Project Value: $147M

The North Dorchester Bay CSO Tunnel is designed to temporarily hold up to 19-million gallons of combined sewer and storm water overflows caused by heavy rainfall. Barletta completed near surface structures, piping, and conduits to separate the sewer systems along the route of the CSO tunnel. Seven (7) CSO structures were constructed to intercept the existing CSO sewer flows and divert flows to the newly constructed tunnels. A 350-ton custom-built tunnel boring machine drilled and lined a two mile long, 20-foot diameter tunnel through glacial outwash sands and Boston Blue Clay at depths of 30 to 50 feet below K Street, Columbia Road, Day Boulevard, and the M Street, L Street, and Carson public beaches in South Boston. The mining and lining of the tunnel was completed 6 months ahead of schedule.