ENGINEERING MONOGRAPHS No. E; . United States Department of the Interior BUREAU OF RECLAl\fATION SOAP LAKE SIPHON by ROBERT SAII.ER Denver, Colorado August 1950 4fj cents United States Department of the Interior OSCAR L. CHAPMAN, Secretary . Bureau of Reclamation MICHAEL W. STRAUS, Commissioner L. N. McCLELLAN, Chief Engineer Engineering Monographs No. 5 .SOAP LAKE SIPHON by Robert Sailer, Engineer, Canals Division . Branch of Design and Construction Technical Information Section Denver Federal Center · Denver, Colorado ENGINEERING. MONOGRAPHS are published in limited editions for the technical staff of the Bureau of Reclamation and interested technical circles in Government and private agencies. Their purpose is to record developments, innovations, and progress in the engineering and scientific techniques and practices that are employed in the planning, design, construction, and operation of Reclamation struc­ tures and equipment Copies may be obtained at 2~ from the Bureau of Reclamation, Denver Federal Center, Denver, Colorado, and Washington, D. C. FRONTISPIECE - Crossing the lower end of the Grand Coulee by the West Canal required construction of the Soap Lake Siphon. The siphon begins on the east aide of the depression (lower center), crosses at the north end of Soap Lake, and climbs the bench to the vest. FRONTISPIECE - Crossi.ng the lover end of the Grand Coulee by the West Canal required constructicin of the Soap Lake Siphon. The siphon begins on the east side of the depression (lover center), crosses at the north end of Soap Lake, and c11mba the bench to the vest. CONTENTS Page INTRODUCTION 1 INVESTIGATIONS 1 Lake Crossing 1 Final Location 3 ALTERNATIVE DESIGNS 5 Plan and Profile 5 Plate Steel Pipe · 5 Savings Possible with Steel-lined Pipe 5 DESIGN OF PIPE 7 General Description 7 Hydraulic Desigri 7 Gravel Trap 7 Inlet and Outlet Transitions 12 Concrete Pipe 13 Steel-lined Monolithic Concrete Pipe 17 1. Unit Stresses 17 2. Design 17 a. Load assumptions 17 b. Weld locations 19 c. Working rule for steel stresses 21 d. Bends 21 . 3. Steel-liner Plate 23 4. Reinforcement 24 5. Contraction Joints 24 Manholes and Blowoff Structures 24 1. Manholes 24 2. Blowoff structures 24 QUANTITIES AND COST DATA 25 INTRODUCTION Samples obtained by core drilling for foundation e:lq)loration showed that a gravel stratum about 120 feet below the water sur­ Soap Lake Siphon, now under construc­ face is overlaid by lake deposits about 90 feet tion by the Bureau of Reclamation, is part thick. The lake deposits are interbedded with of the West Canal of the irrigation system swampy material and grade downward into of the Columbia Basin project. The siphon firm silt and clay. This overlying material, is located near the town of Ephrata; Wa,sh­ upon which the rock fill would have had to be ington, about 50 miles southwest of Grand placed, exhibited unstable characteristics Coulee Dam. In this vicinity, the route of that caused concern ovt:r the ability of the the canal requires ·a crossing of.:the lower undistur.bed saturated material to support Grand Coulee, a large topographical trough, the heavy loads to be imposed by the rock as illustrated in Figure 1. To convey tbe fill. Denison-type undisturbed samples were water across this trough, Soap Lake Siphon, taken for stability tests, to measure triaxial named for a nearby lake, is being buill shear and consolidation properties which were used in the calculation of stability. The siphon is 12,900 feet long, having a Tests of these samples showed conclusively design flow capacity of 5,100 cubic feet per that the lake-bed material overlying the second. The inlet and outlet legs of the si­ gravel stratum had no measurable shear re­ phon are 25 feet 0 inches inside diameter sistance and that a rock fill constructed apd are monolithically constructed of rein­ thereon would be unstable and unsafe. For forced-concrete pipe designed to withstand these r-easons the plan of using rock-fill hydraulic heads up to 100 feet. The central, foundation for the pipe was abandoned. or high-pressure, section, which will be un­ der a maximum head of 225 feet, is 22 feet 4 inches inside diameter and consists of steel-lined reinforced-concrete pipe· cast in The undisturbed samples of the lake bed place. material also showed that little reliance could be placed on it for either frictional or lateral support for piles. It was apparent that the gravel stratum underlying the lake bed deposits must be penetrated to provide· adequate bearing for piling. The water in INVESTIGATIONS the lake showed a high concentration of car- . bonates, sulphates, and chlorides; the total Location of the siphon required a care­ dissolved solids exceed 37,000 parts per ful investigation of a number of alternative million in a typical analysis. Tests indicated Jines and studying construction and main­ that concrete piles exposed to water of this tenance costs. Figure 2, showing the sev­ nature might deteriorate very rapidly. It •eral r9utes considere~, makes it a_pparent was believed steel piles would suffer less that a lake crossing covers the shor.test dis­ damage than concrete in the lake water; but tance; therefore, extensive investigations in penetrating the gravel stratum underlying 'Were made of the lake ·crossing. the lake bed material, the piles would come in contact with fresh water. A concentration A siphon pressure tunnel under the lake of solutions varying over the length of the was first considered, but borings in the lake pile would develop a concentration cell to bed failed to reach rock at a depth of 200 the detriment of the immersed metal, the feet below the water surface. Since this .greater damage being suffered by that por­ depth would have niade the pressure· head on tion in the solution of higher concentration. the siphon about 400 feet, the tunnel scheme Paint as a means of protection was precluded, was abandoned as impracticable. both because of the certainty of damage due to driving the piles and the equal certainty Lake Crossing .that the lake water would remove it rapidly. It appeared that the only practicable method . Comparative estimates were made for a of preventing corrosion of steel piles would steel pipe supported on concrete piers built be cathodic protection, which had proven ef­ on piles driven. into Ute lake .bed, and for a _fective when used on steel pipe and steel steel pipe laid on a rock .fill. sheet-piling. However, uncertainty remained as. to the effectiveness of cathodic protection Although estimates indicated that the for the interior piles of the large pile clus­ latter type of construction would be some­ ters required for each pier, and since no what costlier than the former, favorable adequate estimate of the first cost or main­ consideration was given to the. rc;ick fill, both .ten~ce costs of such an unprecedentedly because greater advantages in· ope.ration and large system of protection could be made, the · maintenanc~ were anticipated, and· becauSe plan of using steel piles for the lake cross­ the estimated difference in cost was small ing was discarded. 1 r- ---­ I ' /GRAND COULEE DAN AND W POWER PLANT · UNITED STATES DEPARTMENT OF THE INTERIOR BUREAU OF RECLAMATION COLUMBIA BASIN PROJECT WASHINGTON FEATURE MAP i SHOWING I MAIN CANAL SYSTEM AND POWER AND PUMPING PLANTS 0 00 0 5C:&L[ OF MIL.(S I . ]'I t PASCO PUMPING PLANT.......... 222-D-12626: Y.IGURE 1 - StdLp lake Siphon 1s an i.mportant link in the We.~t Canal ro-stem of tbe C'olUIIIbia Basin project. La:nd to be brought under 1rr1ptian lies between. tbe West Canal and the _..t R1gb. Canal, extend1Dg south to tbe Columbia River. · .:·'~· · 2 ,--- r' I I I I I , N I ,' ,.,1// _.,,, . ~ \ I - .," I ~ ,' I ' \ • II I/ I \ . I \ I \ I \ I \ I --i~ \ I \ I \ I I ' \II ,I ' ··l - SCAL£ or FE£t '·-WESr CANAL NOTATJON Canol S1p/'lo.o AL.TcRNATIVc LOCATION FIGURE 2 - .Investigations included examination and compara­ tive cost estimates for the 1ocation of the siphon on each of the routes illustrated here. -- - . - Cost studies were made for steel pipe pariso:ns showed that the line passing around supported on concrete piers cai'i'iedto:the· ·the north end of the lake would be the less ex­ gravel stratum by open cofferdam·construc'­ pensive, and this line was adopted as the lo­ tion, but here again the. quest.ion-of damage cation for __ the final design to the concrete by the lake water and. the lin­ certainty as to the efficacy of possi'l;>~~ means Of interest is the result of studies made of protection, as well as the high cost bf ·auch to compare the cost of a ·single pipe with that construction, caused the abandonment of this _of smaller twin pipes designed for the same plan as well, and with it the abandonment of . total capacity. The studies showed that the the idea of a siphon crossing the lake. · : · two smaller pipes would cost about 25 per­ . cent more than a single pipe. Final Location . Consideration was next -given to constrv,ct­ . ALTER~A TIVE I;)~SIGNS ing a siphon around ei.then.· the noitn .or'. the south end of the lake, altii6ugii· tliis'woilld 1n:.:-· cost studies wer·e undert~en for a de­ volve materially longer siphons. Cost com- sign utilizing buried monolithic concrete 3 .\. I l LAKE \ .··t·""•' --Ls1•-ut•S14lSt A.fl I Pl. AN -- ~ eo+CIO ._.,.DO ITATIONI PROF/I.E CONCRETE IINO STEEL-LINEO CONCRI!TE PIPE ili-· ~~ ....._,;•• ··~ HFDifAU&.I &"AIJII:.Itl1 '• '• •MD • t:.. "", _I_ I • : :ii '~ ~----- ·---------- -----+-- ----------- .,., ,,.., .... ~~"···o.. ........ T .. ········-· -----~ _ .... ! --..........~:. l i I•Nrl ,0I11P~ .-(}TIIJI/ttl/ 1"1Jt1411 ~dati t ~ :··s.o ;---- /! .,.~,., ,.,~---l-t---­ ~v ~---c;cm•- n·-o·oo-····· - - - .