The Sunol Valley Water Treatment Plant was a 120 MGD facility. Shimmick secured a contract to increase the plant’s capacity to 160 MGD and make additional facility improvements. The work under this contract included construction of a 40 MGD sedimentation and flocculation basin; modification to the existing flow distribution structure; upgrade of mixed media filters; new filtered water and backwash water piping; a new 3 million gallon chlorine contact tank; a new 17.5 million gallon treated water reservoir; new chemical feed systems with tanks, pumps and piping; new standby generator and fuel tanks; upgrade of the electrical system and instrumentation and controls; replacement of large butterfly valves; a new 78-inch pipeline and tunnel; site excavation and grading.
Shimmick proposed secant wall jacking and receiving pits for the tunneling work and oversaw the design and construction of the structure. The tunnel excavation and the installation of the pipeline within the tunnel were self-performed. A 78-inch diameter welded steel pipeline was installed within this tunnel. Tunnel safety precautions were employed to maintain safe work in the deep, damp, confined space.