DC Water’s New Anacostia River Tunnel Passes First Major Test

Earlier this week, as heavy rains battered the District of Columbia, DC Water’s newly opened Anacostia River Tunnel System prevented approximately 170 million gallons of combined sewage and stormwater from being discharged to the Anacostia River.

DC Water placed into operation the first section of the Anacostia River Tunnel System, from RFK Stadium to the Blue Plains Advanced Wastewater Treatment Plant, in late March. This portion of the system includes a 7 mile, 23-foot tunnel that can store more than 100 million gallons, while continuously processing another 225 million gallons per day at the new Wet Weather Treatment Facility at Blue Plains.

“In its first real test, the new tunnel system worked as designed, storing – then treating—millions of gallons of combined sewage that otherwise would have overflowed to the river,” Henderson Brown, DC Water’s Interim CEO and General Manager, said. “That is great news for the Anacostia, and it will only get better when the rest of the tunnel system is brought online.”

During the storm the new tunnel filled to capacity.  Based upon preliminary data analysis, the flow exceeded the tunnel capacity by between 10 and 20 million gallons, which overflowed to the Anacostia River.  The next portion of the Anacostia River Tunnel system, the Northeast Boundary Tunnel, now under construction, will add approximately 90 million gallons of storage when it is placed into service in 2023.

Once the Anacostia Tunnel System is completed it will capture 98 percent of combined sewer overflows in an average year.