DC Water begins major Potomac River tunnel excavation near Watergate

(UI) — DC Water is set to launch major excavation and drilling work this month on the Potomac River Tunnel Project, part of a sweeping effort to reduce combined sewer overflows into the river during heavy storms.

According to DC Water, the first visible construction activities begin around July 23, 2025, near the Rock Creek Trail west of the Watergate complex. Crews will connect utilities and prepare the site for a deep drop shaft and tunnel support structures.

SEE ALSO: DC Water's Potomac River Tunnel Project to begin controlled underground blasting

The project involves drilling large concrete secant piles to stabilize soil and control groundwater as excavation progresses nearly 110 feet underground. The shaft’s 45-foot diameter is roughly wide enough to fit 72 shipping containers stacked in a circle.

Traffic impacts will include temporary lane closures along Rock Creek and Potomac Parkway NW between Virginia Avenue NW and F Street NW during weekday work hours. A new segment of the Rock Creek Trail will open to reroute pedestrians and cyclists safely around the construction zone.

“This tunnel will capture and store stormwater and sewage that would otherwise overflow into the Potomac,” DC Water stated. “When complete, it will cut overflows by 93%, reducing incidents from roughly 74 times a year to just four.”

The Potomac River Tunnel is part of DC Water’s broader Clean Rivers Project, which complies with a federal consent decree requiring long-term solutions for combined sewer overflows. Once operational, the tunnel will divert excess water to the Blue Plains Advanced Wastewater Treatment Plant for processing.

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