The Grand Coulee Dam

Visit to The Grand Coulee Dam 2002

The aerial view below shows Lake Roosevelt, the reservoir formed behind the Grand Coulee dam (capacity = 9,562,000 acre-feet of water as the Americans quaintly put it) and in the top right corner Banks Lake for which water is obtained from lake Roosevelt via the pump/generator plant at Grand Coulee dam. This facility, located on the west upstream side of the dam, lifts water from the reservoir up 280 feet into the Banks Lake feeder canal above the river gorge.

Construction of the pumping plant began with the original dam construction in the thirties but was delayed by the onset of World War II when power generation was given highest priority. After the war construction was resumed and the plant was finally made operational in 1951. In 1973 the plant was extended. The pump bay was doubled in length to the south and six 67,500 horsepower pump/generators were added (the last in 1983) to the original six 65,000 horsepower pumps providing 12 in all.

Each pump lifts water from Lake Roosevelt up through a 12 foot diameter discharge pipe to the feeder canal above. For most of their length the discharge pipes are buried in the rocky cliff to the west but at the top of the hill they emerge and can be seen as 12 silver pipes leading to the head works of the feeder canal.
Aerial View of Grand Coulee Dam
In the view above the overspill dam section is allowing a thin layer of water as foam to fall into the river below - hence the brilliant white appearance of that section of the dam. (Very handy as a screen for night time laser shows to entertain visitors)

Clearly visible are the three power houses at the bottom of the dam - one each on either side of the overspill section and a third along the nearside of the river. There are 11 dams on the United States Side of the Colorado river and we visited several of them which would have been impressive if we had not seen the Grand Coulee first.

Grand Coulee Dam's hydroelectric generating facilities include (counting the pumping plant) a total of 24 main generators, three station service generators and six pump/generators. These provide a combined generating capacity of 6480 megawatts. This makes Grand Coulee Dam the largest producer of hydroelectric power in the United States and the third largest such facility in the world.

Generators at Grand Coulee Dam
Location Description Number Capacity (MW) Total (MW)
Pumping Plant Pump/Generator 6 50 300
Left Powerhouse Station Service Generator 3 10 30
Main Generator 9 125 1125
Right Powerhouse Main Generator 9 125 1125
Third Powerhouse Main Generator 3 600 1800
Main Generator 3 700 2100
Totals   33   6480

Looking Down

The Tour of The Third Power Station

The conducted tour started by the quay side above the Power Station by entering a lift that was equiped with bench seats which you reached by steps that catered for a slope of 45°. The reason is the track shown at the bottom of the adjacent photo which displays the view from the top... Diagram

Going Down

... and adjacent is the view on the way down.

At the bottom we come to to the Switch Gear Canyon where all the gear is hidden from view behind the Power Houses
The SwitchgearThe lack of any visible structures for terminating O/H cables or for switchgear creates a unexpectedly clean and efficient impression of the site. This must have been a prime consideration in the design and the use of the walls of the power houses and of the dam it self for termination enables this to be achieved.

A bridge crosses the Switchgear Canyon to the Power House from the lift landing
The view of it below has a surrealist feel about it.

Bridge to Powerstation 3
Turbine Hall
The adjacent picture shows the activity of installing one of the units. On the whole of the site it is difficult to visually grasp the scale of all the works. This picture does help to to give an udea of the size invoved
Finally we reach the Turbine Hall - a vast empty space with the six 33ft blue circular covers for the turbine chambers
One can distinguish different frequencies in the steady hum that pervades the space
Turbine being Installed
Aggregate Mountain
All this highly impressive Civil and Electrical Engineering Construction was quite overwhelming - everything well thought out and planned to the nth degree. Too much perfection always worries me too - little humanity - but talking to our guide soon put it right - all the materials for making the cement for the dam (12 million cu.yds) had to be imported to the site but a wrong estimate of the quantity required was made and the adjacent photo shows the "mountain" of aggregate that was left over when the dam was completed.
We stayed overnight by the dam - witnessed the laser show and stayed in a house that had been used by the design engineers and surveyors run by a now retired mayor of the community. After the tour we explored some of the Colorado River towards the Canadian border and found other dams and some fantastic scenery.
Final look
All the photos are by myself except:
The arial photo and the photo showing the installation of a turbine which are from
Bureau of Reclamation - The Grand Coulee Power Office(linked)

The table of generators is an extract from the Hydraulic Power Generation page on a web site entitled
"The Grand Coulee Dam - Columbia Basin Project"(linked)
This site contains a wealth of information, photos and diagrams for the Columbia Irrigaton Project of which this dam is a major part

Web Master/ SWEHS September 2004