RICHMOND TRANSPORT FACILITIES TUNNEL
City and County of San Francisco, Dept. of Public Works
The Richmond Transport Facilities Tunnel project consisted of a 10,200-foot long, 18-foot diameter storage tunnel, a 1,500 foot long NATM overflow structure, and 6,000 linear feet of a large diameter sewage pipe located in the Richmond/Seacliff/Lobos Creek area of San Francisco. The tunnel was driven through 9,000 feet of hard rock and 1,200 feet of sand located below the water table, including a transition zone of mixed face conditions and an inactive fault line. The hard rock portion was mined by a shielded tunnel boring machine. The soft ground section was mined using an open face shield in conjunction with dewatering and chemical grouting for ground stabilization. Compaction grouting was performed from the overlying street surface to successfully control settlement in the soft ground section, which tunneled beneath some of the most expensive real estate in San Francisco.
The project included excavation of an underground overflow chamber built using NATM with drill and blast excavation with shotcrete, steel sets, and rock bolts as support. This vault is 80 feet wide at the largest dimension and contains two interconnecting incline and decline tunnel connections connecting to the Mile Rock Tunnel.
A section of the existing Mile Rock Tunnel was rehabilitated, and the 24th Avenue connector tunnel, a 30 percent incline audit was constructed. From the surface, the project included 2,000 feet each of 120-inch, 42-inch, and 36-inch diameter reinforced concrete pipe installed in open cut trenches and structures to house a sodium hypochlorite tank.
EPC provided construction management services, including Resident Engineering, office engineering and tunnel inspection services.