WASHINGTON — Independent water sampling by the Potomac Riverkeeper Network (PRKN) and University of Maryland researchers has detected elevated fecal bacteria and pathogens in the Potomac River following a January sewage overflow from a collapsed DC Water sewer line near Lock 10, prompting calls for immediate public health advisories from authorities in the District of Columbia, Maryland, and Virginia.
The contamination stems from a January 19, 2026, collapse of a section of the Potomac Interceptor, a 54-mile sanitary sewer line operated by DC Water. The 72-inch pipe, carrying roughly 60 million gallons of wastewater daily from areas including parts of Virginia and Montgomery County, Maryland, to the Blue Plains Advanced Wastewater Treatment Plant, ruptured along Clara Barton Parkway in Montgomery County near the C&O Canal National Historical Park and Interstate 495 interchange.
DC Water estimates approximately 243 million gallons of untreated wastewater overflowed before interim bypass pumping significantly reduced flows, with the majority—about 194 million gallons—occurring in the first five days. Bypass operations began around January 24, and no overflows were reported at the site on some days in early February, though minor residual risks persist during ongoing repairs complicated by a large rock blockage discovered in the damaged pipe. Full repairs could take additional weeks or months.
PRKN President Betsy Nicholas highlighted the severity in a February 5 announcement: “Raw sewage from a 60-year-old pipe has vomited roughly 300 million gallons into the Potomac River and is still not fully contained. Water testing collected nine days after the start of the disaster by PRKN and University of Maryland scientists still shows fecal bacteria levels more than 2,700 times the safe limit established by Maryland and Virginia. We are long past the time for DC authorities to issue a public health warning for recreational use. People want to know if the river is safe. Right now, the Potomac River is not safe!”
Potomac Riverkeeper Dean Naujoks detailed January 28 sampling at nine sites: E. coli at the Lock 10 effluent reached 2,731 times the 410 MPN/100 mL recreational safety limit used by Maryland and Virginia. Contamination extended about 10 miles downstream to Thompson Boat House along the D.C. waterfront, with levels 2 to 59 times above the limit.
February 3 sampling showed worsening conditions at some points, with E. coli at Lock 10 at 4,227 times the safety limit—higher than the January 28 results—and elevated levels persisting 3.6 miles downstream toward Lock 5 and Little Falls. Naujoks noted DC Water’s February 4 statement acknowledging “overflow risks remain” and “slight increases in coliform levels near Lock 10,” contrasting it with PRKN/UMD data showing far more significant contamination.
Preliminary modeling from the Maryland Department of the Environment indicates potential impacts more than 30 miles downstream to Quantico Creek. Maryland issued a shellfish harvesting closure over 50 miles downriver, affecting communities reliant on the river.
Testing also detected Staphylococcus aureus (causing staph infections) and MRSA (an antibiotic-resistant strain) at Lock 10, with S. aureus present at one-third of downstream sites. Naujoks said: “This discovery even more urgently requires a public health advisory from DC and Maryland officials – they must inform the residents about the grave risks to public health from this sewage spill.”
No recreational use advisory has been issued by D.C., Maryland, or Virginia despite public inquiries about fishing, polar bear plunges, and other activities. Nicholas concluded: “At a time when faith in our leaders is dishearteningly low, the wholly insufficient response by the DC government at all levels only adds to that loss of faith. Our conscience should be shocked when we remember that what is at risk here is public health – for millions of area residents.”
DC Water reports improving downstream water quality trends since early February, with some sampling within EPA recreational standards, though independent findings highlight ongoing concerns tied to aging infrastructure vulnerabilities.