Crews began work Monday to rehabilitate a deteriorating 1,700-foot stretch of the regional Potomac Interceptor sewer line.

Last week, D.C. Water announced that inspections determined a portion of the Interceptor, located near Lock 22 on the C&O Canal, in Potomac, Maryland, was significantly corroded and had exposed and missing rebar inside the pipe.

Monday morning crews began laying what will be temporary overground bypass system to carry the Interceptor’s wastewater around the work site, while the compromised pipe is being replaced. A spill near the location of the emergency work could threaten much of the local drinking water supply.

The January 2026 collapse of the Interceptor along the Clara Barton Parkway, which spilled more than 240 million gallons of wastewater into the Potomac River, happened downstream of the drinking water intakes for all three local water suppliers — Washington Aqueduct, WSSC Water and Fairfax Water

However, if a spill occurred near Lock 22, that would jeopardize the drinking water intakes for WSSC Water and Washington Aqueduct. Fairfax Water’s intake is farther up river, and would not be affected.

D.C. Water expects the emergency work to last through September.