D.C. Water crews are racing to build an emergency bypass system after a major section of a sewer line collapsed late Monday along Clara Barton Parkway in Montgomery County, triggering a significant sanitary sewer overflow into the C&O Canal National Historical Park.
The collapse involves a 72-inch section of the Potomac Interceptor, a 54-mile sewer line that carries roughly 60 million gallons of wastewater a day from communities near Dulles International Airport, Loudoun and Fairfax counties, the towns of Vienna and Herndon, and parts of Montgomery County, to the Blue Plains Advanced Wastewater Treatment Plant for treatment.
Response area video (today) pic.twitter.com/66pUQSp1cn
— DC Water (@dcwater) Jan. 20, 2026
To contain the overflow, D.C. Water is constructing a temporary bypass designed to divert wastewater upstream of the collapse.
The plan says flow will be routed through a dry stretch of the C&O Canal — a temporary channel, then go back into the Potomac Interceptor downstream of the damaged section. Officials say the bypass is critical to stopping additional overflow and protecting the Potomac River and surrounding environment.
Once the bypass is operational and flows are under control, crews will excavate the damaged area to assess the extent of the collapse and determine how long permanent repairs will take.
D.C. Water stresses that the incident does not affect drinking water.
The District’s drinking water system is completely separate from the wastewater system and water service remains safe and uninterrupted.
The overflow is located downstream from the Washington Aqueduct’s intakes at Great Falls, and intakes at Little Falls have also been closed as a precaution.
The collapse is located just east of the I-495 interchange along Clara Barton Parkway, forcing the closure of the right inbound lane.
Drivers heading toward D.C. should expect delays during the morning rush and are encouraged to use alternate routes.
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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