Next month DC Water will begin a project in Georgetown to provide the area with separate pipes for stormwater and for sewage. Called sewer separation, it keeps stormwater from entering the combined sewer system, which can overflow during rain events due to the larger volume. The old sewer pipes will carry the stormwater and the new pipes will carry the sewage. Sewer separation is just one component of the plan to mitigate combined sewer overflows to the Potomac River, and is part of the larger Clean Rivers Project that is cleaning up all three waterways in the District.
Due to the age of the Washington DC sewer system, parts of those systems are what is called combined systems where sewer and stormwater are carried through the same pipes. When it rains, untreated sewage and rainwater in the single combined sewage pipe is discharged through what is called a combined sewer outfall into Washington DC’s rivers and creeks. The two outfalls identified in the map below will be converted to stormwater only outfalls.
|from DC Water|
Washington DC conceived agreed to the Clean Rivers Project under a consent order from the Environmental Protection Agency, EPA, to meet new effluent limits for total nitrogen released and better control of the system during rain storms. The Clean Rivers Project is comprised of a system of deep tunnels, sewers and diversion facilities to capture combined sewer overflows and deliver them to DC Water’s Blue Plains Advanced Wastewater Treatment Plant when the capacity is available to treat them.
The Clean Rivers Project was estimated to cost $7.8 billion over 20 years. It includes increased treatment facilities, "diversion facilities" which are the Anacostia River and Potomac River tunnel systems include more than 18 miles of tunnels built more than 100 feet below the ground. At completion the tunnels will be able to store a total of 157 million gallons of sewage until capacity is available at the Blue Plains Advanced Wastewater Treatment Plant for treatment.
DC Water opened the 7-mile-long, 23-foot-wide Anacostia tunnel that runs between RFK Stadium and the Blue Plains Wastewater Treatment Plant on March 20th of 2018. Work continues on the Potomac Tunnel. In addition, Blue Plains treatment capacity was expanded and improved, and green infrastructure added though out Washington DC. In addition to constructing a tunnel, DC Water is using sewer separation to reduce overflows from two of the combined sewer outfalls.
Commenting on the project, DC Water CEO and General Manager David L. Gadis, said, “DC Water’s sewer separation project in Georgetown is an important step in improving the health of the Potomac River. When the Potomac River Tunnel is completed by 2030, these two projects will reduce combined sewer overflows to the river by 92 percent.”
|The Georgetown Waterfront from DC Water|