DC Water has received the go-ahead to build the Piney Branch Tunnel after the National Park Service (NPS) completed an environmental assessment.
The project, on NPS land in Rock Creek Park, will improve water quality and reduce combined sewer overflows to the Piney Branch and Rock Creek.
The tunnel is part of DC Water’s Clean Rivers initiative to improve water quality in the Anacostia River, Potomac River, and Chesapeake Bay watershed.
The 4.2 million-gallon underground storage facility will capture stormwater and untreated sewage during heavy rain, holding it until the overflow can be released back into the system during low flow periods and treated at the Blue Plains Advanced Wastewater Treatment Facility.
The project is expected to reduce the volume of sewage overflows by 96%, reducing pollution in Piney Branch, Rock Creek, and downstream areas including the Potomac River and Chesapeake Bay. The tunnel will also cut down on the frequency of sewer overflow events, from 25 in a year of average rainfall to just once.
Design work is under way for the tunnel project, and construction is expected to start next year. The tunnel is scheduled to be operational by 2029, and all restoration work and other project related improvements finished by 2030.
DC Water’s Clean Rivers initiative is a US$2.7bn project to construct 29km of tunnels to divert sewage overflows and improve water quality.
In May last year, construction started on the Potomac[https://www.tunnelsandtunnelling.com/news/potomac-river-tunnel-construction-commences/?cf-view] River Tunnel. The US$819m (€778m) contract – awarded to CBNA and Halmar – is the largest ever undertaken by DC Water.
