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The Anacostia River Tunnel Project in Washington, D.C., has won an international tunneling award.
The project, designed to prevent raw sewage from overflowing into the river, was named the Sustainability Initiative of the Year by the International Tunneling and Underground Space Association (ITA). The ITA presented nine tunneling awards, with the Anacostia tunnel the only U.S. winner.
The 2.4-mile tunnel was completed in November 2016 as the second of four sewage-overflow tunnels. DC Water, the city’s sewer and water service, is also building surface facilities that will divert overflow sewage to the tunnels instead of into the river. The tunnel is connected to the overflow sewers by 90-foot-deep shafts that are 20 to 60 feet wide. The sewage will travel through the tunnels to a treatment plant, where it will be treated and then pumped into the Potomac River.
“The construction of these facilities is unparalleled in the District,” says DC Water’s website. “Not since the construction of the original sewer system in the early 1900s and the Metro has the District seen construction of this magnitude.”
The tunnel has a design life of at least 100 years, according to an ITA press release, adding that it “was excavated in an urban setting with minimum impact to the environment and the surrounding community.”
The tunnel was excavated by a 26-foot-diameter boring machine called “Nannie,” named after famous District educator Nannie Helen Burroughs. The machine, which mined under sensitive structures and through stiff clay, finished the job in 373 days, according to DC Water. Nannie joins Lady Bird, a boring machine named after Lady Bird Johnson that completed digging a 4.5-mile section of the tunnel system in 2015.
The tunnel is part of the first phase of DC Water’s ongoing Clean Rivers program to reduce sewage overflows into the Anacostia, Potomac and Rock Creek. The phase is scheduled to be completed in March and reduce sewage overflows in the Anacostia by 81 percent, DC Water says.
Other tunnel project ITA award recipients include: