 62.5 = 2.24. A = B + C X S =0.5 S 2 ^ *W = 2.24 A = 1.12S 2 A , = EL_h x g = i^_s j-_q^s x s = 07 s , 2 * P = A' =0.7 S' T , H + 2h S H + h S 3 1.2S + 0.4S V S 1.6S' = I^ST 072 S X 3 = 4^S ' _ 6h +Jh 5h _ 40h' _ 6h + h 3 21 h B + 2C V S . 0.8S+0.4S X S.. 04S "FTC^ X 3 "S s 3 ' expressed in h = 2 h g p = 0.56 S expressed in h = 2.8 h L = B - 0.5 g p = 0.8 S - 0.28 S = 0.52 S expressed in h = 2.6 h * M P = LT = 1.905 h X 0.7 S 2 = 1.33 h S 2 *MW = LW = 2.6 h X 1.125 S 2 = 2.93 h S 2 * Apply multiplier 62.5 to find weight in Ibs. STRUCTURAL TYPES 185 * R = ^ P + W* = 0.7 S< + 1.125 S< = 1.325 S' g PL' B = 2 P "W" " 2 = 0.28 S + ' - 0.4 S = 0.118 S R , 6Rb_ 1.325S' , 0.7 S X 1.325S'_ o 11c = B H B^ ~08S~ ~ 064^~ TABLE 10. CHARACTERISTICS OF THE NORMAL SOLID SPILLWAY SECTION. C = 0.2S, B + C = S, h = C, Osf = 2.2 tA = 0.5S 2 i = 0.5S(S-n) = 0.5S(S-fn) A' = 0.7S 2 =0.7S 2 -nS = 0.7S 2 + nS W = 1.12S 2 =1.128 (S-n) =1.128 (S+n) P = A' GC = 2h = 2(h + 0.95n) =2(h-0.95n) g p = 0.56 S = 0.56 (S - 0.8 n) = 0.56 (S + 0.8 n) L = 2.6 h = 2.6 (h + 0.9 n) = 2.6 (h - 0.9 n) L' = 1.905h = 1.905 (h + 0.9 n) = 1.905 (h - 0.9n) SSf = 1.6 S f = 2.18 to increase O S f by 0.1 add 0.5 S to the section. ARTICLE 66. The shaping of the crest, of the downstream face, and of the toe of the spillway are the remaining features to complete the practical design. The crest's upstream edge should be slightly rounded, without, however, giving it an up-slope of any length, the purpose to be attained being to prevent the lodgement on or against it, during low overflow, of floatage; the square edge would be permissible were it not for the likeli- hood of its chipping off. From the downstream end of this quarter-round of its upstream edge the crest should be inclined downward at about half an inch per foot. The downstream edge of the crest should be on a curve of a radius 2 C 2 C equal to - J the point of curve being from the upstream face plane, o o and the point of the tangent in a horizontal plane, one foot below crest * Apply multiplier 62.5 to find weight in Ibs. t For normal overflow; J for less than normal overflow; for more than normal overflow; n is feet of abnormal overflow. 186 HYDRO-ELECTRIC PRACTICE point; this curve will be slightly fuller than the parabola of the upper film of the overfalling water, the purpose being to secure a shape of crest to which the falling water will constantly adhere in its passage over it. The same argument underlies the inclination to be given to the down- stream face, a condition which, as will be seen, is fully met by the normal section. Fig. 42 shows the parabola C P T in which the ordinates m a, n b, o c, etc., represent the velocity of the water V = ^/2gh, h being the height of overflow, and the abscissae m m, n n, o o, etc., the fall of the water, H = 0.5 g t 2 , H being height of fall, and t time in seconds; from this will be seen that the downstream incline of the normal section prac- TT tically parallels the parabolic curve up to a point Q about -- above the base when the produced spillway face and the parabolic curve approach. This is the point from which the downstream face tangent should be g changed into a curve of a radius equal o forming the toe of the spillway, t the latter having base and altitude equal to 0.1 B; the water on passing from the toe has assumed a horizontal direction and its force is spent upon its own element. The change in area from the normal section due to the shaping of crest and of the toe is represented by the addition of 0.025 A to A. ARTICLE 67. Gravity spillways are types in which the vertical com- ponent of the water pressure is utilized as one of the resistance factors, the upstream face being inclined, resembling section VI, Fig. 38, Art. 64. The analysis of the inclined surface, triangular section, has shown that it lacks in stability when the water stands at the top of the section, because the gravity line, and consequently the resultant, falls too close to the turning point, and this can be overcome only by the addition, to the triangular section at its downstream side, of a rectangle, by which, however, the total section area becomes considerably larger than that of the normal solid spillway section. For this reason a solid section, with an upstream inclined face, is not an economical design, and in order to take advantage of the vertical pressure factor the section must be designed, in part at least, hollow. Timber spillways have been built on this principle for many years, the upstream face being inclined 45 and flatter, but were confined to low structures only; the development of reinforced concrete structures, C m _n o P 4 r _ s t__u___C* ^ -T. r 4:- j * 1 13 Fig. 42 Solid Spillway Crest and Toe H.E.P.99 H.V.S. 187 188 HYDRO-ELECTRIC PRACTICE however, has in recent years broadened the practical application of this principle to spillway designs. Fig. 43 shows a triangular section, I, with its upstream surface in- clined 45, to which is added a rectangle, II, of width equal to the height of the overflow, and to this a downstream triangular section, III, of such inclination that the overfalling water will adhere to it, as found in Article 66, Fig. 42. Height of section .......... S = 15 feet Pressed face deck .......... D = S %/2 =21.21 feet Top or crown .............. C = 0.2 S = 3 feet Downstream side, apron... Ap = JS 2 + (0.6 S) 2 = 17.5 feet Base of sec. I ............. B' = S =15 feet Base of sec. II ............ B" = C = 3 feet Base of sec. Ill ........... B'" = 0.6 S =9 feet Total base ................ B = 27 feet Overflow .................. h = 0.2 S = 3 feet Total height of water ....... H = 1.2 S =18 feet Pressure /actors: A/ n v H + h q /2 1.2 S + 0.2S Pressure area ............. A' - fe v ^ X - = 0.7S 2 \/2 225 sq. ft. Pressure .................. P = A' X 62.5 = 14,062 Ibs. Horizontal component ofP =hP = P-^\/2 = 9,500 Ibs. T , H+2h v D /0 Pressure lever arm ........ I/ = - - X -- v * n. + n o 1.2 S + 0.4 S S v/2 " L2 S + 0.2 S 3 4.2 S Pressure moment ......... M P = P L' = 54,283 ft. pds. Resistance factors: Assuming D, C, Ap to be a concrete-steel shell one foot thick, and omitting for the present the weight of the reinforcing steel: Weight of D is Dw = 21.21 X 140 = 2969 Ibs. Weight of C is Cw = 3 X 140 = 420 Ibs. Weight of Ap is Apw = 17.5 X 140 = 2450 Ibs. = 5,839 Ibs. Lever arm of D is DL = B - 0.5 B' = 19.5 feet Lever arm of C is CL = 0.5 B" + B'" = 10.5 feet Lever arm of Ap is ApL = 0.5 B'" = 4.5 feet STRUCTURAL TYPES 189 Structure's weight moment = Dw X DL + Cw X CL + ApwXApL = 75,530 ft. pds. Vertical water pressure = hP = 9500 Ibs. = and its lever arm = B - L" = 21.37 its moment = vPL" Sliding safety factor, SSf = W + vP -=- hP 1.6 Overturning safety factor = WM + vPM ^ hPM = 5.2 without WM, OSf 3.8 203,015 ft. pds. and this is the distinctive principle upon which gravity spillway designs are based, namely the ratio of L" : L', 21.375 -f- 5.625 = 3.8. " Fig. 43 H.E.P.100 H.V.S. D' Fig. 44 H.E.P.101 H.V.S. Fig. 44, Locus of Resultant. The height of the statical moment G C is the same as in a solid body; GC = 8 B + C ? 9 Q d Zi.A \j ., \3 28 3 its locus is in mm', connecting the bisects of B and C, and is algebraic- ally determined from DD' : Dg = D'E : gn Dg = S - GC V2 = 0.634S V2 = 13.44 D'E = 0.5B - 0.5C = 12 DD' = D = 21.21 gn = 13.44 X 12 H- 21.21 = 7.6 gP = (gn + 0.50)2 = 18.2 190 HYDRO-ELECTRIC PRACTICE Fig. 45 The force diagram is projected by producing P to its intersection with the gravity line at M, laying off MN = W, and completing the parallelogram MNOP, in which the diagonal R represents the resultant of all pressure and R' its locus in the base. Both pressure lines PM and R cut the base in its middle third. Theoretically this gravity section is therefore safe of position. It now remains to be inquired how the parts of the struc- ture must be designed to meet the strains to which they will be exposed. The up- stream face, the deck, may fail under the superimposed weight .of the water, and it must be divided into separate spans, fixed at their ends to suitable supports, when they will represent the conditions of a uni- formly loaded beam secured at its ends. The bending moment on the centre of such a beam is expressed by Mo = - , in which Q is the product of pressure per foot into length of span in feet, 1 is the length of span in inches. The pressures due to the various heights of the water at different points on the deck are shown by the force lines Pb, PC, Pd, etc. on Fig. 45 Pb at the crown with overflow = 5 ft. = bn X 62.5 = 5 X 62.5 = ab X tan a X 62.5 = 312.5, also a b = ^ b n 2 + an 2 bn = an = 5 ft. = 7.071 ab = A (bn 2 )2 = bnV2 = 5 tan a = b m -j- ab b m = b n =5, tan a = 5-r-5V2 = - 62.5 tan a = 62.5 - V 2 = 44.19 Pb, PC, Pd, etc., are = ab + 7 ft. sections X 62.5 tan a, or Pb = (ab + 7) X 44.19 PC = (ab + 14) X 44.19, etc., as per Table 11, MOMENTS FOR SPANS 1 OF Spillway Pi 10ft. 12ft. 14ft. height. 26.0 31,200 44,928 61,152 Crown 51.8 62,160 89,510 121,834 5 feet 77.6 93,120 134,092 182,516 10 feet 103.4 124,080 178,676 243,196 15 feet 129.1 154,920 223,084 303,644 20 feet 154.9 185,880 267,668 364,324 25 feet 180.7 216,840 312,250 435,006 30 feet 206.5 247,800 356,832 485,688 35 feet 232.2 278,640 401,242 546,134 40 feet 258.0 309,680 445,824 606,816 45 feet 283.8 340,572 490,406 667,498 50 feet 309.6 371,520 534,989 728,179 55 feet 335.3 402,360 579,398 788,626 60 feet STRUCTURAL TYPES 191 in which P is this pressure per square foot, P t per square inch of one ft. of beam, and M the moment of external forces, heretofore analyzed, expressed for beams of 10, 12, and 14 feet spans. TABLE 11. CONCRETE-STEEL GRAVITY SPILLWAYS; OVERFLOW = 5 FEET. Moments of Bending Forces. a, P b 312.5 c 621.8 d 931.1 e 1240.4 f 1549.7 g 1859.0 j 2163.3 k 2477.6 1 2788.9 r 3096.2 s 3405.5 u 3714.8 v 4024.1 The external forces must be met by the ultimate resistance of the material of which the beam is constructed, which, for reinforced concrete, is expressed, as per Article 53, O, by Mo = 5505 t 2 , in which t is the thickness of the beam in inches, provided the area of the imbedded steel, per foot of beam width, q = 0.132 t. When Mo = M, the conditions represent theoretical equilibrium, and, in order that the structure may be safe, Mo should be greater than M by a safety factor of not less than "four." To determine t, the thickness of the deck, in this case, for example at point Pb : M = for 10 ft. span 62,160 inch pds. 4 M = 248,640 = 5,505 t 2 t = ^ ^48,640^^^5505 = 6.72 inches, and q = 6.72 x 0.132 = 0.887 square inch steel These values for t and q at points in the deck, designated as b, c, d, e, etc., applying to different heights from the crown downward, are given in Table 12 for 10, 12, and 14 feet spans. 192 HYDRO-ELECTRIC PRACTICE TABLE 12. CONCRETE-STEEL GRAVITY SPILLWAYS; VALUES OF t AND q. Spillway height. Crown 5 feet 10 feet 15 feet 20 feet 25 feet 30 feet 35 feet 40 feet 45 feet 50 feet 55 feet 60 feet If the supports of the deck spans take the form of partition walls, filling the entire space of the interior of the spillway shell as shown in Fig. 46, and are properly designed to take up and transmit the stresses to the foundation, as per section on Fig. 46, the quantities of the concrete and of the. reinforcing steel required are those given in Table 13. The partition walls may be constructed of x concrete, all the other parts are of xx concrete. The distribution of the reinforcing steel is also shown in Fig. 46. TABLE 13. CONCRETE-STEEL GRAVITY SPILLWAY; MATERIAL BILL FOR 10 FEET OF SPILLWAY ACCORDING TO THE DESIGN PER TABLE 12 AND FIG. 46. >ans. 10ft. t. q. b 4.76 0.628 c 6.72 0.887 d 8.23 1.086 e 9.49 1.253 f 10.61 1.400 11.58 1.529 i. . 12.55 1.657 k 13.42 1.711 1 14.23 1.878 r 15.01 1.981 s 15.73 2.076 u 16.43 2.168 v. . . 17.10 2.257 12ft. t. q. 5.71 0.754 8.07 1.065 9.87 1.303 11.39 1.503 12.73 1.680 13.95 1.841 15.06 1.988 16.12 2.128 17.08 2.255 18.00 2.376 18.88 2.502 19.72 2.603 20.52 2.709 14ft. t. q. 6.67 0.880 9.41 1.242 11.52 1.521 13.29 1.754 14.85 1.960 16.27 2.148 17.78 2.347 18.79 2.480 19.92 2.629 21.00 2.772 22.02 2.907 23.00 3.036 23.94 3.160 Heieht.feet. X Concrete : 10 feet span : cub. yds. 1 ft. rise. 10 ............................ '7.2 1.00 20 ........................... 17.2 2.09 30 ........................... 38.1 3.25 40 ........................... 70.6 2.90 50 ........................... 99.5 4.25 60 ........................... 142.0 ---- 12 feet span : 10 ........................... 6.9 0.97 20 ........................... 16.6 2.11 30 ........................... 37.7 3.24 40 ........................... 70.1 2.89 50 ........................... 99.0 3.58 60 ........................... 134.8 ____ 14 feet span : 10 ........................... 6.5 1.12 20 ........................... 17.7 2.14 30 ........................... 39.1 3.21 40 ........................... 71.2 2.59 50 ........................... 97.1 3.31 60... . 130.2 XX Concrete : cub. yds . 1 ft. rise. 8.0 1.52 23.2 0.99 33.1 1.06 43.7 1.16 55.3 1.22 67.5 10.3 1.43 25.0 1.12 36.2 1.07 46.9 1.10 56.9 1.13 69.2 10.8 1.70 17.8 1.30 40.8 1.31 53.9 1.42 68.1 1.54 83.5 . > Reinf. Steel : Ibs. 1,230 2,690 4,190 6,050 8,190 10,340 1,600 2,990 4,650 6,760 9,100 11,660 1,760 3,430 5,100 7,370 9,860 12,520 1 ft. rise. 146.2 150 186 214 215 139 166 211 234 256 166 167 227 249 266 Fig. 46 Gravity Spillway Distribution of *//*/-///fia&. Partition Supports 193 194 HYDRO-ELECTRIC PRACTICE When a gravity spillway of this type is erected on a hard rock bed, its downstream face, the apron, need not be carried to the spillway toe, but may be shortened one-third or one-half, the chief consideration being whether the vertical fall of the water, passing over the spillway, from the end of the foreshortened apron face, will cause erosion of the bed rock and thereby weaken the structure's footing. A partial apron design is shown in Fig. 46; the reduction in material for this type, as compared with quantities in Table 13, consists of about 4 cubic yards of xx concrete and 600 pounds of steel for 10 feet of structure. TABLE 14. CHARACTERISTICS OF THE CONCRETE-STEEL GRAVITY SPILLWAY. Deck, D = S V2 = 1.414 S. Crown, C = 5 feet = 5 feet. Apron, Ap = S V1.36 = 1.166 S. Base, B = S + C + 0.6 S = 1.6 S + 5. Crown is 3 feet thick. Apron is 1 foot thick. Partitions, from top down for each ten feet height, are respectively 12, 14, 16, 18, 21, and 24 inches thick. Thickness of deck is as per Table 12. Steel in deck is as per Table 12. Steel in crown, apron, and partitions is as per Fig. 46. The form of the crown and of the apron toe are in accordance with the theory presented for solid spillways in Article 66. ARTICLE 68. The Open Spillway. The overflow, as has been noted, is an important factor in determining the spillway section, one of its influences being to increase it in area, while the ever-present possibility of the exposure of the spillway to fluctuating pressure strains from this source is, broadly speaking, an undesirable condition. Failures of spill- ways, in the majority of cases, can be traced to excessive overflow; any arrangement, therefore, which allows of some control of the overflow and thereby reduces the pressure fluctuations is a very desirable one. When the rise in the upper pool level becomes of practical utility as a power function by offsetting a corresponding rise of the lower level, thus maintaining a constant power head, this condition must be consid- ered in arranging for the permanent lowering of the overflow. If some of the upper portion of the spillway were removed at the approach of the high water, the excess flow could be passed inside of the spillway height, or nearly so, and the section would not have to be de- signed for the excessive overflow height; furthermore, the lowering of the STRUCTURAL TYPES 195 Fig. 47 Overflow Sluice H.E.P.104 H.V.S. overflow height would materially reduce the upper pool flowage area, which will represent an appreciable economy in the cost of the development. The effect upon the overflow by the lowering of a portion of the spillway appears from the following example. Given a spillway 200 ft. long and 30 feet high, the normal or power flow is 2000 cubic second feet and the flood discharge 10,000 sec. ft.; therefore the maximum volume which passes over the spillway is 8000 sec. ft., and the overflow is 5.2 feet. The discharge through a rectangular opening at the spillway top, Fig. 47, is Q = 0.62 CA^2gh, where C is a coefficient = 0.60, A the area of the opening in square feet, h the height of the water above the sill of the opening. If h = 16 ft., Q = 3 A V16 = 12 A. A = 8000 -5- 12 = 667 sq. ft. Therefore an opening of about 42 feet length and 16 feet height or two openings each 22 feet long and 16 feet high would discharge the flood flow, practically none passing over the spillway crest, and if these openings are closed during the normal flow periods the required power head may be constantly maintained. If openings are made near the base of the same spillway the discharge through them, Fig. 48, is Q = C A ^/ 2 g h, where C is a coefficient of dis- charge through a submerged orifice, A is the area of the opening in square feet, and h is the height of the water surface above the centre of gravity of the opening. For this purpose C is taken at 0.75. Fig. 48 Underflow Sluice 196 HYDRO-ELECTRIC PRACTICE If the opening is 6 feet high, the head h = 27 feet measured from the crest of the spillway and Q = 6AJ27 = 31. 2 A A = 8000 -5- 31.2 = 256.4, and the flood volume of 8000 sec. ft. would be discharged through five openings each 9 feet wide and 6 feet high. The theory of efflux from orifices is developed in Article 74. This is the theory upon which the design of the open spillway is based. The devices by which this result can be realized may be classified as (1) Overflow sluices, being separate openings in the top of the spill- way; (2) Underflow sluices, which are similar openings at the base of the structure, and (3) Movable weirs, representing continuous openings along the top of the spillway. Any of these must be arranged to be readily opened and closed; they should form a water-tight wall of safe strength when closed, be simple of construction and operation and economical in cost and maintenance. The closing devices may be classified as stop-logs, drop, lift, and revolving gates, vertical and horizontal valves, needles, wickets, shutters, and bear-traps. Overflow sluices, Fig. 49, are formed by masonry piers, steel or timber trestles, placed upon and secured to the body of the spillway structure; the openings, as has been shown, are determined by the volume of the water to be discharged; an operating platform is placed upon the piers or trestles. The sections of the sluice supports are so designed that the pressures and bending forces against the closed sluice spans and against their own pressure faces are safely resisted; lateral pressures need not be considered, since the accumulation of pressure heads against support sides is readily avoided. Stop-logs, Fig. 50, may be employed to close overflow sluices; they are square timbers placed horizontally one upon another in the sluice span, their ends resting against shoulders arranged in the supports; they are operated by hand or mechanical devices from the operating platform, and can readily be formed into a water-tight curtain. STRUCTURAL TYPES 197 Needles, Fig. 51, are stop-logs placed vertically side by side, footing against a sill secured in the sluice bed, and supported on the top by horizontal strain members or the platform. They are not as readily manipulated as are stop-logs of the horizontal type, and it is also more difficult to make them water-tight. Fig. 51 Needles H.E.P.108 H.V.S. Valves, Fig. 52, are timber or steel framed shutters revolving around vertical or horizontal steel shafts, their ends set in side supports or in sluice bed and top strain member, and they close up against the sluice supports and sill; they are operated by hand or mechanically, but it is difficult to prevent leakage along their sides and bottom. 198 HYDRO-ELECTRIC PRACTICE Gates, Fig. 53, may be vertical lift, drop, or revolving; they are of timber or steel frames and sheeting and are generally operated by power. Lift and revolving gates must remain suspended above the sluice span when open, requiring extra high supports, or they may be lowered into recesses arranged in the spillway masonry; in the first case they are exposed to the wind pressure and the supports must be designed in accordance; in the latter arrangement the recesses in the spillway are likely to be filled with sand. Gates form effective closing devices and can easily be made water-tight. Shutters, Fig. 54, are constructed of timber or steel and are hinged to a sill; they may also be arranged to operate automatically by folding or dividing them into two or more parts hinged on opposite sides of the sluice bed. When water from a higher level is let in underneath them, they will rise in "A" shape, and may be maintained in that position until the water is withdrawn, when they fall down on their beds. Bear-traps are of this general design. Underflow sluices, Fig. 55, are openings cut out of the spillway body near its base, and may be of rectangular, square, or circular form; they may be closed by lift gates or valves operated from above. Movable weirs, Fig. 56, are devices filling the entire top of the spill- way or the greater portion of it, and consist of separate steel trestles placed transversely of the spillway and hinged to the sluice base. When down they lie in a recess formed in the spillway masonry ; to erect them the first trestle is raised to a vertical position by means of chains from the abutment or pier and secured by some automatic locking arrange- ment; after placing a foot-bridge from this first trestle to the abutment or pier, the second trestle is similarly raised, and so on. Trestles are spaced from 8 to 16 ft. centres and their upstream faces are covered with needles. They may be lowered in the same manner as described for their raising. Shutters and bear-traps may also be utilized for movable weirs. STRUCTURAL TYPES 199 The results aimed at with the open spillway type are to afford ready control of the overflow, to maintain the power head as constantly as practicable, and, generally speaking, to reduce the overflow height, and to accomplish all this without any waste of the water by leakage. It is evident that the ideal flow control will be secured when the over- flow height is reduced by horizontal sections of the smallest areas; sim- plicity and economy of the device and of its operation are of like impor- tance. While the movable weir probably represents the most complete method of accomplishing this, it is also among the most costly and complicated and cannot readily be made water-tight; its field of use- fulness is rather for navigation works than power plants. Both the over and underflow sluices meet the requirements, the first for the solid, the latter for the gravity spillway. For gravity spillways the underflow sluice may be a concrete culvert or a steel plate pipe, the intake being fixed in the deck, the sluice passing through the spillway along its base and terminating at the apron toe; the flow through them can be controlled by valves operated from the interior of the spillway. In solid spillways the underflow sluice is inaces- sible and weakens the structure by reducing its mass at the point where it is most required. 200 HYDRO-ELECTRIC PRACTICE The overflow sluice forms the most recommendable type of the open spillway, and its closing is best arranged by stop-logs. The sluices should be designed of rather small than large areas, as the narrower spans require shorter stop-logs which are therefore more readily handled. Example. The flood flow is 3000 cub. sec. ft. ; the spillway is 200 feet long and the overflow limit 2 feet. The spillway discharge aggregates 1700, and the balance of 1300 cub. sec. ft. is to be passed through overflow sluices. The overflow sluice area required to discharge 1300 cub. sec. ft. is from Q 3 A V h with h = 6, a = 180 (practically) . The programme is to divide the total sluice length of 30 feet into suitable units which will be taken at 10 feet; the loca- tion of these three sluices should preferably be near the end where the power station is situated, without, however, interfering with the tail-race outflow, if the station is near the spillway. The sluice supports are, most economically, concrete piers of the same section as that of the spillway, with shoulders arranged vertically in their sides to serve as stop-log supports, which may be as close to -the upstream face of the spillway as practicable. The sluice pier then becomes a section of the upper six feet of the spillway section, at the base of which the length of the horizontal transverse plane Fig. 55 Underflow Sluice H.v.S. STRUCTURAL TYPES 201 is 9.6 feet, this becomes the base of the sluice; the thickness of the pier is determined from the pressures and bending forces against the sluice span which are transmitted to the pier as the end support of a beam of the length of the span. For a span of 10 feet length, pressure P = 6 2 X 31.25 = 1125 Ibs., and for 10 feet, representing one-half of the two adjacent spans, P = 11,258 Ibs. For a pier three feet wide, the pressure per foot P = 3750, to which is added the pressure against the pier 1125; total pressure against one foot of the pier = 4875 Ibs. The depth of the sluice is taken at 6 feet and the piers should be raised about 2.5 feet to elevate the operating platform to a safe height. The pier becomes 8.5 feet high and its area = 59.5 sq. feet. the weight, at 140 Ibs. per cub. ft = 8330 Ibs. The pressure lever arm = 2 ft., and the weight lever arm = 5.9 ft., Pressure moment is 9750 ft. pds. Weight moment is 49147 ft. pds. Sliding safety factor =1.7 Overturning safety factor =5 The bending moment at end supports of 10 ft. span = 112,500 inch pds. and for the intermediate pier between two sluices = 225,000 inch pds., which is resisted by the working shearing strength of concrete taken at 75 Ibs. per square inch; the pier required therefore is =21 square feet; that of the assumed section is = 28.8 square feet. As a matter of fact, no economy is secured in this case, or when the required sluice length is only a small portion of the spillway length, by confining the thickness of the piers to their theoretical design, a broader pier can be constructed for less cost by permitting of the use of cyclopean concrete; but when the sluice lengths nearly take up the entire spillway, as may be the case when the spillway occupies a narrow gorge, the pier design is thus determined. The thickness of the stop-logs is found from the bending moment at the centre of a beam supported at the ends, for this case, and the lowest beam, P = wh = 62.5 X 6 -375. The bending moment M = PI 2 12 -i- 8 202 HYDRO-ELECTRIC PRACTICE = 375 X 10 2 X 1.5 = 56,250 inch Ibs. The fibre stress of pine being taken at 2000 Ibs. per square inch, M = Fbh 2 -4- 6, b is the breadth (12"), h the thickness, therefore h = A /M -7- 2 F = 3.8 (appr.). In practice the log is 6" X 12". The operating platform may be of 3-inch planks with guard-rails; the stop-logs can readily be raised and put in place by the aid of hand tools or by hand-power winches. Fig. 56 Movable Weir H.E.P.113 H.v& Plan These represent, in the author's judgment, the three important practical spillway types, and in the light of all that has been presented regarding them the closing consideration can now be approached. ARTICLE 69. In determining the spillway type to be adopted for any specific case, adaptability, first cost, and maintenance are the weights, in their logical sequence of importance, to be applied to the inquiry; and the conditions which must guide the choice to one of these three as the best suited are the character of the river bed, the height of the spillway, and the flood volume. The river-bed formation may, for this purpose, be classified as hard and soft, rock and hard alluvial material being embraced in the first and all other alluvial composition under the second ; for the former bearing foundations may generally not be required, while they are essential for any spillway in the soft locations. The spillway STRUCTURAL TYPES 203 height and consequential weight of the structure may have some influence, so will the volume of flood flow, the latter especially as between the open spillway and the other types. Example 1. A 30-feet-high spillway, 200 feet long, is to be erected in a rock river bed; the flood flow excess over the power volume is 8000 sec. ft. The solid type is adapted to these conditions, the overflow being 5.2 ft., or inside of the normal section limit, it contains 3330 cub. yds., and may be constructed of cyclopean concrete in which the ratio of mans tones of 8 cub. ft. volume to concrete is about 1:3, or the material consists of about 1110 cub. yds. of manstones and 2220 cub. yds. of xx concrete. Manstones, if delivered at site for $2.50 per cub. yd., may be estimated at $3.50 per cub. yd. in place; with cement delivered at $2.50 per bbl., sand $1.00 per cub. yd., gravel or broken stone at $0.75 per cub. yd., forming timber at $25.00 per M ft. b.m., skilled labor $4.50 per day and common labor $0.20 per hour, xx concrete may be estimated at $7.00 per cub. yd. in place. The estimated cost of the spillway superstructure then is for 1110 cub. yds. of manstones at $3.50 $3,885 2220 cub. yds. xx concrete at 7.00 15,540 $19,425, being practically $100 per lin. ft. of structure, coffering, preparing bed and foundation not being included. The gravity spillway of the design given in Article 67 is adapted to these conditions, the overflow being only slightly above the standard therein fixed; the material contained in it for 12 ft. deck spans, accord- ing to the design of Article 67, consists of 763 cub. yds. x concrete, 724 cub. yds. xx concrete 93,000 Ibs. reinf. steel. At the same unit cost of material and labor above quoted, x concrete may be estimated at $10.00 per cub. yd. in place, xx concrete may be estimated at 12.00 per cub. yd. in place, and reinforced steel estimated at 60.00 per ton of 2000 Ibs. 204 HYDRO-ELECTRIC PRACTICE The estimate for the gravity spillway will then be for 762 cub. yds. x concrete at $10.00 $7,620.00 724 cub. yds. xx concrete at 12.00 8,688.00 46.5 tons of reinf. steel at 60.00 2,790.00 $19^098.00 or practically the same amount as the estimate for the solid type. The open spillway for these conditions has already been detailed, and the material required in it consists of that given for the solid type less the quantities represented by the three sluice areas, or about 37 cub. yds., which, being divided between manstones and concrete at the stated ratio, makes the estimate 1098 cub. yds. manstones, $3.50 $ 3,843.00 2197 cub. yds. xx concrete 7.00 15,397.00 $19,222.00 and for three sets of stop-logs and the operating platform 250.00 $19,472.00 which is also practically the same estimate as the former two. The maintenance will be very small, if any, for the solid and the gravity type, and only that for the renewals of stop-logs in the open spillway. Operating charges are alike for the first two, while the open spillway calls for constant attention, which, however, when the power station is near or at the spillway, can readily be furnished by the station personnel, but if the station is at a considerable distance from the spill- way, an attendant should be located at that point. Summing up the comparison for the rock location, it appears that each of the three types is adapted to the requirements, that the first cost of all three differs but slightly, and that neither the solid nor the gravity type involves any maintenance or operating charges, which, however, is the case with the open spillway; whether the advantage afforded by the last in controlling the flood flow, reducing the flowage areas, and removing one of the most common causes of danger to spill- ways is of sufficient weight to recommend it in preference to the others must be decided largely from the typical conditions of the case to be served. In this connection it is well to note that the open spillway STRUCTURAL TYPES 205 arrangement affords a ready opportunity to utilize the storage capacity of the upper pool in low-flow periods by accumulating water during the non-operating period of the plant. Example 2. The same structure is to be erected in a soft alluvial location, for which the former comparisons will prevail, with the addition of the foundation cost, which will be somewhat higher for the gravity type than for either of the other two, or practically in ratio to the width of the spillway base, which, according to the designs herein outlined, is 27 feet for the solid and open and 53 feet for the gravity spillway; the cost of coffering is also likely to be greater for the structure with wider foundation. Example 3. When the height of the spillway exceeds 30 feet, a new element enters the search for the most recommendable type, that is, the location therein of the power equipment. The specific treatment of this programme will be found in the description of power stations in Article 78; suffice it to state here that for such spillway requirements, in connection with the direct development programme, the arranging of the power station in the interior of a gravity spillway is perfectly practical, and represents a considerable saving in the first cost of the plant and, in addition, secures the highest obtainable efficiency from power functions, flow and fall. ARTICLE 70. Timber spillways have played an important part in the mill-power plants of the past, and, while the advent of concrete construction and the rapid increase of the cost of timber have well-nigh discontinued their use, occasions may arise where they deserve consid- eration. For low-fall developments in localities where timber is plentiful while concrete material is not so, transportation facilities being limited, this type may prove recommendable because a masonry or concrete structure would be prohibitive in cost. The chief objections to timber spillways are the difficulty of constructing and maintaining them water- tight and the cost of keeping them in repair. As timber is preserved best when constantly saturated, it would be preferable if water passed through and over such a spillway at all times ; but when the conserving of all the flow for power purposes is a fundamental requirement of the develop- ment programme, as will often be the case, this safeguard against early decay of the timber must be forfeited and the limit of the structure's endurance becomes a factor in the determination of its availability, that is, the maintenance cost of a timber spillway should be taken at 206 HYDRO-ELECTRIC PRACTICE not less than five per cent, per annum of its first cost, whereby it could be practically renewed in twenty years. The stability of timber spillways is determined in like manner as of the types heretofore considered, that is, sliding and overturning must be resisted by the weight of the material with which the framed structure is filled, which may be rock, gravel, or sand, a mixture of the latter two being preferable because it represents the most compact mass. The weight of such a fill may be taken at about 94 pounds per cubic foot, or for the purpose of stability discussion at 1.5 that of water. In a crib structure of 8 feet bays the ratio of timber to filled area is about as 1 to 4. The design of the timber spillway should be adapted to uniformity of shaping and framing the material. The upstream face may be vertical or inclined; the downstream side should conform to the inclination found to represent closely the parabolic curve of the overfalling water, but for structural reason it is best formed in steps of short threads so that floatage will not strike them; the rise of the steps should be of even number of feet to facilitate uniform framing, the threads should be of a width to make up the desired slope. Fig. 57, section 1, suggests a timber crib spillway design in which S is vertical, B = 1.5 S, C = 0.5 B, and the stepping is arranged to form the standard overfall slope S = 20 ft., B = 30 ft., C = 15 ft., A = 408 sq. ft., mean area of timber per lin. ft. = 86 sq. ft., mean area of fill per lin. ft. = 322 sq. ft., P' = 0.7 S 2 X 62.5 = 17,500 Ibs., W = 322 X 94 = 30,268 Ibs., SSF = 1.7, L' = 24 + 8 -s- 24 + 4 X (20 -*- 3) = 7.65, MP = 17,500 X 7.65 = 133,875 Ibs. The irregularity of the timber and fill distribution renders a precise determination of L impracticable ; if the body is considered as of a homo- geneous mass, the form being transformed into a rectangle of similar area, or 20 feet high and 22.5 feet long, the error as relating to L will be unimportant and on the side of safety; or L = 11.25, M W = 340,515 ft. Ibs., and OSF = 2.25. Fig. 57 Timber Spillways Sec. I m H.E.P.114 H.V.S. 207 OF THE i r- r-t e> IT" \/ 208 HYDRO-ELECTRIC PRACTICE The framing is shown in the figure, consisting of alternate longi- tudinal and transverse square timbers; the former are staggered one above another excepting in the upstream face, the latter are placed 8 feet centres; the longitudinals are doubled at the apron end and are laid close in the top streak under the crown. The entire structure is covered with 3-inch planking, to make it as water-tight as possible, prevent the washing out of any of the filling material, and protect the crib timbers. The crown is given a slight slope to prevent the lodgement of floatage; its upstream edge is rounded and sheeted with iron plates. The substructure of a timber spillway is of the same type as for concrete spillways, consisting of the cut-off, the bearing piles, if the location is in soft material, and of the apron; for the structural type of the latter heretofore described, a rock-filled trench may be substituted, that is if heavy rock is available, and the trench should be not less than three feet deep, and its width should be equal to half of the spillway height in order to insure that all of the overfall strikes this rock fill. A gravel and earth fill may be placed against the upstream side of the spillway, but it should not be expected to add to the resistance weight of the structure, as the upstream side will always be exposed to the hydro- static head of its full height. As a matter of fact, this upstream side will sooner or later fill in from the sediment and silt carried by the stream. TABLE 15. APPROXIMATE QUANTITIES OF THE MATERIAL REQUIRED FOR TIMBER SPILLWAYS OF THE DESIGN HERE DESCRIBED IN LENGTHS OF EIGHT FEET AND FOR VARYING HEIGHTS. 12 X 12 timbers, Height. ft. b.m. 10 3,000 12 3,800 14 4,700 16 5,800 18 7,000 20 8,300 22 9,700 24 11,000 26 12,300 28 13,700 30 15,000 32 16,400 34 17,800 36 '. .. 19,200 38 20,600 40 22,000 Wrought iron drifts, Ibs. 3X 12 planking, ft. b.m. 250 900 300 1,050 355 1,200 410 475 1,350 1,500 545 1,650 620 700 785 1,800 1,970 2,150 875 965 2,300 2,500 1,060 1,160 2,700 2,900 1,265 1,375 3,100 3,300 1,500 3,500 Spikes, Ibs. 430 500 570 640 710 780 860 940 1,020 1,100 1,180 1,260 1,340 1,420 1,510 1,600 Spillway Apron fill, fill, cub. yds. cub. yds. 26 32 42 55 70 90 115 145 180 220 260 300 340 360 400 450 5 5.5 6 6.5 7 8 9 10 11 12 13 14 15.5 17 18.5 20 STRUCTURAL TYPES 209 Sluices of any type may be arranged in a timber spillway. To decide between timber and concrete spillways is practically wholly a question of comparative cost and of the maintenance and repair charges. Diagram 30 gives the approximate first cost of the timber spillway superstructure of the types here described, per linear foot of the spill- way, and comparatively with the cost of concrete spillways for different heights and varying market values of timber and of concrete, both placed in the structure. Fig. 57, section II, shows a modification of the timber spillway, the upstream side being inclined on half horizontal in one vertical and the apron fully sheeted to the shape of the overfall curve; its charac- teristics are: S = 16 ft., B = 1.75 S, C = 0.357 B. ARTICLE 71. Occasionally it may be desired to construct the spill- way at first to only a part of the total height to be ultimately utilized; this is practicable both with the solid and the gravity types. For the first the downstream slope should then be left in steps with dowels, in order to secure the best practicable connection for the future addition to the original section; the foundation and the apron must be sufficient for the final height. For gravity spillways the partitions are likewise stepped on the apron side and are covered with a timber instead of the concrete-steel apron, the latter being constructed when the spillway is completed to its final height. Or it may be desired to raise an existing spillway, which may also be practicable but cannot .be treated in a general manner; each such case must be considered from its own conditions. ARTICLE 72. Spillway Abutments. The spillway terminates in abut- ments which may be of natural rock walls when the location is in a palisaded gorge; but in the majority of cases the spillway does not complete the empounding of the watercourse, and the additional struc- tures, which are required to dam the river, are joined on the spillway, and the abutments then form the connecting links. Abutments should be of the same height as the adjoining reservoir structures, not less than three feet above the maximum overflow level, and in outline they must be of sufficient dimensions to cover completely the ends of the banks which they are to protect against the overflowing water; they have, however, little in common with bridge abutments, partaking rather of the character of retaining walls. For solid spillways the section proper needs no abutment, which is formed around and 14 210 HYDRO-ELECTRIC PRACTICE overlapping it on all sides as much as the section of the adjoining reservoir structures require; for gravity spillways the abutment becomes a com- plete wall, forming, in part, the end partition of the spillway; while for timber spillways the abutment is a separate structure throughout. The abutments may be of timber, masonry, concrete, or of concrete -steel construction, their design being based upon the theory of earth-retaining structures. Fig. 58, B E K, is an earth bank,

< 3 < V i f 1 rt u \ C. on Cl et e J>i nl lv\ f^ y V \ \ \ \ \ \ Diagram 30 Comparative cost of Timber & Concrete Spillways i \ V ^ V \ ] \ \ \ \ \ \ \ \ i \ \ 1 \ k \ \ \ \ \ " \ \ \ \ k v \ X \ \ \ / \ \ \ \T ' \ \\ ^V Y i / \ ^ v 2 ?\ / / v s > ^ 0, fe \ $ * \ rs ^ / ^ \ I \jT ic 5V ^ / / / ku^ 7 v 3 5\ 1 ^ ^ \^ S r \ \ v / / ^ \ \ \ \ ^ / / / \ s v ^ \ ^/ f / ^ ^ k \ \ \ \ / / t / / \ ^ \ \ ^ / / / \ \ \ \ / ^ / / / \ \ / / ^ ( ^ / \ \ \ / / / / \ , \ \ r^ / / / / f / \ \l \ \ . .> ^ y / ^ ( / \ ' . S \ 5 ' / ^ S y ^ \ \ \ \ \ t ^ y ^ / a Y S S \ *i ^ v /_ ^ \ ^X $ 2 \ \ \ \ \ / f ^ 5 $ > w S \ \' S / / ^ / ^ * - ! S \ \ A / / ^ y _ r- \ \ \ \ / ^ / ^ ^/ L 1 S v, V v / , ^ / / / S ^ ^ >< Sc / ^ /* S V v ^ / i 2 ^ i^ i ^ / / / X * \ A / / / >\ >C \ \ / / / s / \ \ \ \ N / / / S \i \ \ \ X ^ S / S <\ V ^ / s" ^ s S \ S S. / fS S s i> ^ ^ -^. ^ S" S*' v ^v, ^ ^s \, Tl i ^ | ^ ^ ^ ^ 0S# g-i ?> 1 r-i t ^ ^ ^ H V, S. ^ ^ S* ^ &- r ill ^ ^ isa . 1 JL >v \/v J > V O momotn Oioc 211 212 HYDRO-ELECTRIC PRACTICE of the height, then sloping along the plane of rest, approximately as shown in Fig. 59, section I, for clay, gravel, and sand, section II, for clay and gravel, and section III, for clay. The slopes of these three, when contain- ing only normal quantities of water, were found to be practically the same, being from 1.5 to 2.5 horizontal to one vertical; the locations and lines of rupture were likewise similar in each case, the surface break C being generally midway of DB, the top of the slide vertical and then generally curving to the toe of the slide at E, and the vertical sections increased in length as the ratio of sand and gravel decreased. The forces to be resisted by the retaining structure originate in the wedge-shaped portion of Fig. 60, CDE, which would fall if the wall were removed; the area of this part A' is some fraction of the rectangle hd, which will here be assumed in accordance with the observations above detailed to have the following values for different materials: for sand or half gravel and sand or loam A' = 0.5 hd, for clay, gravel, and sand A' = 0.6 hd, for clay and gravel A' = 0.7 hd, for clay A' = 0.8 hd, provided that the subdrainage of the fill is sufficient to prevent any accumulation of water in the bank or against the wall. h = height of retaining wall, and d = h tan = h tan a ; Zi A' = rh 2 tan a, in which r is the ratio of the area hd of the falling part as per class of material; STRUCTURAL TYPES 213 W' = w'rh 2 tan a, in which w' is the weight in Ibs. per cubic foot of the material of which the fill consists; W is assumed to act in the gravity line Gg of Fig. 61, on the line of rupture CE; GR represents the reaction of the bank and, P = W X r the reaction of the wall ^ H.E.P.120 y <* H.V.S. = W'rhd X r = wr d 2 = wrn2 tan 2 a n its horizontal component HP = P cos $ = w'rh 2 tan 2 a cos <, which is the force to be resisted by the wall and is assumed to be concentrated at a point 0, being - above o the base EF. The moment of pressure is the product of P into the lever arm I/ = - o MP = ^- 3 tan 2 a cos * jS 2_ az X'" x x^ a X f \ ./* / s jpE sr s X c 5^""^ , O V r 2 X >^ ^s^ ^ X x .^ ^f^x* x* s' s^ ai^ >^^ _,x /r x' it ^* ^^^ ' X" &>v*^ X ^^ ^*^ s^^- ^ ^ -^ ^-^^ ^x"^ --^^ H.I ..I.I 1 a ^^** ** ^~~- - ^~*~ * l- ^^ - TT_j 'ht in ft ~~-~~ 2^,-<^^,-^ S 2 s^ D / jS 2 / s / / ,x SJ2- B 2^ V" jr f\ ^ QV" s aS^_ pQ s ^^ ^s /^ yOx' "~g* j r ^j^ ^t s 2 S^ s s . s~ s z \ ^^ >^ s*^ 1 s^ _ / /"^ s^ A& ji^ S s' A. ^ *s^^ S ' r ^""*3^' >r *^s^ 2_ fV^X*' ^^ ^^ "^7* ^^ .x ^^~ _^, ^s^ ^^^^ ^^.^^^ <^ ^^ **" _^*^ ^**^^ *o ^^* l^^ \jO*^L ***^ * **~~ -.(^ ^^~~~ a^,^ _^^***~ rrave* Ji^*^^ '* p ^^ \vutf ^^ ' tat\d ^ ^^ ' ^- "" - ^-*~~' 1 \ EP 1 1O h LJ ' U Hv ' i rieiKnt in ft. 1 O ON O -H r* fi'ttnvAOODONC 217 218 HYDRO-ELECTRIC PRACTICE forts. The overturning forces are transmitted to and resisted by the counterforts, the curtain wall between them being designed as beams fixed at both ends and uniformly loaded. Fig. 64, sections I and II, HP as before = wh 2 tan 2 a cos I'> 1.2 n LZ /z n to which the concrete-steel wall at the bottom must be adapted. 18 h B G / EJ' X'l 7. ' - Sp-- ii Fig. 64 Concrete Steel Retaining Wall Cf III Rear Elevation Section H.E.P.122 H.v.S. Fig. 65 shows the section and elevation of a concrete-steel retaining wall. Counterforts are spaced 10 feet and are constructed of x concrete; curtain walls are of xx concrete. h = 20 feet, = 28, r = 0.5. Counterforts HP = 5976 Ibs., MP = 39,800 ft. Ibs. for a span of 10 feet MP = 398,000 ft. Ibs. Mo 4 = 19,104,000 inch Ibs., for a section 12 inches wide the depth at the bottom of the counterfort 220 HYDRO-ELECTRIC PRACTICE section " t " is, from Art. 53, 3620 t 2 = 19,104,000, 19,104,000 70 A - 1 = 3620 = 72 ' 6 mcheS ' and the steel area q = 0.077 t = 5.6 sq. inches; the practical section is 12 inches wide and 6 feet deep. Fig. 65 F^^%sgsx%ss&a Section ^'KConcrete Steel Retaining Wall H.E.P.123 Curtain wall, the bottom beam from Mo4 = " 2 ^040 the actual length between counterforts is only 9 feet, but it is taken at the full span; thickness t is from 5505 t j = 239,040, t = = 6.6 inches; X 5505 STRUCTURAL TYPES 221 the minimum practical section of the wall will be 12 inches at the bottom and 8 inches at the top with the proper section of reinforcing steel. Returning to the consideration of the spillway abutment, it has already been noted that it is a retaining wall only in part, that is, the portion covering the spillway end is not chargeable with resistance to bank pressures which at that point are transmitted to the spillway proper ; only the top and the downstream portion of the abutment, which overlap the spillway, partake of the duties of retaining walls and should be designed in accordance with the theory herein developed and as shown on Fig. 65 in plan, elevation, and section. Approximate quantities of material required for concrete-steel abut- ments of various heights have been given in Part I, Diag. 12, Article 23. The selection of the spillway abutment type is practically entirely determined by a consideration of cost ; the crib abutment, like the timber spillway, will in time call for repairs, however, of no such cost and fre- quency as in the case of the spillway; the gravity and concrete-steel structures are both of like permanent character. In many cases waste-flumes, as will be noted later on, are most economically arranged through the abutments, in which event the con- crete-steel type has the decided advantage on account of its small trans- verse section as compared with the others; this is also true when the water is to be diverted from the upper pool by means of a pressure line, the intake to which is frequently most conveniently and economically arranged through the abutment. ARTICLE 73. Reservoir Dams. When the spillway completes the closing of the river valley and the empounding of the upper pool, i.e., in case the river flows between natural rock banks, which rise above the greatest flood level, no other control works are required in connection with the dam; but where this is not the case, as in the event of the spill- way taking up only a portion of the river valley, generally the natural width of the stream, and the main valley banks are at a distance from the river proper, the reach from the spillway to these banks, where they rise to the required height above the greatest overflow, must be closed by additional structures, which really form the dam, serving the purpose of empounding only, that is, no flow is to pass over it at any time. These structures may be of a variety of types, generally classified as reservoir embankments and bulkheads, the first consisting of rock or earth or both, the latter of masonry, concrete, or concrete-steel. _. HYDRO-ELECTRIC PRACTICE * Earth and rock-fill dams have been constructed for centuries to the greatest heights. Their design must be such that the weight represented by their section safely resists the hydrostatic pressure of the water which stands against them, that no water passes under or through them, and that their exposed slopes are safeguarded against erosion due to rainfall. The stability theories heretofore developed in connection with spillways and retaining walls also apply in this case, and, as the pressed surface of these structures is always inclined from the vertical, the pressure theories involved are specifically similar to those discussed in behalf of gravity spillways, with this exception, however, that, instead of H exceeding the height of the structure, as in the spillway, it is always less than the height of the dam, the highest water level should not rise nearer than 3 feet to the dam crest. Assuming the limits of spillway overflow as before at 0.2 of their heights, and providing this minimum clearance of 3 feet, the height of reservoir structures H' will be at an elevation, referred to the footing level of the spillway, of H' = 1.2 S + 3, while their actual height will depend upon the elevation of the location they occupy. Preventing water from passing under or through a rock or earth-fill dam can be accomplished successfully only by an efficient cut-off below its foundation and a core of some impermeable material in its body. The subject of cut-off is to be treated identically as heretofore discussed in connection with the spillway foundation, and everything that has been there presented applies here; and the core is the upward continuation of the cut-off, and like it may be of various types, namely, a timber or steel curtain, clay or concrete wall, the choice depending upon the height of the structure, availability of material and its comparative cost. The core is joined to the abutment and a drain-pipe is placed at its base on the upstream side, passing through the abutment and discharging below the spillway. Fig. 66 shows the section of an earth and rock-fill reservoir embank- ment, being chiefly conditioned with a view to the preservation of its slopes, and when this is fulfilled its area and the corresponding weight are largely in excess of those required for its stability against the active pressures. The upstream slope is constantly exposed to the water, which may penetrate into the material and have a tendency to wear away the surface, which can be counteracted only by giving it an inclination of not less than two and one-half horizontal in one vertical, and provided the material of which it is formed is of the proper kind and is placed in STRUCTURAL TYPES 223 the manner which will be further on described. At the water surface especially will the wave action, ice, and impact of floatage make inroads into the unprotected bank, and the upper portion of this slope, for a depth, covering the entire range of surface fluctuations, must be covered by a pavement properly laid, and in fact it is good practice to extend this pavement to one-third the water's depth. When the best material for earth dams cannot be obtained, it may be advisable and prove economical Fig. 66 Reservoir Embankment H.E.P.127 H.V.S. to flatten the upstream slope and cover it entirely with a blanket of concrete of a lean mix, which may be maintained in position by driving iron rods one inch in diameter and eight feet long, spaced 8 ft. c. to c., into the bank, their upset ends being imbedded in the concrete sheet; such rods are most conveniently driven by means of a pipe hammer, a five-feet long piece of inch-and-a-half iron pipe closed at one end, which is slipped over the rod and used as a driver, being exchanged for a shorter piece as the rod goes down. As the downstream slope is exposed to the rainfall, its inclination should be at least one and one-half horizontal in one vertical and it should be covered with grass turf; the Bermuda variety 224 HYDRO-ELECTRIC PRACTICE is especially valuable on account of its long roots and thick growth. When the slope exceeds 30 feet in length, it should be broken midway by a horizontal berme, not less than five feet wide, to check the down- flow of the run-off and thereby break its force. The crest should be of a least width equal to half the height and slightly rounded upward in the centre to prevent the collection of pools of water; it should preferably not be used as a highway, but, if serving this purpose, it should be covered with road-metal. It is a good practice to plant trees along the crest, as their roots will strengthen the bank; they should, however, not be set closer than five feet to the break of the crest into slope, nor should they be of rapid growth or of widely branching type which present large sur- faces to the wind. The selection of the material for reservoir embankments deserves the most careful consideration. There is a great difference between the requirements of a railroad embankment and one to maintain a reservoir; in the former proper drainage and the confining of the slope toes will generally be a sufficient guarantee for its permanency, and apparent weak places are readily accessible and can be strengthened in time; not so with the reservoir structure, one side of which is constantly sub- merged, where leaks are not easily traceable and are more difficult of access. The desideratum is an impervious, homogeneous mass, which may be classed as puddle, consisting of such proportions of gravel, sand, and clay that the voids in the mass are practically filled. Gravel, from the largest size passing a six-inch ring down to coarse sand grains, packs with 34 per cent, of its volume in voids, and if deposited in shallow layers, not exceeding six inches in depth, and covered with a 'two-inch layer of fine sand, the latter can be completely washed into the gravel strata, as can a succeeding layer of one inch of clay or preferably loam. This represents an expensive programme and will rarely be adopted, but is outlined here as yielding the ideal conglomerate for reservoir banks. In practice gravel, sand, and loam are spread jointly in 6 to 8 inch deep layers by means of horse-scrapers, well watered from sprinkling carts, and compacted with heavy iron rollers ; all operations and handling of materials should be so arranged as to co-operate in the most thorough compacting of the mass. This treatment would be incomplete without recording a most emphatic warning -against the dumping of material from cable-way or derrick buckets or from tram-cars operating on a trestle, as material so deposited does not compact nor mix as required for reservoir embankments. Fig. 67 Reservoir Bulkhead 15 H.E.P.1I8 H.V.S. 225 226 HYDRO-ELECTRIC PRACTICE Clay should be used but sparingly; in large masses it represents the most unstable and treacherous material, and should be shunned, for the purpose of reservoir embankments, as quicksand in a railroad cut. Clay expands and contracts, in ratio of its degree of dampness, to such an extent that no bank largely formed of it, no matter of what dimensions, represents stability or permanency. Sand, confined in place, forms an excellent bank material, and, as before stated, when combined with gravel and loam, it yields the best. An earth embankment with a concrete core consists of two parts, the upstream and the downstream, the exposure and wear of which differ greatly; the former is submerged and subjected to wave action and whatever effect floatage and ice may have upon it, while the latter merely adds to the weight of the whole and is exposed to the rainfall. It appears, therefore, altogether logical that the two parts should be differently composed; for instance, the upstream section might be built of the before-described puddle, and the downstream of a loose rock-fill with sand and loam washed into the voids and a sufficient thickness of loam slope covering on the top of it to give sustenance to a grass turf. If the core-wall is of sufficient stability, such an embankment will be fully as effective as if it were formed entirely of puddle material, while, with rock available in the vicinity, its cost will be considerably less. The hydraulic-fill dam is a specific type of earth dam, because of the method of its construction, which consists in washing the desired material from a higher bank, conducting it in flumes passing above the dam site, and depositing it in a semi-liquid state. By this process a very compact and thoroughly mixed mass may be secured, and this represents the best method, provided suitable material is in close proximity at such elevations that it can be sluiced by gravity for the major portion of the dam, and provided that the cost of pumping is not too great. Some high structures of this class have been erected on the Pacific coast. Approximate quantities required for earth embankments of various heights are given in Diagram 14, Article 26. Concrete-steel bulkheads (Fig. 67) are available for reservoir duty. They consist of an inclined concrete-steel shell supported by buttresses of like construction, their designs being based upon the same theories heretofore developed in connection with the gravity spillway, with this important exception, however, that no water is to pass over them, as they should rise to the same height as that given for reservoir embankments. STRUCTURAL TYPES 227 The connection of such bulkheads with the spillway is by means of con- crete-steel abutments, and, in alluvial locations, they are founded upon bearing piles and concrete base with a cut-off in the manner described for the spillway. Diagram 15, Article 26, gives approximate quantities of materials required for concrete-steel bulk- heads of various heights. The decision as to the type of reservoir structures is, like that of abutments, chiefly a matter of cost comparison. ARTICLE 74. Appurtenances of Spill- ways and Dams. Provisions must be made to unwater the upper pool in order to ex- amine and repair the dam works on that side and to remove accumulations of sedi- ment and drift. Underflow sluices, already described in connection with the open spill- way design in Article 68, are available for this purpose, and can be arranged through the spillway, the abutments, or reservoir dam, being formed of wooden stave or steel plate pipes or of concrete-steel culverts or conduits. The theory of discharge through submerged orifices is based upon the fundamental law of flow of water, expressed by v = ^2gh, v being the velocity per second, in feet, with which a body, falling freely in a vacuum, passes through the height h, g representing the acceleration of gravity in feet per second = 32.2 ft., which of course changes with the distance from the centre of gravity, the earth's centre, the above value being sufficiently correct for these requirements. In Fig. 68 CB is a partition or wall, nl is a square, rectangular, or circular opening, S is the surface level of the water; then SI - ml = Sm is the head H under which the water passes through the opening. The theo- retical discharge would therefore be expressed by Q = area of opening in square feet into v theoretical velocity, but actually both of these factors are reduced from their theoretical values by coefficients of area and of velocity. 228 HYDRO-ELECTRIC PRACTICE Fig. 69 illustrates the characteristics of the actual approach of the water to such an opening, from which it is evident that a considerable part finds its way to the opening along curved paths, by which some of the energy which moves the water is lost in friction, and the theoretical velocity due to H is not fully realized when the water reaches the opening ; this reduction is expressed by a coefficient of velocity which has been fixed from the results of many observations, for the practical application to this purpose, at a value of about 0.98. Fig. 70 shows the manner in which the water enters the opening and the characteristics of its flow in its passage through the orifice, indicating the close adherence of the films of water to the full perimeter of the opening at the upstream edge, and how, by continuing for a time their curved approach directions, a distinct contraction is formed in the body of the moving water at CC', followed directly by its gradual expansion, and by experiments carried on for long periods it has been found that CC' = 0.7854 nl, and mm' = 0.5 nl. It is apparent that CC' represents the smallest efflux section and in it must prevail the highest velocity, which, however, cannot exceed the velocity of origin, namely that due to the head H. The greatest volume of discharge is therefore represented by that passing through the section at CC', which is the actual volume, to wit: Q = area at section C C' X theoretical velocity X 0.98, CC' :ln = 0.7854 : 1 when In = 1 X 1 then CC' = 0.7854 2 = 0.616, or when In = 2 X 5 CC' = 1.57 X 3.927 = 6.16, or, if the entrance be of circular form, the area being = 0.7854 d 2 , and d = 1, thenCC' = 0.7854' = 0.616; in other words, 0.61675 is the coefficient of contraction, and the ratio of the actual opening area, of whatever shape, which may be accepted as the efflux area and as the actual discharge through an opening in a thin vertical wall is Q = 0.61 a X 0.98 A /2gh = 0.604a A /2gh = 4.85aVh. STRUCTURAL TYPES Fig. 70 H.E.P.131 H.V.S In Fig. 71 the same principles are applied to an underflow sluice, nl is the entrance or intake through which the water enters from the upper pool and, as before, contracts at CC' ; by this contraction, in the interior of a closed conduit, a vacuum is formed around the body of flowing water, and the latter, acting under the influence of the original energy, expands again, and, as appears from many experiments, its velocity is not reduced by reason of its flow area be- ing increased, but the volume of efflux at EE', the section where the entire area of the conduit is again filled with water, is greater than at CC'. This increase has been determined at about 25 per cent, over the efflux from a thin-wall opening, by which the coefficient of discharge from an under- flow sluice becomes 0.61675 X 0.98 X 0.25 = 0.7555, and therefore Q = 6 a /\/H, provided the free efflux is at or near the section EE' where the water first refills the conduit section, which point is about 2.75 nl from the intake section nl. The same characteristics prevail if the conduit protrudes into the upper pool for a similar length = 2.75 nl, but, when it becomes longer than this, energy is expended in overcoming perime- ter roughness, which in turn diminishes the velocity and therefore reduces the discharge; this enters upon the theory of "flow through pipes," which is treated in like detail in connection with the discus- sion of diversion works. Many refinements may be added to above outlined theory when the application is for the purpose of accurately measuring volumes by efflux from orifices, but, for the designing of works herein considered, no com- mensurate advantages can be secured by such reasoning, and the values are sufficiently correct for this practical use when expressed, for square and rectangular openings, by Q = 6 a \/H, and for circular openings, by Q = 4.75 d 2 \/H, where H is always the head above the centre of the intake, a is area of the intake in square feet, and d is diameter of a circular intake. 230 HYDRO-ELECTRIC PRACTICE The areas of the underflow sluices required to draw down the upper pool in a given time can be determined only if the storage volume is known; if this were A and the head maintained constant, then a quantity equal to A would pass through the sluice in A -7- 6 a V H seconds of time, and with a constantly dropping head the time t = 2A -f- 6 a V H ; this, however, represents only the stored volume, to which must be added the continuous flow. Example. Given an upper pool one mile long, 200 feet wide, and 30 feet deep at the spillway, representing a total storage volume of about 16 million cubic feet, to which is to be added the continuous low-flow volume of 1000 cubic second feet, and the pool is to be unwatered in 6 hours; then for the storage volume alone from t = 2 A -r- 6 a V H, 21,600 = 32,000,000 -r- 30a, H being taken at 25 ft., a = 32,000,000 -5- 648,000 = 50 sq. ft., to which must be added sufficient sluice area to discharge the continuous flow of 1000 sf. flow = 1000 X 21,600 = 21,600,000 cubic feet, 21,600 = 43,200,000 -H 30 a, and a = 43,200,000 -*- 648,000 = 67 sq. ft., or the total sluice area required being 50 + 67 = 117 sq. ft., which, if arranged in two sluices, would call for an area in each of 60 square feet, and the practical dimensions would be 8 X 8, or if circular, each sluice would be represented by an 88-inch pipe. In open spillways the area of sluices will always exceed that required for unwatering the upper pool, as they are proportioned to control the flood discharge of the stream. The construction designs of sluices have been treated generally in connection with open spillways in Article 68, and so have the different gate devices. When sluices are arranged through reservoir dams or embankments, the considerations involved do not differ from those herein discussed; the structural designs must provide sufficient safeguards against erosion of any portion of the embankment at the sluice entrance and along its location through the body of the fill. The operation of the gates is most conveniently arranged by a well rising upward from the sluice in the downstream portion of the embank- ment and terminating at some convenient elevation in a gate-house. When log chutes are required, they may be of the general design of overflow sluices, as described in connection with the open spillway in Article 68, with the addition of floating booms to intercept and guide the logs into the sluice, a sufficient operating platform above the log chute STRUCTURAL TYPES 231 from which the logs can be steered through the sluice, and, if the sluice floor is more than 5 feet above the lower pool level, of a log apron below the sluice, which consists of an incline formed of timber trestles or cribs along which the logs will pass into the lower pool without being damaged ; the incline should not be steeper than 3 horizontal in one vertical and the depth of the water at the incline toe should equal half the vertical height of the apron. The log chute is best placed at that end of the spillway where the abutment can be utilized to give support to the log apron, and, if its operation does not interfere with the diversion or power station programme, the power end of the spillway is the preferable one. In many States the law requires the placing of fish-ladders in any structure which obstructs the normal flow of streams, in order to enable the migrating species to reach the upper parts of the watercourse during the spawning periods. The design for fish-ladders may be selected from a variety of types, generally consisting of a trough leading from the spillway crest, at a shallow overflow sluice, to the lower pool. The inclina- tion of the fish-ladder should be from 8 to 10 horizontal in one vertical, its width not less than 6 feet, and the depth such that water will stand not less than 18 inches deep in the steps of the ladder as shown in Fig. 72, where the arrows indicate the leaping or swimming passage of the fish. The structure is best placed at a spillway end where it may find support at the abutment, which latter is to be extended sufficiently downstream- ward; the ladder proper may be supported on timber or steel trestles or on masonry piers, the choice depending chiefly upon the exposure of the ladder to the overflowing water. In open spillways, where the over- flow is under control, fish-ladders may be of timber construction, with proper consideration for winter conditions; in connection with solid spill- ways of considerable overflow, fish-ladders should be of masonry construc- tion. For high spillways 'the ladders are best arranged in several flights. Ice-Fenders. In northern latitudes where ice forms 6 inches and thicker, the resultant thrust against the spillway can be greatly dimin- ished by securing ice-fenders to the upstream face of the solid spillway; these consist of two or more 12-inch square timbers placed as stringers one upon another with staggered joints and secured to the spillway by means of screwbolts set in the masonry; the top stringer is flush with the spillway crest, with an up-slant so that ice will rise up under pressure. Flashboards are devices by which the upper pool level is temporarily raised for the purpose of accumulating an increased volume of water I E c- Timber Fishladder Fig. 72 u Longitudinal Section ,N Transverse Section Concrete Fishladder Transverse Section H.E.P.133 H.V.S. 232 ) _ X5 v> ^ _ -3 ft -<3 - 233 234 HYDRO-ELECTRIC PRACTICE during a non-operating period. In this manner the upper pool by pondage is utilized as a storage reservoir, principally during the low-flow periods, by placing some movable addition upon the spillway crest, arresting and holding the natural flow in the upper pool, no water being allowed to overflow the spillway or pass through the turbines during a certain period, generally some portion of the night, and then using the natural flow plus the accumulated volume during the operating period. When this proceeding is feasible, which is not always nor generally the case, because it interferes with and disturbs the natural conditions of the flow in the stream and thereby is likely to interfere with the rights and ownership, in and to the water, of others, and when the operating period can be confined to ten hours, the power output of the continuous flow can in this manner be practically doubled. Many different devices are employed for flashboard service, mechani- cal, automatic, and hand operated, but their selection should be guided by the conditions under which they are to be used as relating to seasons, periods, and frequency of their service. When they are to be employed during the winter, in northern latitudes, the ice conditions must be considered. Fig. 73 shows different types of flashboards. In sections I and II a plank flashboard is set on edge upon the spillway crest resting against strain pins, inclined downstreamward and placed into holes left in the spillway masonry, or between such strain pins, the latter being arranged in a double row and staggered; these planks may be so placed by being handled from a platform above or from flat-boats held in place above the spillway by guide-lines secured to shore points or to a ferry line crossing the stream above the spillway. This type of flashboards answers well during open seasons for short spillways; the strain pins are of one-inch wrought iron; it is advisable not to fix them permanently into the masonry, but to leave holes into which they are readily set; the planks should be two inches thick and from 8 to 12 inches wide, though the narrower size will be found preferable on account of the greater ease of handling them; and the planks have secured to them, on their sides, iron hooks so set that they can easily be grappled into. The planks must be of uniform thickness and edged so that they will match up to a water-tight wall in any position. It requires two men to set or re- move these flashboards; they are inexpensive and can be quickly handled. Sections III and IV show a shutter flashboard framed of two or three planks in lengths from 6 to 10 feet and swung from rod hinges on the STRUCTURAL TYPES 235 upstream side of the spillway. The shutter is bound by iron strapping and has secured to it two or more strut rods by which the shutter is supported in an upright or inclined position when erected, these rods falling into recesses or grooves left in the spillway crest for that purpose. They are operated by hand, being raised to the surface, strut rods thrown over on the downstream face, and the shutter then raised up where it will be held by the water pressure of the rising upper pool ; or the shutters may be arranged to rest against stationary or removable strain pins as in the case of the plank flashboard. Fig. 74 , ~zri . , ii/Wif j i if ii './Jj'_ili|ir 'li * ii I -"^jr i _ Air vent Air vent H.V.S. Wells and galleries are arranged in solid spillways for the purpose of inspection, means of communication and location of wire cables; as shown in Fig. 74. Access to these is had through the downstream side of the abutments and a casemate entrance arranged in the down- stream slope of the embankment. They are formed of the least required dimensions; air- vents of two-inch galvanized iron pipe are placed 10 feet c. to c. from the gallery wall to the spillway apron face, with a slight downward drop to prevent water from passing through them. Bridges, foot-ivalks, and operation platforms, for one purpose or another, of timber or steel construction, may be arranged on the spillway. ARTICLE 75. Diversion works comprise the structures conducting the water to the power station ; they may be classified as canals, flumes, and pipe lines. 236 HYDRO-ELECTRIC PRACTICE Canals serve to divert volumes exceeding 500 cubic second feet; their design is based upon the theory of flow in open channels. Fig. 75, section I, represents an open channel section the bed of which, AB, is in a horizontal plane, and, if this condition prevails from the source to Fig. 75 II H.E.P.136 H.V.S. the terminal, the water does not flow; in section II the bed AB is down- wardly inclined and the water flows through it, its surface assuming a slope similar to that of the channel bed; the vertical difference of the horizontal plane of the water surface at A and B, or at any two points, Fig. 76 H.V.S. is the head h between such points, which causes the flow and which is generally expressed in terms of slope S = h -=- d, where d is the length of the channel AB and both are in like units, also called the hydraulic gradient. Fig. 76, section I, represents the natural section of a stream, section II that of a constructed channel; ABCD is the wet perimeter, "P"; the cross sectional area A of the stream, divided by the developed length of STRUCTURAL TYPES 237 the wet perimeter, is the hydraulic radius " R." The flow in open channels depends upon the values of S, A, P and the degree of roughness "n" of P, and, from the relations of these, expressions have been developed, as the results of many observations and experiments, for the mean velocity of the flow, the basic form of which is : velocity = coefficient into the square root of R X S, v = C V R S, in which C is the variable quantity which, according to the present acceptation as deduced by Ganguillet and Kutter from results found by M. Bazin, is expressed as C = y -j- [1 + (x -r- y = a + (1 * n) + (m -H s), and x = [a + (m -~ s)] X n, in which 1 is a constant = 1.811 ft., a is a constant = 41.6, m is a constant = 0.00281, and n is variable ; its values for the application to diversion canals are for channels lined with dressed planks or smooth concrete = 0.010 channels lined with rough planks or rough concrete = 0.012 channels lined with smooth natural rock = 0.017 channels lined with hard gravel, clay, and sand = 0.025 channels lined with soft alluvial materials = 0.03 Ex. A = 1000 sq. ft., P = 128 ft., R = 7.8, S = 0.0005, n = 0.025 y = 41.6 + (1.811 -T- 0.025) + (0.00281 * 0.0005) = 119.64 x = [41.6 +(0.00281 -* 0.0005)] X 0.0005 1.18 x -r- VR = 0.42 C = 119.64 -r- 1.42 = 84.3 V = 84.3 ^ 7.8 X 0.0005 = 5.26 sec. ft. Values for the factors "y" and "x" for different slopes and perimeter conditions are given in Tables 16 and 17. 238 HYDRO-ELECTRIC PRACTICE TABLE 16. y = a + (1 S. n = 0.010 .0001 250.8 .0002 236.7 .0003 232.0 .0004 220.7 .0005 228.3 .0000 227.4 .0007 226.7 .0008 226.2 .0009 225.8 .001.. . 225.5 n) + (m H- S). n = 0.012 n = 0.017 220.7 175.7 206.6 161.6 201.9 156.9 199.6 154.6 198.2 153.2 197.3 152.3 196.6 151.6 196.1 151.1 195.7 150.7 195.4 150.4 TABLE 17. x = [a + (m H- S)] X n. .0001. .0002. .0003. .0004. .0005. .0006. .0007. .0008. .0009. .001.. 0.70 0.56 0.51 0.48 0.47 0.46 0.45 0.45 0.44 0.44 0.84 0.67 0.61 0.58 0.57 0.55 0.54 0.54 0.53 0.53 1.18 0.95 0.87 0.83 0.80 0.79 0.77 0.77 0.76 0.75 n = 0.025 142.1 128.1 123.4 121.1 119.6 118.7 118.0 117.5 117.2 116.8 1.74 1.38 1.27 1.22 1.18 1.16 1.14 1.13 1.12 1.11 Analyzing the flow formula and the influence of its variable factors upon the resultant velocity value, in its special application to the design- ing of diversion channels, the range of the coefficient of roughness can be limited to those conditions of lined channels by which permanency of prism is absolutely guaranteed, as only in extremely rare cases would a power canal present any other conditions; that means that the first three values of "n" fully cover the various perimeters to be met with in this subject, and that the value of "y" is between 150 and 250 and of "x" between 0.4 and 1.2, and within this scope the values of the other pertinent expressions in the flow formula, such as x -r- V R and of "C, " are given in the following tables. TABLE 18. [1 + (x + V R)]. x =0.5 x = 0.6 x = 0.7 x = 0.8 x = 0.9 x = 1 1.5 1.6 1.7 1.8 1.9 2 1.35 1.42 1.50 1.57 1.64 1.70 1.30 1.35 1.40 1.47 1.52 1.60 1.25 1.30 1.35 1.40 1.45 1.50 1.22 1.27 1.31 1.36 1.40 1.45 1.20 1.25 . 1.29 1.32 1.37 1.40 1.19 1.23 1.26 1.30 1.34 1.38 1.18 1.21 1.24 1.28 1.32 1.35 1.17 1.20 1.23 1.26 1.30 1.33 1.16 1.19 1.22 1.25 1.28 1.32 R x = 0.4 1 1.4 2 1.28 3 1.23 4 1.20 5 1.18 6 1.16 7 1.15 8 1.14 9 1.13 10 1.12 STRUCTURAL TYPES 239 This completes the analysis of the factor "C" in the flow formula. Example. n = 0.012, S = 0.0003; the channel is to divert 3000 cub. sec. ft. at a maximum velocity of 5 ft., A = 600 square feet, the side slopes of the canal are to be 1.5 horizontal in one vertical, P = 113 ft. and R = A -r- P, = 600 -H 113 - 5.3, y from Table 16 = 201.90, x from Table 17 = 0.61, [1 + (x -r- VR)] Table 18 = 1.26, and therefore C = y -5- [1 + (x -5- VR)] = 201.9 -i- 1.26 = 160. Values for "C" for above y, x, and R are given in Table 19. TABLE 19. C = y -s- [1 + (x -e- v'R)]. y 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0=[l + (x-s-v'R)] 250 . .. 227 208 192 179 167 156 147 139 132 125 240 218 200 184 171 160 150 141 133 126 120 230 209 191 177 164 153 144 135 128 121 115 220 200 183 170 157 147 137 130 122 116 110 210 191 175 161 150 140 131 123 117 110 105 200 182 166 154 143 133 125 117 111 105 100 190 173 158 146 136 127 119 112 105 100 95 180 164 150 138 129 120 112 106 100 95 90 170... . 154 141 131 121 113 106 100 94 90 85 160 145 133 123 114 107 100 94 90 84 80 150 136 123 115 107 100 93 88 83 80 75 Continuing the solution of the previous example, "C" can be taken off Table 19 by interpolation and the velocity found from v = C ^RS, ^RS = 5.3 X 0.0003 = 0.0398. v = 160 X 0.0398 = 6.368. Velocity in a diversion canal should not be excessive; as a rule, it will be important to conserve the available head wherever practicable, and the design of the canal affords one of the important opportunities to 240 HYDRO-ELECTRIC PRACTICE practise this economy. Only where the excavation of the canal prism presents a very costly undertaking, such as when it has to be located through a hard rock ledge, or in case the value of the necessary right of way is practically prohibitive and when the canal section therefore must be kept at a minimum, are high velocities excusable ; five feet per second is a good limit to be adopted for the flow in a diversion canal, and within this limit the value of "v" is given for different slopes and R in the fol- lowing Tables 20 to 24. TABLE 20. VELOCITY FOR S = 0.0001. 0.010 0.012 R C VRS v C v 1 147 0.01 1.47 120 1.20 2 . . 168 0.014 2.35 138 1.93 3 178 0.017 3.02 149 2.53 4 186 0.02 3.92 155 3.15 5. 191 0.022 4.20 160 3.52 6 . 195 0.024 4.68 164 3.93 7 198 0.026 5.34 167 4.34 8 201 0.028 170 4.76 9 203 0.03 172 5.16 10 205 0.03 174 5,40 TABLE 21. VELOCITY FOR S = 0.0002. n = 0.010 0.012 R C V'RS V C v 1 151 0.014 2.11 123 1.72 2 170 0.02 3.40 140 2.80 3 179 0.024 4.29 149 3.57 4 185 0.028 5.18 155 4.34 5 190 0.031 5.89 159 4.93 6 193 0.034 162 5.50 7 196 0.037 165 8 198 0.040 167 9 200 0.043 169 10 201 0.045 170 TABLE 22. VELOCITY FOR S = 0.0003. n = 0.010 0.012 R C VRS V C v 1 152 0.017 2.58 124 2.10 2 171 0.024 4.10 140 3.36 3 179 0.030 5.37 152 4.56 4 185 0.034 156 5.30 5 189 0.038 .... 159 6 192 0.043 162 7 195 0.046 164 8 197 0.049 166 9 198 0.053 168 10 200 0.055 169 0.017 C V 81 0.81 96 1.34 104 1.77 111 2.22 116 2.55 119 2.85 122 3.17 124 3.47 126 3.78 128 3.96 0.017 C V 83 1.16 97 1.94 105 2.52 111 3.11 114 3.53 117 3.98 120 4.44 122 4.88 124 5.33 125 5.62 0.017 C V 84 1.42 97 2.32 105 3.15 111 3.77 114 4.33 117 5.03 119 5.47 121 123 .... 124 .... STRUCTURAL TYPES 241 TABLE 23. VELOCITY FOR S = 0.0004. 0.012 C v 125 2.50 141 3.94 150 5.10 157 6.28 159 161 163 165 167 168 R 1 C 154 n = 0.010 V'RS 0.020 V 3.08 2 171 0.028 4.78 3 180 0.034 6.12 4 184 0.040 5 . . . 188 0.045 6 191 0.049 7 193 0.053 8 195 0.056 9 197 0.060 10.. . 199 0.063 0.017 C 85 98 105 110 113 116 118 120 122 123 1.70 2.74 3.57 4.40 5.08 5.68 TABLE 24. VELOCITY FOR S = 0.0005. R 1. 2. 3. 4. 5. 6.. 7. 9. 10. C 154 175 179 184 188 191 193 196 197 199 n = 0.010 V'RS 0.024 0.031 0.039 0.045 0.050 0.055 0.059 0.063 0.067 0.070 3.68 5.30 0.012 C 125 141 150 156 158 161 163 165 167 168 3.00 4.37 5.85 0.017 C 85 98 105 110 113 116 118 120 122 123 2.04 3.04 4.09 4.95 5.65 By aid of the tabulated values in these nine tables all problems relating to the flow in a diversion canal or flume can be solved or checked ; the frequent query, of what the slope would be in a canal of certain prism and a given velocity of flow, is thus solved. Example. To divert 800 cubic second feet at a velocity of approxi- mately 5 feet per second in a rectangular sectioned canal 5 feet deep and 32 feet wide; what will be the slope? A = 800 -v- 5 = 160 sq. ft., R = 160 -5- 42 = 3.8, n = 0.012, and velocity to be about 5 feet per second. From Table 22 in column of n = 0.012, and between values for R of 3 and 4, the desired velocity appears and the slope is 0.0003. It must be noted that the slope is expressed in the ratio per foot of length, a slope of 0.0001 = 1.2 inch per 1000 feet and 6.33 inches per mile. Location, construction, and operating conditions are the main con- siderations for the designing of the diversion canal. 16 242 HYDRO-ELECTRIC PRACTICE The location should be the economically shortest, which is deter- mined by the cost of the right of way and of the construction, and is most readily proved by the method of elimination, that is, by making paper locations based upon the survey and boring data and rinding the excavation quantities and slope areas for a flow section of one-fifth of the maximum volume to be diverted, thus assuming a trial velocity of five feet. Deviations from a tangent alignment will generally prove justifiable to avoid side-hill cuts, buildings, road crossings, rock outcrops, swamps, and to secure uniformity of the prism, but curvature should be limited to 3. The slope in curved channels is greater than in straight; the excess is determined from Humphrey and Abbott's formula, he = v 2 X 6 d -T- 536 p, where v is the mean velocity, d the total angle of the curve expressed in radians (1 = 0.01745), and p = 3.1415. Example. In a channel with v = 5 ft., on a 3 curve 900 ft. long, the curve slope he = 5 2 X 6 X 27 X 0.01745 -i- 1683, = 70.6725 -f- 1683 = 0.42, which must be added to the slope in a straight channel of the same length, or, if the general slope in this case is 0.00015, the total slope in this curve is 0.135 + 0.042 = 0.177 ft. The construction considerations to be weighed for the purpose of deciding upon the location and design of the canal pertain to the exca- vation of the prism, the lining of the bed and slopes, and the revetting of the superbanks. Excavation cost depends upon the character of the material, the quantities to be moved, and the disposition which may be made of the spoils; all these, together with the depth and width of the cut, will influence the methods which secure the most economical excavation. Rock is most cheaply removed in the dry; the principal operations involved in excavating hard rock, a classification which includes those formations which can be excavated in large masses only by the use of explosives, are drilling, blasting, loading, and disposing. Rock drilling may be done by hand tools or by machine drills operated by steam or compressed air; only machine drilling will be here considered. STRUCTURAL TYPES 243 This operation requires a runner and helper, power being supplied from a central plant. The output varies with the depths of the holes, being from 50 to 60 linear feet for 10 and 20 feet depths per shift of 10 hours. To the operating cost must be added the power cost for 10 horse-power per drill, the drill repairs and drill sharpening; with present wages drill- ing costs from 10 to 15 cents per linear foot, depending on the hardness of the rock and the depth of the holes. The breaking of the rock for the purpose of loading for removal requires from 1 to 1.5 pounds of 60 per cent, dynamite, according to its hardness, per cubic yard of output, and with present cost of explosives a charge of 15 cents per cubic yard should be made for blasting. The broken rock may be loaded by hand, or machinery, into carts, derrick or cable-way buckets, or dump cars, and the cost varies in accordance with the method employed; the output of hand loading averages 10 cubic yards per man per 10-hour shift, by steam shovel it will be between 40 and 60 cubic yards per hour. Disposal cost depends entirely upon the length of haul. With present wages rock excavation will cost from 75 cents to $1.50 per cubic yard. Earth is removed more cheaply by dredging than by dry excavation; the cost of dredging will be generally from 15 to 30 cents, depending upon the hardness of the material and the distance of the disposal. Dry earth excavation may be done by hand tools, horse and power scrapers, or by steam shovels, the operations consisting of loosening, loading, and dis- posing; the output and cost depend upon the methods employed, the character of the material, depth of cut, and distance of haul. With present wages the cost will be from 25 to 50 cents per cubic yard. Com- paratively, the cost of rock excavation is about three times that of earth, and dredging about 0.6 of earth excavation. The quantity of earth excavation is about 1.2 of the flow area up to the water level, and approximately one-third of that area for every foot vertical above water surface. Example. For a canal which is to divert 1000 cub. sec. ft. at a velocity of 5 ft. per sec. the quantity to be excavated to the water level is = 200 X 1.2 = 240 cub. ft. per linear foot of canal, and to a height of 5 ft. above the water level it is = 240 + (200 X 1.66) = 570 cub. ft. or about 22 cub. yds. For side-hill locations the quantities must be determined from cross- sections taken at intervals of 10 feet. 244 HYDRO-ELECTRIC PRACTICE The bed and canal sides (Fig. 77, 1) in rock location should be finished as smooth as practicable, in order to realize the highest flow efficiency, which will generally require hand-tool finishing of the bed, while the sides should be cut out by channelers, which with present wages costs from 15 to 18 cents per square foot surface, depending upon the hardness of the rock and the depth of the channel cut. In alluvial locations the bed and canal slopes should be covered with a lining, in order to guarantee the permanency of the prism and reduce the roughness to a minimum and thereby secure the best flow efficiency. Canal lining may be of timber or concrete-steel. Timber lining (Fig. 77, 2, 3, and 4) consists of 3-inch planking laid longitudinally upon 12 X 12 inch timber sills spaced 8 ft. c. to c. and imbedded in the bed material, being secured in place by con- nection to bearing piles from 8 to 16 ft. long, or by iron rods of the type described for the lining of a reservoir embankment slope in Article 73. A lining of concrete-steel (Fig. 77, 5, 6, and 7) may be laid upon transverse timber sills, as above, or upon concrete sills 8 inches square, which need no further support unless the underlying material is mud, when piles must be driven. The concrete lining is 6 inches thick for sills 8 ft. centres, and is connected with the sills by one-inch dowels set 4 ft. c to c. The concrete lining contains reinforcing steel. The canal slopes should be no steeper than 1.5 horizontal in one vertical; they may be lined in the manner described for the bed, being structurally continuous of the bed lining and terminating, when of timber, one foot below the normal flow level in a berme (shown in Fig. 77, 2) , and, when of concrete, 2 feet above such elevation (as shown in Fig. 77, 5). The superbanks of the canal should be sloped at two horizontal in one vertical and paved. Views 7 and 8 show a rock canal with channelled sides and paved superbanks, Views 9, 10, 11 an earth canal with timber lining. From these data estimates for various locations and prisms can readily be compiled, and their comparative cost will point to the most economical. Appurtenant structures to diversion canals are those required for the safeguarding of the superbanks against erosion from surface run-off, interception of unavoidable lateral stream sources, the devices control- ling the flow in the canal, and means of overhead crossings. Ordinary run-off from rainfall is best intercepted by a longitudinal paved drain located at the top of the superbanks, from which laterals View 7 View 8 Canal in Rock with Channelled Sides Completed THE UNIVERSITY View 9 Canal in Earth, Timber lined Laying the Sills H.IUM41 ''H.V.S.* View 10 ^^ Timber lined Planking If 3* Fig. 77 Diversion Canal In Rock In Earth Timber lined pgep In Earth Concrete lined 245 246 HYDRO-ELECTRIC PRACTICE of similar type are led down the slopes at intervals, depending upon the volume likely to accumulate, of from 100 to 300 feet. When the canal traverses ravines which form stream sources after heavy rainfall, pro- vision must be made to pass such flow under the canal by means of con- crete culverts, unless the ravine can be made part of the diversion canal by securely cutting off its terminal and connecting the canal banks with those of the ravine; when the volume which may pass down the ravine is likely to exceed 0.1 of the canal flow area, an overflow must be con- structed in the canal bank to pass the excess. Generally speaking, it will always prove the safer practice to care for such exterior flow sources by passage under the canal, the structure being of the concrete culvert type and of ample dimensions. The canal entrance is guarded by headgates, which should afford complete and ready control of all flow into the canal; they may be of a variety of types as suggested by the volume of the flow and the operating requirements. Stop-logs, which were described in connection with the open spillway in Article 68, are a simple, effective, and inexpensive device for headgate service, being placed and operated in the same manner as when employed for the closing of overflow sluices. Needles , also described in Ar- ticle 68, may be used, or lift-gates of timber or steel framing. A foot-bridge is arranged at the headgate crossing and serves as an operating platform. Some headgate designs are shown in Fig. 78 and in Views 12, 13, and 14. An intake to the canal is frequently arranged above the headgates for the purpose of creating a readily accessible pool in which floatage can be intercepted and prevented from passing into the canal ; it may also be the means of securing a more complete diversion of the low flow into the canal. A forebay is likewise arranged at the terminal of the canal, being simply a gradual enlargement in which the velocity of the flow is reduced before the water enters the power house; its dimensions are decided by those of the power house and by the character of the turbine installation. A waste weir should be arranged near the end of the canal, being practically a short open .spillway with one or two overflow sluices ; float- age, ice, and surplus flow may be passed over it. Bridges are often required across a canal for operating purposes and to accommodate public traffic. Diversion is secured by flumes when the volume is less than 500 sec. ft. Flumes are rectangular or elliptical timber conduits of designs and construction shown in Fig. 79; they are supported on timber trestles View 11 Canal in Eartr Timber lined Completed Canal Head Gates Stony Sluices OF THE UNIVERSlTv View 14. Timber Headgates. ~^f v '^"?Frfi'VA)WUgt v -XJa^^^k'J>3 ts> M .^ j.^.-.-i-^ -^O^^-^^vn^- * * \ * > * ) BCW 291 292 HYDRO-ELECTRIC PRACTICE 3 represents the runner rim band; 4 represents the cylinder-gate operating; in this case, on the inside of the gate- wheel; 5 represents the guide- vanes; 6 represents the bottom plate or ring of the guide-wheel ; 7 represents the top plate; 8 represents the dome plate of the guide- wheel; 9 represents the box or lid containing lignum vitas bearing; 10 represents the lignum vitse blocks; 11 represents the lid or top cover of the bearing; 12 represents the draft tube; 13 represents the spider; 14 represents the lignum vitse step; 15 represents the gate-rods connecting the cylinder gate to the upper operating device; 16 represents the spur racks; 17 represents the spur pinions by which the movement of the cylinder gate is controlled ; 18 represents the brackets to which the gate rigging is secured ; 19 represents the roller, shown in the horizontal section, con- fining the spur rack to the spur-gear pinion; 20 represents the bevel gear; 21 represents the bevel pinion actuating the spur pinion and rack; 22 represents the horizontal gate shaft; 23 represents the vertical gate shaft; 24 represents the cable wheel; 25 represents the turbine or wheel shaft ; 26 represents the turbine or wheel-shaft coupling; 27 represents the vertical gate-shaft coupling; 28 represents the vertical gate-shaft stuffing-box located below the spur rack; 29 represents the vertical gate-shaft extension finally con- nected to the turbine governor or hand wheel; 30 represents the turbine-shaft extension. The design of the housing or casing of the turbine depends upon the method of operation. When the water is supplied to the turbine by a feed pipe, the casing consists of a shell completely enclosing the turbine; when the turbine is placed in an open bay, the case or draft chest encloses 294 HYDRO-ELECTRIC PRACTICE all but the guide- wheel passages through which the water finds its way into the runner. Fig. Ill shows such a draft chest for a double turbine; it is a cast of two parts with a man-hole in the top or dome. The turbine runners are inserted at the ends EE and the case is secured to the floor structure by its bed flange F. Fig. 112 shows the turbines, runners, and gate-wheels assembled and connected by one shaft, all ready to be placed in the casing or draft chest shown in Fig. 111. ARTICLE 82. Description of a Central-discharge Reaction Turbine. This type is of the general class of Fourneyron turbines; the runner is very shallow, as compared with that of the mixed-flow turbine; the guide passages are of little depth and the guide- vanes are curved; the water enters simultaneously into all guide passages from a scroll-shaped supply pipe which encircles the runner and has openings along its interior periphery through which the water spouts into the guide passages; this supply pipe gradually decreases in area, so that the velocity of the enter- ing water is constant at all points of entry. This special supply feature has given to these turbines the French name of volute. These turbines are especially adapted to high-entry velocities and therefore high heads; such plants as those at Trenton Falls, Niagara, and Shawinigan Falls are equipped with them; the largest turbine yet constructed operates at the latter plant and is of this type with a capacity of 10,500 horse-power. Fig. 113 gives a complete plan of this type of turbines as they are constructed in this country. No. 1 represents the runner; No. 2 represents the guide- vanes; No. 3 represents the guide- vane plates; No. 4 represents the supply chamber passing around the runner; No. 5 represents the crown plate of the turbine casing; No. 6 represents the elbow of the discharge pipe; No. 7 represents the draft- tube ring; No. 8 represents the main-shaft bearing; No. 9 represents the thrust bearing; No. 10 represents the pedestals; No. 11 represents the shaft coupling; No. 12 represents the main shaft; ; - -- > Double Turbine Draft Chest. Assembled Twin Turbines. 295 296 HYDRO-ELECTRIC PRACTICE No. 13 represents the shaft stuffing-boxes; No. 14 represents the man doors in the case; No. 15 represents the supply pipe; No. 16 represents the draft tube; No. 17 represents the governor connections; No. 18 represents the governor. ARTICLE 83. Description of an American Impulse Turbine. In this country the impulse turbines, as a distinct type, are represented by that shown in Fig. 114, consisting of a wheel or disk which carries on its pe- riphery cup-shaped buckets, the whole being encased and operating on a horizontal shaft. The buckets are of double cups, the central partition splitting the striking jet in equal parts as to volume. The water spreads out all over the bucket surfaces and is deflected 180 from the entry direction when it drops from the buckets. This class of turbines is especially adapted to the highest heads and is commonly called the hurdy-gurdy wheel. In the figure showing a plan of it No. 1 represents the wheel disk; No. 2 represents the wheel buckets; No. 3 represents the wheel shaft; No. 4 represents the ring oil bearings; No. 5 represents the base plates; No. 6 represents the nozzle; No. 7 represents the gate valve; No. 8 represents the supply pipe; No. 9 represents the hand-wheel stand; No. 10 represents the hand-wheel; No. 11 represents the wheel case; No. 12 represents the floor plate. ARTICLE 84. Theory of the Draft Tube. The draft tube is an air- tight cylindrical extension secured to the lower or discharge end of the runner. The theory of its service is based upon the atmospheric pres- sure of 14.72 pounds per square inch, which equals the weight of a column of water about 34 feet high; in other words, a column of water of this height, and at rest, is balanced and therefore held in equilibrium by the atmospheric pressure. When the water in this column is in motion, falls, the head represented by the velocity with which it falls at the point of exit from the lower end of the column must also be balanced by the 297 298 HYDRO-ELECTRIC PRACTICE atmospheric pressure, and the theoretic height of the column held in equilibrium, or which can be maintained in a draft tube, is then reduced by this head. If the exit velocity from a turbine runner is that due to a head of thirty feet, or approximately 0.2 ^ 2 g h = 7.2 ft., and the water continues with this velocity to the exit end of the draft tube, the head represented by this velocity is h = 7.2 2 -f- 2g = 0.8 ft., and the theoretic height of the column held in equilibrium in the draft tube is 34 0.8. If the velocity in the draft tube were 46.8 ft. per second, then the corresponding head would be h = 46.7 2 -f- 64.4 = 34 ft. (about), and the theoretic height of the column balanced by the atmospheric pressure would be zero. Any other losses of head occurring during the water's passage through the draft tube, as well as that represented by the energy remaining in the finally escaping water, must be deducted from the theoretical 34 feet. From the foregoing it is apparent that by the use of the draft tube the exit velocity from the runner may be materially reduced during its passage through the draft tube by gradually increasing the flow area in the latter, and that therefore otherwise lost head is conserved and avail- able to produce useful work; That the opportunity of gain from this source is greater with a long than a short draft tube; That the use of the draft tube permits the placing of the turbine at a convenient height above the tail water, while without it the turbine must be placed at or below the lower level; That the draft tube makes it feasible to place the turbine on a hori- zontal shaft at sufficient height above the lower pool to allow of directly connecting it to the electric generator or other machinery; and there- fore it is true that the draft tube brought out the horizontal turbines. It will also be understood from the theory presented that draft tubes cannot be used, as such, with impulse turbines, since the water column passing through the impulse turbine is not continuous. The practical application of the draft tube, its most efficient design and length under differing conditions, is fully treated in a succeeding article. ARTICLE 85. Theory of Deducting Turbine Efficiencies. The useful work represented by the turbine output is the total available energy less EQUIPMENT 299 the losses occurring in the turbine; these losses are of three kinds, hy- draulic, mechanical, and un-utilized residues. The first are of manifold origin, generally caused by friction, impact, and leakage; they are best identified by tracing the water's flow as it passes through the turbine. (a) In passing through the guide-vanes some loss is experienced due to the friction of the passing water against the walls of vanes; the best conditions exist when the walls of the vanes are parallel, thus avoiding contraction of the passing vein, and when the guide-vanes are made of hard metal and their surfaces are polished. It is especially important that the guide-vanes be frequently examined and repolished, as their surfaces are rapidly roughened, which is the common experience when the water carries considerable sand and other suspended matter. (b) When passing from the guide passages into the runner the probable losses are due to impact, to retardation, and to leakage through the clearance be- tween the guide-wheel and the runner. If the water, upon entering the runner buckets, strikes the vanes tangentially, the only other cause of loss from impact is the striking of the edges of the buckets as they pass by the guide openings; of course this can not be avoided, but the effect may be minimized by reducing these bucket-vane edges to the sharpest practical shape and thus maintaining them. Some clearance must be left between the guide-wheel and the runner, as the former is stationary while the latter rotates, and therefore leakage will take place, particu- larly as the interior water pressure exceeds the exterior; the clearance should be a practical minimum, which necessitates accurate and true machining of the runner bands and guide-wheel plates. This loss from leakage through this clearance is one which increases with wear and cannot well be guarded against. (c) Passing through the runner the loss is chiefly that due to the friction against the walls of the bucket vanes, which should be of hard material and polished ; in fact the conditions here are analogous to the passage through the guide-vanes. (d) Passing out of the runner the principal loss is caused by the change in the velocity, which may be kept at a minimum by the proper designing of the draft tube. (e) Passing through the draft tube losses are caused by friction against the tube's walls, which may be considerable, or very small, depending solely upon the proper design and construction of the tube with a view of avoiding joint, rivet, and other obstructions and maintaining the surfaces as smooth as practicable by frequently coating them. (f) Passing out of the draft tube losses may be caused by obstructions to the free escape of the water; the water cushion below the draft tube may be too shallow, the tail-flume dimensions insufficient or badly distributed. These six may be summed as the hydraulic losses or inefficiencies; their aggregate depends upon the conditions pointed out; when design and construction are the most suitable for the purpose and the best, the 300 HYDRO-ELECTRIC PRACTICE hydraulic losses may be taken to aggregate from 10 to 12 per cent., while they may be double of this where design is faulty or construction and finish are indifferent. The losses due to mechanical causes are chiefly those of friction in shaft bearings, which with the best available appliances may be taken for each bearing at from 1 to 2 per cent., while it may be double or much greater when the true alignment of the shaft is permitted to be disturbed. The last of the losses heretofore enumerated is that represented by the unutilized energy remaining in the escaping water; proper design should keep the exit velocity to 0.2 or 0.25 of the velocity of total available head, and beyond this no further reduction of this loss, with a proper use of the draft tube, can be secured. This last loss from unutilized energy will be from 5 to 6 per cent. Summarizing these losses in reaction turbines: hydraulic losses 11 to 12 per cent. mechanical losses for two bearings 2 to 4 per cent. unutilized 5 to 6 per cent. 18 to 22 per cent. representing the best theoretic conditions, and therefore obtainable efficiencies, of output of from 78 to 82 per cent. It will be noted that two of the causes of losses grow out of the use of the draft tube, and these would not occur were no draft tube employed; the significance of this applies only to impulse turbines in which, for this and other reasons, a considerably higher efficiency of output can be realized, frequently reaching 90 per cent, and more. ARTICLE 86. Typical Turbine Installations. Reaction turbines may be installed (a) On vertical shaft, (b) On horizontal shaft, (c) Cased and supplied through penstock, (d) Drowned in open bay, (e) Cased in pairs, (f) Drowned in tandem, (g) Drowned side by side, (h) Drowned superposed. Impulse turbines are always placed in cases and operated on a horizontal shaft. EQUIPMENT 301 The different installations of the reaction turbine are illustrated by succeeding figures, and the principal dimensions, such as are required in planning the power house, are given on diagrams; no particular make of turbine is herein referred to, but the information in these figures and diagrams applies generally to the reaction turbines manufactured in this country and may be safely accepted for the purpose above indicated. Fig. 115 illustrates the vertical turbine drowned. The unit of this installation may consist of one or of several wheels; the generator may be coupled to the vertical shaft, a practice which is quite general abroad, in which case the generator operates horizontally and is sometimes called the umbrella type. The installation of the American Niagara plant is of this arrangement. More frequently the vertical turbine shaft is geared to a driving shaft, the generator being coupled to the latter, and in that case several turbines may be thus installed in one power unit, all being geared to a union shaft, so that each can be cut out separately. The turbines of the same unit may be placed in one or separate bays, the latter arrangement allowing of making repairs to any turbine of the multi-unit without stopping the operation of the remaining wheels. The installation of vertical turbines drowned and geared to a driv- ing shaft represents the oldest, the mill-power, practice in the utilization of water-power; it is also frequently chosen for hydro-electric plants, though it does not yield high output efficiency. Vertical turbines, drowned, with generators coupled to the turbine shaft, constitute the latest devel- oped installation, which is capable of yielding the highest obtainable output efficiency of reaction turbines. This installation is suitable for the lowest and for high heads, the limitations being the length of shaft, the weight of shaft, and the cost of open-bay construction; the Niagara installation represents the high- head limit, to the present time, being 175 feet; the turbines, however, are not strictly of the type here illustrated, but are double Francis tur- bines. The lowest head utilized by a hydro-electric plant, to the author's knowledge, is that at Rechtenstein, Austria, being a trifle less than five feet; the turbines are vertical and drowned, the turbine shaft being geared to the driving shaft. This arrangement is peculiarly adapted to very low heads, on account of the smaller depth of the turbine compared to its diameter. The power-house design suited for this installation is described in Article 76 and illustrated in Figs. 84 and 88. The guide-wheel rests upon 110 105 100 95 90 85 80 75 70 1 Tf i J --ft- i I i / n ^ LL B-- i ' - -7 V ^ A 1^ ' ^ s S f 1 ^ 2 M A-- -*j -^ > r ' / / ' " ^ / ^ ^ ? i x ^ 65 60 55 -^ ' S *^ E jfe / s s 2 ^ / ^ rf- ? ^ 50 - x 1* F"* ^ * j ^ 45 i Z -_^ ^ - -^ ** ^< ^^ ,x* D- ^ ^ ^.^ " <^ ^ 40 ^ ^-*-- - ^ ft* -t ^ ^ 4^^- 35 ^ - g - - ^ x 1 ^ ^-*- ^ 5: s* ** ^ 0*^ i *?. ^ ** IT 30 2 , y ? ^ *; ;z* ~- ^* * -^ 25 \ * ~ x- *_ + ^ ^^ B- rf .-- , - -- e rt. I D )i Ft in ag ir le a TS bi n PF in ne sic r. I \ yt\ 34 cas s. 20 15 10 * **> ^ < ^* V cd. 5 ^ D 4 c c 5 4 IA C C4 C* -D i i/) a a Ble i j >t J ie $ L'l u > u U i -4 -H 9 1 h Ln ,i cl i. 4> S; U V ) 303 304 HYDRO-ELECTRIC PRACTICE supporting frames of steel members secured to the pit structure; the gearing is similarly placed on an upper floor. Diagram 34 gives the approximate exterior dimensions of a single vertical turbine drowned. Example. For a 40" turbine the height from the supporting frame to the shaft coupling, D in the diagram, is 48"; the diameter of the guide- wheel, B in the diagram, is 67"; the total height from the top of the thrust bearing to the lower end of the draft tube, E + C in the dia- gram, is 66" ; the required width of the open bay in which this turbine is placed is 2 B or IF 2"; the length of the bay for two such turbines is double the width or 22' 4". In this manner the dimensions of the turbine bay for this installa- tion, and therefore of the power house, can be readily determined from this diagram. In this category of turbine installations falls that of serial turbines, illustrated in Fig. 87 of Article 76, which is specially adapted to fluctua- tions of head; in this, vertical turbines drowned are placed one above another, a separate tail-flume being provided for each, by which arrange- ment they are available to operate singly or jointly; this represents the only method at present known which solves the problem of utilizing excessive head fluctuations, and is deserving of far more attention than is now given it in the American practice. Fig. 116 shows the installation of vertical turbines cased, the water being supplied through penstocks. The cases are placed upon and secured to supporting frames, the penstock or supply pipe entering the case at the side or top. The shaft connection and generator drive are similar to those described for the vertical turbine drowned. The deter- mination between the drowned and cased installation of vertical tur- bines must be based upon the respective cost of open-bay construction and of turbine casing and penstocks; operation and output efficiencies are alike in both. This installation offers no special advantages with low heads; it is frequently met with in mill-power plants, the turbines being placed un-housed over the tail-race and geared to the driving shaft of the mill. The dimensions of vertical turbine cases are, generally speaking, the same as those given for the open bay of drowned turbines. Fig. 117 illustrates the installation of a pair of horizontal turbines drowned. -H NO 20 p i 3 t o. -e- e o o o 5 1 3 JB- >-K <-i B5 3 re 305 cu f*j a 306 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 Hor. Turbs. drowned. Dimensions. - appr. - -lit IE o ro o . . <* in inch. u> 307 308 HYDRO-ELECTRIC PRACTICE At the outset it may be stated that this represents that type of turbine installation best adapted to low and medium heads and is, next to the vertical drowned and umbrella generator plant, of highest practical efficiency. The turbine runners are secured to the ends of a union draft chest, as was shown in Fig. 112 of Article 81, both connected to one shaft, to which the generator is coupled or belt driven from it if high speed is desired for it. The installation is placed in an open bay, the lower flange of the draft chest resting upon and being secured to a sup- porting frame of steel members, the shaft bearing on floor stands or bridge trees. The gate devices of both turbines are operated by a union gate shaft finally connected to the turbine governor. The economical limit of this installation is found from a comparison of the cost of the turbine bay construction and that of turbine casings and penstocks supplying the water to them. The efficiency obtainable from this arrange- ment, as compared with that of horizontal turbines cased and penstock fed, should be higher, because of the loss of head involved in supplying water through pipes. The power-house design adapted to this turbine installation may be as shown in Figs. 85 and 86 of Article 76, with such variations in details as will be suggested by the local conditions and the power head. Diagram 35 gives the approximate exterior dimensions of this instal- lation for turbines of various sizes, from which the required bays can be planned. Example. For a pair of 35" turbines drowned, the height from the supporting frame to the centre shaft line, E in the diagram, is 3' 3"; the height from the supporting frame to the top of the draft chest, B in the diagram, is 5' 8"; the diameter of the draft tube collar, D in the diagram, is 8' 5"; the total length of the installation, A in the diagram, is 15' 5"; the required width of the turbine bay is 2 B or 11' 4"; the required length of the turbine bay is A + 5' or 20' 5". Fig. 118 shows the installation of three horizontal turbines drowned. This is the same arrangement as has just been described, with the addition of the third wheel, which discharges by separate draft tube. The draft chest of the single turbine is of the quarter-turn shape, the union shaft penetrating it by a stuffing-box. This arrangement is as efficient as that of one pair of turbines and frequently preferable in order to secure a higher generator speed. 309 310 HYDRO-ELECTRIC PRACTICE The dimensions for this installation are found from Diagram 35 for the pair and Diagram 36 for a single horizontal turbine drowned. Example. For three 30" turbines, the height from turbine sup- porting frame to the shaft and to the top of the draft chest is the same as that given for the double turbine on Diagram 35; the diameter of the draft tube collar for the single turbine, D in Diagram 36, is 4' ; the total length is the sum of A on Diagram 35 and B on Diagram 36, or 13' 1" + 11' 11" = 25' 6"; the width of the required bay is the same as that for the double turbine ; the length of the turbine bay is the length of the installation + 5', or 30' 6". The installation may be of a single horizontal turbine drowned, as shown on Diagram 36. In this case the open bay need only be long enough to allow the water to enter the guide wheel as is indicated by the partial bulkhead in the figure on Diagram 36. The dimensions may be readily found from Diagram 36. Fig. 119 illustrates the installation of two pair of horizontal tur- bines drowned. The characteristics of this installation are the same as those of one pair or of three horizontal turbines drowned, the difference being one of dimensions only, and they change merely as to the length, which is double that given on Diagram 35. In this manner any number of turbines can be united into one power unit. The plant on the Spring River, Kansas, recently constructed, consists of units containing four pairs of double horizontals drowned. The wisdom of such a long line of turbines operating one shaft may be questioned, on account of the many shaft bearings which must be free to line to avoid serious friction losses. Figs. 120 and 121 show the installation of a pair of horizontal tur- bines cased. As with vertical turbines, the installation of horizontals may be in cases, single or double, supplied through a penstock entering the case at the top or at the end, the discharge being by one or two draft tubes. This arrangement meets the requirements of heads which exceed the utilization of the drowned type and is available until the pressure head exceeds the economical limit of turbine-case strength. The power-house design for this installation is shown in Fig. 89, of Article 76. The dimensions for this programme are given in Diagram 37. 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 K- D 1 -? x Diagram 36 Single horizontal Turbine, drowned. Dimensions. El fisffisnr-rf^li IA . Tf iA inch. in 311 312 vD 313 314 HYDRO-ELECTRIC PRACTICE Example. For two 40" turbines cased, the height from the sup- porting frame to the centre shaft line, G in the diagram, is 4' 2"; the diameter of the case, A in the diagram, is 10' IV] the total length, F in the diagram, is 31' 8". ARTICLE 87. Reaction Turbine Output. The discussions of the theory of turbines in Article 79 and of turbine efficiency in Article 85 have paved the way for the presentation of this final turbine topic, "the output," a thorough understanding of which is highly essential to determine what is the most resourceful hydraulic equipment for a given case. The turbine output here referred to is the power yield at highest shaft speed with the least quantity of water at three-quarter gate opening, which is the definition of the maximum efficiency output. The condi- tions of this output are rigid as to speed, which, in hydro-electric practice, represents the first essential, because the efficiency of the generator is largely based upon it; in other words, the power yield rises or falls as more or less water is passed through the turbine, while the speed remains approximately constant. The three-quarter gate discharge basis is the most practical, lying midway between full and half, the latter being the low limit of resource- ful efficiency, while it provides a reserve output, from three-quarter gate to full, which is especially valuable in meeting the frequent increase of the generator load. The discharge from three-quarter to full gate is practically proportionate to the gate opening, while that at half gate is somewhat in excess of the half full gate discharge. The efficiency of this output is approximately 80 per cent., provided the conditions of design and construction on which it is based are met. The power constants here given are those of reaction turbines, and the values are those for one foot head; they are distinguished from the output of the same turbine for more than one foot head by the prime mark, thus P', Q', S', representing the power, discharge, and speed out- put of the turbine under one foot head, while P, Q, and S represent the output of the same turbine for a greater head than one foot. Power, in mechanical horse-power, for unit head, P', from 550 x efficiency -= Q' X 0.1136 X 0.80 = 0.09 Q'. 315 316 HYDRO-ELECTRIC PRACTICE For any head greater than one foot the discharge of the same turbine increases with V H, and the power output for any head H therefore is p = p' x V H 3 = 0.09 Q' X V H 3 . Discharge, in cubic second feet, from power constant For any head H, Q = Q' X V H = 11.1 P' X V H. Speed, in revolutions per minute, S', for unit head, from the peripheral speed due to 0.89 ^ 2 g = 7.1378 second feet, or = 428.268 minute feet, and, as turbine diameters are expressed in inches, = 5,139 minute inches, g , = 5139 1635 3.1416 " diam. in inches Diameter is expressed, as will be seen under Design Constants, as 257 D = 6.36 V Q' and inserting in above S' = ~7/y. For any head H, S = S' X V H = 257 V H + V Q'. Diagram 38 gives the standard maximum efficiency output of American reaction turbines, which are designed and constructed on the general lines detailed further on. Example from Diagram 38. For a 35-inch Turbine: Power constant is 2.8 mechanical horse-power, Speed constant is 47 revolutions per minute, Discharge constant is 31 cubic second feet. The output of the same (35") turbine for a 16-f eet head is : Power, constant, X V 16 3 = 179.2 m.h.p., Speed, constant, X V 16 = 188 r.p.m., Discharge, constant, X V 16 = 124 c.s.f. For a 60-inch Turbine: Power constant is 8.28 m.h.p., Speed constant is 27 r.p.m., Discharge constant is 92 c.s.f. Hor. Turbines cased) Dimensions. 317 318 HYDRO-ELECTRIC PRACTICE The output of the same (60") turbine with a head of 25 feet is : Power, constant X V 25 3 = 1035 m.h.p., Speed, constant X V 25 = 135 r.p.m., Discharge, constant X V 25 = 460 c.s.f. The efficiency of this standard output is (for one-foot head) from 62.5 Q' -*- 550, efficiency, E = 8.8 F or = 528 P Applied to above examples, 35" E = 8.8 X 2.8 Applied to above examples, 60" E = 8.8 X 8.28 For the 35" turbine with 16' H, E = 8.8 X 179.2 Q' (second feet) Q' (minute feet) 31 = 79.32 92 = 79.20 124 X 16 = 79.48 For the 60" turbine with 25' H, E = 8.8 X 1935. - 460 X 25 = 79.19 This is representative of the degree of accuracy of deductions taken from Diagram 38, the standard efficiency being 80. ARTICLE 88. Reaction Turbine Design. The elements of the design of the reaction turbine yielding the standard maximum efficiency output are : The diameter in inches, from the area required to pass the volume of water with one-foot head, Q' * -^""g = 0.1247 Q' (c. s. f.), expressed in cubic second inches = 17.9568 Q' (c. s. f.). The circular area which would pass this quantity (theoretically) is D 2 X 0.7854 and D 2 = 17.9568 Q' -f- 0.7854 - 22.863 Q' or D (theoretical diameter of turbine in inches) = 4.78 Q'. To compensate for the obstructions to the free passage of the water, the above theoretical value is increased by the coefficient of 1.33 and the turbine diameter = 1.33 X 4.78 VQ', or D - 6.36 VQ'j_ The vent area is found from the theoretical velocity -^ 2 g and the coefficient 0.60, or for unit head and in minute feet velocity, V = 60 X 0.60^2 g = 288.7 minute feet. The discharge through an opening of one square inch area is 288.7 -H 144 = 2 (appr.), and the required vent area in square inches = 60 Q' -f- 2 = 30 Q'. 160 n 150 - 140 - [ V J , 30 J J - j \ r j _ 120 - r \ / \ Diagram 38. ' ^ / I j 110 ~ Reaction Turbine ! " I ^ " \ t . Maximum / : \ > 1UO \ !> ' ii Efficiency Output j ' M / "^ ! D- i ' on - k / / 1 ^ S - * > I. a) \ J "5P ( an - 5 : \ J . ^/ 5 - ' \ f j| 5 ' s / \ ^ 7ft V t / /u \ ' T ^ -T! y _| V jy fin V SB oU _ r Sl- ^k jS? V Z N i 7 en -i \ nm / ^\ A /** "J !; ^ * ^ j .x 40 - fQ v inn C_, , ' ^ S J * ^ ^ ^ _^ . s ^ K _ ^ 5-3 _ / *5 *c r X an _ 5 ^ ^ s 7e _4 / >> -^. 2J / *, / ^s r^ --.., __ ' _ / ^11 - tf iJL^ n ** ZU ~| * . ;* 1 ' 5.0 5 * = "' J f " w X .*' in - , x *' : I 25 X ^^ i r p ij w t s .-" f h . 7 ^* ^> -* "!C - SI .==r: F I. J a tiik\ i:l < " vtf n o IA o in . in i/} so me! o cs l.t t 319 320 HYDRO-ELECTRIC PRACTICE Guide-wheel or gate openings represent the total vent area, which is generally divided between 12 such openings, the area of each is there- fore = 2.5 Q' (square inches). The dimensions of the guide-wheel or gate openings are generally one of width to four of height. The runner buckets should be fewer in number than the guide-wheel 'or gate openings, so that anything which passes through the latter, like chips, ice, etc., is likely to pass through the turbine proper without becoming clogged in it. The entrance angle to the runner buckets should be such as to avoid shock of the entering water. The clearance between the guide wheel and the runner should not exceed one-eighth of an inch. The bucket vanes are of a helical form, changing the direction of the flowing water nearly 180; their axial depth is fixed by the axial length of the guide openings, for the axially straight part, and the least addi- tional length which is necessary to secure a true helical curve. The draft-tube diameter at the entrance should be such that the velocity does not exceed five feet; the exit diameter should be 1.5 of the entrance diameter; the sum of the entrance diameter and the length above tail-water should be approximately 29 feet for diameters up to two feet, 27 feet for diameters from two to three feet, 25 feet for diameters from three to four feet, 23 feet for diameters from four to six feet, 22 feet for diameters from six to twelve feet. The structural finish of the turbine parts should be as defined in Article 93. ARTICLE 89. Output of Tangential Impulse Turbines. The efficiency of this type of turbines is somewhat higher than that of reaction turbines, owing to the fact that the water does not pass through guides and buck- ets, but is jetted directly upon the bucket faces; the hydraulic losses are therefore much minimized, while those of unused energy and of mechanical origin are about the same as for the reaction turbines. Draft tubes are not of the same value with these turbines as they are with the reaction types, unless the turbine runner is housed in an air-tight casing, EQUIPMENT 321 and then the loss of head is that represented by the height between the elevation of the nozzle delivering the jet of water and the elevation of the tail water. The constants of the maximum efficiency output of tangential tur- bines are based upon the standard efficiency of 85. The deductions of these constants follow the same lines as detailed in Article 87. Power, in mechanical horse-power, for unit head, P' = 0.0966 Q'. Speed, in revolutions per minute, for unit head, S' = 10.6 -f- V Q'- Discharge, in cubic second feet, for unit head, Q' = 10.35 P'. Diagram 39 gives these constants for unit head for the standard size tangential turbines as manufactured in the United States. Example from Diagram 30. For a 24-inch Tangential Turbine: Power constant is 0.0078 mechanical horse-power, Speed constant is 38 revolutions per minute, Discharge constant is 0.08 cubic second feet or 4.8 cubic minute feet. The output of this same 24-inch tang, turbine with a head of 900 feet is : Power, constant X V 900 3 = 21.06 m.h.p., Speed, constant X V 900 = 1140 r.p.m., Discharge, constant X V 900 = 2.4 c.s.f. For a 60-inch Tangential Turbine: Power constant is 0.047 m.h.p., Speed constant is 15.3 r.p.m., Discharge constant is 0.49 c.s.f. The output of this 60-inch tangential turbine with a head of 2500 feet : Power, constant X V 2500 = 5875 m.h.p., Speed, constant X V 2500 = 765 r.p.m., Discharge, constant X V 2500 = 24.5 c.s.f. The chief elements of the design of tangential turbines to yield the output expressed by the foregoing constants are for the diameter, in inches, D = 86.5 Q' (Q in cubic second feet), the nozzle, in inches, N = D -f- 18. Several nozzles may carry water to one wheel, as many as five being frequently used, whereby the same diameter tangential turbine dis- 21 322 HYDRO-ELECTRIC PRACTICE charges about eight times the normal volume, the power output being increased correspondingly while the speed is slightly lower. ARTICLE 90. Summary of Turbine Output Constants. - - These con- stants represent the standard maximum efficiency output of American reaction and impulse turbines at efficiencies of 80 and 85 respectively; the expressions are for unit head, or a fall of one foot, being power, in mechanical horse-power, with one foot head, P', speed, in revolutions per minute, with one foot head S', discharge, in cubic second feet, with one foot head, Q'. Reaction Turbines. Tangential Impulse Turbines. 0.09 Q' Power constant 0.0966 Q' 257 -* V Q' Speed constant 10.6 H- v Q' 11.1 P' Discharge constant 10.35 P' 6.36 V Q' Diameter 86.5 V Q' Nozzle (single) 4.75 V Q' For any head H the corresponding output is obtained for Power, from power constant X V H 3 for reaction and impulse turbines. Speed, from speed constant X V H for reaction and impulse turbines. Discharge, discharge constant X V H for reaction and impulse turbines. Diameter and nozzles remaining as per constants. ARTICLE 91. Determining the Turbine Equipment. As has been stated before, the chief criterion in selecting the turbine equipment for a hydro-electric plant is the speed. From the constants in Article 90 it will be noted that the ratio of speed of reaction and tangential turbines is about as 24 to one, and therefore the first will prove generally prefera- ble for hydro-electric installations until the head, and therefore the speed, becomes too high both for the reasonable wear of the turbine and the speed standard of the best adapted electrical apparatus for the con- ditions. No demarcation line can, however, be drawn between the adapt- ability of the two types of turbines excepting the general limitation of the high head, as for heads above 300 feet reaction turbines will not prove preferable over the tangential; however, there may be conditions, with heads much lower than that stated; where the tangential type should be preferred, as it must not be overlooked that from it can be secured an increase of not less than five per cent, output in power, which may, in small plants, form the deciding argument. -0.8 5*0.7 80 45 40 -0.6 25 -0.4 8-0.3 15 0.2 Z 10 0.1 Diagram 39. Tangential Impulse Turbine, Maximum Efficiency Output. ^5r H.E.P. H. v. S. 0.07 ~ 0.0651 0.06- 0.055- 0.05 0.045Z 0.04 Z 0.0351 0.03 Z 0.025- 0.02 0.0 ir O.OlZ 0.005^ 24 36 Diameter 48 60 72 323 324 HYDRO-ELECTRIC PRACTICE The power functions, available head and flow, being known, the constant output discharge volume is found by dividing available flow by V H; this is the value of Q', and the investigation is ready for con- sultation of Diagram 38 or 39, as the head may be low or medium or high. Example 1. Available flow is 460 c.s.f. and head is 16 ft. Q' = 460 H- V16 = 115. If this quantity is outside of the diagram scope, it exceeds the dis- charge output of a commercially standard reaction turbine, and it must therefore be reduced by division into the least number of parts required to bring the unit quantity within the limit of the diagram. Returning to Example 1, the unit discharge of 115 c. s. f. is found on the left-hand index and traced to the right until the discharge curve is intersected, thence leading downward to the lower index where the turbine size is found of which this quantity is the discharge constant, and from this to the intersections of the dimension index with the power and speed curves these constants are obtained, and from them the out- put for the available head of 16 feet. In this case a 67-inch turbine represents this discharge, and its constants are: P' = 10.5 S' = 24.5 Q' = 115, and the 16-ft. output, P = 672 S = 98 Q = 460; the speed is therefore 98 revolutions, which is too low for direct con- nected electric apparatus. Taking half of the unit discharge, 58 c. s. f., Diagram 38 gives a 48-inch turbine which .meets it ; the output constants are : P' = 5.25 S' =36 Q' = 58, the 16-ft. output P = 336 S = 144 Q = 232. If this speed of 144 r. p. m. is still too low, one-fourth of the flow constant is taken or 29 c. s. f., for this Diagram 38 gives a 34-inch turbine; the output constants are: P' = 2.6 S' = 49 and Q' = 29, the 16-ft. output is P = 166.4 S = 196 Q = 116. Two 34" turbines in one unit yield 332.8 m. h. p. EQUIPMENT 325 The ratio of turbine diameters as above, 67, 48, and 34, is the con- stant representing the ratio of the diameter of one large turbine to the diameter of two smaller turbines with like power output, and vice versa, which is expressed approximately by D = 1.42 d and d = 0.71 D. Example. The power yield of one 54-inch turbine is equalled by that of two 38-inch turbines from 54 X 0.71, and the power yield of two 23- inch turbines is equalled by that of one 33-inch turbine, from 23 X 1.42. The final comparative factors are speed and output expressed in terms applied to the commercial standard types of generators, that is kilowatt, in accordance with the maximum efficiency output of tur- bines, which is higher than the water-power-electric power ratio given in Diagram 3 of the first part of this volume, where a lower turbine efficiency was adopted in order to secure safe conservative estimates for the preliminary investigation of a hydro-electric opportunity. The following arrangement may be found convenient for the equip- ment determination. Q H D P S K.W. Available 1 200 36 Unit. 200 1 Per unit. Total. One turbine . . 90" Two turbines @ 600 36 64" 1,944 153 1,376 2,752 Three turbines @.... 400 36 52" 1,296 188 917 2,751 Four turbines @ 300 36 45" 972 218 688 2,752 Five turbines @ 240 36 40" 778 245 550 2,750 Six turbines @ 200 36 37" 648 265 459 2,754 Seven turbines @ ... 171 36 34" 561 294 397 2,779 Eight turbines @... . 150 36 31" 475 324 346 2,768 Nine turbines @ 133 36 29" 432 336 305 2,752 Ten turbines @ 120 36 28" 388 360 275 2,750 Eleven turbines @ . . 109 36 27" 356 372 252 2,772 Twelve turbines @ . . 100 36 25" 324 396 229 2,748. From this analysis of turbine output all feasible unit combinations can be drawn: Speed. Unit output- Twelve units of single 25" 396 229/ Six units of double 25" 396 458 Five units of double 28" 360 550 Four units of double : 31" 324 692 Four units of three 25" 396 687 Three units of four 25" 396 916 Three units of three 29" 336 905 Two units of three 37* 265 1,377 Two units of two 45" 218 1,376 Two units of single 64" 153 1,376 326 HYDRO-ELECTRIC PRACTICE This represents all the practicable turbine combinations for this set of conditions, covering a range of speed from 153 to 396 and of genera- tors from 229 to 1376 K.W. capacity, and it exhausts the investigation at the turbine end of the equipment, and is continued by the further examination of standard generator units and the final selection of such an arrangement as best harmonizes the three factors, market require- ments, turbine, and generator adaptability. With high heads, of 300 feet and more, the same process is extended to tangential impulse turbines, in which Diagram 39 may be utilized; here the scope of possible combinations is somewhat narrower, unless the feasibility of supplying the water by more than one jet is taken into consideration, which leads into the volute or central discharge turbine, types more frequently employed abroad, but which may now also be procured in this country, and represents the high efficiency of the tangen- tial turbines coupled with a large discharge capacity. ARTICLE 92. Turbine governors are required in connection with the operating of the turbine equipment of a hydro-electric plant when the head or the work to be done by the generated power, the load, fluctuates ; one or both of these conditions prevail in probably every hydro-electric power plant. Like other governors, turbine governors are expected to regulate the volume of the power-generating substance, in this case the water, which regulation, in reaction turbines, must be applied at the turbine gates, controlling the gate openings, while in impulse turbines of the tangential type, where the water is supplied to the buckets by the way of a nozzle, the regulation by the governor must be of the nozzle's opening, which is generally secured by the axial movement of a plug or needle passing in the interior of the nozzle back or forth as actuated by the governor's movements. These conditions are widely different from those prevailing in the regulation of steam-engines, steam being elastic and compressible, while water is not ; the steam valves to be operated by the governor being accurately fitting machinery parts easily moved and controlled, while the gates of turbines are large and heavy, and certainly not to be compared in fit and finish of motion to the valve; a turbine gate is exposed to the water pressure and when once set in motion is not readily stopped or controlled. All these conditions make it necessary that a turbine governor be supplied with some other source of energy, to be applied to the regulating of turbine gates, than that represented by the usual centrifugal balls of the steam governor, and all turbine ca jW- Tvl 'OR SuPPL' ?J PlC TXP F0 Ej'l-IAOST Figure 123 Sturgess Governor EQUIPMENT 327 governors have such additional power source made available through the initiative of the centrifugal speed regulation. This is the relay energy source of the governor, and may be of mechanical, hydraulic, electric, or pneumatic origin, the first two being those applied in American practice. The manufacture of governors of this class is restricted in this country to a few* concerns, and it will serve the purpose best to describe, very briefly, the pertinent characteristics of the different types, which here follow; the illustrations of these governors have been furnished by the respective makers of the machines. The Lombard governor is manufactured by the Lombard Governor Company, at Ashland, Mass. ; it is of the hydraulic type. Fig. 122 shows the elevation of one of the several types and a section with the dimensions of the important features. This governor consists of the following parts: A centrifugal speed regulator, a regulating valve with adjustable valve stem, a pressure tank and receiver, a hydraulic cylinder, power pump, antiracing mechanism, and terminal connections of racks, pinions, clutch, and hand-wheel shaft. The governor's operation is briefly described thus: The centrifugal head is connected to a regulating valve by -a valve stem in two parts connected by a screw coupling, which is adjustable and whereby the normal governor speed may be fixed or altered. The fluctuation of the centrifugal head actuates the regulating valve, which permits fluid under pressure to pass from a pressure tank to the hydraulic cylinder which controls the gate operations. The oil is pumped into the pressure tank by a suitable force pump; where high pressure heads are available, water pressure may be utilized ; the oil which is exhausted by the hydrau- lic cylinder passes back into the receiver from whence it is again returned by the pump to the compressor tank; in this manner the relay energy is practically maintained constant. The Sturgess governor is also of the hydraulic type; it is manufactured by the Ludlow Valve Manufacturing Company, at Troy, N. Y. Fig. 123 shows this type of governor in elevation. It consists of a centrifugal governor, a pilot valve operated by the centrifugal governor, an operating cylinder controlled by the pilot valve and operating puppet valves of the main cylinder, a system of floating levers between the operating cylinder and the puppet valves, puppet valves which control the pressure in the main cylinder, a main cylinder with piston, rack, and pinion operating the gate shaft, and a compensator to prevent racing. 328 HYDRO-ELECTRIC PRACTICE The above outline of the principal parts practically describes the operat- ing method. The centrifugal governor is belted to the turbine shaft, the pulleys being proportioned to secure the desired speed of the gov- ernor; when the governor operates at the normal speed, the pilot valve stands between the two ports of the operating cylinder, while the smallest deviation from normal speed raises or lowers the pilot valve and affords a passage, to the fluid under pressure, to the hydraulic cylinder connected to the turbine gate shaft. The Woodward governor is manufactured by the Woodward Gov- ernor Company, of Rockford, 111. It is a mechanical governor that is, the relay energy is of mechanical source. Fig. 124 shows the elevation of this governor, known as the com- pensating type. The power which operates the governor is taken from the turbine shaft by a belt to a pulley on the main governor shaft, to which a double bevelled friction wheel is keyed through which the power for the gate operation is applied. The friction wheel is made of compressed paper. On both sides of the friction wheel are friction pans whose faces are of the same bevel as those of the friction wheel ; one of these friction pans effects the opening, the other the closing, of the turbine gates. The friction pans are pressed into the hubs of spur pinions which run free on the governor shaft and engage with gears of a back shaft, one direct and the other through an intermediate gear. Friction wheels and pans are cleared by adjusting rollers. The governor's regulating action is initiated by the centrifugal balls, their deviation from normal speed forcing the friction wheel against the respective friction pan and this in turn acting upon the gate operating shaft. The governor is self-contained, consisting of the following principal parts : a revolving double feed cam, a vertical rock shaft, a main friction shaft, a speed governor, a compen- sating device, a friction wheel, and the friction pans, with gears, pinions, and connections. The Lombard-Replogle governor is manufactured at the Replogle Governor Works, at Akron, Ohio; it is a mechanical governor. Fig. 125 shows the elevation of this governor, in which the speed governor is of the horizontal type, being placed in the main pulley which is driven from the turbine shaft. The action of the speed governor is to press friction wheels into -contact at any deviation from the normal speed, when the power developed from these primary or tripping disks brings, the secondary or main operating drive into action. The main FIG. 124. Woodward Governor. j^ OF THE \ UNIVERSITY 1 OF I EQUIPMENT 329 drive consists of two concave disks which are lined with leather and which rotate in opposite directions and engage a spherical pulley placed concentrically between them. The tripping frictions force this spherical pulley out of the centres of the leather-lined friction disks, causing con- tact with the moving surfaces and imparting the power which operates the turbine gates. The movement of the spherical pulley in any direc- tion returns it to its normal position at the centre of the friction disks, this being its position of rest. In addition to the effect of the primary disks in forcing the spherical pulley out of the centre of the friction disks, it also neutralizes the speed of the governor balls and, it is claimed, prevents hunting or racing. This, like any of the other turbine governors, may be regulated, as to the standard speed of the governor element, by electric devices operated from the switchboard of the operating station. The power required to operate turbine gates depends upon so many different conditions that a practical formula cannot be developed. From extensive experiments made with turbines fitted with balanced swinging or wicket gates, which were carried on under the supervision of the author, it was found that the power required to operate the gates of 33-inch reaction turbines under a head of 16 feet, from their closed to their full open position, was 500 foot pounds; with gates of the same type and correctly swung and balanced this power will vary directly as the head and as the cube of the gate's axial diameter. Cylinder gates require more power, and there are other styles of turbine gates which take still more, though these are becoming obsolete. Governing tangential impulse turbines is now generally accomplished by regulating the area of the nozzle through the medium of a plug or needle operating axially in its interior. This may be accomplished by any of the governors described, or by a specially designed hydraulic or electric motor secured directly to the terminal of the supply pipe near the nozzle. Considerations of equally great importance in connection with the governing of these types of turbines relate to the necessary compensation in the supply pipe for the sudden changes and speeds of the volume of the water passing through it and which will be conse- quential of the governing method, that is the regulation of the volume sup- plied to the turbine buckets by the way of the jet issuing from the nozzle. It needs no specific discussion to point to the dangerous conditions which may be created for the safety of the supply pipe and its connections. 330 HYDRO-ELECTRIC PRACTICE Figure 126 Hydraulic relief valves may be placed near the nozzle and connected to the supply pipe, or a by-pass actuated by a valve responding to an excess pressure; stand-pipes are also effective in protecting the supply system. Of all these the hydraulic relief valve is to be preferred; the by-pass incurs a considerable waste of water which, in high-head developments, needs to be conserved, and the stand-pipe will, as a rule, entail con- siderable expense. ARTICLE 93. Electric Equipment; Magneto-dynamic Theory. Electric power is the measure of the useful dynamic work of magneto-electric energy, which is the product of electro-motive force and elec- tric current. Electro-motive force is the expression of stress due to the difference in potentiality of the magnetic flux of sep- arate bodies which are brought within each other's sphere of influence. The magnetic flux consists of the magnetic waves streaming from and surrounding the source and seat of magnetism; the sphere of this flux is the magnetic field. Fig. 126 represents the field of a magnet; it shows the streaming forth of the magnetic flux from one pole, the north, spreading out over more or less space around the body of the magnet, the core, returning reassembled into the other pole, the south, and, presumably, passing through the core back to the north pole. If the two poles are connected by a piece of metal, the keeper, no evidence of the flux can be traced. Alessandro Volta, an Italian physicist (1745-1827), and Luigi Galvani, of Bologna (1737-1798), jointly discovered that two dissimilar metals, or a metal and a metalloid, are capable of forming an electric source when dipped into an electrolyte, or will produce a difference of electrical potential by mere contact. This is voltaic electricity. Many substances become electrified by friction, from which indeed the name, from electrum 208 EQUIPMENT 331 Figure 127 or amber, a material especially susceptible to electrification by friction. Electricity thus created may be conducted through proper mediums- copper, silver, aluminum -and becomes the electric current. Fig. 127 represents a conductor carrying an electric current, by which it becomes the source and core of a magnetic field surrounding it in a manner analogous to that of the magnet shown in Fig. 126, the flux taking the general shape and characteristic of circular whirls; in fact the electricity or current appears to reside largely in this flux, which, upon a rupture of the conductor, retreats into the core and manifests itself by the spark which escapes at the point of the conductor's break. When a conductor, carrying an elec- tric current, is wound about a piece of magnetizable metal, the latter becomes a magnet and displays all the charac- teristics above described; or, if such a piece of metal is pushed into the interior of a conducting coil carrying an electric current, the piece likewise becomes a magnet. From these phenomena it is deduced that the molecules of certain matter, especially metals, are individual magnets resting normally in an unhar- monious state, that is their pole direc- tions are not continuous, and that the influence of the electric current, and the accompanying magneto-electric flux, orders these molecules into a complete chain of magnets, thus opening the way for the flow of magnetic lines through the matter and, therefore, the appearance of the magnetic flux around and about the magnet. Michael Faraday, an English physicist (1791-1867), discovered that the moving of a conductor through a magnetic field and crossing the lines of force induces electro-motive force in the conductor in direction at right angles to that of the conductor's motion and to the lines of force cut by it. This is the basic principle of electric generators and motors, that is, converting mechanical energy into electric current, or vice versa, by means of magneto-electric energy induced by the moving, generally rotary, of a system of electric conductors through magnetic fields. . Magneto-electric Units. The flux lines passing through the air space of a magnetic field are the lines of force, the magneto-electric energy H.E.P. H. v. S. 209 332 HYDRO-ELECTRIC PRACTICE finds its origin in the influence of these lines, and the force they represent upon bodies susceptible to such influence and which cross their paths, their aggregate, the magnetic flux, is denoted by "N," being the measure of the total number of lines of force, which, as appears from Fig. 126, is the same along any direction across their path. The lines passing through the magnet proper are the magnetic lines, which are measured by the number in a unit cross-sectional area, one square centimetre, of the core, and are denoted by "B" or flux density. The magneto-motive force emanating from the magnetic flux is denoted by "H," and is meas- ured by the C. G. S. (centimetre-gramme-second) work unit, the dyne, a force which imparts a velocity of one centimetre in one second to a mass of one gramme; a unit magnetic pole is one which repels a pole of equal strength, at a distance from it of one centimetre and in air, with the force of one dyne; a field of unit intensity exists therefore at a distance of one centimetre from a unit magnetic pole. The functions relating to the generating and conducting of electric currents are somewhat analogous to those concerned with the flow of water, pressure, volume, and friction of conduit being typified by (pressure) electro-motive force, (volume) current, and (friction) resistance in the conductor. The unit measure of electro-motive force, or electric pressure, is the volt (after Volta), which represents that force induced in a conductor cutting 100,000,000 lines of force in one second; its symbol is E. M. F. or "E." The unit measure of current is the ampere, named so by the Inter- national Electrical Congress at Paris in 1881, in honor of the celebrated French electrician Andre Marie Ampere; this unit represents a rate of flow, or transmission of electricity, which will pass, with the pressure of one volt, through a conductor whose resistance is unity; it is symbolized by "C." For the resistance unit the ohm was adopted by the International Electric Congress in 1893, in honor of Dr. G. S. Ohm; this represents such a resistance of the conductor as will limit the flow of electricity under pressure of one volt to a current of one ampere; its sign is "R."' Therefore E = C X R, C = E ^ R, R = E -^ C. The electric energy or power unit is the watt, named in honor of the Scottish engineer and inventor James Watt (1736-1819), which represents EQUIPMENT 333 that rate of work resulting from unit current flowing under unit pressure, therefore also called the volt-ampere. One watt equals 1 -5- 746 horse-power, or one electric horse-power, Ehp = 746 watts and 1000 watts are one kilowatt. The electro-motive force represents the origin of the final output, its advent through induction, just as the head in hydraulics renders the flow, or the current, available; and, since its magnitude is proportional to the number of force lines cut in a given time, it is evident that it de- pends upon the three functions, force lines, conductor, and movement. " N," the number of force lines cut in one second, depends upon the section, the magnetic permeability, and the magnetization of the magnet. The section may be any which adapts itself to the purpose; generally speaking, it is a good feature of a dynamo to have the field magnet or magnets of super-large section ; the field may be that of several magnets of suitable form and conveniently placed for the economic and efficient design of the machine. The magnetic permeability of the materials used for dynamo magnets differs considerably; wrought iron probably is of the highest degree, followed by cast-iron and mild steel. The mag- netization may be to any degree within the limit of saturation; it is pro- vided by passing conductors around the magnet core, and its measure is expressed in ampere-turns, which represents the unit of magneto-motive force and is equal to that produced by a current of one ampere flowing around a single turn or spiral of the conductor and is denoted by "C S." "Z," the second function of electro-motive force, is the number of conductors which cut the lines of force; they may be as numerous as the machine's arrangement will allow; Z represents the number of con- ductors connected in series. The third function, "n," relates to the motion or movement of the conductor, and therefore is a question of speed and of mechanical con- sideration chiefly. The theoretical magnitude of the electro-motive force is expressed by E = n X Z X N + 100,000,000, or = n X Z X N -T- 10" ARTICLE 94. Some Current Symptoms. Alternations. As the electro- motive force, and therefore the current, finds its origin in magnetic 334 HYDRO-ELECTRIC PRACTICE Figure 128 stresses, it follows that it will fluctuate in magnitude and change in direc- tion as the number of force lines traversed by the conductor increases or decreases, and that therefore the generated current alternates. Fig. 128 illustrates the simplest method of current generating by one conductor, being a loop, revolving axially between the two pole faces of a magnet. Reference to Fig. 126 of the general grouping of the lines of force makes it clear that when the loop is in the vertical position it embraces the least number of force lines; while turning through a right angle the number of lines cut by the conductor gradually increases, and they become greatest when the loop reaches the horizontal position; during this path the electro-motive force has constantly risen and has maintained the same direction. Descending through the second quarter turn, the num- ber of force lines cut by the conductor decreases until the vertical position is reached and with it the low point of magnitude. Rising through the third and fourth quarters the same process is repeated. H.E.P. H. v. S. 210 Figure 129 H.E.P. H.v. S. 211 Fig. 129 shows diagrammatically the linear development of these alternations of the current in magnitude and direction during one com- plete revolution of the conductor; the horizontal line corresponds to the vertical position of the conductor as above described, the upper and lower points typify the horizontal position of the conductor. The EQUIPMENT 335 Figure 130 movement of any fixed point, "P," may be traced around the circum- ference of a circle the radius of which corresponds to the amplitude of the highest point which is reached by the current's magnitude, and from this it is apparent that the electro-motive force at any point, or at any period of time, in the path of the alternating current equals the sine of the angle through which the conductor has turned from its initial vertical position. Frequency. The current wave due to one complete revolution of the conductor is called a period, and the number of periods occurring in one second are denominated the periodicity _____ or the frequency, or the cycle of alterna- tions, and are symbolized by "n." The frequencies equal the product of conductor revolutions per second and the number of the field magnets passed by the conductor during one complete revolution. Example. With a speed of conductors of 240 revolutions per minute, or 6 per sec- ond, a six-pole (3 magnets) dynamo will generate current of 18 frequencies. Phase. When, as in Fig. 128, one con- ductor is provided for each magnet, being a group of conductors for each pole, the alternations of the current are monophase, that is, there is one phase only in the complete period ; if, however, the number of conductors is doubled, a two- phase current results, and three-phase when six groups of conductors are provided. Fig. 130 shows the two- and three-phase current waves, the alterna- tions in the first being of quarter periods, or the phase angle 90, while in the three-phase current the alternations differ by 60. Any alternat- ing current other than single-phase is called polyphase. Inductance, Self-induction, Reaction. As has been shown in Fig. 127, a conductor carrying an electric current is surrounded by a magnetic field, and, according to the general theory of the origin of electro-motive force being due to magnetic stress, it is evident that the current carried by the conductor will, when brought into the sphere of another magnetic field, undergo changes corresponding to the relative stress conditions. H.E.P. H.v. S. 336 HYDRO-ELECTRIC PRACTICE Such an influence upon a conductor is called inductance, and manifests itself in destroying the harmonious flow of volts and amperes by the reaction of the self-induced electro-motive force and its retardation of the current's phase, the amperes, which fall behind the volts, this con- .dition being called the lag; the extent of this disturbance is expressed by the angle of lag, which is the measure of that portion of the angle of phase represented by the lagging of the ampere behind the volt wave. Impedance. Inductance must be overcome by increased electro- motive force, that is, whereas the normal expression for "C" is E -f- R, E being the impressed voltage and R the resistance of the circuit, in the presence of inductance C becomes, as illustrated in Fig. 131, C = E^'R 2 + C'L, in which L is a coefficient of self-induction. E of this value is the impedance, the impressed voltage or the ratio of produced volts to amperes. When there is no induction, that is in steady currents, impedance equals resistance. Capacity, Reactance. The opposite effect of inductance occurs in a current when charging a condenser; this causes the amperes to lead the volt phase, which condition is termed capacity, being caused by reactance of the condenser. Inductance and capacity, being opposite in effect, may be created for the purpose of counteracting each other, when the current is said to be non-inductive, and in that event C = E -f- R. Watt-less Current. When the phase of volts and current differs considerably by reason of lag or lead caused by self-induction or capacity, the actual watt output is less than what would be indicated by the prod- uct E X C. Fig. 131 shows the two components, and these may be considered as representative of the working and the watt-less magnitudes. Continuous Current; Commutator. The alternate current (Fig. 132) may be made continuous in direction by connecting the terminals of the conductor to separate segments of a ring, the segments being insulated from each other, and by passing metallic brushes over the circular seg- ment surfaces in such a manner that the gap between the two segments is closed by the brush contact at the period when the alternation of the current reversal takes place ; the exterior circuit is connected to the brushes and the commuted current flows into it in continuous direction. EQUIPMENT 337 Figure 131 H.E.P. H. v. S. 213 The apparatus through which the alternate current is changed into con- tinuous current is called the commutator. ARTICLE 95. Dynamo Parts; their Purpose and Design. Electric dynamos serve the purpose of generating electric energy, the origin of which may be continuous or alternating current; electric energy may therefore be generated by continuous or alternating current dynamos commonly called D. C. generators and alternators. Any dynamo consists in general of the same parts, the magnets, which are assembled in the field, and the conduc- tors, which are grouped in an armature; one of these parts revolves, and then is the interior, the other is fixed, and is the exterior; both are concentric of each other. The fixed or exterior part becomes 'also the frame of the machine, terminating below in a base and frequently having connected to it shaft- bearing stands; the interior or revolving part is connected to the shaft. The variations of types and forms of parts are manifold, and it is not the purpose here to describe any particular make, but to give such an outline of the purpose and theoretical design of the principal parts as to enable the investigator to recognize compliance with or any gross departure from these essentials. Continuous-Current Dynamos. The field consists of the magnets and their windings. The magnets are radial arms or shoes connected to a yoke; the ex- treme ends of the magnet shoes are the poles. In dynamos of large output, such as are employed in the equipment of hydro-electric plants, the field is multipolar, as distinguished from that of small continuous-current dynamos, in which the field consists of one magnet or two poles, being termed bipolar; the multipolar dynamos have four, six, eight, or more poles arranged along the interior periphery of the fixed field, the frame part becoming the yoke, or to the exterior periphery of the rotating field in which the hub represents the yoke. 22 figure 132 214 338 HYDRO-ELECTRIC PRACTICE Magnet arms are generally built up of laminated (insulated) metal disks of wrought iron or mild steel, being of circular or other shape. The field of all large dynamos consists of electro-magnets, that is, the magnetization is created by passing an electric current through con- ductors wound around the magnet limbs; this is called excitation of the field. The field of a continuous-current dynamo is self-excited; the electric current, in other words, carried by the field conductors is gen- erated in the dynamo armature; this is not the case in alternators, as will be seen later on. The field winding may be of the continued armature conductors, which is called series wound; or it may be of a smaller con- ductor than the armature coils and connected with the armature winding as a sort of splice; this is called the shunt-wound field; and finally the field winding may consist of a combination of the series and shunt method, the latter overlying the former, and this is called a compound wound field. As will be seen later, the field excitation, and therefore its winding, forms one of the most important means of regulation of the output, and therefore this characteristic of the field winding practically conveys, in a large sense, a conception of the efficiency of the dynamo as to the regularity of its output. There are many reasons for the desirability of the compound winding of the field, and it is practically the general practice with dynamos of large output. The section of the magnets and the amount of the winding depend upon the permeability of the material of which the magnet is formed and the required magnetization of the field, that is of the flux density as expressed by "N" in the formula of electro-motive force, E = n Z N + 10 8 . The winding is measured by ampere-turns, which represent the product of the current, in amperes, carried by the wire and the number of turns around the magnet limb. The permeability of magnets of wrought iron and cast iron is given in the following table, which is according to Prof. Sylvan B. Thompson, where H is magnetic force, or the number of lines per square inch of the field; B is the flux density, the number of lines per square inch of the magnet section; and u is the magnetic permeability, or the specific conductivity, for magnetic lines, of the material in the magnet. EQUIPMENT 339 TABLE 30. WROUGHT IRON. H 30,000 10.2 2926 40,000 14 2857 50,000 20.9 2392 60,000 27.7 2166 70,000 40 1750 80,000 63 1368 90,000 105 856 100,000 245 407 110,000 686 161 120,000 1850 64 130,000 4500 28 140,000 7630 18 CAST IRON. B H u 25,000 30 843 30,000 53.5 445 40,000 163 245 50,000 447 112 60,000 940 64 70,000 1750 40 The required ampere turns for the field winding are obtained from different formulas; the result of the following equation, while not exact, will give practical useful values: S C = (B X L -f- 2.02) X 1.25, where S C are ampere turns (current in spirals) , L is the length of the air gap in inches, and 2.02 is the number of ampere turns required to produce unit flux density in an air space one inch long, 1.25 is a coefficient to compensate for the drop of magnetic potential. It may also be stated, as a general excitation rule, that dynamos up to 200 kilowatts output require exciting currents of 0.05 to 0.025 of their ampere output, and of 1000 kilowatts, 0.015 and less. The magnet section may be determined from N -=- B; N is the total number of lines of force and B the flux density as per Table 30. It is common practice to make the magnet section 1.66 of the armature core of ring and 1.25 of drum type. The size of the field magnet conductor is determined from the ampere turns, available winding space, and considerations of the conductor's resistance; the usually adopted density of field-coil current is limited to 2000 amperes per square inch. A convenient formula for the finding of field coil wire is S C = e -f- r, where S C is ampere turns ; e, the voltage at the terminals of the field coils; and r, the resistance of one turn of the wire. 340 HYDRO-ELECTRIC PRACTICE Resistance in copper wire is as per the following table. TABLE 31. TABLE OF COPPER WIRE, SIZE, DIM] Gauge B. & S. Brown & Sharpe Mils ilium. 0000 460 3NSION, WE Circular mils c.m. = d 2 . 211,600 167,800 133,100 105,600 83,690 66,370 52,630 41,740 33,100 26,250 20,736 16,384 12,966 10,404 8,281 6,561 5,184 4,096 3.249 IGHT, AND RESISTANCE. Weight in Ibs. per Resistance in 1000 feet ohms per M ft. bare. 0.04904 640 0.06184 508 0.07797 403 0.09827 320 0.12398 253 0.15633 201 0.19714 159 0.24858 126 0.31346 121 0.39528 99 0.491 63 0.6214 50 0.7834 39 0.9785 32 1.229 25 1.552 20 1.964 15.7 2.485 12.4 3.133 9.8 000 410 00 365 325 1 289 2 . 258 3 229 4 204 5 182 6 162 7 144.3 8 128.5 9 114.4 10 101.9 11 90.74 12 80.81 13 71.96 14 64.08 15. . . 57.07 Wire Formulas. c.m. is circular mils; R is resistance; W is weight; L is length. R = 11 X L -T- c.m.; c.m. = 11 X L -f- R; W = L 2 -r- 30,000 R; L = c.m. X R - 11; R = L 2 -5- 30,000 W; c.m. = 1,000,000 W * 3.03 L; L = W X R X 30,000. The armature consists of the core and the conductor. The cores may be of the ring or drum shape; they are built up of laminated sheet iron or steel disks, commonly from 25 to 50 mils in thickness, the ratio of external to internal diameter of ring disks being 5:3. Drum armature cores are generally greater in diameter than they are long. The exterior disk perimeter is shaped for the convenient and safe placing of the con- ductors, the forms for conductor seats, or beds, being generally of the tooth or slot type; sometimes they are circular holes near the exterior periphery. The armature winding consists usually of closed rectangular copper bar coils; the schemes of windings are of many different kinds, parallel, series, or mixed groupings, and in either of them the winding may be EQUIPMENT 341 of lap or wave. The number of armature conductors is ascertained from Z in E = n Z N -r- 10 8 ; E is the sum of the volts required for the exterior circuit and those lost in the armature ; the latter are expressed by r a C a , where r a is the armature resistance and C a the armature current. The size of the armature conductors is found from the wire table, the practice being to allow a current density of 3000 to 4000 amperes per square inch of conductor. The core section is found from the determination of the winding and size of the conductors. The commutator, sometimes called the collector, consists of bars and brushes. The commutator bars are usually of copper drop forgings and of a length equal to 1.2 inches per 100 amperes; their number is pro- portionate to that of the number of armature coils. Armature brushes are of woven copper wire gauze, or of spring copper strips, or they may be of carbons, but the use of the latter requires longer commutator bars. Mica is most generally used for the insulation of the commutator bars from the armature hub and from each other. Brush holders are the device by which commutator brushes are maintained in position; they are of various designs. Alternators for large output, as required for the equipment of hydro- electric plants, are generally polyphase, of 25 to 60 cycles and of high voltage; owing to the greater economy and safety with which insulation for high voltage can be secured in a stationary rather than a moving mechanism, the high-voltage alternators for transmission service are of the revolving-field type, the armature being the stationary or fixed part. The field is of the drum type, the magnet yoke being the hub and core, the limbs are secured to it radially; the poles are more numerous than in the continuous-current dynamo. The magnets are of like material and construction as described for the D. C. generators, but the flux density of the magnets is taken at a considerably lower constant, approx- imately 42,000. Excitation is not practicable by the alternating current, and there- fore is generally provided from a separate continuous-current dynamo; a larger inductive drop, due to the choking in armature coils and the demagnetization effect of the armature current, must be allowed than in the D. C. dynamo in determining the ampere turns of the field winding which is always compounded. The relation of speed, number of poles and of frequency has already been noted; it is expressed by n = 0.5 p X (N -r- 60), where n is the 342 HYDRO-ELECTRIC PRACTICE frequency of alternations, the cycles or periodicity, p is the number of poles (not of magnets), and N the revolutions per minute, which is the usual measure of speed. The armature of the revolving-field alternator is a cast-iron ring into which the laminated armature disks are dovetailed along the interior periphery; armature disks are somewhat thinner than those used in continuous-current dynamo armatures because of the higher voltage, usually from 0.012 to 0.008 inch. The armature winding is determined in like manner as that for D. C. generators, with proper consideration of the difference between the impressed and the actual volts which was presented in Article 94; the lap winding is preferable for high voltage. ARTICLE 96. Current Reorganization. The generated current is, as has been shown in Article 94, continuous or alternating, and the latter is monophase or polyphase; to change the generated current into any other kind of current, for the purpose of service, is characterized as reorganization of the current. The generated continuous current may be changed to alternate current by the aid of a motor-generator, being a composite machine con- sisting of a motor supplied and operated by the generated continuous current, which in turn operates an alternator connected to it, its output being alternating current of mono- or polyphase. The generated alter- nating current may be rectified into continuous current by means of the same device, in which case the motor, of the induction type, is supplied with and operated by the generated alternating current and itself operates the continuous-current dynamo. The same result may be obtained through the agency of a rotary convertor, and by a shorter process, this machine being a continuous- current dynamo fitted with collecting rings in addition to the commutator. The alternate current passes by way of these rings into the armature coils and thence through the rotary and its commutator, and therefore issues as continuous current. The general design of these reorganizing machines is similar to that of generators, as presented in Article 95. The phase of the current may be changed from mono- to polyphase, and vice versa, by the aid of a phase transformer, being of the type of a motor generator, in which the phase reorganization is brought about by the addition to the commutator of slip rings and by their appropriate connection to the armature conductors. EQUIPMENT 343 Fig. 133 ARTICLE 97. Current Transformation. When the voltage (E. M. F.) of any current is raised or lowered, it is said to be transformed. As may be inferred from the origin and characteristics of continuous current, as briefly presented in Article 94, this type of current can be transformed only by means of moving apparatus. Continuous-current dynamos may be connected in series, in which case the voltage in the exterior circuit is the aggregate of the voltages of the D. C. dynamos thus connected; the only other process of trans- forming continuous current is by the agency of the motor generator mentioned in the previous article. Alternating-current voltage may be raised or lowered by the aid of static transformers, in accordance with the fol- lowing theory. It has been noted in Article 93 that when a conductor carry- ing current is passed around a closed magnetizable core, magneto-electric force is set up in the core; when the current in the coil is of the alternating kind, the induced magnetic force retains the char- acteristics of alternations both in direc- tion and flux density, and by virtue of this condition magnetic stress is set up which becomes the source of an electro- motive force other than that of the current in the circuit which passes around the core. This induced electro-motive force acts in opposition to that of the magnetizing circuit and thus incites the latter to increased activity. If another conductor circuit is passed around the same core and is not connected with the magnetizing circuit, the increase of E. M. F. in the latter finds an outlet, or overflow so to speak, into this other conductor, and, under the constant pressure from its source, and the continued conflict between it and the back E. M. F. due to the magnetic stress set up in the core, it continues to pass into the second conductor. This is the principle of alternating current transformation illustrated by Fig. 133, in which C is the core above mentioned, P is the magnetizing circuit called the primary, and S is the second circuit, being the secondary. H.E.P. H.v. S. 210 344 HYDRO-ELECTRIC PRACTICE It may be pointed out that this current phenomenon may be likened to what transpires in the operation of a generator, that the primary is like the field and the secondary the armature, while mechanical motion is represented by the alternations, that is the continuous coming and going of flux density and direction, which is practically of the same effect, as far as cutting of magnetic lines in a space of time is concerned, as when the armature revolves and passes through the field in that manner; and from this it will at once be clear that no such phenomenon can occur with continuous current that, though the core would be magnetized, there would be no current in the secondary. Static Transformer Analysis. When the secondary is an open circuit, there is no transformation of E. M. F. ; the magnetization of the core originates a back electro-motive force of practically the same value as that of the primary, being diminished only by the voltage required to overcome the resistance of the primary coil. When the secondary is closed, a current is set up in it opposing that in the primary, its first effort being to demagnetize the core, and, since it is the expressed purpose of the primary to magnetize the core, a conflict or stress is set up which calls forth greater efforts of the primary to overcome the opposition of the demagnetizing influences, with the result that a distinct current passes into the secondary, being of like frequency and other characteristics as the primary excepting as to the E. M. F., as it is the purpose of the process to alter or transform this by raising or lowering the voltage of the primary to any desired in the secondary. The E. M. F. in these two circuits is proportional to the number of turns in each which pass around the core, which is analogous to the principle of field excitation explained in Article 95. In Fig. 133 the primary is shown of one turn while the secondary has four turns around the core; the .voltage of the secondary will therefore be four times that of the primary, while the current, amperes, in the secondary will be one-fourth of those of the primary. In this case the voltage is raised by a step-up transformer, the lowering of the voltage would be secured through a step-down transformer, both being of the same design and construction excepting as to the respective winding of the primary and secondary coils, which represents the ratio of transformation. In this connection it should be noted that with like current density per conductor section unit (square inch) the ratio of transformation must be accompanied by EQUIPMENT 345 a corresponding adaptation of conductor cross-section; thus the con- ductor in the secondary of a step-down transformer must have an increased copper section over that of the primary which is inversely to the voltage drop. Static transformers consist of the core, the windings, and the shell. The cores are of many different shapes, being generally formed of lami- nated iron disks; the windings are of insulated copper wire. There is no particular limit to the transformation ratio, the principal consid- eration in this regard being the heat which, is generated in the trans- former and may rise to a degree at which the insulations would suffer destruction; high- voltage transformers are therefore especially designed to keep this feature well insured by employing different methods of cooling the transformer and its various parts. Transformer coils are often placed in oil, which receives the heat and transmits it to the shell where it is readily radiated; the oil is also separately cooled by passing water through pipe coils immersed in it; again cooling is effected by passing cold air through the transformers, either by a blower or fan system. The losses in static transformers may be kept very low by proper design and construction; they are due to the resistance of the sec- ondary coils, to magnetic flux friction in the core, and to idle or eddy currents which are set up in the core; the aggregate need not exceed 2 per cent. ARTICLE 98. Current Transmission. Theory. Electric energy may be conducted to any distance, as its flow will always continue from a high to a lower potential, but, as in transmission of energy of any form, work is constantly being performed during its passage through the con- ductor, and, at some point or other, the energy thus expended may be- come so great a part of the impressed volume that its transmission, under such conditions, represents a waste rather than a gain. The work of the current during its transmission is that of overcoming the conductor's resistance to its free passage; just as the flow of water through a pipe is impeded by the roughness of the pipe's perimeter or its change of section, which is overcome by the expenditure of head, so the transmission of electric energy is made possible only by the over- coming of the conductor's resistance, which is accomplished by the expenditure of E. M. F. By Ohm's law C = E -- R and E = C R and 346 HYDRO-ELECTRIC PRACTICE R = E -r- C, from which R, the resistance in any length of a certain conductor, may be ascertained from 1 X r -=- cm, where 1 is the length of the conductor in feet; r is the resistance unit, being the resistance of one foot of copper wire of one mil section (one mil foot), which = 10.8 ohms, but is taken as 11 ohms, whereby the irregularities of the wire's section and the faults of joints are compensated for; cm stands for the area of the conductor's section in circular mils; therefore R = 11 X 1 -j- cm, and, inserting this in above equation for R, R = E -r- C, it becomes 11 X 1 -r- cm = E -r- C, in which C is the current (amperes) which is to be delivered for service, E is the electro-motive force to be expended in overcoming the resistance of the conductor, being termed the transmission loss or the voltage drop. Aluminum wire is well adapted for the purpose of transmission conductors; the ohmic resistance coefficient of aluminum is 17 per mil foot instead of 11, the coefficient for copper, and this value must be inserted in above formula when aluminum wire is being investigated instead of copper wire. Since, from above formula, the resistance may be found for any size of conductor, so may the size be determined from it to transmit a fixed current at a given line voltage over a known distance ; that is, from above cm = 1 X 11 X C H- E for copper and cm = 1 X 17 X C -T- E for aluminum. The weight of 1000 feet of 1000 cm copper wire is approximately 3 Ibs. The weight of 1000 feet of 1000 cm aluminum wire is approximately 1.5 Ibs. By symbolizing 1000 feet of the conductor's length as L, the weight of the conductor may be expressed from the foregoing formula by W = L 2 X33 XC-^E for copper conductors, and W = L 2 X 23.5 X C -* E for aluminum conductors. This refers to a single conductor. EQUIPMENT 347 From these expressions and from formerly discussed current char- acteristics, it is apparent that E is the principal factor controlling the value of W, for instance when the ratio of percentage of line drop from the impressed electro-motive force is fixed, the doubling of the impressed voltage will halve C, double E, and reduce W to one-fourth; therefore, the weight of the transmission conductor for given length, current, and drop varies inversely as the square of the impressed voltage, and for given current and drop and impressed voltage in direct proportion to length of transmission, the weight remains constant; while for given current and drop the weight increases as the square of the length. For the purpose of hydro-electric practice all current transmission factors may be determined from these formulae with sufficient accuracy to estimate the transmission conductors and their cost, but many refine- ments enter the problem when considered from a scientific stand-point. Diagram 16, appearing in connection with Article 28 in Part I. of this book, has been calculated for copper wire from above formula and is correct, within its scope, for the purpose of estimating the wire quantity. Transmission of continuous and of single and two-phase alternating currents is by two wires, all the current passing over every part, while three-phase alternating current may be transmitted by three conductors, each of which carries the current of its particular phase. In the above formulae, for determining cm or W of transmission-line conductors, the length, when considering continuous and single and two-phase alternat- ing currents, or in two-conductor circuits, is the developed length of the conductors or double the transmission distance, while for three-phase alternating current transmission the length is equal to the transmission distance. In finding the weight, therefore, L is multiplied by four for two-conductor lines and by three for three-conductor lines ; for this reason a three-conductor transmission line (of three-phase current) requires only 75 per cent, of the weight of copper needed in a two-conductor line of the same energy. Of the current symptoms briefly outlined in Article 94 those specially applying to current transmission are : inductance, which is the absorption of electric energy while producing a magnetic field around the conductor, or the setting up of an electro-motive force opposite to that impressed in the alternate current conductor, resulting in voltage drop at the line terminal; capacity, being the reactance of the transformation of alter- 348 HYDRO-ELECTRIC PRACTICE nating current and resulting in an increase of current in the circuit; and resonance, which is the neutralization of inductance and capacity with the effect of a considerable rise in the line voltage. The effects of all these in transmission are best met by an addition of not less than five per cent, to the cm or W of the transmission conductor as found from the quoted formulae. ARTICLE 99. Current Regulation. This subject, like the preceding electrical topics, will be treated herein only to the extent of presenting the apparatus and the purpose which it serves, as it may have to be considered in connection with the planning of the hydro-electric operat- ing plant and its equipment and for the preparing of the estimate cover- ing these. Regulation of current generating is, as has been pointed out in Articles 94 and 95, first secured by the turbine governor and second by field excitation, the first maintaining, as near as practicable, constancy of mechanical speed, the second of electro-motive force or pressure. The former is practically automatic, but the latter needs more or less personal attention, depending upon the current reorganization and transforma- tion methods and means, the character of the current service, and the fluctuations of the loads. At any rate certain apparatus is required to indicate output characteristics and detect irregularities, while others are needed to furnish ready correction for these. The purpose of regulation is generally to maintain constancy of pressure, voltage, in the exterior circuit, which, in the case of hydro- electric plant output, is the transmission line. At the generator, as has been noted, this is principally accomplished by regulating the exciting current, as this is the origin of the electro-motive force; on the line, regulation may be secured through static transformers with alternating current. Transformation is generally effected through a bank of trans- formers of equal units connected in series, but, as the cause of the fluctuations is mainly to be found at the service end of the line, regulation is best arranged for at this terminal, the substation. Regulating apparatus may be classified into switches, testing instru- ments, and correctors, most of which are collected on the switchboard, which consist of marble or slate tablets or panels placed against a suitable frame in the generating room and in the substation. The circuit con- ductors are led to the back of the switchboard panels, the latter being EQUIPMENT 349 perforated at the places where the switches or apparatus are to be secured so that they can be connected with the conductor circuits. Switches, or circuit breakers and closers, are devices by which con- ductor circuits are closed or opened; they are of various designs, all aiming to make or break the current by avoiding any arcing across. High- voltage switches are therefore necessarily of special designs and con- struction, and wherever practicable the switching of such currents is arranged for on the low-voltage side of the circuit. Circuit breakers may be of air or oil break type, the latter being always employed in high- voltage practice, and, when the voltage is very high, 20,000 and more, oil circuit breakers are operated by secondary pneumatic or electric power devices and are removed from the vicinity of any of the other electric equipment. Testing instruments comprise ammeters (amperemeters), which are of the galvanometer type, indicating the current strength by the deflection of a magnetic needle placed inside or over a coil of insulated wire through which the current to be measured is passed. Voltmeter is an instrument similar to the ammeter, of electro-magnetic type, its purpose being to indicate the voltage of the current. Wattmeter is the third of this class of testing instruments, indicating the watts ; though voltage and amperes are indicative of the watt output of the continuous current, this is not necessarily the case with the alter- nating current, where the product of the volts and amps represents the apparent watts, while the wattmeter indicates the effective watts. Phasemeters indicate the power factor of the current, which is the ratio of effective and apparent watts, or the phase difference. Syn- chronizers or phase indicators, as their name implies, indicate when synchronism, that is union of frequencies in the alternating current, exists between different alternators which are to be operated in parallel. Pilot lamps are connected across the dynamo terminals for the ready indication of the approximate pressure by the degree of their incandescence. Ground detectors are required for detecting and measuring grounds and leaks. Correctors are lightning arresters, which may be placed at the gen- erating plant, along the transmission line, and at the substation, for the purpose of diverting lightning charges. There are various types of these; 350 HYDRO-ELECTRIC PRACTICE one in common use consists of a number of air gaps between conductor plugs set in a porcelain block. Guard wires are also employed for light- ning diversion from transmission lines; they are metallic circuits (iron) grounded at intervals of 1000 feet. Choking coils are of copper wire so wound on or around iron core pieces as to possess high self-induction when used on alternating cir- cuits; their purpose is to obstruct or cut off alternating current with a smaller loss of energy than if it were used as ohmic resistance. Booster is a dynamo connected to a separate circuit for the purpose of raising its voltage above that of the other system of which it forms a part. Rheostats are adjustable resistance coils. ARTICLE 100. Electric Generating Plant. The character of the gen- erating equipment is to be determined with a view of securing high efficiency of resourceful output at reasonable first and lowest practicable maintenance, depreciation, and operating cost. The matters to be determined are: (a) the kind of current to be generated, (b) the generator voltage, (c) the generator units, (d) the mechanical power application to generators and exciters, (e) the types of generators, exciters, and governors, (f) the arrangement of the apparatus; the controlling features in this quest are: (g) the distance to the current market, (h) the character of the current service, (i) the available hydraulic and mechanical factors, and (j) the output efficiency, time delivery, and cost of apparatus. The current to be generated must be determined from the character of the current service and from the market distance. Continuous current is largely employed for arc lighting, exclusively for electrolithic opera- tions and accumulator charging, and is preferable, at the present state of the practice, for power service in which the fluctuations of the load are sudden and excessive, such as electric traction and lifting. The alter- nating current is largely used for incandescent lighting and mechanical EQUIPMENT 351 power application for factory and shop machinery and tools, pumps and elevators. The influence of the distance to the market is most potent with a transmission system, and, as far as it has a bearing upon the choice of the kind of current to be generated, it is largely a question of economics. The principal items in the cost of the transmission plant are the con- ductors, and the weight of these, as has been noted, with fixed output, distance and line drop, depends entirely upon the impressed or generat- ing voltage. The voltage of continuous-current generators is limited, by reason of the commutator device, to approximately 2000 volts; if several D. C. generators are connected in series the voltage sent into the exterior circuit will be the aggregate of all the generators thus connected. Alternators may be designed to generate at high voltages, 200,000 being now altogether practicable. Transformation of continuous-current voltage is practicable only by the aid of motor generators, while that of alternating current is accomplished through static transformers. All these limitations of the continuous current point to the alternating cur- rent as preferable when transmission to a considerable distance is required, even though the service calls for continuous current only. Example 1. An electrolithic plant is to be furnished 1000 kilowatts of continuous current at a voltage of 250 from a hydro-electric power plant one mile distant; the drop or loss of pressure in transmission is to be kept within 5 per cent. If continuous current is generated at a voltage of 275 and transmitted at this voltage to the electrolithic plant, the generating plant will consist of one or two D. C. generators and the transmission line; the conductors for the latter are two strands of wire of aggregate weight found from W = 4 L 2 X 33 X C -f- E. L is in 1000 feet units, the length of a transmission mile of con- ductors being taken at 5400 feet to compensate for the sag between supports; C is the current in amperes to be delivered at the electrolithic plant, being = 1,000,000 + 250 = 4000; E is the line voltage drop = 275 X 0.05 = 14; therefore W = 156.64 X 33 X 4000 -*- 14 = 1,470,857 Ibs. If alternating current is generated at 2300 volts, which is a standard type alternator, and transmitted at this voltage to the customer in ques- 352 HYDRO-ELECTRIC PRACTICE tion, one mile distant, with a line drop of 5 per cent., the generating plant will consist of one or two alternators, the transmission line, and a rotary converter by which the current is reorganized to the required continuous current. The conductors for this line will consist of three strands of wire, the current being of the three-phase type, and the weight of the line wire is found from W = 3 X L 2 X 33 X C -*- E, in which C = 1,000,000 -r 2185 and E = 2300 X 0.05; therefore W = 3 X 29.16 X 458 + 115 = 11,500 Ibs., to which should be added for induction 5 per cent., making the total weight = 12,075 Ibs. The alternator may generate at a higher voltage without the neces- sity of raising the line voltage, and thus the weight of the required con- ductors may be still further reduced; however, it is clear that this plant should generate alternating current. Example 2. An electric power crane unloading iron ore and fuel from vessels is to be supplied with 500 kilowatts of continuous current at a voltage of 400 from a hydro-electric power plant half a mile distant. For continuous current the generating plant would consist of one D. C. generator and the transmission line, and the weight of the required con- ductors is again found from W = 4 X 2.600* X 33 X 1259 -*- 20 = 55,688 Ibs. If alternating current is generated for this service, the plant will consist of the alternator, the line, and a rotary converter; the current may be generated at a voltage of 2300 and thus transmitted without step-up transformers being added; the line would consist of three strands of wire and the weight from W = 3 X 2.600* X 33 X 234 * 115 = 1364 Ibs., to which should be added 5 per cent., making the total conductor weight approximately 1432 Ibs., being 54,256 Ibs. less than required for the continuous-current line. The question to be decided is, the comparative cost of this quantity of conductor and that of the rotary, to which the operating and maintenance cost of the rotary may have to be added EQUIPMENT 353 unless the customer will take over its operation. From this it appears that the distance limit at which continuous-current generation, for continuous-current service taking up the entire output, is to be preferred to alternating-current generating and current reorganization, lies inside of the one mile for outputs of less than 1000 kilowatts, and that for greater distances or larger outputs the alternating current proves the more economical for the generating plant. With the current decided, the next question is as to the phase and the frequency. A great deal might be said on this topic as having a bear- ing one way or the other, but, after all, the safest guide may be found in practice, which, in this country at least, at present is largely in favor of the three-phase current at the generating end. The important influence of phase characteristic on the transmission-line conductor has already been noted and distinctly points to the preference of the three-phase current. The question of frequency is not so positively settled, as it depends largely upon the character of the current service. When the bulk of the current is intended for power service, the lower frequency of 25 cycles lays claim to several advantages over a higher one. The cost of rotary converters rises with the frequency, as it requires more poles and more costly armature construction than for low frequencies; on the other hand, the cost and weight of static transformers is greater for low than for higher frequencies, and therefore as far as the cost item is concerned the most economical mean between transformers and reorganizers should readily offer the solution. When the service load is fairly distributed between lighting and power production, the 60-cycle current appears to be preferable over that of lower frequencies. The next current characteristic to be decided is the generator voltage, and for transmission duty there is little doubt that every desideratum points to the highest practicable. Alternators of high voltage should be less costly than low-voltage generators plus step-up transformers, though their depreciation and maintenance may be somewhat greater. However, the factor of transformer loss, which with high-generator voltage may be avoided, carries 'considerable weight in the summing up. For transmission distances up to ten miles it will generally be found more economical to generate at a sufficiently high voltage to make step- up transformers unnecessary, and this distance may even be doubled if the alternator voltage comes up correspondingly. ^ 23 354 HYDRO-ELECTRIC PRACTICE Generator units are more largely to be determined by the hydraulic conditions than any other factor. It will now be fully realized that high generator speed is much to be desired, and if the drive is to be by direct coupling to the turbine shaft the choice of the generator unit will generally not be doubtful. As a rule, it is advisable to have duplicate units of like capacity to meet unforeseen emergencies by which any of them may be put temporarily out of commission, and, with this important proviso and the desideratum of high speed, the units are preferably of the largest practicable output, that is within the limits of economical standard designs. This leads to the fourth point to be determined in connection with the composition and character of the generating equipment, the mechanical power application for generators and exciters. There exists at the present day a certain almost hysterical clamor for direct-connected apparatus; ostensibly it is influenced by the desire to make the greatest showing of economical energy utilization, to avoid the loss due to other than direct drives, while frequently the stickling for this arrangement results in far greater energy waste, because the most suitable generating equipment is barred out, and in this manner a rational study and analysis of the opportunity is overshadowed by the desire to have things "up to date," at least as far as appearances go. There are quite a number of the present important hydro-electric plants which might have been bettered by several per cent, of output if equipment were belt driven instead of being direct connected. At any rate direct-connected apparatus may not always be the most economical (or, rather, efficient) solution of this problem. Speed lies at the root of it all, and by this the size, voltage, and cost of apparatus are fixed; a balancing of the value of the lost energy through belt drive, as compared with direct connection, against the difference in cost of the generating and transmission plant which is required for either programme, will, as a rule, plainly point to the one to be preferred. There is much less to be said in favor of gear-driven equipment, which, how- ever, comes under consideration with low-head developments and may then be the only solution of this question of mechanical power application. Exciters are preferably driven by separate turbine units. The type of the generator equipment should generally be decided in favor of that offered by the lowest competitive tender who guarantees prompt delivery of the specified apparatus. All of the leading American manufacturers of electric dynamos produce equally reliable and efficient machines, and, EQUIPMENT 355 when the desired characteristics and output efficiencies are clearly specified, as will be outlined in the last chapter dealing with specifica- tions, this question should be satisfactorily solved by adopting approved business methods. The arrangement of the equipment in the power station must be made with ample allowance of operating space around every machine and accessory apparatus, good light should be available for switchboards, and the station should be planned not merely to hold the outfit but also to move it about, in and out, without interfering with operations, and, finally, possible additions must be taken into consideration, as a paying plant is also a growing one. Diagram 40 gives the approximate dimen- sions of alternators of different output and speeds at 2300 volts, which is standard and well adapted to most conditions. The following table gives a list of generators, their capacity and speed, which are of standard types with American manufacturers, and can therefore be obtained within reasonable delivery periods and on competitive tenders. TABLE 32. STANDARD GENERATORS, ALTERNATORS, 2 AND 3 PHASE, 2300 VOLTS AND UP. Drive. K.W. Frequency. Pole; Coupled. . . . .. 100 69 24 Coupled. . . . .. 100 60 8 Coupled .... . . 105 60 28 Coupled. . . . .. 110 30 6 Coupled. . . . .. 115 60 8 Coupled. . . . . . 125 60 32 Coupled. . . . . . 125 60 26 Coupled. . . . .. 120 25 6 Coupled. . . . . . 120 25 4 Coupled. . . . . . 150 60 32 Coupled. . . . . . 150 60 26 Coupled. . . . . . 150 60 20 Coupled. . . . .. 150 60 14 Coupled. . . . . . 150 60 12 Coupled .... . . 150 60 8 Coupled. . . . . . 175 60 36 Coupled. . . . . . 175 ' 60 12 Coupled .... . . 180 60 3 Coupled. . . . . . 200 60 36 Coupled. . . . . . 200 60 32 Coupled. . . . . . 200 25 6 Coupled. . . . . . 200 50 12 Coupled .... . . 200 60 14 Coupled. . . . . . 200 60 12 Speed. 300 900 257 600 900 225 277 500 750 225 227 360 514 600 900 200 600 900 200 225 500 500 514 600 Drive. K.W. Coupled 225 Coupled 250 Coupled 250 Coupled 250 Coupled 250 Coupled 250 Coupled 250 Coupled 275 Coupled 275 Coupled 300 Coupled 300 Coupled 300 Coupled 300 Coupled 300 Coupled 300 Coupled 300 Coupled 300 Coupled 300 Coupled 325 Coupled 330 Coupled 350 Coupled 350 Coupled 360 Coupled 360 Frequency. Poles. Speed. 60 12 600 60 36 200 60 32 225 60 28 257 60 24 300 60 16 450 60 12 600 60 16 450 60 12 600 60 72 100 60 48 150 60 36 200 60 32 225 60 28 257 60 24 300 60 18 400 60 16 450 60 12 600 60 36 200 50 16 375 60 16 450 60 12 600 25 8 375 25 6 500 356 HYDRO-ELECTRIC PRACTICE TABLE 32. STANDARD GENERATORS, ALTERNATORS, 2 AND 3 PHASE, 2300 VOLTS AND UP. Continued. Drive Coupled. . . . K.W. F . . 360 requency 25 . Poles. 4 Speed. 750 Coupled. . . . . . 375 60 30 240 Coupled. . . . . . 380 60 16 450 Coupled. . . . . . 380' 60 12 600 Coupled . . . . . 400 25 20 150 Coupled. . . . . . 400 60 36 200 Coupled. . . . . . 400 60 28 257 Coupled. . . . . . 400 60 24 300 Coupled. . . . . . 400 60 16 450 Coupled. . . . . . 420 60 24 300 Coupled. . . . . . 420 25 18 167 Coupled. . . . . . 420 25 6 500 Coupled . . . . 425 60 30 240 Coupled. . . . . . 425 50 16 370 Coupled. . . . . . 450 60 60 120 Coupled . . 450 60 48 150 Coupled. . . . . . 450 60 40 180 Coupled. . . . . . 450 60 24 300 Coupled . 450 60 20 360 Coupled. . . . . . 450 60 36 200 Coupled. . . . . . 450 60 16 450 Coupled. . . . . . 450 60 12 600 Coupled .... . . 500 25 24 125 Coupled. . . . . . 500 30 20 180 Coupled. . . . . . 500 60 32 225 Coupled. . . . . . 500 60 26 257 Coupled. . . . . . 500 60 20 360 Couoled. . . . . . 500 60 16 450 Coupled. . . . . . 500 60 12 600 Coupled. . . . . . 500 60 6 1200 Coupled. . . . . . 540 60 36 200 Coupled. . . . . . 540 25 12 250 Coupled. . . . . . 540 25 10 300 Coupled. . . . . . 540 60 20 360 Coupled. . . . . . 540 25 8 375 Coupled. . . . . . 540 25 4 750 Coupled. . . . . . 550 40 10 480 Coupled. . . . . . 550 60 12 600 Coupled. . . . . . 600 60 36 200 Coupled. . . . . . 600 60 32 225 Coupled. . . . . . 600 60 20 360 Coupled. . . . .. 600 25 8 375 Coupled. . . . .. 600 50 16 375 Coupled . . . .. 600 33 10 400 Coupled. . . . . . 600 60 18 400 Coupled. . . . . . 600 60 16 450 Coupled . . .. 600 60 12 600 Coupled. . . . .. 650 60 20 360 Couoled. . 700 60 20 360 Drive. K.W. Frequency. Poles. Speed. Coupled. . . . .. 700 60 18 400 Coupled. . . . .. 720 25 8 375 Coupled. . . . .. 750 60 60 120 Coupled. . . . .. 750 60 48 150 Coupled. . . . .. 750 60 40 180 Coupled .. 750 60 36 200 Coupled. . . . .. 750 60 24 300 Coupled. . . . .. 750 60 20 360 Coupled. . . . .. 750 60 18 400 Coupled. . . . .. 800 60 36 200 Coupled. . . . .. 800 60 24 300 Coupled. . . . .. 900 60 56 150 Coupled .. 900 60 48 128 Coupled. . . . .. 900 60 40 180 Coupled. . . . .. 900 60 20 360 Coupled. . . . .. 900 60 16 450 Coupled. . . . .. 1000 60 44 163 Coupled. . . . .. 1000 60 36 200 Coupled. . . . .. 1000 60 28 257 Coupled. . . . .. 1000 60 24 300 Coupled. . . . .. 1000 60 20 360 Coupled. . . . .. 1000 60 18 400 Coupled 1000 60 16 450 Belted . . . 100 60 8 900 Belted . .. 110 30 6 600 Belted . . . 125 25 6 500 Belted .. . 150 60 . 12 600 Belted . .. 200 25 6 500 Belted ... 150 60 12 600 Belted . . . 200 25 6 500 Belted . . . 200 50 12 500 Belted . . . 200 60 12 600 Belted . . . 250 60 20 300 Belted . . . 300 60 16 450 Belted . . . 300 25 6 500 Belted . . . 330 50 16 375 Belted . . . 425 50 16 375 Belted . .. 450 60 20 360 Belted . . . 540 25 8 375 Belted . . . 540 60 20 360 Belted . . . 550 40 10 480 Belted . . . 600 33 10 400 Belted . .. 600 25 8 375 Belted . . . 600 50 16 375 Belted . .. 690 60 20 375 Belted . . . 650 60 20 360 Belted . .. 750 60 24 300 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 -B M IT JJiagPHB X 16 15 14 13 12 11 10 s> 5 T> Diagram 40 Generators 2300 Volt Dimensions for Preliminary Use FT E7 -Il^kvS. o 10 QO K .W. 357 358 HYDRO-ELECTRIC PRACTICE ARTICLE 101. The transmission plant equipment consists of trans- formers, the line, and its terminal, the substation. When the transmission voltage is to exceed that of the generator, which is generally the case with transmission distances exceeding fifteen miles, step-up transformers are required at or near the generating plant, since it is preferable to locate them in a separate room or even building from that where the generators are operating; and if the line voltage exceeds that at which the current is to be served, which will almost always by the case, step-down transformers become necessary at the terminal of the line, and the place where they are located is called the substation. It may be noted here that current service contracts are frequently made for the delivery of the current at line voltage to the customer's step-down transformer; this is especially probable when such delivery is of a large or major portion of all of the transmitted current, and if all of it is disposed of in this manner there is no need of a substation. It is understood therefore that the transformer equipment may consist of step-up and step-down installations, or of the latter only, or that none may be required as a part of the power-plant equipment. Transformers are of the same design and construction for either service, differing only as to the winding of the primaries and secondaries, as has been explained in Article 97. The line consists of the supports, conductors, and fastenings. The supports may be timber, concrete, or iron poles or posts, or steel-framed towers, their choice depending upon (a) the height of the conductors above the surface, (b) the length of the spans between sup- ports, and (c) the cost of available material. The line conductor may be of copper or aluminum. The weight of aluminum wire is about 0.47 that of copper wire of the same length and resistance, and when the cost of aluminum is therefore 1 -r- 0.47 = 2.13 that of copper wire or less the aluminum conductor will cost no more than copper conductor. The resistance of one mil foot aluminum wire is 17.0 ohms. Some of the advantages of aluminum wire for the use of transmission line conductors are that sleet will not readily adhere to it, on account of its greasy surface; it is more economically transported and handled, on account of its lesser unit weight. Some of the disadvantages are that it cannot be readily soldered, on account of the greasiness of the surface, EQUIPMENT 359 and therefore joints are less conveniently made than with copper wire; also its surface is more easily injured in handling, dragging over rough ground or stones, because of its greater softness than that of hard drawn copper wire; and, as the melting point of aluminum is much lower than that of copper, there is more danger of its being fused by arcing across conductors. The following table gives some of the characteristics of aluminum wire which are to be considered in connection with its use for electric transmission line conductors. TABLE 33. ALUMINUM WIRE. Elastic limit 14,000 Ibs. per square inch. Ultimate strength 26,000 Ibs. per square inch. Resistance quoted is at 75 F. Resistance per mil foot = 16.949 ohms. Area in Size. sq. inch. 500,000 cm 0.3930 450,000 cm 0.3540 400,000 cm 0.3141 350,000 cm 0.2750 300,000 cm 0.2360 250,000 cm 0.1965 0000 B. &S 0.1661 000 B. & S 0.1317 00 B. &S 0.1045 B. & S 0.0829 1 B. &S 0.0657 2 B. &S 00521 3 B. &S 0.0413 4 B. &S 0.0327 The height at which line conductors should be strung will principally be determined by legal requirements, the general provisions being from 30 to 35 feet high when paralleling highways or crossing other aerial wire lines, and 20 to 25 feet when strung across country. It is therefore not always an economical programme to secure transmission line loca- tions along public highways, as the cost of the higher supports may be much greater than the cost of private right of way across country, the latter affording the additional important advantage of guaranteeing con- trol over the line and therefore making it practicable to protect it against interference from the public. The length of the span is determined from the weight of the conductor and the consequential tension which is developed in its section, and the effects due to the temperature, wind, and sleet. Theoretically the sus- Lbs. per Feet per Ohms per Ultimate strength 1000ft. pound. 1000 feet. in pounds. 460 2.041 0.03082 10,210 414 2.415 0.03766 9,190 368 2.718 0.04237 8,170 322 3.106 0.04843 7,150 276 3.623 0.05652 6,130 230 4.348 0.06780 5,110 194.7 5.733 0.08010 4,320 154.4 6.477 0.10100 3,430 122.4 8.165 0.12740 2,720 97.1 10.300 0.16050 2,150 77.0 12.990 0.20250 1,710 61.0 16.400 0.25540 1,355 48.5 20.620 0.32200 1,075 38.5 25.970 0.40600 852 360 HYDRO-ELECTRIC PRACTICE pended wire takes the form of a catenary between supports, but it is altogether permissible to discuss the subject by considering it a parabola, whereby it is much simplified without the introduction of any con- siderable error. If L is the length of the span, s the sag of the wire, its deflection from the horizontal, w the weight of the wire per foot length, then T the ten- sion = L 2 Xw^-8sors = L 2 XwH-8T; therefore the tension of a given wire varies inversely as the sag for the fixed span length, and for given tension and wire the sag increases as the square of the span length. To prevent collision of the wires of a multiconductor line the sag should not be greater than twice the lateral distance between conductors. The tensile strength of hard drawn copper is 17 tons. The tensile strength of aluminum is 16 tons. The expansion coefficient for copper wire is 0.0000096 per degree F. The expansion coefficient for aluminum wire is 0.0000128 per degree F. The sag of the span may be found from these values. Example. 0000 copper wire is to be strung in spans of 120 feet length; then from above formula s = L 2 X w-=-8T, where L = 120, and w from copper wire table = 0.64 Ib. s = 120 2 X 0.64 -f- (8 X 5460) X 4; this latter factor represents the safety factor for normal conditions. s=0.81 foot or 9.75 inches. This represents the minimum admissible sag in order to avoid raising the tensile stress above the basic safety factor of four, and from this the sag which is necessary to compensate for contraction due to low tem- peratures must be found. If this line is to be constructed in the Northern latitudes, in Michigan, Wisconsin, or Canada, a low temperature minus 20 F. or lower must be provided for, and for this condition the proper sag is to be found from the actual length of the conductor in the span which is based upon the minimum sag as shown above. Thus, Lw (the length of the conductor in the span) = L + 8s J -f- 3L, or Lw for above example = 120 + 8(0.8P) -=- 360 = 120.0146 feet, EQUIPMENT 361 If we assume the normal summer temperature at 65 F., then the difference in temperature to be compensated for by increased sag will be 85, and the contraction of the copper wire will be = 85 X 0.0000096 X 120.0146 = 0.098 foot, which must be added to the length Lw = 120.0146 + 0.098 = 120.1026 feet. The sag will be, from Lw = Lx8s 2 -r-3Lors= ^'3L (Lw - L) -s- 8, for this case s = ^360 (120.1026 -- 120) * 8 = 30 inches. The safety factor in transmission line wire calculations should be adjusted to the climatic condition of the locality; if the prevalent wind movements are ordinary and no sleet storms to be expected, the factor of four above used is sufficient for practical purposes; where high winds prevail, such as should be credited with pressures of 40 and 50 Ibs. per square foot, or if sleet storms are of yearly occurrence, the factor must be raised to six, and, in specially exposed locations, as for instance along the shores of the ocean or the Great Lakes, the factor should be taken at eight. For aluminum wire the same method of calculating the span length and the sag applies, provided the proper values of weight, tensile strength, and expansion coefficient are substituted. The ordinary practice is to make spans of a timber-pole line from 90 to 150 feet long; 106 feet is taken very commonly, requiring fifty poles to the mile. Steel-framed towers are chiefly used when the transmission line is of double conductor circuits, which is always recommendable with high line voltage and large output plants ; such towers are fifty feet and higher and the spans correspondingly longer. Watercourses or wide swamps may have to be crossed on trestles. Submarine cables are rarely applicable in high- voltage transmission; they require an extra set of step-up and step-down transformers, as they are not reliable for any higher pressure than about 3000 volts. Supports for a height of line conductors up to 35 feet may be of timber poles; they should be set one-seventh of their length into the ground, the buried portion and one foot above the surface being well tarred, and the top wedge shaped and painted. Concrete poles are now being constructed economically and make excellent line supports. 362 HYDRO-ELECTRIC PRACTICE Steel-framed towers may be of various designs; some are shown on Fig. 134. Conductor fastenings consist of cross-arms, insulator pins, and insulators. Cross-arms (Fig. 134) are rectangular pieces of timber 3| X 4| X 4 to 5 feet long, or 3f X 4f X 6 to 8 feet long. They are preferably of yellow pine which is kiln dried and well boiled in linseed oil, and they are slightly rounded on top the better to shed the rain. Cross-arms are secured to the poles by being gained 1^ inches and fastened with a }- inch round wrought-iron screw bolt passing through the cross-arm and the pole. The longer cross-arms should be further secured to the pole by two diagonal braces, which, for high voltage lines, should be of hard wood instead of iron straps. The upper cross-arm is placed about two feet below the pole top, and the others are spaced in accordance with the distance required between conductors, being from two to three feet. Insulator pins (Fig. 135) form a very important part of the line. They carry the insulators, to which the conductors are secured, and are fastened to the cross-arms; they have to take up and resist all the lateral strain to which the conductors are exposed, and they also form the only available path for current leakage. Therefore they must be of suitable material, sufficient section, securely connected to their sup- ports, the cross-arms, and should be well insulated. Insulator pins are preferably of oak or locust; they should not be of iron where high volt- ages are to be transmitted. Small section pins are to be avoided; they should be not less than 2J inches in diameter and 10 inches long, and as much heavier in section and longer as the weight of the conductor, which is to be secured to the pin, requires. Insulator pins must be thoroughly dried and well boiled in linseed oil. Pins are set into holes bored in the top faces of cross-arms and secured by a treenail driven through the shank of the pin and the cross-arm; spikes should not be used for this purpose. The top end of the insulator pin is threaded for about three inches to receive the insulator. Insulators (Fig. 135) carry the conductor. They are made of glass, porcelain, or earthen-ware, consisting of one or more superposed bells (petticoats so called) , their purpose being to shed the rain away from the insulator pin. Insulators should be tested for the voltage to be trans- mitted and for their breaking strength. The conductor passes over the Transmission line Towers & Poles Reinforced Concrete tower ; \\^\\v<%V^%=\\\^\\\^W^\\Ng T^^*flw Structural steel tower 363 364 HYDRO-ELECTRIC PRACTICE top of the insulator, lying in a groove, and is secured to the insulator by a wire binding. The substation is a suitable structure where the line terminates, and contains the required switchboard, the reorganizing and transforming equipment. The entry of the line conductors into the substation must be carefully planned. It is generally effected by passing the conductors through insulator disks set into circular openings, of 12 inches or larger diameter, in the wall of the substation building, with some shelter over the point of entry to protect the conductors at the entry from rain and snow. This closes the treatment of the electrical equipment of a hydro- electric plant, which has been necessarily very brief, as its detail dis- cussion would assume the proportions of a separate volume. Figs. 136 to 140 give some general views of the partial installation of electrical equipment of the hydro-electric plant at Sault Ste. Marie, Mich.; the output capacity is about 32,000 kilowatts in 80 units of 400 kilowatts. Both continuous and alternating currents are being generated; the speed of all direct-connected generators is 180 revolutions per minute. This plant was designed by the author and constructed under his charge as chief engineer. Fig. 136 shows the sectional armature of a 400-kilowatt 3-phase 30-cycle alternator, and Fig. 137 the revolving field of the same machine. Fig. 138 presents a fine modern specimen of a continuous-current 400-kilowatt dynamo coupled to the turbine shaft, and Figs. 139 and 140 give a general view of the partial generator installation. In Fig. 139 the first three machines are D. C. dynamos, the others are alter- nators; the switchboard panels are on the left, which was a temporary arrangement, as they were finally placed along the wall on the right upon elevated platforms; in the foreground of Fig. 140 stands a rotary converter. ARTICLE 102. Auxiliary Power Plant. A very good and learned friend of the author remarked once that he could always find a hydro- electric plant by looking for a smoke-stack near a river, and this is as it generally should be if the development is a complete utilization of the opportunity. It is only exceptionally that the net earning capacity of a hydro-electric plant cannot be materially enhanced by the addition of a supplementary plant; this indeed is only the case when nature has provided a well-balanced ratio of power functions by furnishing a con- Fig., 135 High Tension Low Tension Insulators & Pins Section c- d b d H.E.P. H. v. S. 213 365 366 HYDRO-ELECTRIC PRACTICE stant volume of flow and non-fluctuating head, or by supplying the means to maintain such an equilibrium in the shape of sufficient reservoir capacity. It is precisely the degree of deficiency of the natural supply, or of facilities to accomplish this, which represents the utility of the auxiliary plant, provided always that a demand for the current exists. It is not the intention to go into any of the details of this topic here, as to the character and the make-up of the auxiliary power plant, whether it should be a plant of steam boilers and engine or steam tur- bine, or whether oil or gas engine, this forming a topic of operation rather than equipment. Here it must suffice to remind the investigator that the design and estimate of a hydro-electric plant is generally incomplete without taking into consideration this feature of an auxiliary power plant. Therefore the power station should be located and designed with this probable future requirement in view. The capacity of the auxiliary should be prima facie of at least one generator unit, and in this respect may influence the determination of the unit question. The auxiliary plant will be rarely called for until the hydro-electric plant has been in operation some years, but in estimating upon the whole project and deducing the net earning capacity of the proposed enterprise this factor must be included as an item of investment, of maintenance and depre- ciation charge, and of operating cost. The storage battery or accumulator should also be considered as an auxiliary power plant factor. It consists of two inert metal plates, or of metallic oxides, which are placed in glass, earthen-ware, or wooden receptacles holding an electrolyte, which is a compound liquid separable into its constituent ions by the passage of electric currents through it. A storage battery is a collection of such elements chargeable by contin- uous current, which produces decomposition of the inert electrolyte between plates, whereby cathions, electro-positive radicals, are deposited on the plate which is connected with the negative pole of the charging generator, and anions, the electro-negative radicals, on the plate which is connected to the positive pole of the charging source. When the ter- minals of such a storage battery which is charged are connected outside of the electrolyte, an electric current is set up, flowing from the plate on which the positive radicals are deposited to that of the negative radicals, which is in direction opposite to that of the charging current. It may be noted here that it is erroneous to speak of the storing of the electric current, since the charging current is simply the means of and initiates ^ - ! HE " \ iSiTY ) H. v. S. EQUIPMENT 367 the setting up of the battery current caused by the decomposition of the electrolyte, as above briefly outlined. Storage battery elements ordinarily represent electro-motive force of from 2^ volts up, but their range is very limited. They may be charged by the surplus output of the hydro- electric plant and discharged to add to the generating plant output in supplying additional current to carry the maximum, the peak, loads, and in small installations, when night water storage is necessary during low- flow seasons to accumulate the necessary day-load water supply, accumu- lators of this type can frequently be utilized to take care of the part night current loads made up of lighting business. Storage plants are also used for regulation purposes, and may then be located at the generating plant or along the transmission line; when they are to carry part loads they are preferably placed at the substation. CHAPTER X CONSTRUCTING THE PLANT THE burden of all that has gone before is encompassed in the topic of this chapter, the realization of the development, and it does not seem essential to the treatment of the subject of hydro-electric practice to go very far either into the generalities or the details of this topic, which for hydro-electric plants does not necessarily present features which may not be found in the construction of other works. However, something, the author feels, should be said of the preparations for this final step, the construction, and of some features which are perhaps peculiar to this particular class of structures. ARTICLE 103. Plans. The proper plans for a hydro-electric plant are perhaps much more complex than those of any other single engineer- ing undertaking, as they cover the wide range represented by hydraulics, hydrostatics, structures of timber, earth, rock, masonry, concrete, rein- forced concrete, steel, hydrodynamics, mechanics, and electrical theories and practice; and they must necessarily be elaborate in details based upon calculations of functions, factors, dimensions, sections, etc., per- taining to all these various branches. Every pertinent detail should be designed to a sufficiently large scale readily to detect errors and, wherever practicable, algebraic calculations should be checked diagram- matically. All calculations should be made in a computation book devoted to that particular project, and in a clear and precise manner, preferably in ink, each separate calculation of importance should be given a separate page, and when this book is completed with a comprehensive index it will prove a great labor and trouble saver in the future checking and even during the construction progress. All sheets containing plans should be of uniform size; dimensions should be given in figures and identified by dimension lines; the lettering should be plain; the author uses stamp- ing machines for this purpose wherever practicable. Every structural feature should be shown in location, plan, longitudinal and transverse sections, followed by each important detail, and these latter should be numbered consecutively throughout the entire set of plans. 368 CONSTRUCTING THE PLANT 369 Originals should be inked before any of them are traced, which will obviate errors caused by the misinterpretation of pencil designs on the part of the tracer. ARTICLE 104. Estimates should never be made until the designs are completed and checked, and their original form should take the shape of a comprehensive detail tabulation, giving title of structure, number of detail and sheet, dimensions, quantities, and unit price of cost of material and of operation. The delivery cost of the material must be fully covered, as well as the insurance of construction plant, material, and of the per- sonnel employed. A net profit of at least 15 per cent, should be added, and finally ten per cent, must be allowed for engineering and control. Estimates should be analytical, as, for instance, Concrete of 1 : 2 : 4 mixture: 1J bbl. Portland cement, deld., @ 2.25 per bbl $3.38 \ cub. yd. sand, deld., @ 1.00 per cub. yd 0.50 1 cub. yd. broken stone, deld., @ 0.75 0.75 Mixing by machine 0.30 Conveying to site by barrows Placing concrete, monolithic, or Placing concrete in forms, at respective price Timber forms, used three times, cost of lumber deld., $30.00 per 1000 ft. b. m. per cub. yd. Removing forms per cub. yd., according to dimensions of structure Finishing, if outside wall floor or facing. Every item should be treated this way in estimating its cost. And finally the estimate should be concluded by a summing up of all the different material required and grouped in accordance with proper classifications as to its character and cost. ARTICLE 105. Specifications. The practice in this respect is so cha- otically diversified that it may almost be called an individual business. The author believes this subject should be approached as far as practicable from the view-point of the constructor, with a full realization of his posi- tion, if he is seriously inclined to make a proper tender. The principal purpose, it seems, therefore, is to convey clearly the ideas and intentions of the designer of the plant. The structures of a hydro-electric plant dif- fer considerably from those of like general character for other purposes. For instance, a diversion canal appears to many constructors not at all different from any other kind of water way, merely to pass the water, while it is, or should be, designed in accordance with definite scientific principles, and must be constructed in strict conformity to these in order 24 370 HYDRO-ELECTRIC PRACTICE that the desired results be fully realized. So it is with the power station, which appears to be simply an ordinary kind of building, while in fact it is one of very peculiar and important details not met with in other building structures of even much heavier masonry sections. Earth embankments seem so much like those so common in railroad construc- tion that it is an exceedingly difficult task to create the proper impression of their absolute specific purpose and therefore their entirely different construction. And so on along the line from the first to the last, and for these reasons the specifications for a hydro-electric plant cannot be too specific in clearly conveying their purpose, followed by the explicitly definite detailing of the structural methods by which these results are to be secured. It is also well to bear in mind, when one prepares specifications, that the main purpose is to get this plant constructed, and to have this done as expeditiously and economically as can be, and have it done well, and that such results can only be hoped to be secured by a complete co-operation between the constructor and the engineer looking after the interests of the owners. It is absolutely useless in this respect, in the author's judgment, to burden the specifications with restrictions of the constructor's freest latitude of utilizing his own experience and ingenuity for the purpose of securing the best, speediest, and most economical realization wherever practicable. Methods so specified, but made appli- cable or not solely upon the dictum of the engineer, or elastic conditions depending upon the future interpretation or decision of the engineer, are calculated only to inject costly uncertainties into the undertaking, that is, costly to the owners of the plant, not to the contractor, who is forced by all considerations of self-protection to discount them heavily, as it is not his province to take chances. Quantities should always be quoted in positive figures; if they are uncertain the specifications should so state, and the probable fluctuations should be provided for upon a fixed and equitable basis of values. The majority of specifications contain severe penalties for default in completing the works within a specified or agreed-upon time limit; few, however, provide any reward for anticipation of such a limit. Again, it is not to be expected that the enterprise is to be financed by the con- tractor, who should receive such a percentage of his earnings that they vail meet his actual outlay. CONSTRUCTING THE PLANT 371 These are generalities, nor can the subject be treated in any other manner, that is, no hard-and-fast form can be defined as adapted to any certain range of conditions. As to details, the author's meaning is best illustrated by an example. Specifications of the Anchoring of a Spillway in Rock Location. 1. The site of the spillway is shown on Plan 3 and the dimensions are as thereon given. 2. All elevations are referred to Bench mark " D," being the top of an iron bolt 2 inches in diameter, which is set and leaded in the top of a granite boulder on the west side of the river on the north line of the spillway location, as shown on Plan 3, and about 15 feet from the crest of the natural bank; the elevation of this bench is 654.76 ft. above mean tide, New York. 3. So much of this area as can be conveniently coffered against the water at one time is to be entirely freed from all water, and is to be maintained in this condition at all times until the constructions described in this article, "Anchoring the Spillway," are fully completed, inspected, and accepted by the engineer. 4. The methods of coffering and of maintaining the dry condition may be as elected by the contractor. 5. The area is to be cleaned of all vegetable and earthy substances, and all loose rock or such as can be dislodged from the ledge by the ordinary use of a 12-lb. miner's pick, which is to be removed, and the material thus taken up may be disposed of as the contractor elects. 6. Anchor holes of the size and to the depth shown in Detail 22 on Sheet 11 are to be drilled into the rock bed and freed from all loose stone: they are to be spaced as shown in location Plan 3. 7. Anchor bolts of 3-inch round wrought iron 4 feet long are to be set in the anchor holes, the bottom six inches of the bolts being split open by one cut and spread to a diameter of 3 inches. Grouting, consisting of one part Portland cement, two parts of sand, and three parts of fine gravel, is to be poured into the hole while the anchor bolt is being held at the bottom and in the centre of it. 8. The anchor bolts, cement, sand, and gravel, and the mixing of the grouting are to conform to the specified material and method as given in the second article of these specifications. In other words, there is no operation so unimportant but that it deserves to be clearly analyzed and so described in the specifications. ARTICLE 106. Engineering control of the construction of this kind of a plant cannot be any too thorough; short-sighted economy in this respect may be exceedingly expensive in the end. 372 HYDRO-ELECTRIC PRACTICE All material should be inspected and tested; each operation should be carefully overseen; and, no matter how small the plant, the author has always found it justifiable to keep a daily progress record of each separate construction feature on specially prepared forms, of the time performance and therefore the cost; such a record is as valuable to the contractor as it is to the owner and certainly to the engineer. Nor should the camera be omitted in chronicling progress stages. Such a plant well constructed is a monument to all the parties concerned, and to the engineer who conceives and brings it into activity it should be a source of pride and satisfaction. If the man who makes two blades of grass grow where formerly was only one is entitled to the plaudits of mankind, how much more is he who harnesses the now wasting energy of falling water! GENERAL INDEX PAGE Abutment, quantities for, Diagram 12 ... 66 Abutment, spillway, described 209 Accumulator (see Storage battery) Air vents in spillways 235 Alluvials, characteristics of 132 Alternate current, definition 333 Aluminum wire 346-358 Aluminum wire, characteristics, Table 33.. 359 Ammeters 349 Amp&re, definition of 331 Ampdre turns, definition of 333-338 Analysis of current market 4 Analysis of hydro-electric project 1 Apron of solid spillway, form of 186 Arc lights, service 1 Armature, dynamo, description 340-342 Armature winding, description 340-342 Auxiliary power, definition 42 Auxiliary power plant 364 Auxiliary power, value of 44 Backswell above dam, analyzed 149 Backswell above dam, definition of 149 Backswell slope, Diagrams 20-25 152-156 Backswell slope, formula for 149 Base benches (survey) , Fig. 1 92 Bearing piles, capacity 138 Bearing piles, description of 138 Bear-traps, described 198 Benches, base, for survey, Fig. 1 92 Block concrete, definition of 140 Boom, floating 230 Booster, definition 350 Borings, Figs. 7 and 8 99-100 Brackets, supporting, for survey, Fig. 1 .... 92 Breakwater, description of 142 Bulkheads, concrete steel 226 Bulkheads, reservoir, quantities, Diagram 15 72 B. & S. (Brown & Sharpe) gauge of wire, Table 31 340 Canal, designs of bed and sides 244 Canal headgates 246 PAGE Canal intake 246 Capacity, current, definition 336-347 Case of reaction turbine 292 Cement, Portland, specifications of 139 Central discharge reaction turbine, descrip- tion of 294 Central discharge reaction turbine, design of, Fig. 113 295 Channels, curved, slope in 242 Channels, open, flow in, theory of 236 Channels, open, slope in, Tables 16-19. . 238-239 Channels, open, velocity in, Tables 20-24 . . 240-241 Charges, fixed, for plants 500-1000 H. P., Diagram 5 57 Charges, fixed, for plants 1000-5000 H. P., Diagram 6 58 Charges, fixed, for plants 5000-10,000 H. P., Diagram 7 59 Choking coil, definition 350 Circular mil measurement of aluminum wire; Table 33 359 Circular mil measurement of copper wire, Table 31 340 Classification of turbines 285 Clay, characteristics of 133 Clay for earth dam 226 Coefficient of perimeter roughness 103-237 Coffering, definition of 135- Coffering, description of 143: Coffer structures, quantities for, Table 8. . . 144 Collector (see Commutator) Commutator, description of 336-341 Compound winding of field magnets 338; Concrete, block, definition of 140) Concrete, characteristics of, Table 4 140) Concrete, cost of, Diagram 11 65 Concrete, cyclopean, definition of 140 Concrete, monolithic, definition of 140 Concrete, reinforced, definition of 140 Concrete-steel beams, constants of, Table 6. 141 Concrete-steel beams, designs, Table 7 141 Concrete-steel bulkhead 226 373 . 374 GENERAL INDEX PAGE Concrete-steel dam, quantities for, Diagram 10 64 Concrete-steel, definition and description of 139, 140 Concrete-steel piles, description of 138 Concrete-steel pipe, cost of 67 Concrete-steel retaining walls, described. .. . 214 Congressional act for power project 47 Constants for concrete-steel beams, Table 6. 141 Constants of flow over flat-crested weirs, Diagram 2 39 Constants of flow in open channels, Tables 16, 24 238, 241 Constants of flow through overflow sluices. . 195 Constants of flow in pipes, Tables 27-29.250,251 Constants of flow through underflow sluices . 195 Constants for gravity spillway sections, Tables 10-14 191-194 Constants of impulse wheel output, Dia- gram 39 323 Constants of reaction turbine output, Dia- gram 38 319 Constants for normal solid spillway sections, Table 10 185 Constructing the plant 90 Constructing the plant, engineering control. 371 Constructing the plant, estimates 369 Constructing the plant, plans 368 Constructing the plant, specifications 369 Continuous current, definition 336 Continuous current dynamos 337 Continuous current transmission 346 Control of Government over rivers 47 Control of rivers by War Dept., Table 3. . . 50 Control of rivers by States 53 Copper wire, characteristics of, Table 31. .. 340 Copper wire, resistance of, Table 31 340 Copper wire, weight of, Table 31 340 Core wall, description of 139 Correctors (see Lightning arresters) Cost, comparative, of timber and concrete spillways, Diagram 30 211 Cost of concrete, Diagram 11 65 Cost of dam 61 Cost of development 61 Cost of diversion works 67 Cost of pipe, concrete steel 67 Cost of pipe, steel plate 67 Cost of pipe, wood stave 67 Cost of power equipment 70 Cost of substation 70 Cost of transformers . . 70 PAGE Cost of transmission line 70 Cribs, log, description of 136 Cribs, timber, description of 137 Cross-arms, transmission line 361 Crushing of spillway, theory of 170 Current, alternate 333 Current alternations, definition of 333 Current capacity 336-347 Current, continuous 336 Current frequencies, definition of 335 Current to be generated, determined 350 Current impedance 336 Current inductance 335 Current market, analysis of 4 Current market, canvass for 5 Current, monophase 331 Current phase 335 Current, polyphase 335 Current rates, H. P. and K. W., Diagram 8. 60 Current reactance 336 Current reaction 335 Current regulation 348 Current reorganization 342 Current, self-induction of 335 Current service, industrial 2 Current service, lighting 1 Current service, special 2 Current service, traction 4 Current, single-phase 335 Current transformation 343 Current transmission 345 Current, three-phase 335 Current, two-phase 335 Current, wattless 336 Curtain, steel, description of 139-146 Curtain, timber, description of 139-146 Curved channels, slope in 242 Cut-off wall, description of 139 Cut-off wall, quantities for, Table 9 147 Cyclopean concrete, definition of 140 Cylinder gate of turbine 289 Dam, concrete-steel 64 Dam, cost 61 Dam, description, general 131 Dam, earth and rockfill 222 Dam, foundation, detail description. . . . 144-147 Dam foundation, functions of 131 Dam, height of, analyzed 149 Dam, hydraulic-fill 226 Dam, length analyzed 149 Dam, masonry, dimensions, Diagram 9 63 GENERAL INDEX 375 PACK Dam, masonry, quantities, Diagram 9 63 Dam, reservoir, described 221 Dam and spillway appurtenances 227 Dam, superstructure of 148 Design of canal bed and sides 244 Design of central discharge turbine, Fig. 113 295 Design for foundation, Fig. 18 145 Design for foundations 144 Design of gravity spillway, Tables 11-14 191-194 Design of gravity spillway, characteristics, Table 14 194 Design of horizontal turbines, four, paired and drowned, Fig. 119 312 Design of horizontal turbines, paired and cased, Figs. 120, 121 313, 315 Design of horizontal turbines, paired and drowned, Fig. 117 306 Design of horizontal turbines, three paired and drowned, Fig. 118 309 Design of impulse wheel, Fig. 114 297 Design of power house for fluctuating head, Fig. 87 263 Design of power-house foundation 254 Design of power house for high head, Fig. 89 267 Design of power house for low head, Figs. 84-86-88 259-262, 265 Design of power house for medium head, Fig. 89 267 Design of power house, submerged 266 Design of power-house substructure 255 Design of power-house superstructure 256 Design of reaction turbine, Figs. 109, 110. 291, 293 Design of reaction turbine, theory 318 Design of sluice 201 Design for solid spillway apron 186 Design for solid spillway, characteristics, Table 107 185 Design for solid spillway crest 185 Design for solid spillway, practical 180 Design for solid spillway, theoretical 176 Design for solid spillway toe 186 Design of stop-log section, theory 201 Design of timber spillway, analysis of 206 Design of vertical turbines, paired and drowned, Fig. 115 302 Design of vertical turbines, paired and cased, Fig. 116 305 Designing and constructing the plant 90 Development cost 61-74 Development programme, direct 116 PAGE Development programme, distant 117 Development programme, scope 129 Development programme, short diversion. . . 117 Dike, description of 135 Dike, sheet pile, description of 142 Dike, steel pile, description of 142 Dimensions for concrete-steel beams, Table 7 141 Dimensions of dams, masonry, Diagram 9 . . 63 Dimensions of generators, Diagram 40 357 Dimensions of gravity spillways, Table 12. . 192 Dimensions of horizontal turbines, cased, Diagram 37 317 Dimensions of horizontal turbines, drowned, Diagram 35 307 Dimensions of single horizontal turbine, drowned, Diagram 36 311 Dimensions of solid spillways, Table 10. ... 185 Dimensions of .turbine draft tubes 319 Dimensions of turbine guide-wheel openings 319 Dimensions of turbine runners, theory 318 Dimensions of turbine runners vent area. . . 318 Direct development programme 116 Discharge, central reaction turbine, descrip- tion of 294 Discharge curve of stream 103 Discharge curve of stream, Diagram 19. ... 106 Diversion programme, distant 117 Diversion programme, short 117 Diversion works 235 Diversion works, cost of 67 Draft tube, turbine, dimensions 319 Draft tube, turbine, theory of 296 Drainage area, characteristics Ill Drainage area, definition 9 Drainage area, geology of 27 Drainage areas of rivers, Table 1 10 Drainage areas, topography of 26 Dynamic energy, definition 276-277 Dynamo armatures 340 Dynamo commutators, collectors 341 Dynamo, continuous current 337 Dynamo excitation 338-341 Dynamo field 341 Dynamo parts, description 337 Dynamo poles, definition 337 Dynamo winding 338-340 Earth embankments, quantities, Diagram 14 71 Earth and rockfill dams 222 Earth and rockfill excavation from canal . . . 243 Efficiencies, maximum, of impulse wheel, out- put, Diagram 39 323 376 GENERAL INDEX Efficiencies, maximum, of impulse wheel, theory 320 Efficiencies, maximum, output constants of all turbines 322 Efficiencies, maximum, of reaction turbine output, Diagram 38 319 Efficiencies of turbines, theory of 298 Electric equipment 330 Electric generating plant, character of 350 Electric and water power, Diagram 3 43 Electro-motive force 330-331 Electro-motive force, magnitude of 333 Elevations (survey) 93 Embankments, reservoir, cost of 68 Embankments, reservoir, quantities, Dia- gram 14 71 Energy, dynamic, definition of 276 Energy, hydro-dynamic, definition of 276 Energy, mechanical, defined 276 Energy of water 276 Engineering control of construction 371 Equipment, electric 330 Equipment, hydraulic, theory 276 Equipment, power 276 Equipment, power, general cost of 70 Equipment of transmission plant 358 Equipment, turbine, determination of 322 Estimates of plant, 369 Evaporation, definition 9 Evaporation and precipitation, flow deduced from 108 Evaporation records 34-109 Examinations of maps 90 Excavation of earth and rock from canals . . 242-243 Excavation quantity for canal prisms 243 Excitation of dynamos, definition 338-341 Fall, available 40 Feasibility of hydro-electric project 47 Field, dynamo, description 341 Fishladders, design of 231 Fixed charges of plants, 500-1000 H. P., Diagram 5 57 Fixed charges of plants, 1000-5000 H.P., Diagram 6 58 Fixed charges of plants, 5000-10,000 H. P., Diagram 7 59 Flashboards, design of 231 Floats, surface, subsurface, and rod 102 Flood flow, determination of 159 Flora and culture of drainage area 28 PAGE Flow deduced from precipitation and evap- oration 108 Flow deductions 36 Flow, definition of 8 Flow, determination, Ex 109 Flow over flat-crested weirs, Diagram 2 .... 39 Flow, flood, determination of 159 Flow, low monthly, of rivers, Table 1 10 Flow measurements 37 Flow measurements by weir, Fig. 11 107 Flow measurements, rod to mean velocity, Diagram 18 105 Flow measurements, surface to mean veloc- ity, Diagram 17 104 Flow in open channels, constants, Tables 16- 24 238-241 Flow in open channels, theory 236 Flow through overflow sluice, theory of. ... 195 Flow in pipes, constants, Tables 25-29. 249-251 Flow in pipes, discharge volume, Table 26. . 249 Flow in pipes, theory 249 Flow in pipes, velocity of, Tables 27-29 250-251 Flow, power, definition 41 Flow from reservoirs, Diagram 4 45 Flow, stream, deductions 36 Flow, stream, determination 30 Flow through turbines, definition 287 Flow through turbines, theory of 278 Flumes, diversion 246 Flux, magnetic, density 331 Forebay 246 Forms, concrete, definition 140 Foundation floor, description of 148 Foundation of power house 254 Foundations, dam, functions of 131 Foundations, design 144-147 Foundations, quantities for, Diagram 12 ... 66 Frequencies of current 335 Galleries through spillways 235 Gate, cylinder, of turbine 289 Gate, register, of turbine 289 Gates, described 198 Gates, operation 230 Gates, reaction turbines 289 Gate valve 252 Gauge, B. & S. (Brown & Sharpe), of wire, Table 31 340 Gaugings of stream, Figs. 9 and 10. ... 100-102 Generator, dimensions of, Diagram 40 357 Generator, how driven, determined 354 Generator (see Dynamo) GENERAL INDEX 377 PAGE Generator, standard sizes, Table 32 355 Generator, type of, determined 354 Generator, units, determined 354 Geology of drainage area 27 Gneiss, characteristics of 131 Governing tangential impulse wheels 320 Government control over rivers 47, 50 Governors, turbine 326 Governors, turbine, Lombard 327 Governors, turbine, Lombard-Replogle 328 Governors, turbine, Sturgess 327 Governors, turbine, Woodward 328 Gradient, hydraulic, definition 251 Granite, characteristics of 131 Gravel, characteristics of 133 Gravity spillway, design of, Table 10-14 191-194 Gravity spillway, theory of 187 Ground detectors 349 Ground flow diagrams 113 Ground storage, definition Ill Ground water, definition 8 Guard wires 350 Guide passages of reaction turbine, described 289 Guide passages of reaction turbine, dimen- sions 319 Guide vanes of reaction turbine, described. . 289 Guide wheel of reaction turbine, described . . 289 Headgates of canal 246 Height of dam, analyzed 149 Horizontal turbines, cased, described 310 Horizontal turbines, cased, dimensions 317 Horizontal turbines, drowned, described.... 304 Horizontal turbines, drowned, dimensions, Diagram 35 307 Horizontal turbines, four, drowned, design, Fig. 119 312 Horizontal turbines, paired and cased, de- sign, Fig. 120 313 Horizontal turbines, paired and cased, de- sign, Fig. 121 315 Horizontal turbines, single drowned, dimen- sions, Diagram 36 311 Horizontal turbines, three drowned, design, Fig. 118 309 Horse-power, definition 8 Horse-power, electric 8 Horse-power and kilowatt, Diagram 1 3 Horse-power and kilowatt rates, Diagram 8. 60 Hydraulic equipment, theory 276 Hydraulic-fill dam 226 Hydraulic gradient, definition 251 PAGE Hydraulic losses of energy in turbines 299 Hydraulic radius, definition. 237 Hydraulic radius of pipes, Table 25 249 Hydraulic relief valves 330 Hydro-dynamic energy, definition 276-277 Hydro-electric project, analysis of 1 Ice fenders, design of 231 Impedance in current, definition 236 Impulse, definition 276 Impulse turbine, defined 286 Impulse turbine, description 296 Impulse wheel, design of, Fig. 114 297 Impulse wheel, governing 329 Impulse wheel, maximum efficiency output, Diagram 39 323 Impulse wheel, output, theory 320 Incandescent light service 2 Inductance, current, definition of 335-347 Installations, turbine, typical 300 Insulator pins, transmission line 361 Insulators, transmission line 361 Intake to canal 246 Investment balance, Ex 55 Kilowatts and horse-power, Diagram 1 3 Kilowatts and horse-power rates, Dia- gram 8 60 Kinetic energy of water 276-277 Lease from War Department 48 Length of spillway, analyzed 159 Levels ( survey ) 93 License from War Department 49 Lighting, current service 1 Lighting, power for, Diagram 1 3 Lightning arresters 349 Lights, arc 1 Lights, incandescent 2 Limestones, characteristics of 132 Lining of canal bed and sides 244 Loam, characteristics of 133 Location of canal ; . . 242 Location of pipe line 251 Location of power house ." 254 Log chutes 2,30 Log cribs, description of 136 Lombard governor 327 Lombard-Replogle governor 328 Losses of energy in turbines 299-300 Magnet, field, conductor, size of 339 378 GENERAL INDEX Magnet, field, section of 339 Magnetic field 330 Magnetic flux 330-331 Magnetic lines 331 Magneto-dynamic theory 330 Magneto-electric units 331 Magnets, permeability of, Table 30 339 Maps, examination of 90 Market, current, analysis of 4 Market, current, canvass 5 Market for electric current 1 Marl, characteristics of 133 Mean and rod velocity, Diagram 18 105 Mean and surface velocity, Diagram 17 .... 104 Mechanical energy, defined 276 Mechanical losses of energy in turbines . 299-300 Mixing concrete, description of 140 Moment of moving water, defined 278 Moment, pressure, retaining walls, Diagrams 31-33 215-217 Moment, pressure, solid spillways, Diagrams 26-29 165-168 Monolithic concrete, definition of 140 Monophase current, definition 335-342 Motor generator, description 342 Movable weir, described 198 Mud, characteristics of 133 Needles, described 197 Ohm, definition 331 Open channels, flow in, theory of 236 Open channels, slope, Tables 16-19 238-239 Open channels, velocity, Tables 20-24.. 240-241 Open spillway, description of 194 Orifices, submerged, discharge theory 195 Output of impulse turbine, theory of 320 Oiitput of impulse wheel, maximum effi- ciency, Diagram 39 323 Output of maximum efficiency, constants for all turbines 320 Output, power, definition 40 Output of reaction turbine, theory of 314 Output of reaction turbines, maximum effi- ciency, Diagram 38 319 Overflow sluice, described 196 Overflow sluice, discharge, theory of 195 Overturning of spillway, theory of 170 Paving, description of 142 Peat, characteristics of 133 Perimeter, coefficient of roughness 103 PAGE Perimeter of channel, definition 236 Perimeter of channel, roughness coefficient. 237 Permeability of magnets, Table 30 339 Phase, current, definition of 335 Phase indicators 349 Phasemeters 349 Phase transformer, definition 342 Phototopographic survey, Figs. 3 to 6 .... 94-97 Pile, sheet, dike, description of 142 Pile, steel, dike, description of 142 Piles, bearing capacity 138 Piles, bearing, description of 138 Piles, concrete, description of 138 Pilot lamps 349 Pins, insulator, for transmission line 361 Pipe areas, Table 25 248 Pipe, concrete-steel, cost of 67 Pipe, diversion, location of 251 Pipe, recommendable size of. 252 Pipe, steel plate, cost of 67 Pipe, wood stave, cost of 67 Pipes, discharge, volume of, Table 26 248 Pipes, flow in, constants for, Tables 25-29 . . 248-251 Pipes, flow in, theory 248 Plans for construction 368 Platform, operating 230 Poles of dynamos, definition 337 Poles for transmission line 358 Polyphase current, definition 335-342 Pondage, definition 41 Portland cement, specifications of 139 Potential energy of water 276-277 Power auxiliary, definition 42 Power equipment 276 Power flow 41 Power house, appurtenances 264 Power house, equipment, general cost 70 Power house for fluctuating head, Fig. 87 . . 263 Power house, foundation 254 Power house, general 67 Power house for high head, Fig. 89 267 Power house, location 254 Power house for low head, Figs. 84-86, 88 . . 259-262, 265 Power house for medium head, Fig. 89 267 Power house, quantities, Diagram 13 69 Power house, submerged, design 266 Power house, substructure 255 Power, lighting, Diagram 1 3 Power opportunity 8 Power output, definition 40 GENERAL INDEX 379 PAGE Power plant, auxiliary 364 Power required to operate turbine gates. . . . 329 Power, water and electric, Diagram 3 43 Practicability of hydro-electric project... 47-54 Precipitation, definition 8 Precipitation and evaporation, flow deduced from 108 Precipitation profiles 35 Precipitation records 28 Presentation of project 75 Pressure moments on retaining walls, Dia- grams 31-33 215-217 Pressure moments in solid spillways, Dia- grams 26-29 165-168 Pressure and resistance, theory of 160 Privileges (see Control, Title) Puddle, definition 139 Quantities Quantities Quantities Quantities 10 Quantities Diagram Quantities Quantities Quantities Diagram Quantities Quantities Quantities Quantities Quicksand, for coffer structures, Table 8. ... 144 for cut-off walls, Table 9 147 for dam abutments, Diagram 12. 66 for dam, concrete-steel, Diagram 64 for 14. dam, earth embankments, for dam foundations, Diagram 12 66 for dam masonry, Diagram 9 ... 63 for dam, reservoir bulkheads, 15 72 of excavation from canal prisms. 243 for gravity spillway, Table 13. .. 192 for power house, Diagram 13. .. 69 for timber spillway, Table 15 208 characteristics of . . .133 Rack, trash, for pipe intakes 252 Eadius, hydraulic, definition 249 Rates, current, H. P. and K. W., Diagram 8. 60 Reactance, current, definition of 336 Reaction, current, definition of 335 Reaction, definition 276 Reaction turbine case 292 Reaction turbine, central discharge, descrip- tion of 294 Reaction turbine, defined 286 Reaction turbine, design, Figs. 109, 110... 291, 293 Reaction turbine, design, theory 318 Reaction turbine, gates of 289 Reaction turbine, guide wheel, described... 289 Reaction turbine, maximum efficiency out- put. Diagram 38 319 PAGE Reaction turbine, mixed flow, described .... 287 Reaction turbine output, theory of 314 Reaction turbine runner, described 287 Reconnaissance 91 Records of evaporation 33 Records of precipitation 28 Records of precipitation, Ex 31 Register gate of turbine 289 Reinforcing steel, characteristics of, Table 5 144 Report on hydro-electric project, Ex 75 Reservoir bulkheads, quantities, Diagram 15 72 Reservoir dams, described 221 Reservoir embankments, cost of 68 Reservoir, flow from, Diagram 4 45 Reservoir sites 115 Reservoir storage, value of 44 Resistance of aluminum wire, Table 33 350 Resistance of copper wire, Table 31 340 Resistance and pressure, theory of 160 Retaining wall, concrete-steel, described. . . 214 Retaining wall, pressure moments, Diagrams 31-33 215-217 Retaining wall, theory of 210 Rheostat, described 350 Rights (see Control, Title) Riparian title 53 Riprap, description of 142 Rock, characteristics of 131 Rock, drilling 242 Rock and earth excavation from canals. 242-243 Rock and earth fill dams 222 Rod floats, stream gauging 102 Rod to mean velocity, Diagram 18 105 Rotary converter, description 342 Roughness of perimeter, coefficient 103-237 Runner of reaction turbine, described 287 Runner of reaction turbine, vent areas 318 Run-off, monthly, profile 35 Run-off, ordinary dry year, Ex 114 Run-off, storm, definition 8 Safety factor for spillway 174 Safety factor for transmission line 360 Sand, characteristics of 133 Sand for earth dam 226 Sand, specifications of 139 Sandstone, characteristics of 132 Self-induction current, definition 335 Series winding of field magnets 338 Service, current, industrial 2 Service, current, lighting 1 Service, current, special 2 380 GENERAL INDEX PAGE Service, current, traction 4 Sheet pile dike, description of 142 Sheet, steel, description of 136 Sheet, timber, description of 136 Short diversion programme 117 Shunt winding of field magnets 338 Shutters, described 198 Sienite, characteristics of 131 Silt, characteristics of 133 Single phase current, definition 335 Sliding of spillways, theory 169 Slip rings, dynamo 342 Slope of backswell above dam 149 Slope of backswell, Diagrams 20-25 .... 152-156 Slope in curved channels 242 Slope in open channels, Tables 16-19. . . 238-239 Sluice design 201 Sluice, overflow, described 196 Sluice, overflow, theory of discharge through 195 Sluice, underflow, design 230 Soil, characteristics of 133 Span, length of transmission 359 Specifications for construction 369 Speed of standard generators, Table 32 355 Spillway abutments, quantities for, Diagram 12 66 Spillway air vents 235 Spillway apron, shaping, theory 186 Spillway, concrete-steel, quantities for, Dia- gram 10 64 Spillway crest, shaping, theory 185 Spillway crushing, theory of 170 Spillway and dam appurtenances 227 Spillway foundation 131, 144, 147 Spillway foundation, quantities for, Dia- gram 12 66 Spillway galleries 235 Spillway, gravity, design, characteristics of, Table 14 194 Spillway, gravity, design of, Tables 11-14. . 191-194 Spillway, gravity type, theory 187 Spillway, height of. 149 Spillway, length of 159 Spillway, masonry, quantities for, Dia- gram 9 63 Spillway, open, description of 194 Spillway, pressure and resistance, theory of 160 Spillway, safety factor for 174 Spillway sliding, theory of 169 Spillway, solid, design characteristics, Table 10 .. 185 PAGE Spillway, solid, practical design 180 Spillway, solid, pressure moments, Diagrams 26-29 165-168 Spillway, solid, theoretical design 176 Spillway superstructure 148 Spillway, timber and concrete, comparative cost, Diagram 30 211 Spillway, timber, described 205 Spillway, timber, design, analysis of 206 Spillway, timber, quantities for, Table 15.. 208 Spillway toe, shaping, theory 186 Spillway wells 235 Stand pipes 330 State control of rivers 53 Static transformers 343 Steel concrete, definition of 140 Steel concrete beams, constants of, Table 6. 141 Steel concrete beams, Table 7 141 Steel curtain, description of 139 Steel pile dike, description of 142 Steel plate pipe, cost of 67 Steel, reinforcing, characteristic of, Table 5. 141 Steel sheet, description of 136 Stop-logs, described 196 Stop-logs, section, theory 201 Storage battery, described 366 Storage, definition 42 Storage, ground, definition Ill Storage, ground, depletion 112 Storage reservoir, value of 44 Storm run-off, definition 8 Stream discharge curve 103 Stream discharge curve, Ex., Diagram 19 . . 106 Stream flow, determination of 30- Stream gaugings, Figs. 9 and 10 100-102 Stream gaugings, reductions 103 Structural types 131 Sturgess governor 327 Submerged orifice, theory of discharge through 227 Submerged power house, design of 266 Substation 364 Substation, general cost of 70 Subsurface floats, stream gauging 102 Superstructure of dam, description of 148 Superstructure of power house 255-264 Surface floats, stream gauging 102 Surface to mean velocity,.Diagram 17 104 Survey 90 Switchboard 348 Switches 349 Synchronizers (see Phase indicators) ...... 349- GENERAL INDEX 381 PAGE Theory of crushing of Spillway 170 Theory of current transmission 345 Theory of deducting turbine efficiencies .... 298 Theory of design of reaction turbine 318 Theory for design of stop-log section 201 Theory for design of timber spillway 206 Theory of discharge through overflow sluice . 195 Theory of discharge through submerged ori- fices 227 Theory of flow in open channels 236 Theory of flow in pipes 249 Theory of flow through turbines 278 Theory of gravity spillway 187 Theory of hydraulic equipment 276 Theory of impulse wheel output 320 Theory of magneto-dynamic energy 330 Theory of overturning of spillway 170 Theory of pressure and resistance 160 Theory of reaction turbine output 314 Theory of retaining wall design 210 Theory of shaping spillway apron 186 Theory of shaping spillway crest. 185 Theory of shaping spillway toe 186 Theory of sliding of spillway 169 Theory of solid spillway design 176 Theory of static transformers 344 Theory of transmission line span length. . . . 360 Theory of turbine draft tube effect 296 Theory of weir flow measurement 107 Three-phase current, definition 335 Timber and concrete spillways, comparative cost, Diagram 30 211 Timber cribs, description of 137 Timber curtain, description of 139 Timber, definition of terms 137 Timber sheet, description of 136 Timber spillway, description of 205 Timber spillway, design, analysis 206 Timber spillway, quantities for, Table 15.. 208 Title, riparian 53 Toe of solid spillway, shape of 186 Topography of drainage area 26 Topography ( survey) 94 Traction current service 4 Transformers, cost of 70 Transformers, static 343 Transmission of continuous current 346 Transmission of current 345 Transmission, general cost of 70 Transmission line conductors 358 Transmission line fastenings 358 Transmission line supports 358 PAGE Transmission line wire, weight, Diagram 16 73 Transmission plant equipment 358 Trash rack for pipe intake 252 Trenching for cut-off 146 Triangulation 92 Tripod and target (survey), Fig. 2 93 Turbine, central discharge, design of 295 Turbine draft tubes, dimensions 319 Turbine draft tube, theory of 296 Turbine efficiencies, theory of 298 Turbine equipment, determination of 322 Turbine, flow through, definition of 287 Turbine, flow through, theory of 278 Turbine gates, power required to operate. . . 329 Turbine governor 326 Turbine governor, Lombard 327 Turbine gorernor, Lombard-Replogle 328 Turbine governor, Sturgess 327 Turbine governor, Woodward 328 Turbine guide-wheel openings, dimensions.. 319 Turbine, horizontal cased, described 310 Turbine, horizontal cased, dimensions, Dia- gram 37 317 Turbine, horizontal drowned, described 304 Turbine, horizontal drowned, dimensions, Diameter 35 307 Turbine, horizontal, four drowned, design, Fig. 119 312 Turbine, horizontal, paired and cased, de- sign, Figs. 120, 121 313, 315 Turbine, horizontal, paired and drowned, de- sign, Fig. 117 306 Turbine, horizontal, single, drowned, dimen- sions, Diagram 36 311 Turbine, horizontal, three drowned, design, Fig. 118 309 Turbine, impulse 286 Turbine, impulse, description 296 Turbine, impulse, design of, Fig. 114 297 Turbine installations, typical 300 Turbine, losses of energy in 299-300 Turbine, reaction 286 Turbine, reaction, case 292 Turbine, reaction, central discharge, descrip- tion of ' 294 Turbine, reaction, design of, Figs. 109, 110. 291, 293 Turbine, reaction, design of, theory 318 Turbine, reaction, gates 289 Turbine, reaction, guide wheel, described... 289 Turbine, reaction, maximum efficiency out- put, Diagram 38 319 382 GENERAL INDEX PAGE Turbine, reaction, mixed flow, described .... 287 Turbine, reaction, output, theory of 314 Turbine runner, dimensions 318 Turbine, tangential impulse, maximum effi- ciency output, Diagram 39 323 Turbine, vertical, cased, described 304 Turbine, vertical, cased, dimensions, Dia- gram 34 303 Turbine, vertical, paired and cased, design, Fig. 116 305 Turbine, vertical, paired and drowned, de- sign, Fig. 115 302 Turbines, classification of 285 Two-phase current, definition 335 Underflow sluice, design of 230 Value of project 75 Valve gate 252 Valves, described 197 Valves, hydraulic relief 330 Vanes, guide, of reaction turbines 289 Velocity in open channels, Tables 20-24, 240-241 Velocity in pipes, Tables 27-29 250-251 Velocity, rod to mean, Diagram 18 105 Velocity, surface to mean, Diagram 17 1"04 Vents, air, in spillways 235 Vertical turbine cased, described 304 Vertical turbine cased, dimensions, Diagram 34 303 Vertical turbine drowned, described 301 Vertical turbine paired and cased, design, Fig. 116 305 Vertical turbine paired and drowned, de- sign, Fig. 115 302 Volt, definition of 331 Voltage drop (loss) 346 Voltage of standard generators, Table 32 . . 355 PAGE Voltaic electricity 330 Wall, core, description of 139 Wall, cut-off, description of 139 Wall, cut-off, quantities for, Table 9 147 War Department, control of rivers, Table 3. 50 War Department, lease from 48 War Department, license from 49 Waste weir in canals 246 Water power and electric power, Diagram 3 43 Water-shed, definition 9 Watt, definition of 331 Wattless current, definition 336 Wattmeters, described 349 Weight of aluminum wire, Table 33 359 Weight of copper wire, Table 31 340 Weight of transmission line wire, Diagram 16 73 Weir, flow over flat-crested, Diagram 2 39 Weir, flow measurement, Fig. 11 107 Weir, movable, described 198 Weir, waste, in canals 248 Wells in spillways 235 Wicket gate of reaction turbine 289 Winding of armature, described 340 Winding, compound, of field magnets 338 Winding, series, of field magnets 338 Winding, shunt, of field magnets 338 Wire, aluminum 346 Wire, aluminum, characteristics of, Table 33 359 Wire, copper, characteristics of, Table 31. .. 340 Wire formula 340 Wire gauge, B. & S. (Brown & Sharpe), Table 31 340 Wire, transmission line, weight of, Diagram 16 73 Wood-stave pipe, cost of 67 Woodward governor 328 UNIVERSITY OF CALIFORNIA LIBRARY, BERKELEY THIS BOOK IS DUE~0^ THE LAST DATE STAMPED BELOW Books not returned on time are subject to a . . 50c per volume after ^^ d s ^ day. Books not in expiration of loan period. N 4 1930 NOV 1 3 1930 nr~ -E DEC 21 1931 m -. flpB**^ 1 20m-ll,'20 YE 01938 I74385 /