The California Department of Fish and Wildlife has executed Lake and Streambed Alteration Agreement number EPIMS-RIV-15797-R6, pursuant to Section 1602 of the Fish and Game Code to the Metropolitan Water District of Southern California.
The Project is limited to the stream impacts associated with the one-time dewatering and shutdown of the Upper and Lower Feeder pipelines. Dewatering will begin March 1, 2021 and continue through March 2, 2021. The Project will allow staff to perform inspections and maintenance of the pipeline. Dewatering will occur at the four locations listed above and involves releasing untreated water from either a pipeline blow-off (Lower Feeder 80+40) or a pump well outlet structure (Upper Feeder 40+00, Lower Feeder 155+55, Lower Feeder 593+02) into ephemeral tributaries of the Santa Ana River and the Temescal wash. At blow-off structures, the water will be discharged via gravity through an existing permanent corrugated pipe to the discharge point in a stream channel and any remaining water left in the pipe will be manually pumped out and released. The velocity of the water being released into the channel will be manually controlled at the blow-off structure. At the pump well stations, water will be pumped through a six-inch diameter hose and discharged into a nearby ephemeral wash. Dissipation socks will be used to dissipate flows at two dewatering locations and existing riprap, rock and concrete at the dewatering locations will help dissipate water velocity and decrease erosion potential. Dewatering activities typically involve a 1-2 crew members and staging utility truck equipped with a generator adjacent to a dewatering structure.