News Release
| Release Number: | 01-171 |
| Dated: | 12/26/2001 |
| Contact: | Matt Rabe, 503-808-4510 |
Portland, Ore.- The U.S. Army Corps of Engineers is seeking comments on a proposal for construction work to improve juvenile salmon passage at Bonneville Lock and Dam.
The proposal, as outlined in the Corps' environmental assessment, is to construct and operate a juvenile surface collection and bypass system at the Bonneville Second Powerhouse. This work will include modifying the ice and trash sluiceway, and constructing a transportation channel along the north shore of Cascades Island and a high-flow outfall off the downstream tip of the Island. The system would increase survival of juvenile migrants passing through the Bonneville project by increasing the number of juveniles diverted away from the turbines.
To comment on, or to receive a copy of, the environmental assessment, write to: District Engineer, U.S. Army Engineer District - Portland, Attn: CENWP-PM-E (Hamilton), P.O. Box 2946, Portland, OR 97208-2946. Written comments should be mailed no later than January 22, 2002. Questions may be directed to Lynne Hamilton, Environmental Resources Branch, at (503) 808-4772. Please refer to Public Notice number CENWP-PM-E-01-14 in any correspondence.
This project is needed to meet the requirements of the National Marine Fisheries Service's 2000 Biological Opinion, which established survival standards and goals for salmon migrating past the dams. The new bypass system would work in conjunction with the existing systems, thus providing higher project survival (an estimated 1 percent) than is presently provided at the facility. Biological testing in 1998 showed that 35 percent to 50 percent (dependent on species) of juvenile salmon that approached the second powerhouse passed through the chute. The chute, however, was not designed to safely pass fish. Therefore, modifications will be made to ensure high fish survival of those fish entering the system.
The existing sluiceway would be slightly modified by installing a new operating gate at the intake and a concrete cast-in-place ogee (an s-shaped "slide") to direct water flow downward smoothly at the intake. This also will increase flow into the chute, which is expected to increase the number of fish guided into the system. A 3,000-foot-long rectangular concrete transportation channel and supporting concrete "monolith" would be constructed on the northern edge of Cascades Island. Fish would travel down the channel to the outfall structure. Juvenile fish will move from the outfall into a plunge pool excavated in the river below the outfall.
About 30,100 cubic yards of sand, gravel and rock would be excavated to form the plunge pool. Some or all of this excavated material would be disposed of in-water. The sides of the pool and outside perimeter would then be lined with rock mattresses to provide erosion protection.
Fishing access on the north side of Cascades Island would be closed for the majority of the 18-month construction period. Following construction, the north side will be open for fishing access at high water, but there will be no low-water access. The Corps plans to develop a low-water handicapped-accessible fishing access site across the river, at the existing fishing access road turn-around downstream from the Hamilton Island (Washington) boat ramp, to provide replacement access. An area about 250 feet long would be graded and improved with gravel and a dirt path would be improved with gravel. Two parking spaces would be paved and marked for handicapped use.
This action is one of many being undertaken by the Corps to improve fish passage at its Columbia and Snake River dams. The Corps continues to work with its regional partners - government, public and private - to preserve the valuable fish runs on the Columbia and Snake rivers.