The DC Water Board of Directors announced the approval of a design-build contract for construction of the Potomac River Tunnel (PRT). The $819 million contract is the largest ever awarded by the Authority. The 8.8-km (5.5-mile) long tunnel will control combined sewer overflows (CSOs) to the Potomac River, improving water quality in this critical natural resource. This work is part of the larger Clean Rivers Project, a $2.99 billion program to improve the water quality of the Anacostia and Potomac rivers and Rock Creek by increasing the capacity of the sewer system.
A joint venture of CBNA and Halmar was selected based on its lowest price proposal and second highest technical score, therefore providing the best value.
“We do not take these decisions lightly. This is a huge investment of ratepayer funds, but one we know will pay great dividends for the District of Columbia, the Potomac River and everyone who lives, works, and plays on this great waterway. It will also help mitigate the growing impacts of climate change on the nation’s capital,” Board Chair Tommy Wells said in a statement.
The 5.4-m (18-ft) diameter tunnel will run deep underground beneath the Georgetown waterfront, along the edge of the National Mall and East Potomac Park, past Hains Point and connect by gravity to the existing Anacostia River Tunnel. Construction will require two tunnel boring machines. Starting from West Potomac Park, one machine will mine south through mostly soft ground, and another machine will head north to bore through rock.
Work on the project is expected to begin in 2024 with completion in early 2030, in accordance with the schedule stipulated in the Consent Decree DC Water signed in 2005 with the U.S. Environmental Protection Agency, the Department of Justice, and the District of Columbia. Once the PRT is operational, it will reduce combined sewer overflows (CSOs) to the Potomac River by 93 percent 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.”
The Clean Rivers Project is DC Water’s ongoing program to reduce combined sewer overflows (CSO’s) into the District’s waterways – the Anacostia and Potomac Rivers and Rock Creek. The Project is a massive infrastructure and support program designed to capture and clean wastewater during rainfalls before it ever reaches our rivers. The project also includes improving the capacity of the system to mitigate chronic flooding that has plagued some areas of the District since the early 1900s.
The Clean Rivers Project is comprised of a system of deep tunnels, sewers, and diversion facilities to capture CSO’s and deliver them to DC Water’s Blue Plains Advanced Wastewater Treatment Plant. The Clean Rivers Project is also installing Green Infrastructure or “GI” to assist with the reduction of CSO’s to the Potomac River and Rock Creek. The Anacostia River and Potomac River tunnel systems include more than 29 km (18 miles) of tunnels that are larger than the Metro tunnels and are constructed more than 30 m (100 ft) below the ground.