DC Water Just Finished Digging A 5-Mile Tunnel 100 Feet Below The City The tunnel will help make the Anacostia River safe to swim and fish in.
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DC Water Just Finished Digging A 5-Mile Tunnel 100 Feet Below The City

An underwater view of the front of tunnel boring machine, Chris, as it breaks through into a vertical shaft filled with water. Courtesy of DC Water/ hide caption

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Courtesy of DC Water/

Chris has been underground since 2018, diligently digging, starting at RFK Stadium and slowly moving northwest. Now, Chris's work is complete — a 5-mile long, 23-ft. wide tunnel that will soon prevent sewage overflows into the Anacostia River and stop flooding in low-lying neighborhoods, including Le Droit Park and Bloomingdale.

Chris is a massive tunnel boring machine, longer than a football field, that simultaneously digs the tunnel and constructs its concrete walls, all 100 feet below ground. The tunnel runs underneath Metro's tunnels (and everything else humans have built underground) and is wider than a Metro tunnel, too.

"It's amazing accomplishment," says Carlton Ray, vice president of DC Water's Clean Rivers Project. The project aims to build 18 miles of such tunnels, capturing sewage overflow that would otherwise flow into the Anacostia, the Potomac, and Rock Creek. This sewage overflow is a result of D.C.'s antiquated sewer system, and one of the major reasons the city's water bodies are too polluted to swim or fish in.

"The federal government left D.C. this undersized sewer system that basically when it rains, we have raw sewage or combined sewage overflows into the river," Ray says. "We're capturing that that sewage and ultimately are going to make the Anacostia River fishable and swimmable."

Chris, the tunnel boring machine, at a ceremony in 2018 before being lowered into the earth. Jacob Fenston/WAMU/DCist hide caption

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Jacob Fenston/WAMU/DCist

When the new tunnel is in operation — anticipated in the summer of 2023 — it will divert sewage and stormwater to the sewage treatment plant at Blue Plains, at the southern tip of the District. There, the overflow can be treated and discharged into the Potomac River. The $2.7 billion project is expected to prevent 98% of sewage overflows into the Anacostia.

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Prior to starting work on the project, D.C's century-old combined sewer system overflowed into the city's rivers 75 times a year on average, dumping more than 3 billion gallons of sewage mixed with rainwater. The first tunnels to prevent overflow in the Anacostia went online in March, 2018, and have so far prevented 89% of overflows.

The new tunnel will also reduce flooding in the neighborhoods it serves by between 7% and 50% in any given year, according to DC Water.

The 650-ton tunnel boring machine was christened at a ceremony in June, 2018, before being lowered into a shaft near RFK Stadium to begin digging. The machine was named after Christopher Allen, a DC Water official who oversaw the Clean Rivers Project prior to his death in 2017.

From RFK, Chris proceeded roughly 50 ft. a day, under the vacant asphalt surrounding the stadium, under the cleats of soccer players in the Fields north of RFK, under the golfers on the Langston course, under the roots of the Azalea Collection at the National Arboretum, under Mt. Olivet Rd. through Trinidad and Ivy City, under commuters stuck in traffic on New York Ave., under the train cars at Amtrak's Ivy City rail yard, under the Rhode Island Ave. Metro Station, under Brentwood, Eckington, and Bloomingdale, before finally arriving at the intersection of 6th and R St. NW.

Upon finishing mining and building the tunnel, Chris's final task was to break through into a 50 ft. wide shaft filled with water, connecting the 5 mile tunnel to DC Water's construction site in what used to be a small triangle park at the intersection of 6th St., R St. and Rhode Island Ave. The shaft's gaping mouth is visible in satellite imagery.

The new tunnel, known as the Northeast Boundary Tunnel, is the biggest piece of the Clean Rivers Project, and there is still a fair amount of work to be done before it can be put in operation. For one thing, DC Water has to remove Chris, which will now be unceremoniously dismantled and hauled out by crane. The tunnel also needs to be connected to the existing sewer system, via a series of shafts and smaller tunnels.

The Clean Rivers Project, which DC Water plans to complete by 2030, was a long time coming: D.C.'s rivers have been used to dump sewage since the city was founded. Sewer pipes were installed starting in the late 1800s, but they served only to conduct sewage out of homes and directly into the rivers. There was no sewage treatment whatsoever until 1938, when the Blue Plains facility was built.

Over the decades, many studies were conducted to fix the sewage overflow problem, but over and over, they were rejected or never implemented due to cost. Finally, in the late '90s, the Anacostia Watershed Society filed a lawsuit and in 2002, DC Water and the Environmental Protection Agency agreed to the plan to fix the sewer overflow problem.

Construction on the next major phase of the Clean Rivers Project, the Potomac River Tunnel, is expected to begin in 2023.

This story is from DCist.com, the local news website of WAMU.

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