EPRI's Evaluation of the Elwha Dam Eicher Screen and Subsequent Design Changes and Hydraulic Tests.
Fish Passage Policy and Technology: Proceedings of a Symposium
American Fisheries Society
The Electric Power Research Institute (EPRI) has conducted two years of biological evaluations of an Eicher Screen installed in a 9-foot (2.7 m) diameter penstock at the Elwha Hydroelectric Project in Washington state. Testing has shown passage survival to equal or exceed 98.7% for steelhead trout Oncorhynchus mykiss smolts and coho salmon O. kisutch and chinook salmon O. tshawytscha smolts and fingerlings. Scale loss injuries were minimal at velocities of 4-6 fps, but increased at higher velocities. Most injuries occurred from fish contacting the screen in an area where it transitions from 63% porosity to 32% porosity wedgewire material, where the velocity component perpendicular to the screen was relatively high. Hydraulic model studies conducted in 1992 indicated that a more gradual reduction of the porosity in the downstream end of the screen would reduce the observed velocity peak by approximately 10%, but would not achieve a fully uniform flow distribution.