Supplement Analysis for the Watershed Management Program EIS - Idaho Model Watershed Habitat Projects - L-9 Irrigation Diversion Modification

The Bonneville Power Administration is proposing to fund a fish passage improvement project at the L-9 diversion on the Lemhi River in Lemhi County, Idaho with the Lemhi Soil and Water Conservation District. The project proposes to replace the existing rock push-up irrigation diversion dam with a single rock weir that will incorporate a geotextile membrane to create a permanent diversion. The new weir will be a v-shaped vortex weir with a six-foot wide notch for fish passage. In addition, a ramp flume will be constructed in the diversion canal between the headgate and existing fish screen to provide for water measurement. The new diversion will provide better water delivery/control and improved passage for adult and juvenile resident and anadromous fish