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Grand Coulee Powerplant

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Columbia Basin Project
Grand Coulee Dam
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Grand Coulee Powerplant Performance (pdf)
RegionFacilities in Pacific Northwest | Pacific Northwest Home Page
RiverColumbia River
PurposeGrand Coulee Dam is a key feature of Reclamation`s Columbia Basin Project in central Washington. A multi-purpose project, it provides flood control, irrigation, hydropower production, recreation, stream flows, and fish and wildlife benefits. Facilities at the dam include three powerplants, a pump-generating plant, and three switchyards. Franklin D. Roosevelt Lake behind the dam is 151 miles long with over 5,000,000 acre feet of active storage. Water is pumped for irrigation in the Columbia Basin to irrigate approximately 670,000 acres with an ultimate potential of 1.1 million acres.
FactsGrand Coulee Dam is the largest concrete structure built in North America. Raising the water surface 350 feet above the old riverbed, the dam is 5,233 feet long, 550 feet high, and contains 11,975,500 cubic yards of concrete. The original dam was modified for the Third Powerplant by a 1,170-foot-long, 201-foot-high forebay dam along the right abutment approximately parallel to the river and at an angle of 64 degrees to the axis of Grand Coulee Dam.
FactsThe power facilities at Grand Coulee Dam consist of a powerplant on both the left and right sides of the spillway on the downstream face of the dam. The Third Powerplant, on the downstream face of the forebay dam, the pumping generation plant on the left abutment of the dam, and a 11.95/115-kilovolt switchyard, a 230-kilovolt consolidated switchyard, and a 525-kilovolt Third Powerplant cable-spreading yard and switchyard are located high on the hills west of Grand Coulee Dam.
HistoryConstruction of the original project started in 1933 and was completed in 1941. The first power was generated in 1941 and the last of the original 18 units (Right and Left Powerhouses) began production in 1949. Pumping for irrigation commenced in 1951. Six pumps(P-1 through P-6) were installed from 1951 to 1953. In addition, six pump-generators were installed from the mid-1970`s (P/G-7 and P/G-8) to the early 1980`s (P/G-9 through P/G-12). Construction of the Third Powerplant and Forebay Dam commenced in 1967 with the first unit (G-19) commissioned in 1975 and the last (G-24) in 1980. The 18 original generators in the Right and Left Powerhouses have had the stator windings replaced increasing the rating from the original 108,000 kW to 125,000 kW. The last three generators in the Third Powerplant (G-22, G-23, and G-24) had their stators and cores replaced increasing their rating to from 700 MW to 805 MW at 825,640 kva and power factor of 0.975. Six banks (18) of the original transformers in the Left Powerhouse have been replaced with the ratings increased to 129,000 kilovolt amperes. Turbin runners for units G-1 through G-18 were replaced between 2000 to 2010.
FactsThe Left Powerhouse contains three station service generators rated at 10,000 kW and nine generators rated at 125,000 kW. The Right Powerhouse contains 9 generators rated at 125,000 kW. The Third Powerplant contains three generators nameplate rated at 600,000 kW but able to operate up to 690,000 kW, and three generators rated at 805,000 kW. The Pump-Generating Plant contains six pumps rated at 65,000 horsepower, two pump-generators rated at 67,500 horsepower, and four pump-generators rated at 70,000 horse-power. Each of the generators is fed by an individual penstock with the largest (Third Powerplant) approximately 40 feet in diameter and carrying up to 35,000 cubic feet per second of water. One switchyard has 11.95 kilovolt distribution and four 115 kilovolt transmission lines; one switchyard has 230 kilovolt generation (from eighteen 125,000 kW units) and eleven transmission lines; the third switchyard has 525 kilovolt generation (from six Third Powerplant Units) and six transmission lines. There are electrical connections through transformers between the 115 and 230 kilovolt switchyards and the 230 and 525 kilovolt switchyards. The main dam contains 11 drum gates, each 135 feet long and 40 outlet tubes with 102-inch ring seal gates for spilling water. The average water released from Grand Coulee Dam is 110,000 cubic feet per second. The average power generation is 21 billion kilowatt hours per year
Present ActivitiesReplacing 500 kV Cables with Overhead Lines: The degraded condition of high voltage cables that transmit power from the Third Power Plant to the switchyard constitutes an unacceptable risk for loss of generation. The nine oil-filled cables for G-19, G-20, and G-21 have been operated near or above their continuous current rating for 30 years. It has become apparent that the condition of the high voltage cables transmitting power from the Third Power Plant to the 525KW switchyard have degraded. These cables are nearing the end of their useful life and therefore present an increasing risk of failure during operation. At the same time it has been determined that G-19, G-20, and G-21 could each be up-rated from 700MW to 770MW if the cables transferring power to the grid were also replaced with a means of transmission having higher capacity. Replacing these cables with overhead transmission lines will solve several problems: Overhead transmission lines can be inspected and maintained more safely than oil filled cables. The new lines can be of adequate size to allow up-rating Third Power Plant generators. Replacing these cables with overhead transmission lines will remove the potential of one cable failure causing the loss of 2,100MVA or more of generation. The new overhead lines are expected to be installed by December 2012. The removal of the existing oil filled cables is expected to be completed by December 2013.
Present ActivitiesModifying the Fixed-wheel Gate Repair Chamber for Blasting and Painting: This project will modify the chamber to allow blasting and painting of Third Power Plant fixed-wheel gate components and be in compliance with Life Safety and Electrical Codes. At present, the wiring is not explosion-proof, ventilation is inadequate, separation from dam galleries is inadequate, and lighting is inadequate. All these factors lead to potential violations of code requirements if work is undertaken during seasons when blasting and painting cannot be done outdoors. Fixed-wheel gates from the six Third Power Plant penstocks can be moved by gantry crane from their individual chambers to this modified chamber for repair or refurbishment. Completion of this project is scheduled for December 2012.
Present ActivitiesRehabilitating Third Power Plant Cranes: There are six cranes which will see heavy use during the Third Power Plant unit overhauls. There are three upper bridge cranes, one 2,000-ton lower bridge crane, one draft tube gantry crane, and one forebay gantry crane. It is imperative that they all be in excellent working order prior to the overhaul work for use by contractors and the GCPO in order to prevent unplanned crane outages that could result in costly delays in the overhaul schedule. Repairs and upgrades of these cranes are underway. This project is expected to be completed in January 2013.
Present ActivitiesA contract was awarded to replace eight station air system air compressors with installation completed in FY 2005. A contract was awarded to upgrade the 11.95-kV switchgear. A new arrangement of switchgear is currently being installed which will provide better reliability for station service power to the switchyards. Completion of this upgrade is scheduled for FY2009.
Present ActivitiesInstallation of a new Supervisory Control and Data Acquisition (SCADA) System is underway.
Present ActivitiesNew Material Storage Building: Overhaul of the Third Power Plant turbines and generators requires lay-down space for all turbine and generator parts as they are removed. These and other incidental parts will occupy nearly all of the Third Power Plant floor space. There are a variety of spare parts and pieces presently being stored in the Third Power Plant that need to be removed in order to provide the needed overhaul lay-down space. These valuable and easily damaged spare parts need to be kept in a secure, covered, and heated storage space. Plans for this building include a 100-foot by 200-foot floor area with 30-foot walls, 30-foot by 28-foot door (same opening as the north Third Power Plant door), insulated walls and ceiling, heating and cooling, forced ventilation, power, compressed air, and a life safety system with fire suppression. The GCPO facilities are considered part of a historically significant area. As such, this new storage building cannot detract from the overall appearance of the area. The storage building will be much smaller than the Third Power Plant and has been designated to retain the historical context of the site. Construction of the building is underway and expected to be complete in November 2012.
Future Planned ActivitiesFailure of a single phase transformer on Unit G10 resulted in re-evaluation of the need for replacement transformers. Additional replacement transformers for four units in the Left Powerplant will be purchased. Installation of the units will begin in 2013.
Future Planned ActivitiesThe Third Powerplant generating units are in need of complete mechanical overhauls. Each unit will be taken apart and worn parts will be refurbished or replaced. In addition, the excitation systems, governor control systems, station service equipment, and switchyard circuit breaker replacement for each of the six generating units (G-19 through G-24) will also be replaced. An intial contract has been awarded for units G-22 through G-24 and is expected to be completed in 2017. A second contract wil be awarded in the future for Units G-19 through G-21.
Special IssuesSince Grand Coulee has such a large amount of generation; it is used as a peaking facility by BPA. Fluctuations in the downstream tailbay/river have required extensive downstream stabilization measures, including elaborate monitoring and pump systems to maintain riverbank stability.
Special IssuesWater releases from Grand Coulee play a significant role in providing water for the fish that have been listed under the Endangered species Act. In addition, to the extent possible, spill is minimized to keep the Total Dissolved Gas (TDG) below the state standards. As part of the power peaking operation the pumps and pump-generators in the Pump-Generating Plant are load factored (use for pumping during light load hours) to allow BPA to sell more power during peak hours and also to provide a load during light load hours (to reduce spill). The pump-generating plant provides an approximate load swing - from consuming 600 MW with all 12 units pumping to generating 300 MW with 6 pump-generators generating.
NERC RegionWestern Electricity Coordinating Council, Northwest Power Pool Area
PMA Service AreaBonneville Power Administration
Plant TypeConventional
Powerhouse TypeAbove Ground
Turbine TypeFrancis
Original Nameplate Capacity1,974,000 kW
Installed Capacity6,809,000 kW
Year of Initial Operation Left Powerplant - Year of Operation of Right Powerplant1941 - 1949
Year of Operation - Third Powerplant1975
Year of Operation - Pump-Generator Plant1951 (6 original pumps) - 1973 (6 pump-generators)
Net Generation24,609,129,875 kWh
(Fiscal Year)2011
Rated Head330 ft
Production ModeIntermediate
Remotely OperatedNo
Project AuthorizationThe Columbia Basin Project began with fund allocation for Grand Coulee Dam pursuant to the National Industrial Recovery Act of June 16, 1933. The project was specifically authorized for construction by the Rivers and Harbors Act approved August 30, 1935. The Columbia Basin Project Act of March 10, 1943 (57 Stat. 14), reauthorized the project, bringing it under the provisions of the Reclamation Project Act of 1939.
Project AuthorizationConstruction of the Third Powerplant was authorized by Public Law 89-448 (80 Stat.200) dated June 14, 1966, as amended by Public Law 89-561 (80 Stat. 714) dated September 7, 1966.
Project PurposeThe Columbia Basin Project is a multi-purpose development using part of the resources of the Columbia River in the central part of the State of Washington. The key structure, Grand Coulee Dam, is on the main stem of the Columbia River about 90 miles west of Spokane, Washington. The extensive irrigation works extend 125 miles southward on the Columbia Plateau to the vicinity of Pasco, Washington, where the Snake and Columbia Rivers join. The project irrigation facilities are designed to deliver a full water supply to 1,095,000 acres of land previously used only for dry farming or grazing. Of the 1,095,000 acres, approximately 550,000 are currently irrigated. Power production facilities at Grand Coulee Dam are the largest in North America.
First namePower Manager
Last name 
TitlePower Manager, Grand Coulee Power Office
AddressPO Box 620
CityGrand Coulee, WA 99133-0620
Phone (Fax)509 633-9138
Phone (Individual)509 633-9507

Last updated: Mar 07, 2014