TwentyMile creek fish passage

The Lake County Umbrella Watershed Council and the US Bureau of Land Management led this fish passage and screening project on Twentymile Creek, located in the Warner Valley Watershed.  This project provided fish passage over a 70 ft. concrete diversion dam on Twentymile Creek. The existing concrete diversion dam, known as the Dyke Diversion was originally constructed in the 1950s and rebuilt in 1991. The dam creates sufficient hydraulic head to divert stream flow into a diversion ditch that then delivers water for flood irrigation.  A steep-pass fish ladder was constructed on the river-right side of the dam when the structure was rebuilt in 1991. The fish ladder no longer met current Oregon Department of Fish and Wildlife (ODFW) fish passage criteria for suckers or trout, and was an upstream passage barrier.

 River Design Group, Inc. was retained to prepare fish passage and screening designs to accommodate fisheries requirements for Warner Sucker, a Threatened and Endangered Species.  Overall, the project entailed retrofitting a concrete diversion dam with a structural concrete fish ladder, while abandoning the existing fish ladder. The project required excavation of rock, concrete, and sediment to accommodate the fishway.  Construction included placement of reinforced concrete, wood timbers, and cobbles for the fishway.  This project also installed a Farmers Flat Screen within the irrigation ditch located on the west side of the diversion dam.