Draft U.S. study endorses dam safety work at 3.65-MW Stampede Dam

SACRAMENTO, Calif., U.S. 12/5/11 (PennWell) — The Bureau of Reclamation has issued a draft environmental assessment endorsing a plan to modify 3.65-MW Stampede Dam to prevent dam failure during extreme floods on California’s Little Truckee River.

Reclamation performed risk analyses of Stampede Dam, near Truckee, Calif., finding the dam cannot safely pass floodwaters in accordance with Reclamation’s Public Protection Guidelines. It said modifications are needed to prevent potential overtopping during an extreme flood.

The environmental assessment chooses a preferred alternative that would increase in the height of the 239-foot-tall zoned earthfill dam by 11.5 feet. The mechanically stabilized earth increase would provide additional emergency storage.

The spillway would be modified to accommodate the raised embankment and limit peak flows through the spillway to maintain current flood operations. Additionally, two small earthen dikes would be constructed in low-lying areas on the south rim of the reservoir.

Reclamation said there would be no changes to the operation of Stampede Reservoir and that reservoir levels and flow releases to the Little Truckee would continue unchanged.

Part of Reclamation’s Washoe Project, Stampede Dam provides water primarily for fishery enhancement along the Truckee River and Pyramid Lake Fishway facilities operation.

Reclamation is taking comments on the draft environmental assessment until Dec. 22. The document may be obtained from the Reclamation Internet site at http://www.usbr.gov/mp/nepa/nepa_projdetails.cfm?Project_ID=8182.