DC Water declared the Potomac River healthy again on Wednesday, Oct. 7. The announcement came nine months after a ruptured sewer line dumped more than 240 million gallons of raw sewage into the river near Cabin John.

Expanded water testing at six locations in Maryland found bacteria, oxygen, nutrient and metal levels all within normal range, the utility said in a press release. The results "found no current signs of harm from the overflow," DC Water said.

"That is why we did more testing. These results are reassuring," DC Water Interim General Manager Matthew T. Brown said. "They reconfirm what earlier testing indicated — that the river has returned to normal."

The spill site sits along the C&O Canal corridor between Lock 10 and Minnie's Island, where Potomac residents paddle, fish and hike.

What happened in January

On Jan. 19, a section of the 72-inch Potomac Interceptor sewer line collapsed along the Clara Barton Parkway in Montgomery County, near Lock 10 of the C&O Canal National Historical Park. The pipe, built in the 1960s, carries roughly 60 million gallons of sewage per day from Northern Virginia through Maryland to a treatment plant in Washington, D.C.

An estimated 243 million gallons of untreated wastewater poured into the river over eight days before a bypass was installed Jan. 24, the Southern Maryland Chronicle reported. Emergency repairs finished March 14, and full flow returned to the interceptor.

Water samples taken Jan. 23 at the spill site found E. coli levels 60 times above the safe-contact standard, according to the Potomac Riverkeeper Network. The West Montgomery County Citizens Association called it the largest raw sewage spill in U.S. history.

Montgomery County lifted all remaining health advisories for the shoreline between Lock 11 and Minnie's Island in early August, reopening the stretch for recreation. The C&O Canal Trust confirmed Lockhouse 10 and its parking lot have also reopened.

Questions remain

Sediment is another story. DC Water's all-clear covers water-column testing but does not address sediment. Maryland's Department of the Environment found sewage-related markers in sediment near Minnie's Island, and no established health thresholds exist for that kind of testing. The Potomac Riverkeeper Network expanded its own monitoring from 28 to 37 sites this season and has urged continued sediment sampling.

A survey of 643 people conducted by the Riverkeeper Network between March 23 and April 20 found 77% of respondents did not trust information from DC Water. Only 40% said they would feel comfortable returning to the river even if monitoring showed safe bacteria levels.

In April, American Rivers ranked the Potomac the most endangered river in America, citing the spill and expanding data center development in the watershed.

Maryland and the U.S. Justice Department filed separate lawsuits against DC Water on April 20. WSSC Water joined the state's suit in September. A class-action lawsuit was filed March 6.

Repairs ahead

DC Water identified four other sections of the interceptor needing critical repairs after the collapse. Two were completed as of Sept. 3. Work at the remaining two sites was ongoing, with the agency expecting most projects to finish this fall, according to the Washington Sun.

Long-term rehabilitation of about 2,700 feet of pipe is expected to take nine to 10 months as part of a 10-year, $625 million program to overhaul the full 54-mile interceptor. The District of Columbia's environment agency plans a fish and wildlife survey in spring 2027.