Wanapum Dam

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Wanapum Dam
Wanapum Dam from West Shore - downstream 10360031.jpg
Dam viewed from downstream on the west bank
Official name Wanapum Dam
Location Grant / Kittitas counties, Washington
Coordinates 46°52′31″N 119°58′16″W / 46.875213°N 119.971004°W / 46.875213; -119.971004Coordinates: 46°52′31″N 119°58′16″W / 46.875213°N 119.971004°W / 46.875213; -119.971004
Construction began 1959
Opening date 1963
Construction cost US$93,277,690[1]
Dam and spillways
Impounds Columbia River
Height 185 feet (56 m)[1]
Length 8,320 feet (2,540 m)[1]
Creates Lake Wanapum
Total capacity 796,000 acre feet (982,000,000 m3)
Power station
Commission date 1963
Turbines 10 x 104 MW Kaplan-type[2]
Installed capacity 1,040 megawatts (1,390,000 hp)
Pacific Northwest River System

Wanapum Dam is a hydroelectric project located on the Columbia River downstream (south) from Vantage, Washington where Interstate 90 crosses the Columbia from Grant County into Kittitas County. It is owned by the Grant County Public Utility District. Its reservoir is named Lake Wanapum.

The dam, and its lake, are named after the Wanapum Indians. The dam has a rated capacity of 1,040 megawatts and annually generates over 4 million megawatt-hours.[3]


The Wanapum dam was originally licensed in 1955 for a period of 50 years. Construction was initiated in 1959 with initial beneficial operation in 1963. The initial license expired in 2005, after which the Grant County PUD operated the dam on yearly license extensions while negotiations for license extension proceeded. The Federal Energy Regulatory Commission approved a license extension of 44 years for both the Wanapum dam and the downstream Priest Rapids dam on April 17, 2008. The license extension was conditioned upon programs to achieve the following goals:[4]

  • modernize the power generation capability of the dam
  • monitor water quality
  • improve wildlife habitat
  • protect nearly 700 Wanapum Tribe archaeological sites in the vicinity
  • enhance recreation with new campsites, picnic areas and trails

Spillway crack[edit]

On 27 February 2014, a 2 inches (5 cm) wide crack was discovered by inspection divers on one of the 65 feet (20 m) tall concrete monoliths that make up the spillway of the dam. A spokesman for the Grant County PUD indicated that the level of the water was to be lowered by 26 feet (8 m) over a period of days to "reduce the pressure on the spillway while inspectors investigate".[5][6]

Basalt bluff over the Columbia River near Wanapum Dam
Vantage Bridge crossing Wanapum Lake


  1. ^ a b c Grant County Public Utility District Website
  2. ^ "Hydroelectric Plants in Washington". IndustCards. Retrieved 4 March 2014. 
  3. ^ Grant County Public Utility District Website
  4. ^ "License OK'd for Columbia Dams". Tri-City Herald (Kennewick, WA: McClatchy Company). 2008-04-20. p. A6. 
  5. ^ "Crack found in Washington dam on Columbia River". USA Today (Gannet Company). 2014-03-01. "A 65-foot-long crack in a Columbia River dam in central Washington has prompted officials to begin lowering the water level by 20 feet so inspectors can get a better idea of how serious the damage is." 
  6. ^ Johnson, Eric M. (2014-03-01). Crack found in dam in Washington state, authorities lower water levels. Reuters, 1 March 2014. Retrieved on 2014-03-03 from http://www.reuters.com/article/2014/03/01/us-usa-dam-washingtonstate-idUSBREA200JD20140301.