This project was to construct two crossover/isolation valve vaults, (8)78-inch, (2) 48-inch and 20 (16-inch) valve assemblies and piping along with two electrical vaults containing electrical control systems for Bay Division Pipe Lines No’s 3 & 4 on both sides of the Hayward Fault crossing as part of seismic upgrades and improvements to the Hetch Hetchy Water System. The work was in 2 confined locations known as the North Shutoff Station and South Shutoff Station, both located in Fremont California, in residential neighborhoods. Both sites had constrained site conditions as space and scheduling were limiting factors. Each pipeline 3 & 4 was worked on separately at both locations, and was dependent upon a specified City shutdown and dewatering schedule. The excavations were deep, and required detailed and complicated shoring along with temporary support and protection of the existing pipelines while work proceeded on the concrete vault buildings. Work included 3 separate microtunnels (of 2,220 feet) plus pilot boring, and Jack and Bore of 1,511 feet (5 tunnels). Work involved civil, structural, mechanical, electrical and landscaping work, as there were various trades and subcontractors working on the project the scheduling and tracking of the project was extremely complex.
Category: Water Transmission
Client Type: City, San Francisco