The tunnel is part of RiverRenew, an initiative to reduce CSOs. The proposed sewer will be 2 miles (3.2km) long with a 19ft (5.8m) outside diameter (12ft inner), approximately 100ft (30m) below ground in primarily Potomac clay.
According to the environmental assessment tunnelling would take two and a half years. Price estimates are USD 370M to USD 555M, based on a conceptual level of design.
