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A “rainbow-colored sheen” that was first reported in the Potomac River on Wednesday has led the District to activate its federal resources in a multi-agency environmental response.

According to the U.S. Coast Guard, as of Thursday oil sheens had stretched “approximately eight miles” along the river with a point of origin somewhere near Arlington. Eighteen “oiled geese” have been reported. Although the precise source or nature of the sheen has not been confirmed, local officials have conducted surveillance and clean-up missions on the Potomac, and sample results are expected soon. The sheen has not hit the Anacostia River.

“This is a complex situation compounded by the residual snowfall, recent precipitation, and multiple avenues of impact to the river,” USCG Chief Petty Officer Joshua Miller said Thursday. “Our hope is the combined efforts of the Coast Guard, Virginia Department of Environmental Quality, and District Office of Energy and Environment will quickly resolve this situation.”

Julia Robey Christian, a spokesperson for the District Department of Energy & Environment, says DOEE was notified of a spill on Thursday near Reagan International Airport, specifically around Roaches Run and Gravelly Point, which abut either side of the George Washington Memorial Parkway. Christian says when they arrived, respondents did not believe the substance was jet fuel because it lacked the distinctive smell. DOEE along with USCG, the U.S. Fish and Wildlife Service, and the Maryland and Virginia departments of environment are each investigating potential sources of the sheen while samples get tested. It is not a “public-health concern per se,” says Christian.

“Part of the issue is that the sheen in the river right now is so diluted, it’s hard to determine what it is and what’s in it,” Christian explains. “The U.S. Coast Guard is doing a flyover [this afternoon] and our team will be there.”

As of mid-morning Friday, the Tri-State Bird Rescue & Research had recovered eight oiled geese, according to Christian. Residents can report wildlife-impacts and spills they see along the Potomac and Anacostia to 311.

Update 3:45 p.m.: As of mid-afternoon Friday, the sheen has remained at about the same length but diluted even further, Christian tells City Desk. “All sources are pointing to that it’s emanating directly from the Roaches Run and Gravelly Point spot,” she said, adding that the decrease in sheen suggests it’s been successfully contained. The U.S. Coast Guard will maintain oversight of the response in the coming days—there is no advisory to avoid the Potomac.

So far, only 18 geese have reportedly been affected by the sheen, samples of which haven’t yet come back from tests.

Photo by Darrow Montgomery