When part of the 80-year-old Battery Park large diameter sewer collapsed near downtown Richmond, the city was forced to pump 11 million gallons of sewage per day until an emergency tunnel could be constructed. Schnabel was an essential part of the project team hired to design and construct the tunnel in just 18 months. Besides the short schedule, the routing and design of the tunnel were further complicated by the presence of a large urban landfill over the majority of the project area.
Schnabel performed the geotechnical investigation to characterize subsurface conditions, which included delineation of the municipal solid waste material. Particular attention was given to the risk associated with tunneling in the waste material, which was impossible to avoid completely. We developed design alternatives and prepared a cost estimate for each. The selected alternative involved a 3,300-foot-long, 12-foot diameter tunnel primarily constructed in a stiff Miocene clay.
Our scope of work included preparation of contract drawings and specifications for the tunnel and NATM shafts. We also provided construction management services, including the review of all tunnel- and shaft-related submittals and evaluation of contractor value engineering proposals.