U.S. narrows Yakima dam, reservoir proposals

The Bureau of Reclamation has found two dam and reservoir proposals in the Yakima River Basin sufficiently viable to merit further study. The agency found both could have hydropower potential.

BuRec said it found the proposed Wymer Dam and reservoir to be sufficiently viable for study in more detail over several months. It joins a proposal for Black Rock Dam and reservoir, which BuRec previously found to be technically viable. (HNN 12/30/05)

The Yakima River Basin Water Storage Feasibility Study, authorized by Congress in 2003, is to evaluate storage options to improve anadromous fish habitat, boost reliability of the 25-MW Yakima project’s water supply during dry years, and provide water to meet future municipal demand. The Yakima project has six storage reservoirs, five diversion dams, and the 12-MW Chandler (HNN 3/2/06) and 12.9-MW Roza hydropower developments.

BuRec and the state of Washington are sharing Yakima Basin study costs. The federal agency and the state also have been cooperating on a study of 11 large Columbia Basin off-stream reservoirs, all with a potential for hydropower. (HNN 2/23/06)

Wymer chosen from three alternatives to Black Rock

BuRec chose Wymer Dam and reservoir from three alternatives assessed for study with the Black Rock Dam and reservoir alternative. It eliminated two alternatives from further consideration: construction of a new Bumping Lake Dam and enlarged reservoir, and a Keechelus-to-Kachess pipeline.

�Reclamation has concluded from its appraisal-level assessment that the Wymer Dam and reservoir alternative is the only alternative of these three that appears to be technically viable and potentially capable of meeting the goals of the storage study,� Upper Columbia Area Office Manager Jerry Kelso said. �Further, more detailed analysis will determine whether either alternative �- Wymer or Black Rock �- is sufficiently viable and economically justified for intensive, feasibility-level study.�

Wymer Dam and reservoir would be built on Lmuma Creek, about 1.5 miles upstream from its confluence with the Yakima River. BuRec said the total project could cost from $340 million to $380 million.

Wymer outlet designed to accommodate powerhouse

A 415-foot-tall dam would create a 174,000-acre-foot off-stream reservoir. A 400-cfs pumping plant would fill the reservoir when Yakima River flows are available and not required downstream.

BuRec said Wymer Dam outlet works were designed at the appraisal level to permit the addition of a hydropower plant in the future. It did not include any estimate of installed capacity.

The agency said further investigations of Wymer Dam and reservoir could include various operating scenarios and the potential for storage of Columbia River water.

Black Rock hydro could exceed 390 MW

A Black Rock reservoir would store up to 1.3 million acre-feet and would be part of a project that could include as many as four new hydropower plants totaling more than 390 MW.

In 2005, BuRec estimated total project costs to be between $3.5 billion and $4 billion. That same year, BuRec initiated geological investigations at the Black Rock site.

A feasibility report and environmental impact statement are to be completed by the end of 2008, outlining the most viable storage alternative. BuRec and the secretary of Interior then will decide whether to seek congressional authorization for project construction.

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