George Mason wins $299,886 grant to study Potomac spill’s possible ecological effects

George Mason University researchers have received a $299,886 National Science Foundation grant to investigate whether January’s Potomac River sewage spill had longer-term effects on the estuary’s water quality and aquatic life. The university announced the project on September 24. Its researchers are collecting water and organism samples, but the announcement did not report ecological findings.

The project addresses a question that routine water-quality readings alone cannot settle: whether the spill changed the mix of organisms living in the river or the food web that connects them. George Mason says its team will compare new observations with a Gunston Cove sampling record that dates back to 1984. That history gives the researchers a basis for examining change, though the university has not said when it will publish results.

What the researchers will measure

Amy Fowler, interim director of George Mason’s Potomac Environmental Research and Education Center, and environmental science associate professor Jennifer Salerno lead the project. Fowler said the team samples water quality and organisms each month at 11 locations. Researchers began sampling in February with university seed funding, before receiving the NSF RAPID grant during the summer.

The team’s water measurements include temperature, salinity, clarity and nutrients, along with tests for PFAS and heavy metals. George Mason says partners including the Potomac Riverkeeper Network and the Smithsonian Environmental Research Center are helping with sampling along the river. The measurements are intended to examine possible effects; the grant announcement does not establish that the spill caused a change in any of them.

The long-running Gunston Cove record is central to that work. According to George Mason, its water samples reach back to 1984, offering points of comparison for the newer samples. The university says its regular water and organism sampling in the cove, funded by Fairfax County, will continue after the NSF grant funding ends in May 2027. The funding end date is not a stated publication deadline for the spill study.

What monitoring has shown so far

The spill began when the Potomac Interceptor sewer pipe collapsed on January 19. According to the Environmental Protection Agency, about 240 million gallons of untreated wastewater entered the river before a bypass began operating on January 24. Episodic overflows continued into early February, but the EPA says none from the collapse reached the river after February 8. Emergency repairs restored flow through the interceptor on March 14.

In a status report updated May 8, the EPA said contamination shown by its monitoring was relatively localized near the collapse site. It also cautioned that E. coli levels in the Potomac vary with rain, runoff, river flow and other discharges. The agency said drinking-water intakes serving the Washington area were upstream of the collapse and that monitoring available for its report showed no signs of concern at those intakes. Those statements describe the EPA’s assessment at the time of that report.

DC Water said on August 7 that recent bacteria readings had returned to normal, apart from the usual changes after rain. It also reported that Montgomery County had lifted its remaining shoreline and sediment advisories the previous week and reopened Minnie’s Island. Based on months of testing, the utility said it did not expect long-term impacts from the overflow. That was DC Water’s outlook; George Mason’s investigation of possible ecological effects had not produced reported findings.

DC Water’s August 7 notice scheduled a change from daily testing to twice-weekly testing at six Maryland locations closest to the collapse, through September 10. Its planned Thursday samples covered E. coli, oxygen, nutrients, metals and other substances, so the utility’s testing extended beyond bacteria. The notice set out a schedule; it did not establish whether testing was completed as planned or describe any later schedule.

What remains to be answered

The university project adds repeated sampling of organisms and environmental DNA to the picture of river conditions. Its central question remains open: whether the spill was followed by a lasting ecological change, and, if so, how that change relates to the river’s food web. Neither the grant award nor the utility’s expectation resolves that question. George Mason has not announced a date for findings.