The unusual substance found in the Rappahannock River and other Fredericksburg waterways that stumped local officials in May was actually a harmless biological formation similar to algae, said Fredericksburg Fire Department spokesman Mike Jones.

In late May, someone called the Department of Emergency Management to report what looked to be a petroleum-based product in the Rappahannock River. When local officials responded, they also originally thought it was some kind of oil in the water.

The substance was found in the Rappahannock Canal, Gayles Pond, Cossey Pond and the Rappahannock River downstream from the Rappahannock Canal outfall to the river. The substance spread over a half mile on the river, near the shoreline and a few feet off it.

The fire department conducted a preliminary test and discovered it was not a petroleum-based product, and that stumped everyone.

Jones said the Virginia Department of Environmental Quality made a site visit to the different waterways and determined that the oily sheen was a lot like algae and harmless.

"The Virginia Department of Emergency Management spoke with the EPA and Coast Guard regarding the matter and they agreed—this has actually been appearing up and down the Chesapeake Bay and its tidal rivers for a couple of years now," Jones said.

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