Maryland Department of the Environment Lifts Precautionary Shellfish Harvesting Closure in Potomac River

Three weeks of water quality sampling show no effects from Potomac Interceptor collapse; Fishing is encouraged in Prince George’s County and points south

BALTIMORE (March 10, 2026) — The Maryland Department of the Environment (MDE) today announced that a precautionary shellfish harvesting closure in a portion of the Potomac River has been lifted.

The closure was instituted following the collapse of the Potomac Interceptor sewage pipe in Montgomery County. To ensure that shellfish waters were not affected, the department conducted continuous testing in designated areas nearly 60 miles from the incident site. Samples collected over three consecutive weeks—from the Port Tobacco River region down to the U.S. Route 301 bridge in Charles County and bordering Virginia waters—showed bacteria levels below the laboratory detection limit. Results from Feb. 12, Feb. 17, and March 5 match historical data going back decades.

“Our decisions are dictated by science and data,” said Maryland Department of the Environment Secretary Serena McIlwain. “Three weeks of test results confirm that water quality meets the rigorous standards for shellfish harvesting. Everyone can confidently enjoy seafood from the Potomac River and the Chesapeake Bay.”

The oyster harvesting season in Maryland typically ends March 31, but the Department of Natural Resources (DNR) extended the commercial season by two weeks to April 14. DNR also released a survey this week showing that the concentration of new oysters in 2025 was nearly six times higher than the long-term average and the second highest ever recorded in 41 years.

MDE, along with the Maryland Department of Health and Maryland Department of Natural Resources, oversees the safety and integrity of commercial shellfish production and uses stringent national criteria under the National Shellfish Sanitation Program to evaluate waters for shellfish harvesting. Oysters on the market are harvested responsibly and in approved waterways.

Routine water quality sampling, generally monthly, will continue across the state to ensure proper classification of all shellfish harvesting waters. There are nearly 2,000 monitoring stations in Maryland waters.

MDE has also collected water samples in the Potomac River in Charles, Prince George’s and Montgomery counties. While fluctuations in water quality can be influenced by various factors in addition to the Potomac Interceptor incident, such as runoff from rainfall or snowmelt, sampling in the Washington metropolitan area has generally shown decreased bacteria levels over time and distance from the incident site.

D.C. Water, the operator of the sewage line, has reported no spills into the river since Feb. 9.

Recreational contact health advisories have been lifted in Prince George’s and Charles counties. Anglers and boaters can resume activities in these areas on the Potomac River, and should follow all regulations regarding limits on catching and harvesting different species of fish. Generally, it is safe to consume fish when following recommended consumption guidelines.

Montgomery County’s recreational water health advisory remains in effect until further notice. There continues to be no recreational water advisory necessary for the Potomac River in St. Mary’s County.

More information and detailed sampling data is available on our website.