The US Bureau of Reclamation has released a technical report that presents the findings of a water seepage study for the prospective Black Rock reservoir in Central Washington, US.
The project is one of the alternatives being evaluated by USBR 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 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 analysis indicates that a majority of seepage from the proposed Black Rock reservoir site would move in the direction of the Hanford Nuclear Reservation. The modelling is based on previous hydrogeologic studies of the Columbia Plateau and also incorporates results of recent geologic drilling and aquifer testing by USBR at the proposed dam site.
An earlier report prepared for USBR 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 analysd 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, US Congress authorised USBR 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 authorisation included the study of a potential Black Rock dam and reservoir, to be located in the Black Rock Valley in Yakima County.