News Release
| Release Number: | 97-080 |
| Dated: | 7/30/1997 |
| Contact: | Heidi Y. Helwig, 503-808-4510 |
Portland, Ore. -- At 8 a.m. tomorrow, U.S. Army Corps of Engineers biologists and engineers will implement a short-term solution to a complex fish passage problem at Bonneville Dam's second powerhouse. The dam is 40 miles east of Portland on the Columbia River.
By strategically locating bulkheads and reversing the function of certain system valves, the Corps will create an "upstream" flow to attract any fish out of the dam's auxiliary water system (AWS) at the base of the second powerhouse. From the AWS, the fish will be able to swim into a flume known as the ice and trash chute. This chute leads back below the dam to the tailrace where fish can safely find their way back into a fish ladder.
The upstream flow will provide a stimulus for any migratory fish that may be in the system to swim against the current and out of the AWS, said Corps fisheries biologist Gary Johnson.
"This plan is targeted specifically toward fish that need to get on with their migration to other spawning grounds," Johnson said. Other non-migratory species of fish that may be in the system, such as sturgeon, may not be affected by the flows, he said. The Corps and the region continue to consider alternatives for removing any additional fish out of the system. At this time, no decisions have been made on what future work might entail. Discussions continue in the development of a long-term plan to prevent future problems with debris at the fish facilities.
When the work begins tomorrow, large equipment will be used on the lower deck of the dam's second powerhouse. Out of concern for visitor safety, the Corps will close the Cascades Island fishing area to visitors from Thursday to at least Sunday.
High flows and large amounts of debris brought down in the Columbia River this summer caused gratings on the floor of Bonneville Dam's second powerhouse fish ladder to dislodge. This provided an opportunity for fish to enter the AWS, which does not allow fish passage over the dam. Adult fish continue to pass the dam through other ladders on the project. Last week, divers surveyed the fish collection channel and discovered 25 grates had been pushed out of place due to excess pressure caused by debris buildup. Divers repaired and reattached the grates to keep other fish out of the AWS. The Corps has already shut down fish water attraction turbines, and allowed an exit through a few opened grates for any fish that may be in the AWS.
Yesterday (Tuesday) fisheries agencies, the Columbia River Intertribal Fish Commission and other resource agencies representing the region met again with the Corps to discuss and finalize this plan. A consensus was reached to begin attracting the fish out tomorrow.