By Rose Bell
Following a ground-breaking ceremony hosted by DC Water, the building process of the Potomac River Tunnel Project was officially commissioned.
As the next major phase of the DC Clean Rivers Project, Washington DC’s Potomac River Tunnel is DC Water’s ongoing program to improve the water quality of the Anacostia and Potomac rivers and Rock Creek by increasing the capacity of the sewer system.
A large-diameter deep sewer tunnel, diversion facilities, drop shafts, as well as support structures to capture flows from existing combined sewer overflows (CSOs) along the Potomac River and convey them to the Blue Plains Advanced Wastewater Treatment Plant, are the contents of this project. The scheduled date for completion of this 8.9km-long tunnel will be 2030, while providing a 93% reduction in the volume of CSOs to the Potomac River in an average year of rainfall.
Currently, the quantity of estimated CSOs that enters the Potomac River each year by way of average rainfall is 654 million gallons.
Stretching beneath the Georgetown waterfront, along the edge of the National Mall and East Potomac Park, past Hains Point, this 5.5m-diameter tunnel links by gravity to the existing Anacostia River Tunnel. Using two TBMs, construction starts from West Potomac Park, whereas one machine will mine south through mostly soft ground, and another will head north to bore through rock.
The design-build contract was handed to a joint venture of CBNA and Halmar by DC Water in October last year, and the US$819m (€778m) contract is the largest ever awarded by the authority.
The ground breaking ceremony was attended by city leaders and agency partners.
According to DC Water CEO David Gadis: “Today we break ground with a sense of purpose and responsibility. This project is critical to ensure we reduce the CSOs that contribute to water quality impairment of the Potomac. Together we can shape a future where cleaner water flows and the Potomac River thrives as a beacon of environmental vitality.”
