DC’s new tunnel is keeping billions of gallons of sewage out of the Anacostia

After years of work, the Anacostia River Tunnel is starting to see results. Since the end of construction on the massive tunnel project in March, it has already prevented billions of gallons of sewage from flowing into the Anacostia River.

Once known as “DC’s Forgotten River,” the Anacostia is on track for a comeback. After failing its annual health check for more a decade due to years of underinvestment, the river finally recieved a passing grade of 63 or a “D” in June of this year, up from a score of 49 in 2017. It may even be fishable and swimmable by 2025.

The Anacostia River Tunnel is one phase in DC Water’s Clean Rivers Project, which aims to drastically cut down on the pollution in the area’s waterways. The $2.6 billion project has been going on since the 1990s, and the completion of the Anacostia River Tunnel is a major milestone in returning the region’s rivers back to health.

The District’s aging water infrastructure includes large segments of combined sewers. In events of heavy rain, storm water will collect in these sewers until they start to overflow, dumping large amounts of untreated sewage into local rivers.

The longterm benefits of the Clean Water project include preventing 96% of District-wide overflows and reducing one million pounds of nitrogen from flowing into the Chesapeake Bay.

The scope of the construction to make this all happen is spectacular. The diameter of the new tunnel is 23 feet, and it runs 80 to 120 feet below the surface. Boring the tunnel required a 26-foot diameter machine named ‘Nannie’ after Nannie Helen Burroughs as well as a joint American-Italian team of workers who mined for more than a year.

The Anacostia River Tunnel itself is 2.3 miles long, running from RFK Stadium to Poplar Point. It collects combined sewer overflows that would otherwise dump into the river. It then transports the sewage to the Blue Plains Advanced Wastewater Treatment plant.

Because of the Anacostia River’s years of neglect and the Chesapeake Bay’s high level of pollution, there is still much work to be done to return these bodies of water to good condition. By the time it is complete, the Clean Water Project will have more than 18 miles of tunnel, including the future Northeast Boundary Tunnel and the Potomac River Tunnel.

Eventually, the new tunnel should reduce combined sewage overflows into the Anacostia by around 80%. This has been particularly important this summer. DC has had a number of heavy rains, and the tunnel has already prevented billions of gallons of resulting sewage from reaching the river.