On January 19, 2026, DC Water workers discovered a Sanitary Sewer Overflow (SSO) from the Potomac Interceptor (PI) sewer line in C & O Canal National Historical Park in Montgomery County, Maryland.
A break in a 72 inch diameter sewer pipe caused wastewater to spill into a creek bed leading to the Potomac River. The sewer overflow entered the Potomac River downstream from the Washington DC Aqueduct’s water intakes at Great Falls.
The PI carries about 60 million gallons of wastewater daily from areas near Dulles Airport to the Potomac Pumping Station. The pipe rupture occurred near the Clara Barton Parkway, just east of the 495 interchange.
Containment Efforts
After identifying the source of the overflow, DC Water mobilized its crews and contractors to mitigate the overflow, assess the damage, and begin repairs.
In response, DC Water developed a plan to build the temporary bypass system. Crews began clearing access, installing pipes, coordinating with the National Park Service to adjust canal structures, and setting up pumps to redirect the flow into a contained section of the C & O Canal and then rerouted into the sewer pipe further downstream.
The upper lock gates at Locks 11, 12, and 13 on the Canal were removed, allowing wastewater to flow downstream, and eventually pumped back into the sewer pipe.
On January 24, DC Water completed a bypass to reroute wastewater around the collapsed section of pipe and back into the sewer system.
During work, the Washington, DC region was hit with a major winter storm. Efforts to control wastewater flows were impacted hampered by significant snowfalls, high winds, and bitter cold temperatures,
In early February, additional wastewater overflows occurred at the pipe failure site. DC Water attributed the overflows to increased flow from groundwater infiltration attributed to snowmelt, along with periodic clogging of the bypass pumps.
Crews began constructing an earthen dam in the nearby stormwater ditch to contain minor overflows. Workers also discovered large boulders and rocks inside the pipe which were restricting flow.
Shellfish Closures
On January 25, MDE issued a shellfish closure of Maryland shellfish growing areas from the spill location to the Harry W. Nice (Dahlgren) Bridge (Route 301).
The closure includes the Potomac River from Charles County and bordering Virginia areas, extending from the Port Tobacco River region down to the Harry W. Nice (Dahlgren) Bridge (Route 301).
Potomac River Recreational Water Advisory
On February 13, the Virginia Department of Health (VDH) issued a recreational water advisory for Virginia residents.
VDH advised Virginia residents to avoid recreational water activities in the Potomac River, such as swimming, wading, tubing, white-water canoeing or kayaking, where full-body submersion is more likely to occur.
The advisory area extends for 72.5 miles from the American Legion Memorial Bridge (I-495) in Fairfax County to the Governor Harry W. Nice Memorial Bridge (Route 301) in King George County.
Updates on the ongoing advisory can be found on the VDH website.
Potomac Interceptor Project
DC Water is in the process of rehabilitating the Potomac Interceptor, as part of a 10-year, $625 million high priority project in the Authority’s Capital Improvement Program. The project will rehabilitate the most vulnerable sections in the aging sewer line, which is more than 60-years old.
source: DC Water
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