On January 19, 2026, a section of the 54-mile Potomac Interceptor (PI) sewer line collapsed along Clara Barton Parkway, in Montgomery County, resulting in a significant overflow into the C & O Canal National Historical Park. The PI carries about 60 million gallons of wastewater daily from as far away as Dulles Airport to the Blue Plains Advanced Wastewater Treatment Plant in Southwest DC for treatment. 

DC Water crews and contractors began work immediately to construct a bypass to contain the overflow. The bypass was completed and activated on January 24, utilizing powerful pumps and the C&O Canal to reroute wastewater around the collapsed section of pipe and back into the sewer system. The focus now is on clearing debris from the damaged pipe so that crews can begin repairs. 

As work progresses at the site, we are working to develop cleanup and remediation plans, which remain in the early stages and will be focused on immediately impacted areas such as the canal, drainage channels and portions of the Potomac River. Cleanup measures will be determined in conjunction with federal, state, and local regulatory agencies.

DC Water is providing daily updates on the progress to clean out and repair the PI. You can see the latest information by clicking on the links on the right side of this page.

Bacteria Sampling

Utilizing a contracted environmental firm and certified laboratory, DC Water initiated daily sampling for E. Coli, an indicator bacterium, at six (6) locations beginning on Jan 29, 2026. To assess water quality conditions, sampling locations including the overflow area as well as upstream and downstream sites.  The locations are shown on the following map, and the results are provided in the table below.

Overall, results show mostly decreasing trends since the start of sampling.  Results at these sites, particularly the elevated concentrations observed at the overflow site in recent days, are expected as a result of limited overflow events that occurred. These are likely influenced by ice and snowmelt, which may increase system flows, contributing to overflow events during this emergency repair. Although the overflow is now mostly contained, E. coli levels are expected to continue fluctuating over time due to residual impacts from the incident and ongoing influences from weather conditions such as precipitation, snowmelt, temperature variability, and other natural sources of E. coli bacteria such as wildlife.

DC Water’s E. Coli Sampling Locations

Water Quality in the Potomac River

Consistent with public health and U.S. Environmental Protection Agency standards, swimming is not recommended when E. coli levels exceed 410 MPN/100 mL.

Historical data indicate typical E. coli levels in the Potomac River can range from 10 to 5,000 MPN/100mL. Variability in E. coli results are common and are influenced by multiple factors, such as weather (rainfall/snow melt and associated runoff) and subwatershed activities and conditions, including aging sewer infrastructure and illicit discharges. 

Drinking Water is not Impacted

It’s important to note, DC Water's drinking water system is separate from the wastewater system, and we want to reassure the public the drinking water is safe, and water service is NOT affected by this incident. The overflow is downstream from the Washington Aqueduct’s (Aqueduct) intakes at Great Falls. In coordination with the Aqueduct, the intakes are also closed at Little Falls downstream. 
 

Avoid the Area

The public is reminded to avoid contact with untreated sewage as it may carry bacteria and viruses. Anyone who comes in contact with the wastewater overflow should:

Leave the area immediately.
Wash exposed skin thoroughly with soap and clean water.
Disinfect any affected areas or items.
Do not consume food or water that may have been exposed.
Seek medical attention if symptoms occur.
Report exposure to DC Water at (202) 612-3400.