Potomac Riverkeeper Network released testing results January 26, 2026, in Washington, DC, revealing severe E.coli contamination in the Potomac River from an ongoing sewage spill near Lockhouse 10 in Montgomery County, Maryland. The nonprofit’s sampling, conducted January 23, showed levels up to 11,900 times above safe limits for human contact, prompting warnings of catastrophic health and environmental risks.
PRKN President Betsy Nicholas announced the findings, stating the spill has discharged nearly 300 million gallons of raw sewage into the river. “These measurements of E.coli bacteria show contamination which is nearly 12,000 times what authorities limit for human contact. And so far, almost 300 million gallons have entered the Potomac River. The long term impact cannot be overstated,” Nicholas said. The group compared results to standards from Virginia’s Department of Environmental Quality and Maryland’s Department of the Environment.
Potomac Riverkeeper Dean Naujoks, who sampled with PRKN Volunteer Coordinator Evan Quinter, detailed the data. At the sewage discharge from the broken interceptor pipe near Cabin John at Lock 10, E.coli measured 4,884,000 MPN—11,900 times the 410 MPN limit for safe human contact. Nearby at the Lockhouse 10 public river access, a recreation site for kayaking, fishing, and wading, levels reached 7,000 times above the limit. Four miles downstream in DC waters at Fletcher’s Cove, E.coli was 60 times higher than the standard. Upstream at Old Angler’s Inn, baseline testing showed 4.1 MPN, confirming the spill as the contamination source.
Naujoks attributed the disaster to infrastructure failure. “Infrastructure failure is at the root of this disaster – the six foot diameter sewage interceptor pipe located this close to the river should have been better maintained in order to avoid this catastrophe,” he said. He criticized DC Water’s response, noting, “DC Water needs to come up with a better plan than using a one hundred year old dry canal ditch to capture and contain future sewage releases instead of discharging hundreds of millions of gallons of sewage to the river! One of the largest sewage spills in US history could have been avoided.”
E.coli serves as an indicator of fecal contamination from sewage, signaling risks from pathogens, bacteria, parasites, and potential health effects including gastrointestinal illness, kidney issues, and nervous system damage. The spill, originating from a collapsed section of the Potomac Interceptor—a major sewer line managed by DC Water—began around January 19-21, 2026, with initial flows estimated at tens of millions of gallons per day.
Naujoks described the scene as alarming after eight days of discharge. “Our sample data collected right at the sewage outflow revealed shockingly high numbers that could have long term impacts to water quality. The vile and putrid smell from the torrent of sewage discharging to the Potomac River for eight straight days is one of the most disturbing things I have ever seen in 25 years as a Riverkeeper,” he said. He noted reduced flow recently but highlighted absent public health monitoring. “We have seen no response from public health agencies to determine whether this type of raw sewage will impact public health and the environment. Raw sewage is not only harmful to humans, but it can also harm the environment through excessive nutrients, toxic contaminants, and disease exposure. This can lead to dead zones in the river, harmful algal blooms, and fish kills.”
The spill affects the Potomac River corridor, including areas near the C&O Canal National Historical Park where Lockhouse 10 is located. Public access points have faced closures, and warnings advise avoiding contact with affected waters.