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The tailrace from the power plant discharges in the river at a point upstream from the normal downstream toe of the dam. It was necessary to provide special construction at this point to avoid weakening the dam and reducing its percolation factor. This was accomplished by excavating the tailrace to a depth of 10 feet below its required bottom and placing thereon an 18-inch layer of screened gravel to serve as a drain and filter for seepage water. An 8-foot 6-inch layer of heavy rock fill was placed over the gravel layer.
$15, 610 132,054
5, 267 15,000
Examination and surveys.---
and unwatering foundations.
nance. Excavation: Classes 1 and 2, stripping -------
841 Classes 1 and 2, cut-off trenches..... 13, 739 Classes 1 and 2, cut-off walls....
9,967 Class 3, cut-off walls.......
1, 582 Classes 1 and 2, spillways and trashrack 3,113
structure. Class 3, spillways, placed for riprap on 9,649
upstream slope of dam. Class 3, spillways, placed in downstream | 104, 131
portion of dam. Class 3, trashrack structure, placed for 4, 001
riprap in upstream portion of dam. Classes 1 and 2, tunnel approaches.... 21, 274 Class 3, tunnel approaches...--.-.
14, 871 All classes, tunnels and shafts
40, 144 Hauling selected materials for embankment 35,050
upstream blanket and backfill. Embankment, sluiced gravel..------------| 349, 950 Gravel sluiced into base of rock portion of dam. 14. 916 Upstream blanket, sluiced earth.------------ 1, 425 Drilling grout holes..-----Cutting, threading, fitting, placing, and 431
anchoring connecting pipes in grout holes. Pressure grouting..------
155.4 Drilling holes for anchor bars and grouting 4, 340
bars in place. Placing 4-inch or 6-inch drain tile under spill
3, 852 way lining. Concrete:
Cut-off walls in dam abutments.-------| 220
155.7 Retaining walls in tunnel inlet and north 1,955
19.7 Placing and bending reinforcement steel..- 756, 740 Placing and paintingstructuralsteelin trashrack. 166, 868 Installing and painting Stoney gates in spill- (1, 168, 436
way and power outlet. Installing and painting drum crests in spillway. | 535, 551 Installing and painting 5- by 5-foot hydraulic 189, 508
operated slide gates. Installing and painting metal lamp posts.--.. Installing electric conduit fittings and boxes... 3, 297 Placing and painting pipe for handrail...----- 2,712 Placing and painting structural steel stairs... 16, 140 Construction of north spillway gate house.... Extra work by contractor.--------------Work done by Government forces... Engineering, inspection, superintendence,
accounts, and general expense.
The gravel and clay fill of the dam was placed by the semihydraulic method. The material was transported from the borrow pits by trains, and dumped from trestles on the upstream and downstream sides of the embankment. A pool of water was formed between the piles of dumped material, and the finer materials sluiced into the pool by a hydraulic giant mounted on pontoons floating in the pool. The finer materials sluiced into the pool form the puddle core, and the coarser, gravelly, material is left in the upstream and downstream portions of the embankment. The borrow pits from which the embankment material was obtained contained clay, sand, and gravel in about the right proportions for the embankment, except that additional clayey material was added during construction to furnish sufficient extra clay required for the puddled core. The rock material excavated from the tunnels, the spillways, and from other structures was placed on the upstream and downstream slopes of the embankment.
Plans called for placing an earth blanket on the reservoir floor, immediately above the upstream toe of the dam. This earth blanket was partially placed, as contemplated; but was largely secured by the natural settling of silt from the water impounded above the upstream cofferdam during the diversion period.
The north spillway gate leaf was assembled on a trestle built 15 feet above the channel floor. For transferring the weight of the gate to the counterweights, the counterweight wells were sufficiently filled with sand to allow the chain connection to be made. When the chain was connected to the counterweight stem, the sand was removed from the bottom of the counterweight well by an air jet, allowing the counterweight to settle slowly until it took the full weight of the gate. The hoists then raised the gate and the trestle support was removed.
The Guernsey Dam and power plant were constructed under contract by the Utah Construction Co., of Ogden, Utah. Work was commenced in May 1925, and completed in January 1928.
2,966 2,069 45,059
4, 347 42, 353 11,661 20,838 74, 757
3,045 133, 401 17, 121 24, 003
The principal items and approximate quantities of work involved in the construction of the dam and power plant were as follows:
Building the Guernsey Irrigation and Power Dam. F. F.
Smith, Eng. N. 100: 264-8 Feb. 16, '28, illus. Guernsey Dam Contract Awarded. New Reclamation
Era 16:95 June '25. Guernsey Dam Helps Irrigate Lands in North Platte
Valley. C. H. Vivian. Comp. Air M. 33: 2373–7 April
'28, illus. Guernsey Dam, North Platte Project, Nebraska-Wyoming.
W. H. Nalder. New Reclamation Era 19:184–7 December
'28, illus. Guernsey Dam; Relation to Water Supply and Power.
A. Weiss, New Reclamation Era 16: 30 February '25. Guernsey Power Plant, North Platte Project, NebraskaWyoming. H. F. McPhail. New Reclamation Era 19: 60–2 April '28, illus.
Guernsey Surge Tank, North Platte Project, NebraskaWyoming. R. E. Glover. New Reclamation Era 18: 136–7 September '27, illus. Same: Hydraulic Eng. 3:
20, 30 November '27. New Slackline Cableway Bucket Used on Guernsey Dam.
West. Constr. N. 1: 33 Dec. 10, ?26, illus. North Platte Irrigation Project. E. H. Simpson. Eng.
World 31: 3-5 July ’27, illus. North Spillway Gate and Hoist, Guernsey Dam, Wyoming,
P. A. Kinzie. West. Constr. N. 4: 174-82 Apr. 10, '29
illus. Power and Irrigation Work Financed by PWA. Eng. N.
111: 251–3 Aug. 31, '33, illus. Sluiced Gravel Forms Main Embankment for Guernsey
Dam. Const. Methods 10: 26-8 April '28, illus.
SALT LAKE BASIN PROJECT, UTAH
BY O. L. RICE, ENGINEER, BUREAU OF RECLAMATION
ECHO DAM was the first unit constructed on the Salt Lake Basin project in Utah. It was built across Weber River about 1 mile upstream from the town of Echo, a junction point on the main line of the Union Pacific Railroad. The dam is located about 45 miles by highway from Salt Lake City. It provides a storage reservoir which is used almost wholly as a supplemental water supply for 80,000 acres of irrigated lands in the Ogden and Utah Lake Valleys which are supplied with water under existing canals, taking water from the Weber and Provo Rivers.
The development of the supplemental water supply created by the reservoir requires exchanges of Weber River water for Echo Reservoir storage and the diversion of certain surplus flood waters from the Weber River watershed to the Provo River watershed. The diversions are made through the Weber-Provo diversion canal of 210 second-feet capacity, constructed as a unit of the Weber River division of the Salt Lake Basin project. The diversion works are located on Weber River near Oakley, about 24 miles upstream from Echo Dam.
The building of Echo Dam necessitated the relocation of the Park City branch of the Union Pacific Railroad and the Lincoln Highway around the east side of the reservoir; also the reconstruction of a portion of the Coalville City water main and the construction of a farm road around a portion of the west side of the reservoir as well as reconstruction of portions of telephone and electric lines located in the reservoir and borrow pit areas.
The dam site lies at the lower end of a flat mountain valley, at a point where the canyon walls are relatively close together. The foundation rock consists of Wasatch conglomerate on the left abutment and river bottom portions, and grades into a sandstone on the right abutment. The bedrock lies at an almost constant elevation in the river bottom and rises abruptly on the right abutment. At the left abutment the rock surface rises rather abruptly for a height of approximately 50 feet, then flattens out again. The conglomerate is made up of coarse sand, fine grit, small pebbles, and cobbles up to 6 or 8 inches in diameter, all weakly cemented together. Both the conglomerate and sandstone are soft, somewhat porous, and break down rather readily due to weathering.
A considerable depth of overburden lies above the foundation rock, except for a narrow section cut by the river. The depth to bedrock is about 26 feet below the stream bed and increases to approximately 65 feet at the east half of the dam where a large terrace of alluvial material has accumulated.
The upper portions of the overburden consist of clay intermixed with coarse materials forming a reasonably tight section, while the bottom portion consists of porous sediments of sand and coarse materials varying from thin layers to layers several feet in thickness.
Some preliminary testing was done at the dam site as early as 1905, but the major part of the testing was accomplished during the years 1924 to 1926. Suitable embankment materials were located at various points near the dam site. Concrete aggregates were located in the river channel below the dam.
Echo Reservoir has a storage capacity of 74,000 acre-feet and a drainage area of 730 square miles. The lake formed by the dam is 434 miles long, with a maximum width of 1 mile and a surface area of 1,470 acres at the normal water surface elevation 5,560. The average annual run-off into the reservoir is about 280,000 acre-feet.
A contract with Heiselt Construction Co., dated April 26, 1928, provided for the clearing of the reservoir site. All trees and brush over 5 feet in height lying below the flow line were cut as close to the ground as possible, and all logs, trees, brush, and combustible debris not salvaged by the contractor were burned.
The dam consists of a moistened and rolled embankment of clay, sand, and gravel, with a heavy downstream section of gravel, cobbles, and rock fill. The upstream 3:1 slope was covered with a 4-foot layer of dumped conglomerate riprap, and the berm and 5:1 slope portions were covered with a 2-foot layer of sand and gravel excavated from the cut-off trench. The maximum height of the dam is 125 feet above stream bed or 151 feet above bedrock. It has a crest length of 1,887 feet, including the spillway channel, a crest width of 25 feet at elevation 5,570, and a base width of 830 feet at the maximum section, exclusive of the upstream dry earth blanket. Concrete parapet and curb walls are constructed along each edge of the crest.
The upstream slope is 3:1 from the crest to a berm 20 feet in width at elevation 5,482, and 5:1 from the edge of the berm to the ground line. A dry earth blanket with a 20:1 slope extends approximately 300 feet upstream from its intersection with the 5:1 slope at elevation 5,462.14. The downstream slope is 2:1 from the crest to a break in slope at elevation 5,477 in the river bottom and elevation 5,499.2 on the sides adjacent to the river channel, and 6:1 extending to the ground line, except for the section in the river bed which breaks again to a 1)2:1 slope near the ground line at the downstream end. Toe drains of 8- and 12-inch drain tile were laid in gravel-filled trenches excavated at the downstream toe of the dam.
Outlet works and spillway are located at the left abut
ment, and the relocated railroad and highway are located at the right abutment. The right end of the dam is turned upstream into a projecting face of the abutment, to provide suitable contact with the abutment and to minimize the highway fill at its junction with the dam. The railroad grade is about 25 feet below the crest of the dam at the axis, and a puddled core was constructed in the central portion of the highway to protect the railroad against seepage from the reservoir.
The axis of the dam was located somewhat parallel to the upstream face of the terrace and at such distance that the cut-off trench, extending to bedrock, would lie largely in the river bottom without increasing the cut-off trench excavation or quantity of dam embankment.
The concrete cut-off wall was constructed continuously across the dam from the center of the highway at the right abutment and to a point 206.5 feet into the left abutment, beyond the center line of the spillway. The portion of the cut-off in the river bottom lies in the center of an open trench with 20-foot bottom width and 1:1 side slopes excavated to bedrock. Sections of vertical side trench, 2% feet in width, located in the center of a smaller open cut and extending 1.5 feet into bedrock, were excavated at both abutments where the previous layer was relatively thin and where bedrock occurred at a depth of approximately 40 feet. A stoped concrete cut-off, 4 feet in width, was constructed at the left abutment where the depth of overburden exceeded 40 feet. The stope was excavated 1.5 feet into the foundation rock and extended through the porous layer a minimum of 5 feet into the overlying impervious material. It was entirely filled with concrete and grout.
A reinforced concrete cut-off wall, 12 feet high, 12 inches thick at the top and 18 inches thick at the base, with footings approximately 3 feet wide extending 1.5 to 4 feet into excavated trenches in the bedrock, was constructed in the open cut-off trench. The vertical side trenches were backfilled with concrete to a minimum of 5 feet above the porous layer and backfilled with puddled clay from the top surface of the concrete to the bottom of the excavated trench above.
A section of the cut-off at the right abutment was begun as a vertical side trench; but, before completion, a slide occurred destroying the compaction of the foundation and the section was changed to a cut-off trench in open cut. An additional cut-off wall was constructed to further insure safety against seepage along the rock cliff at the right abutment.
The base of the dam was stripped of unsuitable foundation materials. Pockets of soft silt mixed with clay and humus were encountered in the river bottom and were entirely removed before placing the earth fill.
It was originally contemplated that the downstream portion of the dam, beginning at the lower 1.6:1 earth fill slope, would be constructed of gravel and cobbles obtained from necessary excavation or from borrow. During the progress of work it developed that insufficient suitable materials were available and conglomerate rock fill was substituted to complete the section. The principal quantities involved were as follows:
............... 1,376,800 cubic yards. Gravel and cobbles. ........... 39,550 cubic yards. Rock fill ........
: . 158,300 cubic yards.1 Riprap. .......
:. 43,850 cubic yards.1 Concrete . .......
. . 9,546 cubic yards. Reinforcement steel. .......... 416,700 pounds. Metalwork ............... 828,800 pounds.
1 Excavation measurement.
capacity of 15,000 second-feet at normal water-surface elevation of 5,560. The discharge is controlled by four 18by 17-foot, counterbalanced, radial gates, located near the axis of the dam. A transition begins at the downstream end of the gate structure and terminates at the chute section having 1:1 side slopes.
The chute is built on a steep slope and terminates in a stilling basin, serving both the spillway and outlet works. The stilling basin has a bottom width of 40 feet and a depth of 31 feet, the bottom being 17 feet lower than the outlet channel to the river which is an unlined channel with a 30foot bottom width and 1%: 1 side slopes.
The gate structure and upper portion of the chute section rest on earth materials, and the lower portion of the chute section and major portion of the stilling basin are founded on conglomerate rock. The portion of the spillway resting on earth materials was thoroughly drained with sewerpipe drains, laid in a gravel trench; also by a 6-inch layer of screened gravel laid under the spillway floor and sides. Drainage in the stilling basin was provided through 2-inch weep holes at 5-foot centers, drilled through the concrete lining to the rock surface. Counterforted side walls were designed for the upper and lower portions of the spillway where active earth pressures exist.
An extensive cut-off, located directly above the stoped cut-off wall, was constructed as a collar around the spillway gate structure, extending 21 feet below the floor and 30 feet on each side of the spillway to provide additional safety and to prevent seepage from the reservoir.
The stilling basin floor was lowered 11 feet and the basin lengthened 60.07 feet after the spillway excavation had begun, due to the absence of substantial rock foundation. A section of rubble concrete paving was constructed at the end of the stilling basin to protect the portion of the bottom and sides of the channel founded on earth.
The two center gates operate automatically through electrical contact produced by actuating floats installed in wells in the two outer piers. The operating mechanism consists of electrically driven gear hoists with gas engine installation for emergency control. The water level in the piers is maintained through 4-inch piping leading to the reservoir. The automatic gates are raised or lowered in increments of 4 inches in accordance with a rising or falling reservoir. A change of water surface of 0.01 foot produces the electrical contact.
Electric lines, together with the necessary transformers, are connected with the Utah Power & Light Co.'s power line near the left end of the dam.
The spillway, located at the left abutment, is a concretelined channel with a bottom width varying from 80 feet at the intake to 30 feet in the chute section. It has a designed
The diversion tunnel, 838 feet in length, located at the left abutment, was designed to house the outlet works after serving its purpose for diversion. The upstream portion