Drinking Water for WSSC Water Customers Not Impacted by DC Water Sewer Main Collapse

Read DC Water's Latest Updates on the Potomac Interceptor Collapse and Cleanup

• What is the Potomac Interceptor?
• What Happened?
• Is Drinking Water Safe?
• Is DC Water Performing Water Quality Testing of the Potomac River?
• How is WSSC Water Involved?
• What's Next?
• Briefing for the WSSC Water Commissioners
• Downloadable Fact Sheets

What is the Potomac Interceptor?

• The Potomac Interceptor is a 54-mile-long regional sanitary sewer pipeline with two river crossings and was constructed in the early 1960s by an Act of Congress.
• DC Water owns, operates and maintains this pipeline. DC Water is primarily overseen by the U.S. Environmental Protection Agency (EPA), which enforces federal drinking water and wastewater standards. Locally, the DC Department of Energy and Environment (DOEE) monitors environmental impacts.
• The interceptor line, about 60 years old, carries about 60 million gallons of wastewater daily from a 376 square-mile service area, which includes: Loudoun and Fairfax counties, areas near Washington Dulles International Airport, Vienna, Herndon and portions of Montgomery County to DC Water’s Blue Plains Advanced Wastewater Treatment Plant.

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What Happened?

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• A section of the Potomac Interceptor collapsed on Monday, January 19, 2026, along Clara Barton Parkway and the I-495 interchange in Montgomery County, causing a sanitary sewer overflow in the C&O Canal National Historical Park that entered the Potomac River.
• 194 million gallons overflowed before bypass pumps activated (first 5 days) and there have been approximately 243 million gallons total overflow since the incident began.
• This section carries wastewater from Loudoun and Fairfax counties in Virginia and parts of Montgomery County to DC Water’s Blue Plains Advanced Wastewater Treatment Plant.
• DC Water mobilized to install a bypass pumping system to reroute wastewater flows around the collapsed section. The bypass was activated on January 24.

Is Drinking Water Safe?

Yes! WSSC Water’s drinking water is safe and is not affected by this incident. 

The drinking water we provide to most of our customers comes from the Potomac Water Filtration Plant (WFP) in Potomac, Maryland, which is located well north of the collapsed pipe. 

We created the following video to show customers the location of our Potomac WFP in relation to Potomac Interceptor collapse. 

WSSC Water continuously monitors water quality at our WFPs and will continue to monitor sampling data for the northernmost testing site monitored by Maryland Department of the Environment.

Is DC Water Performing Water Quality Testing of the Potomac River? 

• DC Water and DOEE are performing water quality testing in the river, including around the overflow area as well as upstream and downstream sites.
• DC Water is publishing their testing results on their Potomac Interceptor Collapse webpage.
• DOEE is publishing their testing results on their Potomac Interceptor Update and FAQs page.
• Additionally, the Maryland Department of the Environment is also posting test results and FAQs on their Potomac Interceptor Sewer Overflow webpage.

How is WSSC Water Involved? 

• WSSC Water is the water and wastewater utility serving most of Montgomery and Prince George’s counties.
• DC Water provides wastewater services to WSSC Water and our service area under a longstanding multi-jurisdictional agreement. Under this agreement, WSSC Water contributes to the costs associated with construction work on the Potomac Interceptor based on wastewater flow. That framework includes costs associated with emergency repairs.
• For this segment of the interceptor, WSSC Water’s current cost share is 30.9 percent, with a portion of that share allocated to and paid for by the City of Rockville at 15.87 percent.
• Repair costs to the jurisdictions served by this pipeline should be reduced if DC Water receives federal funding for this emergency.

What's Next? 

• DC Water estimates it will take several weeks to clear a blockage in the pipe and another nine months for permanent repairs.
• According to DC Water, they are developing an Environmental Restoration Plan in conjunction with federal, state and local regulators.
• EPA Administrator Lee Zeldin has visited the Potomac Interceptor collapse site and EPA continues to monitor the repair and remediation work.
• The Metropolitan Washington Council of Governments also provides a collection of regularly updated sewer pipeline collapse information and resources. 

Briefing for WSSC Water Commissioners 

The following information was presented to WSSC Water's Commissioners as part of our February 18, 2026, monthly meeting. 

Downloadable Fact Sheets

• Information from WSSC Water on the Potomac Interceptor Collapse 
  (PDF 618 KB)
• Potomac Interceptor: Segment Details & Multi-Jurisdictional Agreement 
  (PDF 125 KB)