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.
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, the Washington, DC region was hit with a major winter storm which impacted efforts to contain the spill and repair the damaged infrastucture.
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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