Draft EIS reviews Yakima water plan including new dams, civil work

YAKIMA, Wash., U.S. 12/1/11 (PennWell -– A federal proposal to improve the Yakima River Basin’s water supply and ecosystem includes construction of two dams, modification of another, new fish passage at six dams, and numerous structural and operational changes within the basin in Washington.

Although hydropower is not included in the current proposal, the Bureau of Reclamation said the estimated 450,000 acre-feet of additional water storage could create opportunities for new hydroelectric development.

Reclamation and the Washington Department of Ecology seek comments by Jan. 3 on a draft environmental impact statement that reviews the proposal, which is based on 30 years’ study of the Yakima Basin. The basin suffers from shortages of irrigation and municipal water and from depleted fish populations due to altered stream flows.

The draft EIS examines the proposed integrated water resource management plan alternative as well as a «no action» alternative, under which some of the plans might be implemented piecemeal or not at all. While the draft EIS declares that most impacts of the integrated water resource management plan alternative would be beneficial, it declines to identify a preferred alternative.

A previous proposal for dam construction to serve the Yakima Basin’s water supply needs was dropped in 2008, when Reclamation chose a «no action» alternative over a plan to develop Black Rock Reservoir, a water project that would have included two new hydropower plants expected to generate 196,751 megawatt-hours annually. Reclamation balked at project costs and fears that Black Rock could cause groundwater migration toward the federal government’s 586-square-mile Hanford Nuclear Reservation.

Wymer Dam, new Bumping Lake Dam plans revived

The new integrated water resource management plan alternative revives other options examined in 2008 and earlier, including a proposal to build the 450-foot-tall Wymer Dam, creating a 162,500-acre-foot off-channel reservoir on Lmuma Creek, an intermittent tributary of the Yakima. Wymer Reservoir would be filled by a pumping plant with water from the Yakima River during high flows. An average of 82,500 acre-feet of its capacity would be used to improve stream flows.

The new plan also revives previously discarded options: to replace Bumping Lake Dam on the Bumping River with a new dam downstream, increasing its reservoir capacity to 190,000 acre-feet from 33,700 acre-feet; and to build a five-mile pipeline to carry water from Keechelus Reservoir to Kachess Reservoir to reduce flows, improve habitat during high flows, and provide water storage for downstream needs.

The integrated water resource management plan alternative also proposes constructing a new outlet in Kachess Dam that would be 80 feet lower than the existing outlet, making it possible to withdraw another 200,000 acre-feet of currently inactive storage from the reservoir on the upper Yakima River. Two options are being considered for that project, a gravity-flow tunnel or a pipeline and pump station.

Other proposals include:

o Modifying spillway gates on Cle Elum Dam on the Cle Elum River to raise its reservoir three feet, increasing available storage by 14,600 acre-feet.

o Modifying Kittitas Reclamation District irrigation canals on the Yakima River to reduce leakage and allow greater flexibility in water supply management;

o Improving Wapatox Canal to allow more efficient distribution of water;

o Studying using pumps for an inter-basin exchange of water with the Columbia River Basin; and

o Construction of fish passage at Cle Elum, Bumping Lake, Keechelus, Kachess, and 13.6-MW Tieton dams and improvement of fish passage at Clear Lake Dam on the Tieton River.

The integrated water resource management plan alternative also calls for more water to be left in the river for instream flows, rather than used for power generation at Reclamation’s 12.9-MW Roza and 12-MW Chandler hydro plants. Some water already goes to instream flows at Roza and Chandler, which are part of Reclamation’s Yakima Project along with six storage reservoirs and five diversion dams. The new plan would further reduce the water used for generation at certain times of the year, cutting annual generation to 82,000 MWh from 107,000 MWh.

However, the plan anticipates that proposed surface water storage projects would be built to accommodate future hydroelectric power equipment.

«The Surface Storage Element could create additional opportunities for hydropower in the Yakima River Basin at the new Wymer Reservoir, the expanded Bumping Lake Reservoir, the Kachess inactive storage site (if the tunnel option is used, and the Keechelus-to-Kachess pipeline,» the draft EIS said.

The Draft Programmatic Environmental Impact Statement on the Yakima River Basin Integrated Water Resource Management Plan may be obtained from the Bureau of Reclamation Internet site at http://www.usbr.gov/pn/programs/yrbwep/2011integratedplan/index.html. Comments may be submitted to Reclamation until Jan. 3.

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