Washington Post | Source of Potomac oil spill still a mystery as sheen begins to dissipate Washington Post While the Coast Guard and the District's Department of Energy and Environment reported Saturday that the oil sheen which had coated the Virginia side of the river last this week had “largely dissipated ... with minor wisps and streaking observed ... Coast Guard: Oil sheens in Potomac River mostly gone Crews clean oil-covered birds from Potomac River Some birds lost feathers, oil clean-up continues on the Potomac |