License No.986594

Chabot Dam Seismic Upgrade

Project Owner

East Bay Municipal Utility District

Project Location

Oakland, California

Project Value

$15m

Project Description

Improved the stability and safety of the Chabot Dam and Reservoir Outlet Works located in San Leandro, CA to increase the facility’s resilience to a major earthquake on the adjacent Hayward Fault. Seismic improvements were made to two areas of facility: 1) In-situ treatment of the dam’s foundation soils and installation of a seepage trench near the downstream toe of the dam; 2) Demolition of the existing outlet tower and retrofitting the existing outlet vertical access shaft, associated piping and mechanical controls.

Work near the downstream toe of the dam included excavating a portion of the downstream face of the dam to construct a level working platform, constructing shear walls beneath the working platform utilizing Cement Deep Soil Mixing (CDSM), constructing a 35-foot deep seepage interceptor trench with associated discharge piping and seepage measuring weir, installing geotechnical monitoring instrumentation, conduits, and wiring to a central recording device on the dam, and restoring the dam face using the CDSM spoils material. The outlet works improvements included demolishing the existing pavilion structure, removing the existing inlet pipe within the reservoir, upgrading the outlet tower for use as a temporary cofferdam, procuring and installing an epoxy- coated steel lining in the existing 55-foot deep vertical access shaft, procuring and installing a new inlet pipe from the reservoir to the access shaft, with new gates, operators and miscellaneous metals within the access shaft, and plugging the abandoned tower waste chamber and sluiceway with concrete.