DC Water Investigating Sanitary Sewer Overflow from Potomac Interceptor in Maryland

January 19, 2026
Map of the impacted area.

WASHINGTON, DC — DC Water is investigating a Sanitary Sewer Overflow (SSO) from the Potomac Interceptor (PI) sewer line in C & O Canal National Historical Park in Montgomery County, Maryland. Flow was observed coming out of the PI this evening, and DC Water has mobilized its crews and contractors to mitigate the overflow and keep it contained as much as possible so they can assess the damage and begin repairs.

The damaged pipe is close to the Clara Barton Parkway, just east of the 495 interchange, and workers have closed the right inbound lane as a precaution. Drivers should anticipate delays during the morning rush hour and consider alternate routes. Trails and parking areas along the Parkway may also be impacted. 

The overflow is expected to reach the Potomac River. It is important to note that DC Water's drinking water system is separate from the wastewater system and is NOT affected by the overflow. The overflow is downstream from the Washington Aqueduct’s intakes at Great Falls.

The PI carries about 60 million gallons of wastewater daily from areas near Dulles Airport to the Potomac Pumping Station in the District. Flows from the pump station are then sent to the Blue Plains Advanced Wastewater Treatment Plant for treatment.

Untreated sewage can contain many pathogens causing a variety of illnesses ranging from E. coli to hepatitis. If people come in contact with the untreated overflow, they risk getting sick and bringing these pathogens into their homes; and should take the steps below:

  • Leave the area immediately.
  • Wash exposed skin thoroughly with soap and clean water.
  • Disinfect any affected areas or items.
  • Do not consume food or water that may have been exposed.
  • Seek medical attention if symptoms occur.
  • Report exposure to DC Water at (202) 612-3400.

Residents who live near the impacted area may notice an odor from the overflow. Emergency measures will be taken to prevent further spillage. The extent of the repairs and duration are still being determined. 

If you have additional questions or need information you may contact DC Water’s Customer Care team at (202) 354-3600 (Monday-Friday, 8 a.m. to 5 p.m.) or the 24-Hour Command Center at 202-612-3400.

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DC Water and its contractor have taken significant steps toward repairing the Potomac Interceptor. The repair process currently underway involves reinforcing the damaged section of the pipe using geopolymer. This material is known for its concrete-like strength and durability.

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Repair efforts continue as we reach 23 days in which no overflows have entered the Potomac River. Crews finished pressure washing the pipe upstream of the damaged section of the Potomac Interceptor and preparations are underway for the application of the geopolymer lining to reinforce and strengthen the pipe.

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