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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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Excavators in the canal digging up soil and another excavator removing the soil to a dump truck to be hauled away

DC Water and its contractor have made significant progress on soil removal, reaching the clay liner between locks 13 and 14 of the C & O Canal, which was used as a bypass for wastewater during the Potomac Interceptor repairs.

Work continues to remove sludge between locks 10 and 13, which is expected to be completed by mid- to late-April. The soil will then be removed down to the clay liner as the final step, and the canal reconstructed to meet National Park Service specifications.

Soil Removal Underway with Excavator in Canal

Today, DC Water and its contractors began removing contaminated soil between locks 13 and 14 in the C & O Canal, which was used as a temporary bypass during the Potomac Interceptor repair effort. Clean-up efforts are ongoing at Lock 10 with work to remove sludge now getting underway between locks 11 and 13.

Aerial shot of Blue Plains Advanced Wastewater Treatement Plant

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Monday 9:00 AM

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Map of lane closure
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Tuesday, 9:30 AM

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Payment Plan Incentive: provides a credit back of 50% of the last 3 payments made. Eligible participants are residential customers who have had an outstanding balance for 60 days or greater and with an outstanding balance of $500 or more.