Federal officials say emergency environmental remediation tied to the collapse of the Potomac Interceptor sewer line has now been completed, marking a major milestone nearly four months after more than 200 million gallons of raw sewage spilled into the Potomac River.
The U.S. Environmental Protection Agency (EPA) announced May 6 that it has fully demobilized its onsite federal response after restoring the area to what officials described as pre-collapse conditions. The effort followed the January 19 collapse of a section of the interceptor line, which triggered health advisories and shellfish harvesting restrictions downstream.
Wastewater flow was restored to the Potomac Interceptor on March 14, a week ahead of schedule, allowing response efforts to shift toward environmental cleanup and restoration.
The remediation effort was led by the EPA in coordination with the Federal Emergency Management Agency, U.S. Army Corps of Engineers, National Park Service and other federal partners.
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Cleanup activities included water and soil sampling, removal of sewage-impacted soils and contaminated materials, erosion control measures, debris removal and flushing the C&O Canal with fresh water from the Potomac River.
DC Water continues targeted soil remediation work between Locks 10 and 11 of the C&O Canal, with completion expected by the end of May.
The National Park Service previously issued a special use permit allowing DC Water to proceed with environmental restoration following the collapse. During repairs, the C&O Canal was temporarily used as a bypass system for up to two billion gallons of wastewater.
According to DC Water, the first phase of comprehensive restoration work is expected to be substantially complete by late summer 2026. Current efforts remain focused on removing remaining affected soil from the canal area.
“We understand just how important transparency is for our customers and the community, and ensuring our decisions are guided by science,” said Matthew Brown, chief operating officer at DC Water. “After analyzing hundreds of our own samples along with extensive sampling by others, it is clear that Potomac River water quality is back to how it was before the incident.”
To supplement daily monitoring at 10 sampling sites, crews also conducted intensive weekend sampling at high-use recreational areas along the river corridor.
A second phase of restoration work is expected to continue through the fall and will include replanting native vegetation, restoring wetlands and natural hydrology, repairing the canal’s clay liner, adding topsoil and restoring structural canal features.
