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Pacific Northwest Region
Boise, Idaho
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John Redding
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Joye Redfield-Wilder
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Released On: September 18, 2007

Report Looks at Seepage Issues at Proposed Black Rock Reservoir Site
A technical report released today by the Bureau of Reclamation presents findings of a water seepage study for the prospective Black Rock reservoir in Central Washington.

The report estimates a range of volume and direction of seepage that might be expected if the Black Rock reservoir were to be constructed. The report is available online at: http://www.usbr.gov/pn/programs/storage_study/index.html.

The Black Rock reservoir is one alternative being evaluated by Reclamation and the Washington Department of Ecology as part of a study to investigate opportunities to increase water storage capacity and improve conditions for fish in the Yakima River Basin.

The analysis released today indicates that a majority of seepage from the proposed Black Rock reservoir site would move in the direction of the Hanford Nuclear Reservation. The modeling is based on previous hydrogeologic studies of the Columbia Plateau and also incorporates results of recent geologic drilling and aquifer testing by Reclamation at the proposed dam site.

An earlier report prepared for Reclamation by the Pacific Northwest National Laboratory described the effect that a rise in the water table at Hanford would have on certain contaminants buried in the sediment layer. This report is available at the same website.

Water seepage impacts and possible mitigation measures are currently being analyzed in the Yakima River Basin Water Storage Feasibility Study. A draft version of the feasibility study's planning report and EIS will be available for public comment in early 2008.

In 2003, Congress authorized Reclamation to initiate the Yakima River Basin Water Storage Feasibility Study to examine the feasibility and acceptability of storage augmentation in the Yakima River basin. That authorization included the study of a potential Black Rock dam and reservoir, to be located in the Black Rock Valley in Yakima County, Wash.

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Reclamation is the largest wholesale water supplier and the second largest producer of hydroelectric power in the United States, with operations and facilities in the 17 Western States. Its facilities also provide substantial flood control, recreation, and fish and wildlife benefits. Visit our website at www.usbr.gov.