DESCRIPTION
In 2005, CCNRD constructed a fish ladder, or fishway, at the Peshastin Irrigation District diversion structure on lower Peshastin Creek. This structure allows fish to access spawning and rearing habitat for steelhead, bull trout and Spring Chinook. The structure consists of a roughened channel fishway at a channel slope of 3.9% upstream from the dam axis on the left abutment. The project also included installation of fish screens at head gates. The dam was notched for a 16ft width. From that notch the roughened channel fishway extends upstream for approximately 87 feet. The fishway has two training walls for the entire length that extend to elevation 1180 (same as the left abutment elevation) and it was constructed with steel plate sections with rock support. Boulders were placed in the fishway invert to create a meandering flow pattern and provide shelter for fish. Two boulder weirs were placed immediately downstream from the fishway exit to backwater flashboard weirs at the channel's upstream exit. These weirs are required to meet hydraulic drop criteria of 6 inches. The existing dam notch will be closed when the fishway is in use.
Chelan County used this funding to improve fish passage around the Peshastin Irrigation District diversion dam which is located near RM 2.4 in lower Peshastin Creek. The project included installation of a fish passage structure to provide access to ~17 miles of spawning and rearing habitat upstream for steelhead, bull trout, and spring Chinook. The fish passage structure was installed by cutting a 16' section out of the diversion dam on river left. The fish passage structure consists of a roughened channel fishway that extends upstream for approximately 90 feet. The roughened channel consists of steel plate sections with rock support. Water flows through the trapezoidal channel with 1.5:1 side slopes and a 3 foot wide bottom. Boulders placed at the fishway invert upstream create a meandering flow pattern and provide shelter for fish. Two boulder weirs placed immediately downstream from the fishway exit provide a backwater flashboard at the channel's upstream exit. These weirs also meet the hydraulic drop criteria of 6 inches. Chelan County Natural Resources Department was the project sponsor with US Bureau of Reclamation, Peshastin Irrigation District, WA Department of Fish and Wildlife, and the private landowner as project partners.
