The sediments jeopardize the reliable and efficient operation of the dams and powerhouses. Approximately 5.4 million cubic meters of sediments, deposited in the two reservoirs since they were placed in service in 19, partially obstruct the dams` low level outlets and pipe inlets supplying water for spillway gate operations. The reservoirs are part of the 182,000 kW Rock Creek-Cresta Project hydroelectric development. Throughout the demonstration, turbidity levels and total suspended solids concentrations remained well below allowable levels set by the California Regional Water Quality Control Board - no more than a 25 NTU turbidity increase over ambient background nor more than 80 mg/I total suspended solids, = (SMP) to control sediments at Rock Creek Reservoir and the downstream Cresta Reservoir on the North Fork Feather River in Plumas County. Increases in turbidity and total suspended solids downstream of the discharge site were minor. The dredged sediment was pumped 600 m upstream of the pump head and discharged back to the surface of Cresta Reservoir. Dissolved oxygen downstream of the pump head remained near saturation. Turbidity and total suspended solids concentrations of water samples collected adjacent to and downstream of the pump head were similar to those of samples collected adjacent to and upstream of the pump head. The technique, developed by PBMK Consultants and Engineers, uses the EDDY Pump, a patented submerged slurry pump system with a higher solids-to-liquid ratio and lower re-suspension of sediment than achieved by conventional suction dredging. ![]() During a prototype demonstration at Pacific Gas and Electric Company`s (PG&E`s) Cresta Reservoir, the feasibility of a new dredging technique was tested for its reported ability to produce only minimal water quality impacts.
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