BETHESDA, Md. — Expanded testing of the Potomac River has found no current evidence of lasting harm from a massive sewage spill caused by the collapse of a regional sewer line in January, DC Water announced Wednesday.
The utility said new measurements of dissolved oxygen, nutrients and metals at six Maryland locations were within the river’s normal ranges. The findings supplement months of bacteria monitoring that previously showed E. coli levels had returned to their usual range and led authorities to lift health advisories.
“These results are reassuring. They reconfirm what earlier testing indicated – that the river has returned to normal,” DC Water Interim General Manager Matthew T. Brown said in the utility’s Wednesday announcement.
The January 19 failure of the Potomac Interceptor along Clara Barton Parkway near the Capital Beltway sent an estimated 243 million gallons of wastewater into the surrounding watershed, according to DC Water’s earlier accounting. Roughly 194 million gallons spilled during the first five days before emergency pumping significantly reduced the overflow.
The collapse prompted restrictions and concern among boaters, anglers and other residents who use the river and the C&O Canal corridor. Crews built a bypass pumping system to route wastewater around the damaged section while engineers investigated the failure and undertook repairs.
The utility began daily sampling shortly after the collapse, testing at as many as 10 sites upstream and downstream. That work continued for more than six months. In August, DC Water expanded its measurements beyond E. coli to examine conditions that can affect fish and other aquatic life.
For the expanded study, samples were collected five times at six Maryland locations on both sides of the overflow site. DC Water said all the results were consistent with ordinary river conditions. The announcement describes present water quality; it does not mean the spill caused no temporary damage or resolve questions about responsibility for the sewer failure.
DC Water has posted the expanded results and historical bacteria readings on its Potomac Interceptor monitoring page. Environmental restoration and litigation related to the collapse have continued separately from the water testing.
