Between the power-house sections at the ends of the dam is a spillway section 1, feet long over which water not required for storage or for power generation or irrigation will be allowed to flow, forming a spectacular waterfall twice as high as Niagara. The rate of flow, and to a certain extent the quantity of water held in storage, will be controlled by 11 drum gates at the crest of the spillway each gate 28 feet high and feet long.
The spillway will have a capacity of a million cubic feet a second; and, if that capacity should ever be realized, it will be necessary to dissipate at the foot of the dam the energy of the falling water equivalent to 32 million horsepower.
This will be accomplished, and erosion of the river below the dam will be prevented, by an upwardly curved bucket at the toe of the dam, where a trough feet wide and 30 feet deep is formed behind a concrete wall across the river bed at elevation , 33 feet below low tail-water surface.
The tunnels are arranged in pairs, and their entrances are protected by trashracks. The upstream ends of the outlet tunnels are lined with heavily ribbed semi-steel conduits, set in the concrete as protection against erosion and the effects of cavitation, which will be reduced or eliminated by the scientific shaping of the entrances to the tunnels.
A ring-follower sliding-leaf valve, hydraulically operated, and an electrically operated "paradox" valve, with leaf and wedge on rollers, will control the flow of water so each tunnel for the purpose of regulating the flow of the river in seasons of low water, or emptying the storage reservoir.
The outlet tunnels will have a capacity of , cubic feet per second and the turbines fully loaded will pass 81, second-feet. These, with the spillway will have a total capacity nearly three times the maximum recorded flow of the river, and nearly double the estimated flood of Diamond drill holes to the extent of about 33, feet were put down into the granite foundation on which the dam rests.
Occasional holes were drilled to depths varying from to feet. In all instances there was found light-colored, dense granite, suitable, according to the board of consulting engineers, to bear any load that might be put upon it. After uncovering bedrock, additional exploratory work was done with Calyx drills, extracting rock cores 36 inches in diameter, which permits a detailed examination to be made of both the core and the hole from which it was taken.
Eighteen such holes were drilled to depths varying from 29 to 68 feet. At its conclusion, President Franklin D. In the Grand Coulee, life changed dramatically and quickly once work on the dam began in Not only did the undertaking of this massive project change forever the shape of the river, but overnight it created towns where nothing but sagebrush, sand and rocks had previously existed. Thousands came to the Grand Coulee looking for work in the midst of the Depression. They worked around the clock to finish the dam by Altogether, a total of 11 dams have been built on the river in the United States as it winds its way from the Canadian border toward the Pacific Ocean; Grand Coulee Dam is the keystone of the Columbia River system dams.
Grand Coulee Dam dwarfs the Great Pyramids of Egypt and generates more power than a million locomotives. Grand Coulee Dam is one of the largest concrete structures in the world, containing almost 12 million cubic yards of concrete. It towers feet above bedrock as high as the Washington Monument and is feet wide at the base. There is enough concrete in the dam to build two standard six-foot wide sidewalks around the world at the equator.
Actually, Grand Coulee Dam has three important functions: irrigation, power production and flood control. There are three powerhouses at Grand Coulee Dam with a total rated capacity of 6, megawatts, making this dam the largest hydro-electric producer in the United States.
Water supplied by Grand Coulee Dam irrigates more than , acres of rich farmland in the Columbia Basin annually. Water from Lake Roosevelt behind the dam is lifted feet up a hillside to flow into the Banks Lake reservoir, where it starts a journey that eventually covers an area more than twice the size of the state of Delaware. Originally, Grand Coulee was to be a low dam with plans to raise it higher at a later time.
Other towns sprang up, including Engineers Town, built by Reclamation to house its engineers, and the rowdy Grand Coulee, known for its taverns and gambling halls. From the town of Odair, rails extended to the construction site, where MWAK used an innovative conveyor belt, rather than trucks, to carry the tons of rock and earth excavated each day.
The dam, as well, was to be built in two sections--west and east. That summer MWAK constructed two cement plants, one for each side of the dam, capable of producing cubic yards or , gallons of concrete every hour. As workers excavated, exposing the bedrock foundation for the dam, others drilled test holes from 30 to feet deep. Then, men were lowered into the holes to inspect the quality of the rock.
Twenty to foot deep grout holes also were drilled; the grout pumped in to provide a secure seal beneath the dam. Concrete placement began in the fall of but, as winter set in, the air turned so cold that several concrete pours actually froze and had to be blasted away and replaced. In January, concrete work halted altogether until spring, when it picked up again, only to halt again the next winter, then pick up in the spring and summer at ever increasing speeds, setting several records for concrete placement.
Nearly 11, men worked more than 27 million hours to divert the river, excavate the foundation, and place concrete. Forty-five workers died in the process. CBI of Oakland, Calif. The company had changed its name from Interior Construction at the orders of the Interior Department.
In , Congress directed the US Army Corps of Engineers to make a detailed study of the Columbia River which later favoured the idea of constructing a dam. Grand Coulee Dam receives water from Lake Roosevelt. It is pumped using a feeder canal into an equalising reservoir Banks Lake. Banks Lake has been formed by building two earthfill dams on either side of the Grand Coulee. The main canal begins at the Dry Falls Dam. The water is distributed to various canals from the main canal. The dam measures ft in height and 5,ft in length.
Consisting of More than 12 million barrels of cement, 77 million pounds of reinforcing steel and ten million pounds of steel for the penstocks have been utilised in constructing the dam. A mile railroad facilitated transportation during construction. Grand Coulee was initially constructed as a low dam due to budgetary constraints. It underwent a design change in after Roosevelt visited the site and permitted the construction of a high dam, which was eight times bigger than the low dam.
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