LAKE MEAD Construction of Boulder Dam

SUMMARY

The first work for the present program of construction was initiated on July 5, 1930, two days after the first appropriation was made available by Congress.

The contract was awarded Six Companies, Inc., on March 11, 1931, the first excavations for diversion tunnels took place on May 16, 1931, the tunnels were excavated by May 27, 1932, and lined by March 8, 1933. Initial diversion occurred on November 13, 1932, the cofferdams were completed April 1, 1933, the first concrete for the main Dam structure was poured on June 6, 1933, storage of water in the reservoir started on February 1, 1935, all blocks in the Dam raised to crest elevation on March 23, 1935, and the dam, intake towers, spillways, powerhouse and canyon wall outlet works practically finished in the summer of 1935.

Assuming a normal flow of water in the Colorado River and a continuation of the rate of construction usual on the project, the first power will be generated in the summer of 1936. All construction except the installation of the remaining power units should be completed in 1936, at least 18 months ahead of the construction program outlined in the original schedule.

Transmission Tower Los Angeles Bureau of Power and Light

RESULTS

Completion of the project will solve many problems that have confronted communities and irrigated lands, in the regions downstream from the dam. The Colorado River when in flood is a dangerous, turbulent stream, but when the snows are melted in the headwaters, it dwindles to only a shadow of its former size.

In the delta region, near its mouth, the river runs on a rim above the Imperial Valley, and in 1905 broke through its silt banks, destroying lands and threatening inundation of the entire valley. Eighteen months unremitting toil and the expenditure of two million dollars were required to turn the stream into its old channel again.

Flash floods may occur in the Colorado River in any month, but generally the river flow is above the mean only from April to July. In the other eight months, it does not carry sufficient water for extensive irrigation or to assure a supply of domestic water for city use.

Another aggravation and tremendous expense to the farmers taking water from the stream, is the mud that is deposited in ditches and on the land. The average weight of silt carried by the river through Black Canyon is 300 tons a minute, or sufficient to cover 170 square miles a foot deep in one year. This load is deposited whenever the water velocity is reduced.

The fact has long been recognized that a solution to these problems was the construction of a high dam, but the project was not economically feasible until a market for power had been developed to carry the major construction charge by purchase of the electrical energy developed.

All these phases were considered in the design of the dam, reservoir and power plant. The dam will be built of sufficient height to impound 30,100,000 acre feet of water in the reservoir, an ample volume to control all upstream floods, store water for regulated distribution downstream and provide a basin for the deposit of silt. The dam, reservoir and power plant will have adequate proportions to produce 663,000 H.P. of firm electrical energy to pay all construction charges.

Contracts for power were signed, before Congress appropriated any funds for the project, with the City of Los Angeles, Southern California Edison Company, and Metropolitan Water District of Southern California.

Upstream View at Commencement of Construction . . . Spring of 1931

Upstream View in Spring of 1934, When Dam Was Nearing Half Height

Upstream View in the Spring of 1935, When Dam Was Nearing Completion

The world's largest power transmission line is now being built, by the Bureau of Power and Light of the City of Los Angeles, from Boulder Dam to Southern California, where demands for large blocks of cheap power were instrumental in financing the Boulder Canyon Project.

Two rows of great towers 109 feet high and spaced 800 to 1,000 feet apart have been erected from Boulder Dam to Cajon Pass, a distance of 230 miles, and the two circuits will be carried on a single tower 144 feet in height—nearly that of a twelve-story building—for the remaining 40 miles to Los Angeles.

Research was conducted continuously for four years to find a type of conductor that was best suited to the transmission of 275,000 volts for a distance of 270 miles. The highest voltage previously transmitted has been 220,000 to 230,000. The Heddernheim type of conductor was selected. This is a hollow-core copper tube of 1.4 inches outer diameter made up of interlocking spiral segments and although of comparatively light weight contains sufficient area to carry the electrical and mechanical loads involved and to minimize corona losses.

Work was started on the line June 3, 1933, following a loan of $22,800,000 from the Reconstruction Finance Corporation to the Bureau of Power and Light. Among the more important items of construction are 26,457 tons of structural steel, 1,626 miles of conductor, 1,000 miles of counterpoise, and 253,700 porcelain insulators, 10 to 10-1/2 inches in diameter. Seven camps were established along the single circuit section of the line, and more than 200 miles of new road were built in virgin territory to transport men and materials to the scenes of construction.

In order for the lake back of the dam to supply all demands of electrical production, irrigation and domestic water requirements, as well as the control of silt and floods, 9,500,000 acre feet of water in the reservoir has been allocated for flood control, 5,000,000 to 8,000,000 acre feet for silt pocket, and 12,000,000 to 15,000,000 acre feet for water storage.

The deposition of silt in the reservoir will be tremendous, but if upstream development continues as it has in the past twenty years, the reservoir will be only one-tenth filled with silt at the end of 50 years.

Recreational possibilities offered by the lake behind the dam have not been mentioned among the other benefits, but will be of considerable consequence. The reservoir at high water level will cover an area of 145,000 acres, and have a shore line 550 miles in extent. The water near the surface will be clear and warm offering opportunities and inducements for boating, fishing, swimming and exploratory excursions into the relatively unknown regions bordering the lake.

Downstream View in Fall of 1935. The Lake Surface Is 423 Feet Above the Base of the Dam

PERSONNEL

Principal officials of the Government and contractors on the project who were engaged in construction of Boulder Dam are listed below.

ACKNOWLEDGMENT

Grateful acknowledgment is hereby made to the Bureau of Reclamation, Six Companies, Inc., the Babcock & Wilcox Company, and The Los Angeles Bureau of Power and Light for photographs supplied, and assistance rendered in the preparation of this booklet.