Potomac River Tunnel project enters construction phase beneath Washington, D.C.
(UI) — DC Water has launched tunneling work for the 5.5-mile Potomac River Tunnel Project, a key component of the District’s Clean Rivers Program designed to capture and treat combined sewage and stormwater overflows.
The milestone was marked by a ceremonial “blessing” of Mary, the tunnel boring machine (TBM) that will dig the tunnel’s northern leg. The event, held at West Potomac Park, featured Mayor Muriel Bowser, who symbolically blessed the TBM with DC tap water before it begins boring beneath the Potomac River.
“The DC Clean Rivers Program plays such an important role in ensuring that we are the safe, clean and beautiful city that we are today,” said Bowser. “Whenever you make this type of investment in world-class infrastructure, that’s an investment in our collective future, it’s an investment in safe neighborhoods and clean, swimmable waterways, and it’s an investment in our position as a beautiful waterfront city."
The TBM is named after abolitionist Mary Edmonson, who, with her sister Emily, attempted a daring escape from slavery via the Potomac in 1848. Her sister TBM, Emily, is expected to arrive later this year to construct the tunnel’s southern leg. Together, the machines will excavate twin drives to intercept nearly one billion gallons of combined sewage and stormwater each year, dramatically reducing pollution in the Potomac River.
“Today we celebrate not just a machine, but a movement,” said David L. Gadis, DC Water’s CEO and general manager. “The Clean Rivers Program has been a game-changer for our city. We’ve watched the Anacostia River come back to life, and now, with Mary leading the way, we’re turning our focus to the Potomac. This tunnel is one of the final pieces of a legacy that will leave our rivers cleaner, our communities healthier, and our future brighter.”
Following the ceremony, attendees toured the launch shaft — about 100 feet deep — where Mary will begin excavation. The tunnel will carry stormwater and wastewater to DC Water’s Blue Plains Advanced Wastewater Treatment Plant.
Once completed in 2030, the Potomac River Tunnel will cut overflow events from 74 to just four per year and reduce overflow volume by 93%.
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