Silver Lake Reservoir Complex Storage Replacement Projects

To meet tougher state and federal water quality standards, the Los Angeles Department of Water and Power (LADWP) is taking the Silver Lake Reservoir Complex out of service and replacing it with the Headworks Reservoir, a new 110-million-gallon (416 ML) buried tank. Headworks Reservoir will be located at the site of the former Headworks Spreading Grounds between the 134 Freeway and Forest Lawn Drive, north of Griffith Park in Los Angeles. Jacobs Associates is assisting LADWP with the design of two tunnels that will convey flow from the new reservoir to existing service areas.

The Silver Lake Bypass Tunnel will be constructed in the residential Silver Lake district of Los Angeles. The project includes three tunneling shafts, approximately 4,600 feet (1,402 m) of 9.5- to 10-foot-diameter (2.9 to 3 m) tunnel, a 66-inch-diameter (1,676 mm) welded steel pipe, and a flow regulator station. Tunnel excavation will be in very weak to weak, weathered sedimentary rock. Ground cover will range from 50 to 130 feet (15 to 40 m). Groundwater levels will be as high as 60 feet (18.3 m) above tunnel invert, and high groundwater inflows are anticipated because of the tunnel’s close proximity to the reservoir.

The River Supply Conduit Lower Reach Unit 1A is part of a series of new trunklines replacing the existing River Supply Conduit. It will connect a new four-megawatt hydroelectric generating station to the Headworks Reservoir. The connecting pipeline will be approximately 6,400 feet long (1,951 m), with about 3,200 feet (975 m) constructed in a tunnel beneath Griffith Park. Ground cover will range from about 20 to 130 feet (6 to 40 m). Geologic conditions include weathered granitic rock and alluvial soils. The tunnel will have a 96-inch-diameter (2,438 mm) welded steel lining.

For both projects, Jacobs Associates is a subconsultant to AMEC on a design team led by LADWP geotechnical engineers.

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