Six days after a massive sewage spill into the Potomac River upstream of the District of Columbia, the city’s water utility, DC Water, announced that the overflow was “nearing full containment.” The spill, which sent hundreds of millions of gallons of untreated wastewater into the river, was caused by the Jan. 19 collapse of an aging six-foot-diameter sewage pipe between the river and the Clara Barton Parkway, just east of Interstate 495.
A repair timeline has yet to be determined as crews conduct additional tests and confirm the extent of the damage. An estimated 40 million gallons of wastewater entered the river and a nearby small tributary each day before the spill was contained.
The damaged section is along the Potomac Interceptor (PI) line, a 54-mile long sewer pipe running from near Dulles Airport to the Blue Plains Advanced Wastewater Treatment Plant in southeast DC. Crews have installed six bypass pumps along the line to reroute wastewater — first to a dry section of the Chesapeake & Ohio Canal and then back into the interceptor line 4 miles further downstream.
John Lisle, DC Water’s vice president of marketing and communications, said each of the pumps is capable of moving seven million gallons a day out of the Potomac Interceptor. The bypass pumps were turned on late in the day January 25.
Potomac Riverkeeper Dean Naujoks said that proper maintenance would have prevented this disaster, which he called “one of the largest sewage spills in U.S. history [and] one of the most disturbing things I have ever seen in 25 years as a Riverkeeper.”
“DC Water needs to come up with a better plan than using a 100-year-old dry canal ditch to capture and contain future sewage releases,” Naujoks said in a Jan. 26 press release from the Potomac Riverkeeper Network.
“Infrastructure failure is at the root of this disaster,” he said. “[A] six-foot-diameter sewage interceptor pipe located this close to the river should have been better maintained in order to avoid this catastrophe.”
Since September 2025, this particular section of sewer line has been undergoing a nearly $10 million rehabilitation, expected to be finished this spring. It is a part of an ongoing $625 million upgrade of the entire line, funded by the District of Columbia’s Capital Improvement Program.
Most of the emergency repairs were accomplished before the arrival of the winter storm that affected much of the country over the Jan. 24-25 weekend. The accumulation of snow and ice, worsened by bitter-cold air, complicated post-storm operations more than initially anticipated, according to DC Water — which had to bring in more backup pumps than might otherwise have been required to help offset shutdowns caused by round-the-clock freezing temperatures.
“We’ve been working as we would even if there wasn’t a storm coming,” Lisle said prior to the storm. “We have the pieces in place to plow the work area and get equipment to and from the site.”
Currently, the affected areas will need to be pumped and excavated to determine the extent of damage to the pipe. Lisle expects some initial difficulties due to the high volume of redirected wastewater but has been reassured by on-site engineers that the downstream pumps — where the water reenters the interceptor — can handle the additional flow.
At this point, the exact cause of the collapse is undetermined. DC Water, the Maryland Department of the Environment, the DC Department of the Environment, the U.S. Environmental Protection Agency and other relevant agencies spent the days immediately after the rupture getting the leak contained and running assessments.
The Potomac Riverkeeper Network ran its own assessments Friday and concluded that E. coli levels were thousands of times higher than the limit for human contact.
Naujoks and other Riverkeeper volunteers collected samples and tested for E. coli contamination in several places on the river. Near the spill they found those bacteria counts many thousands of times higher than the safety threshold for human contact.
“These measurements of E. coli bacteria show contamination which is nearly 12,000 times what authorities limit for human contact,” Potomac Riverkeeper Network president Betsy Nicholas said in the organization’s Jan. 26 press release. “And so far, almost 300 million gallons have entered the Potomac River.”
Samples taken upstream of the spill, meanwhile, were well within safe limits for human contact. The potential impact of this released wastewater is unknown.
Officials say people in the vicinity of the spill likely have experienced unpleasant odors and are encouraged to avoid the affected areas. Individuals who come into contact with untreated wastewater are encouraged to seek medical attention.
“Raw sewage is not only harmful to humans, but it can harm the environment through excessive nutrients, toxic contaminants and disease exposure,” Naujoks said. “This can lead to dead zones in the river, harmful algal blooms and fish kills.”
DC Water emphasized that drinking water is unaffected by this leak. The Little Falls drinking water intakes downstream of the spill were closed, Lisle said, and the utility is drawing water only from the unaffected Great Falls intakes upstream.
As crews try to fully contain the wastewater in the wake of the winter storm, Nicholas and the Potomac Riverkeeper Network look ahead with concern.
“The long-term impact cannot be overstated,” Nicholas said.
