LAKE MEAD The Story of Boulder Dam

The Dam

Where is Boulder Dam located?

In Black Canyon on the Colorado River where it forms the Arizona-Nevada state boundary, about 25 miles airline southeast of Las Vegas, Nev.

What does the Boulder Canyon project include?

Construction of a dam and power plant in Black Canyon and of the All-American Canal in southern California.

What will the project cost?

The Boulder Canyon Project Act authorized appropriations not to exceed $165,000,000, divided as follows: Dam and reservoir, $70,600,000; power development, $38,200,000; All-American Canal, $38,500,000; interest during construction, $17,700,000. Subsequent authorizations have increased the estimated over-all cost of the project to $205,000,000, of which $140,000,000 is allotted to the dam and $65,000,000 to the All-American Canal, including the construction of distribution and drainage systems which were not contemplated in the original act.

How much has been expended?

To June 30, 1940, $126,300,000 for Boulder, $31,900,000 for All-American Canal.

How high is Boulder Dam?

The maximum difference in elevation between the foundation rock and the roadway on the crest of the dam is 726.4 feet. The towers and ornaments on the parapet extend 40 feet higher above the crest.

How does this height compare with other dams?

Boulder is by far the highest dam in the world. Second is Grand Coulee Dam in Washington, 550 feet in height, until the completion of Shasta Dam in California, which will be 560 feet high. All three dams are constructed by the Bureau of Reclamation.

What type is Boulder Dam?

The concrete arch-gravity type, in which the water load is carried by both gravity action and horizontal arch action.

What is the maximum water pressure at the base of the dam?

Forty-five thousand pounds per square foot.

What is the volume of concrete masonry?

Three million two hundred and fifty thousand three hundred and thirty-five cubic yards in the dam alone, or 4,400,000 cubic yards in the dam, power plant, and appurtenant works. This amount of concrete would build a monument 100 feet square 2-1/4 miles high or, if placed on the ordinary city block, would rise to a height greater than that of the Empire State Building in New York City (1,248 feet). It would build a standard paved highway 16 feet wide from Miami, Fla., to Seattle, Wash. Mass concrete was placed in the dam at the rate of approximately 160,000 cubic yards per month, with a peak placement of 10,462 cubic yards a day (which includes some concrete placed in intake towers and powerhouse) and slightly over 225,000 cubic yards a month. The first concrete was placed on June 6, 1933, and the last concrete was placed in the dam on May 29, 1935.

What is the weight of the 3,250,335 cubic yards of concrete in the dam?

More than 6,900 tons.

How much cement was required?

More than 5,000,000 barrels. The daily demand during construction of the dam was from 25 to 36 cars (7,500 to 10,800 barrels). The Bureau of Reclamation used 5,862,000 barrels in the 27 years of construction activities preceding June 30, 1932.

How was chemical heat, due to setting of the cement in the mass concrete, dissipated?

By embedding in the concrete a system of pipes containing over 3,000,000 feet, or 582 miles, of 1-inch steel tubing, through which cooling water circulated from a cooling and refrigeration plant. The plant had sufficient capacity to produce 1,000 tons of ice from water at 32° F. in 24 hours. Cooling was completed in March 1935.

What was an unusual feature of Boulder's construction?

The dam was built in numerous blocks or vertical columns varying in size from sections approximately 60 feet square at the upstream face of the dam to sections 25 feet square at the downstream face. Adjacent columns were locked together by a system of vertical keys on the radial joints and horizontal keys on the circumferential joints. Specifications restricted the rate of placement in any one block to a maximum height of 5 feet in 72 hours. After the concrete was cooled, grout (cement and water) under pressure was forced into the spaces opened up between the columns by the contraction of the cooled concrete, to form a monolithic structure.

What were the principal items of work?

Excavation, all classes, diversion tunnels, 1,500,000 cubic yards; excavation, common, for foundation of dam, power plant, and cofferdam, 1,330,000 cubic yards; rock excavation for dam foundation, 430,000 cubic yards; excavation, all classes, for spillways and inclined tunnels, 750,000 cubic yards; earth and rock-fill for cofferdams, 1,000,000 cubic yards; excavation, all classes, valve houses and intake towers, 410,000 cubic yards; concrete, 4,400,000 cubic yards; drilling grout and drainage holes, 410,000 linear feet; pressure grouting 422,000 cubic feet; all excavation, more than 5,500,000 cubic yards; total earth and rock-fill, more than 1,000,000 cubic yards.

How much reinforcement steel was used?

About 45,000,000 pounds.

What were the quantities of other principal materials?

Gates and valves, 21,670,000 pounds; plate steel outlet pipes, 88,000,000 pounds; pipe and fittings, 6,700,000 pounds, or 840 miles; structural steel, 18,000,000 pounds; miscellaneous metal work, 5,300,000 pounds; cement, 5,000,000 barrels.

Did the Government buy these materials?

Yes. The purchasing was handled by the Bureau of Reclamation, United States Customhouse, Denver, Colo.

What are the geologic conditions at the dam site?

The foundation and abutments are rock of volcanic origin, geologically termed "andesite breccia," hard and very durable.

What is the depth below low-water surface of the river to foundation rock?

From 110 feet to 130 feet. The lowest point of excavation in the upstream cut-off trench was at elevation 506, or 139 feet below low-water surface (elevation 645).

What are the canyon widths at the dam site?

From 290 to 370 feet at low-water level, and from 850 to 970 feet at elevation 1,232, the crest of the dam.

What was the time required to build the dam, power plant, and appurtenant works?

The contractors were allowed 7 years from April 20, 1931, under their contract. Placing of concrete in the dam was completed May 29, 1935.

How many men were employed by the Government and labor contractors during construction of the dam?

An average of 3,500 and a maximum of 5,218, occurring in June 1934. The average monthly payroll was approximately $500,000.

What construction work was necessary before operations were started at the dam site?

(1) Construction of Boulder City to house both Government and contractors' employees. (2) Seven miles of 22-foot, oil-surfaced highway from Boulder City to dam site. (3) Building 22.7 miles of standard-gage railroad from the Union Pacific main line to Boulder City, and 10 miles from Boulder City to the dam site. (4) A power transmission line 222 miles long, from San Bernardino, Calif., to the dam site to furnish power for construction purposes.

The Reservoir (Lake Mead)

How much water will the reservoir hold?

When full, 32,359,274 acre-feet. An acre-foot is the amount of water that will cover 1 acre 1 foot deep. The water in the reservoir would cover the State of New York to a depth of 1 foot. The reservoir will store the entire average flow of the river for 2 years.

What is the area of the reservoir?

One hundred forty-six thousand five hundred acres, or 229 square miles. For comparison, Lake Tahoe in California-Nevada has an area of 193 square miles.

What is the length and width of the reservoir?

It is about 115 miles by river from Black Canyon to Bridge Canyon, the limit of the backwater. The reservoir extends up the Virgin River about 35 miles. The width varies from several hundred feet in the canyons to a maximum of 8 miles.

What is the elevation of the high-water line?

One thousand two hundred and twenty-nine feet above sea level. All lands below elevation 1,250 have been retained for reservoir purposes.

How will the reservoir capacity be utilized?

Nine million five hundred thousand acre-feet for flood control, 5,000,000 to 8,000,000 acre-feet silt pocket; 12,000,000 to 15,000,000 acre-feet active or regulation storage.

Who operates the dam and reservoir?

The Bureau of Reclamation operates and maintains the dam, reservoir, pressure tunnels, outlet works, and penstocks to but not including shut-off valves at the inlets to turbine casings. The National Park Service administers the Boulder Dam National Recreational Area.

How much silt will be deposited in the reservoir?

The estimated average volume of silt carried by the river into Black Canyon is about 137,000 acre-feet annually under present conditions, and this amount will decrease with upstream development. It is estimated that the total silt deposits in the reservoir will not exceed 3,000,000 acre-feet at the end of 50 years.

What is the length of the shore line?

About 550 miles.

What is the estimated annual evaporation on the reservoir?

Six hundred thousand acre-feet.

Diversion Works, Spillways, and Outlet Works

How was the river diverted during dam construction?

By a temporary earth and rock-fill cofferdam, through four 50-foot diameter tunnels, excavated to 56 feet and lined with 3 feet of concrete (300,000 cubic yards), and driven through the rock of the canyon walls, two on each side of the river. These tunnels could carry over 200,000 second-feet of water. The river was diverted through the two Arizona tunnels on November 13, 1932.

What was the length of these tunnels?

The four tunnels had a total length of 15,946 feet, or 3 miles.

After their use for river diversion, how were the tunnels used?

They were plugged with concrete at locations approximately one-third their length below the inlet ends of the inner tunnels and about midway in the outer tunnels. The two inner tunnels contain 30-foot diameter steel pipes connecting the intake towers in the reservoir with the penstocks to the power plant and the canyon wall outlet works. The lower portions of the two outer tunnels are used for spillway outlets.

What is the gate installation in the tunnels?

When river diversion through the tunnels was discontinued, the inlet ends of the two outer tunnels were permanently closed with 50-by-50-foot bulkhead gates. Each gate with steel frame weighs about 3,000,000 pounds and required 42 railroad cars for shipment. At the outlet ends of the two inner tunnels, 50-by-35-foot Stoney gates are installed, which may be closed when it is desired to unwater the tunnels for inspection or repairs.

What are the intake towers?

There are four reinforced-concrete towers located above the dam, two on each side of the river and about 165 feet apart in a direction parallel with the river. These towers are 75 feet in average diameter (82 feet at the base, 63 feet 3 inches at hoist house floor, and 29 feet 8 inches inside), 375 feet in height (338 feet tower, 37 feet hoist house), and each tower controls one-quarter of the supply of water for the power-plant turbines. The towers contain 93,674 cubic yards of concrete and 15,299,604 pounds of steel.

How are these towers connected to the power plant and outlet valves?

By 30-foot diameter plate-steel pipes installed in 37- and 50-foot diameter concrete-lined tunnels. Thirty-seven-foot inclined tunnels connect the upstream intake towers to the 50-foot diameter inner diversion tunnels, and 37-foot diameter tunnels lead from the downstream towers to the penstocks and outlet works at elevation 820,180 feet above the diversion tunnels.

What method of control is used in the intake towers?

Two cylindrical gates, each 32 feet in diameter, and 11 feet high, one near the bottom (elevation 895) and the other near mid-height (elevation 1,045) of each tower, protected by trashracks located in front of the entrances to the tower. Total weight of the eight gates is 5,892,000 pounds, and of the trashracks, 7,024,000 pounds.

What pipes are installed in the tunnels for reservoir outlets?

Four thousand seven hundred feet of 30-foot diameter main headers, 1,900 feet of 25-foot diameter pipes below the branch penstock tunnels to the power plant, and 2,000 of 8-1/2-foot diameter pipes in 11-foot diameter tunnels leading to the needle valve outlets. The maximum thickness of the largest pipe is almost 3 inches.

How are the 30-foot-diameter pipes connected to the power plant turbines?

By sixteen 13-foot diameter plate-steel penstock pipes totaling 5,800 feet in length installed in 18-foot diameter concrete-lined tunnels.

What were the principal items in the contract for fabrication and installation of the steel penstock and outlet pipes?

Forty-four thousand tons of steel were formed and welded into 14,000 feet of pipe varying from 8-1/2 feet to 30 feet in diameter. One length of the largest pipe, 12 feet long, 30 feet in diameter, and 2-3/4 inches thick, was made from three steel plates, of such weight that only two plates could be shipped from the steel mill to the fabrication plant on one railroad car. Two such lengths of pipe welded together comprised one erection section weighing approximately 135 tons and at intersections with the penstocks as much as 186 tons. For comparison, the weight on the drivers of the Consolidation type of steam locomotive on the project was 99 tons.

What outlets are used?

Six 72-inch needle valves in each inner diversion tunnel plug outlet, and six 84-inch needle valves in each canyon-wall valve house, there being one house on each side of the river at elevation 820, which is about 180 feet above river level, The valve outlets are pointed downstream at an angle of 60°. Canyon wall valves are not used except under emergency or flood conditions. Each 72-inch valve is capable of discharging a maximum of 3,670 cubic feet per second at a velocity of about 175 feet per second.

What is the total maximum capacity of these works?

One hundred and twenty-five thousand cubic feet per second, of which 25,000 cubic feet per second is for power generation and 100,000 cubic feet per second is valve discharge.

What are the Arizona and Nevada spillways?

Each consists of a concrete-lined open channel, about 650 feet long, 150 feet wide and 170 feet deep, with the side next to the river formed into an ogee-shaped crest. The two spillways required 601,419 cubic yards of rock excavation. There were 127,500 cubic yards of concrete placed, the walls being lined with 18 inches of concrete, and the floors 24 inches.

How is water discharged from the spillways?

Through inclined shafts, 50 feet in diameter and 600 feet long, into the outer diversion tunnels.

What will be the maximum water velocity in the spillway tunnels?

About 175 feet per second (120 miles per hour).

What gate installation was made at the spillways?

Four 100-foot by 16-foot drum gates on each spillway crest controlled either automatically or manually. Each gate weighs 500,000 pounds.

What is the maximum capacity of the spillways, valves, and power plants?

Five hundred and twenty-five thousand cubic feet per second. Each spillway has a maximum discharge capacity of 200,000 cubic feet per second. Should a flood occur of sufficient volume to require the full capacity of the spillways, the energy of the falling water would be about 25,000,000 horsepower, the flow over each spillway would be about the same as the flow over Niagara Falls, and the total drop would be more than three times as great.

The Power Development

What was the installed capacity of the power plant at Boulder Dam on January 1, 1941?

Nine hundred and seventy-five thousand horsepower (ultimate 1,835,000 horsepower). For comparison, Niagara is 452,500 horsepower; Conowingo 378,000 (ultimate 594,000); and Wilson 250,000 (ultimate 600,000); Dnieprostroy (U. S. S. R.) 750,000. The installed capacity of Boulder's power plant on January 1, 1941, in kilowatts was 704,800, including 2 station service generators of 2,400 kilowatts each, with 247,500 kilowatts being installed. The ultimate capacity is 1,322,300 kilowatts.

What is a horsepower in terms of falling water?

One second-foot of water falling 8.81 feet equals 1 horsepower at 100 percent efficiency. A second-foot of water is 1 cubic foot, or nearly 7-1/2 gallons, passing a given point in 1 second of time.

What is the ultimate continuous firm power output?

About 663,000 horsepower, based on 83 percent plant efficiency, and 10 percent maximum shortage.

How much electrical energy is ultimately available yearly?

Approximately 4,330,000,000 kilowatt-hours of firm and 1,550,000,000 kilowatt-hours of secondary energy on completion of the power plant, decreasing each year an estimated 8,760,000 kilowatt-hours as a result of upstream development, and a consequent reduction in stream flow.

What is a kilowatt-hour?

The energy resulting from an activity of 1 kilowatt for 1 hour. A kilowatt is 1,000 watts. One horsepower equals 0.746 kilowatt. 663,000 (horsepower) X 0.746 X 24 (hours) X 365 (days) = 4,330,000,000 kilowatt-hours.

How is the income from the sale of power used?

To pay all expenses of operation and maintenance of works incurred by the United States and to repay the major part of the cost of construction of the dam and power plant, with interest not exceeding 3 percent, within a 50-year period. Repayment of $25,000,000 of the cost allocated to flood control is deferred beyond the 50-year period, when further action will be subject to congressional direction. Arizona and Nevada each are to receive $300,000 annually in lieu of taxes which may have been collected by the two States, and $500,000 annually is set aside from revenues for the further irrigation and power development of the Colorado River Basin.

Where is the power plant located?

Just below the dam, one-half on the Nevada side of the river and one-half on the Arizona side, forming a U-shaped structure 1,650 feet long built of steel and rein forced concrete. Each wing is 650 feet long, 150 feet high above normal tailrace water surface, and 229 feet (nearly 20 stories) above the lowest concrete in the powerhouse footings. There are 10 acres of floors.

How does the water reach the turbines?

Through four pressure tunnels, two on each side of the river, each provided with shut-off gates and trashracks.

What are the power installations?

Fifteen 115,000-horsepower and two 55,000-horsepower vertical hydraulic turbines ; eleven 60-cycle and four 50-cycle main generating units of 82,500 kilovolt-ampere capacity each, and two 60-cycle main generating units of 40,000 kilovolt-ampere capacity each. The larger units were the largest in the world.

What facilities were provided for transporting power-plant machinery from the canyon rim to the power plant?

A permanent cableway of 150 tons normal capacity, electrically operated, with a span of 1,200 feet across the canyon, is used to lower not only power-plant machinery, but also handled the outlet pipes and other machinery, materials, and equipment.

Under what heads do the turbines operate?

Maximum head 590 feet, minimum 420 feet, average 530 feet.

How is the firm power generated at Boulder Dam allocated?

Metropolitan Water District of southern California 36 percent, States of Arizona and Nevada 18 percent each, Southern California Edison and other private utilities 9 percent, city of Los Angeles 13 percent, other cities 6 percent.

Who operates and maintains the power plant?

The City of Los Angeles and the Southern California Edison Co., under the general supervision of a director of power appointed by the Secretary of the Interior. The city generates power for the States, municipalities and the Metropolitan Water District. The Southern California Edison Co. generates power for itself and other private utilities.

Who are the principal contractors?

The Bureau of Power and Light of the City of Los Angeles, the Southern California Edison Co., the Nevada-California Electric Corporation, the Metropolitan Water District of Southern California, the municipalities of Burbank, Glendale, and Pasadena, and the State of Nevada.

How is power transmitted to market?

The contractors for power build transmission lines at their own expense.

Who pays the cost of transmission of power?

The contractors who buy the power.

Colorado River Water Allocation

What is meant by an allocation of water?

Authority to use and reuse water until stream flow is decreased by the amount of the allocation.

What is the allocation of water under the Colorado River compact?

Based on a mean annual run-off of 16,000,000 acre-feet, the compact allocated 7,500,000 acre-feet to the upper basin States and 7,500,000 acre-feet to the lower basin States, with the right of the latter in any one year to increase their beneficial consumptive use of such water by 1,000,000 acre-feet.

How much of the water allocated to the lower basin States does California get?

California has agreed that the aggregate annual consumptive use of the river water shall not exceed 4,400,000 acre-feet of the 7,500,000 allocated to the lower basin by article III (a) of the compact. In addition, California can use one-half of the surplus waters available above the 7,500,000 acre-feet allocated.

How much water is allocated to Nevada and Arizona?

The Boulder Canyon Project Act authorizes Arizona, California, and Nevada to enter into an agreement which shall provide that Nevada gets 300,000 acre-feet and Arizona 2,800,000 acre-feet for exclusive beneficial consumptive use; also, that Arizona may annually use one-half of the surplus water unapportioned by the compact, and, in addition, shall have the exclusive beneficial consumptive use of the Gila River and its tributaries within the State. Such an agreement has not yet been made.

What agreement as to division of water has been made by the various California interests?

(1) Three million eight hundred and fifty thousand acre-feet of water per annum for beneficial consumptive use for irrigation, as follows: First, to Palo Verde Irrigation District, 104,500 acres; second, to Yuma Reclamation project, 25,000 acres in California; remainder to lands in the Imperial and Coachella Valleys served from the All-American Canal and to 16,000 acres on the Lower Palo Verde Mesa; (2) the next 550 000 acre-feet to the Metropolitan Water District for domestic water supply; (3) the next 662,000 acre-feet to the Metropolitan Water District (550,000) and the City of San Diego (112,000) for domestic water supply; (4) the next 300,000 acre-feet to the Imperial and Coachella Valleys and to 16,000 acres on the Lower Palo Verde Mesa; (5) remainder for irrigation use in the Colorado River basin in California.

Boulder City

Where is Boulder City located?

The location is about 7 miles west of the dam site, at the summit and near the terminus of the Union Pacific section of the branch railroad.

How large is Boulder City?

Population now (1941) about 3,000.

What is the source of the domestic water supply?

Water is pumped from the Colorado River to the town, a distance of nearly 7 miles, with a total lift of about 2,000 feet. The intake is about 3,500 feet downstream from the dam site on the Nevada side. The water first goes to a presedimentation basin 100 feet above river level, then to a 100,000-gallon receiving tank at Boulder City, from there to a filtration and purification plant, and finally to a 2,000,000-gallon storage tank.

What other improvements were necessary?

Sewage and lighting systems were installed; sidewalks and curbs have been provided and streets surfaced and paved.

Did employees of the contractors on the dam and power plant live in the town?

Yes. A portion of the town was set aside for the contractors' use. The contractors arranged for the housing of their workmen, with construction subject to Government approval. They built mess halls, dormitories, hospital, clubhouse, commissary, machine shop, storehouses, garage, laundry, and 700 employees' cottages. The 12 great dormitories were heated in winter and artificially cooled in summer and were equipped with electric lights, running water, and shower baths.

Who owns the lands in the town site?

The Government owns the land, all of which is under first form of withdrawal.

How is a town lot obtained for business purposes?

The land is leased to those awarded business permits. The Government retains ownership and supervisory control. Continuation of the leases is contingent upon compliance with the terms of the contract.

How much money has been expended at Boulder City?

1t cost the Government about $1,700,000 to build the town.

What provisions were made for erecting buildings suited to the climatic conditions in that section?

A city planner, well acquainted with the type of building construction required, was employed. Government buildings are largely of the Spanish type of architecture, and the main buildings are air-conditioned. The Bureau of Reclamation encountered somewhat similar climatic conditions during construction of the Yuma and Salt River projects in Arizona.

What is the form of town government?

The city-manager plan is followed. The city manager is responsible to the Director of Power for Boulder Dam, who is appointed by the Secretary of the Interior and directly responsible to the Commissioner, Bureau of Reclamation.

What is the range of temperature in that locality?

From 20° to 120° F.

How near is Boulder City to Las Vegas, Nev.?

About 21 miles southeast in an airline, 24 miles by highway, and 32 miles by railroad.

What is the elevation of the town?

About 2,500 feet above sea level.

Irrigable Areas

How much irrigable land is there below the Boulder Canyon Reservoir, in the United States?

About 1,900,000 acres, according to present estimate.

How is the area divided between the States?

Arizona 700,000 acres; California 1,175,000 acres; Nevada 25,000 acres. These areas may be changed materially when more complete surveys are made.

What is the present area under irrigation from the Colorado River below the dam site?

About 660,000 acres, divided as follows: California 600,000, Arizona 60,000.

What are some of the existing and potential projects in Arizona?

The Gila River Valley with a gross area of about 600,000 acres in the southwestern part of the State, the Colorado River Indian project of about 110,000 acres near Parker, and the Mohave Valley with an irrigable area of 33,000 acres near Needles, Calif. The Yuma Reclamation project, Arizona-California, adjacent to the city of Yuma, is an active Federal project, with about 53,000 acres irrigated at the present time, and a total ultimate irrigable area of 112,000 acres, including about 45,000 acres of undeveloped mesa hands. The first unit of the Gila project, consisting of 139,000 acres of new land and providing a supplementary water supply for 11,000 acres, is under construction by the Bureau of Reclamation. The Colorado River Indian project is under construction also, by the Office of Indian Affairs.

All-American Canal

Is the All-American Canal a part of the Boulder Canyon project?

Yes. The Boulder Canyon Project Act of December 21, 1928, authorized the building of a main canal from the Colorado River to the Imperial and Coachella Valleys.

Why the name, "All-American"?

Because the canal is built entirely in the United States. The Imperial main canal, which the All-American Canal replaces, is largely in Mexico.

What is the estimated cost of the All-American Canal?

Sixty-five million dollars, including drainage and distribution systems.

Is this expenditure reimbursable?

Yes. Under repayment contracts between the Imperial Irrigation District and the Coachella Valley County Water District, California, with the United States, the cost will be returned to the Government under the terms of Reclamation law.

Will the District have to pay for water?

There will be no charge for the use, storage, or delivery of water for irrigation or water for potable purposes.

Where is the intake?

At the Imperial diversion dam, about 15 miles northeast of Yuma, Ariz., and 5 miles north of Laguna Dam, which is the diversion point for the main canal of the Yuma Reclamation project.

What type of structure is the Imperial Dam?

The Imperial Dam is a hollow reinforced concrete structure raising the water surface about 22 feet. At its west abutment is located the headworks structure for the All-American Canal and at its east abutment the headworks structure for the Gila Canal in Arizona. Below the headworks on the California side is located the All-American Canal desilting works consisting of six large desilting basins designed to remove the silt picked up by the river on its 300-mile journey from Boulder.

How much water will the canal carry?

A maximum diversion of 15,155 cubic feet per second, which includes 2,000 cubic feet per second to be diverted at Siphon Drop for the Yuma project and 3,000 cubic feet per second returned to the river at Pilot Knob for power development.

What are the dimensions of the canal?

The maximum section is about 232 feet in width at the water surface, 160 feet in width at the bottom, and 20.6 feet in depth. There are only two larger canals in the United States, both ship canals.

What is the length?

The All-American Canal to Imperial Valley, 80 miles long, is completed. The branch canal to the Coachella Valley, under construction, is 130 miles long.

Are sand hills crossed by the canal?

Yes. The canal for 10 miles passes through a ridge of shifting sands. The deepest cutting is over 100 feet.

What structures were needed?

Siphons or culverts were used to carry the canal under many washes and at other washes the discharge from the wash was carried over the canal in concrete overchute type structures. The All-American Canal was also carried across the Alamo and New Rivers. Several highway and railroad bridges were also required.

Is additional water supply for the city of San Diego tied in to All-American Canal plans?

A repayment contract was negotiated between the city of San Diego and the Secretary of the Interior for providing capacity in the All-American Canal for carrying water to some point near the end of the canal from which point it would be taken by an aqueduct to San Diego.

Will San Diego pay for this water?

The contract calls for a payment of about $400,000 of the cost of the All-American Canal.

Is there opportunity for power development?

Yes. An estimated total capacity of 87,400 kilowatts may be developed in five plants. The largest will be at Pilot Knob, 7 miles west of Yuma, Ariz., where surplus water is returned to the Colorado River. It will have a capacity of 41,400 kilowatts. Of four other potential plants at drops on the All-American Canal and the Coachella branch, installations of 30,000 kilowatts have been made at two. The total capacity of the four plants is 46,000 kilowatts. The Bureau of Reclamation will develop Pilot Knob, and the Imperial Irrigation District will develop the four other drops.

What are the principal California projects which may be benefited by the All-American Canal?

The Imperial Valley has a present irrigable area of 522,000 acres, and about 357,000 acres of valley and adjacent mesa lands which can be irrigated under the All-American Canal. The Coachella Valley in Riverside County near Indio has an irrigable area of 160,000 acres, which will be served by a branch of the All-American Canal.

Where is the irrigable acreage in Nevada?

Areas aggregating about 25,000 acres may be irrigated by pumping along the Colorado River near Searchlight and from the Boulder Canyon Reservoir near Las Vegas.

What is the approximate classification of the total irrigable lands?

Public, 44 percent ; private, 40 percent; State, 1 percent; railroad, 2 percent; Indian, 8 percent; and public land entered, 5 percent.

Imperial and Coachella Valleys

What is the irrigable area of the Imperial Irrigation District?

Five hundred and twenty-two thousand acres, requiring 1,700 miles of canals and laterals.

How much land is now irrigated?

From 400,000 to 450,000 acres.

What is the present irrigated area in Mexico (Lower California) from the Imperial Main Canal?

About 200,000 acres.

What are the principal crops in the Imperial Valley?

Alfalfa, cantaloups, lettuce, barley, corn, milo maize, and small fruits. About 30,000 carloads of cantaloups and lettuce are shipped out of the Imperial Valley each season.

What are the crop yields?

Alfalfa, as much as 7 to 10 tons per acre, a ton to a cutting; cantaloups, 96 crates per acre.

What is the growing season?

Three hundred and sixty-five days.

What is the elevation of the valley?

From 250 feet below sea level at the Salton Sea to 50 feet above sea level. The adjoining mesas or high lands vary in elevation from 50 to 250 feet.

What is the Salton Sea?

An inland sea in a depression in the northern part of Imperial Valley. Immediately prior to 1905, it was only a small lake, but the Colorado River break of 1905-7 increased the water surface area of the sea to 515 square miles, a length of 42 miles and maximum depth of 80 feet. The present area is 287 square miles and the elevation of the water surface is about stable at 244 feet below sea level. The Salton Sea is salty, because of its saline bed.

What is the rainfall in this section?

About 3 inches a year.

How large is the Coachella Valley?

The gross acreage is 187,000 acres. The estimated irrigable area under the proposed canal system is 162,000 acres. There are now about 15,000 acres under cultivation.

What is the total irrigable area in the Imperial and Coachella Valleys and adjacent East Mesa, West Mesa, Pilot Knob Mesa, and Dos Palmas unit, which may be served by the All-American Canal and its branches?

The estimated area is about 1,000,000 acres.

What is the status of these lands as to ownership?

Approximately 30 percent public, 65 percent private, and 5 percent State, railroad, and Indian.

Gila Valley

What is the Gila Valley?

River bottom and adjacent mesa lands along the Gila River from Yuma to Aztec, with a net irrigable area below elevation 600 of about 500,000 acres.

How may these lands be irrigated?

Water can be diverted from the Colorado River at the Imperial Dam and pumped by successive stages to canals serving the lands. The pumping lift to the highest lands will be nearly 500 feet. Present plans provide for the irrigation of 150,000 acres, including 11,000 acres with supplemental water, as the first unit, now under construction by the Bureau of Reclamation.

The Colorado River Aqueduct

Is the aqueduct a part of the Boulder Canyon Project?

No, but one of the purposes of the project is to provide a supplemental domestic water supply for Los Angeles and 12 other cities in southern California. The aqueduct transports water which is stored in the reservoir behind the Boulder Dam.

What is the Metropolitan Water District?

A municipal corporation comprising 13 cities, including Los Angeles, in southern California that will use this water supply.

What portion of the Colorado River water will the district receive?

The district has contracted with the Secretary of the Interior for delivery each year from the reservoir up to but not exceeding 1,050,000 acre-feet. This corresponds to a flow of about 1,500 cubic feet per second, or about a billion gallons daily from the river. The district will pay to the United States 25 cents per acre-foot for the actual amount used, or an average annual payment of about $250,000.

Will the district obtain power from the plant at Boulder Dam?

Yes. Its allocation in 36 percent of the firm power produced, with a preferential right to the use of dump or secondary power, which will be transmitted over lines built by the district.

Where on the Colorado River is the intake for the aqueduct located?

At Parker Dam in Upper Parker Canyon, about 155 miles below Boulder Dam, and 12 miles above Parker, Ariz. Parker Dam was constructed by the Bureau of Reclamation with funds advanced by the Metropolitan Water District.

How is the diversion effected?

By pumping from the reservoir back of the Parker Dam. This dam is 320 feet high, but only 85 feet of the structure protrudes above the river bed. It is of the concrete arch type superinmposed by five 50-by-50-foot Stoney gates for river control.

What is the pumping lift to cross the mountains?

One thousand six hundred and seventeen feet. Five pumping stations are required.

What is the total length of the aqueduct?

About 242 miles of main aqueduct and 150 miles of feeder lines.

What power is developed at Parker Dam?

Ultimate installation is 120,000 kilowatts, half of which is reserved to the United States, the other half belonging to the Metropolitan Water District. Three units of a combined capacity of 90,000 kilowatts were being installed at the beginning of 1941, and the fourth was on order.