After the collapse of a large-diameter, 80-year-old arch sewer located near downtown Richmond, the Battery Park Trunk Sewer Emergency Tunnel project was born. On a fast-track schedule, the entire 3,300-ft long, 12-ft diameter tunnel project was designed and constructed in only 18 months. Schnabel was an essential part of the team that helped the city get the tunnel project up and running quickly and safely.

The presence of a large urban landfill located above the majority of the project area complicated matters. We performed site reconnaissance, researched historical geotechnical information, and aided in the evaluation of various route alternatives. Our preparation of the geotechnical profiles helped identify the limits of municipal solid waste (MSW) located along the alignment and allowed the development of alternatives that minimized its impact. Two factors demanded particular attention: the effects and risk associated with tunneling in the MSW, which would be impossible to avoid completely, and the ground response to tunneling through the primary host material, a stiff Miocene Clay.

We developed separate cost estimates for each of the major tunnel alignment alternatives proposed and, based on the selected alignment, were responsible for completing the tunnel design. The effort included design of NATM shafts and all required tunnel initial support and final lining, preparation of contract drawings and specifications for the tunnel and shafts, development of the project geotechnical baseline report, and preparation of the Engineer’s Opinion of Probable Cost. During construction, we provided construction management services including review of all shaft and tunneling related submittals, and evaluation of contractor value engineering proposals.