The US$819m (€778m) contract – the largest ever awarded by the authority – covers construction of an 8.9km tunnel to control combined sewer overflows (CSOs) to the Potomac River in the US capital. It is part of the larger Clean Rivers Project, a US$2.99bn (€2.84bn) programme to improve the water quality of the Anacostia and Potomac rivers and Rock Creek by increasing the capacity of the sewer system.
The Anacostia River and Potomac River tunnel systems include more than 29km of tunnels.
The 5.5m-diameter Potomac River Tunnel will run beneath the Georgetown waterfront and connect by gravity to the existing Anacostia River Tunnel. Construction will require two TBMs. One will be launched from West Potomac Park to mine south through mostly soft ground; the other will head north to bore through rock.
Work on the project is expected to begin next year, with completion in early 2030. Once in operation, the scheme will reduce the volume of CSOs to the Potomac River by 93% and the number of CSOs from around 74 to four in an average year of rainfall.
“The Clean Rivers Project is a gamechanger for the District,” said DC Water CEO and general manager David L Gadis. “We have already seen the impact the completed Anacostia River tunnel system is having on the health of that river, and we expect similar results for the Potomac as a result of this project.”
