DC Water reports normal-range results in expanded Potomac tests

Five rounds of expanded testing at six Maryland sites found oxygen, nutrient and metal results within the Potomac River’s normal range, DC Water said Oct. 7. The utility said the tests showed no current signs of harm from the January sewage overflow and described its broader assessment as finding no evidence of lasting harm.

Those conclusions apply to the locations and measures tested; they are DC Water’s assessment, not a finding about every part of the river or the entire ecosystem. The October 7 release did not print individual readings in its body, but linked to a separate monitoring-results page.

Expanded testing followed months of bacteria monitoring

DC Water said the expanded tests measured oxygen, nutrients and metals at six locations upstream and downstream of the overflow. The utility had previously collected daily E. coli samples for more than six months at as many as 10 upstream and downstream locations. It said it added the broader testing in August after community members, particularly river users, raised concerns or questions.

The Potomac Interceptor collapsed in Montgomery County, Maryland, on Jan. 19. EPA estimates about 240 million gallons of untreated wastewater overflowed before a bypass came online Jan. 24. The agency says no collapse-related sewage overflow reached the river after Feb. 8.

EPA’s status page, updated May 8, listed Virginia’s recreational advisory as lifted, Maryland’s as partially lifted for Montgomery County, and the District’s as lifted. That is a dated status snapshot, not a description of advisory conditions on Oct. 9. In an Aug. 7 update, DC Water said Montgomery County had lifted its remaining shoreline and sediment health advisories the prior week, including those around Minnie’s Island. That update referred to those county advisories, not every Maryland river-recreation advisory.

Cleanup milestones had different timelines

EPA reported its federal remediation and demobilization complete as of May 6. Its May 8 page said DC Water’s separate targeted soil remediation between Locks 10 and 11 was then expected to finish by the end of May. DC Water’s project page separately projected substantial completion of the first phase of environmental restoration by late summer 2026.

Whether DC Water completed the targeted soil work or met the first-phase restoration target by Oct. 9 is unclear. The October testing announcement did not say cleanup or restoration was complete, and it did not announce new public-use guidance.