Rock Island Dam
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Rock Island Dam is a hydroelectric dam located on the Columbia River downstream from Wenatchee, Washington and Rock Island, Washington. It was the first dam to span the Columbia. The reinforced concrete dam is anchored to solid basaltic bedrock. The dam and associated buildings and machinery are referred to as the Rock Island Hydro Project. By river, the dam is 235 miles (378 km) below the Canadian border and 453 miles (729 km) above the mouth of the Columbia at Astoria, Oregon.
The first powerhouse, with four generating units, to provide power for the greater Seattle area, were built by Stone and Webster Engineering Corporation for Puget Sound Power & Light Company (now Puget Sound Energy) between 1930 and 1933. It is currently owned and operated by the Chelan County, Washington Public Utility District (PUD). The PUD installed eight more generating units between 1951 and 1953, and a second powerhouse, with eight more generators between 1974 and 1979. The power is distributed to local customers, the US Bonneville Power Administration grid, and the Puget Sound area.
The un-named reservoir behind the dam extends upstream about 21 miles (34 km), and the covers an area of about 3,300 acres (13 km²). Like most dams on the Columbia, it has a fish ladder (three, actually) for adult salmon and steelhead returning to spawn; research on how to increase survival rates of the young fish going downstream is on-going.