About 840 gallons of heavy fuel oil spilled into Port Angeles Harbor Wednesday.
The spill happened while a fuel barge was being filled at the Tesoro Port Angeles Terminal, according to Curt Hart with the Washington Department of Ecology.
An oil spill containment boom was already out while the barge was being filled.
"Fortunately in the State of Washington, whenever we have these large fuel transfers over water, we make sure that oil spill containment boom is placed before the transfer starts," said Hart.
Hart said it's unlikely any oil escaped the containment boom, but ecologist will fly over the area to assess the spill.
"We're concerned about all of the ecosystem in that area, from water quality to birds to marine mammals to fish," he said.
The area where the spill occurred is in a relatively calm area, protected by shoreline and perhaps preventing the spill from spreading.
The Department of Ecology is working with the U.S. Coast Guard, the Marine Spill Response Corporation, and Global Diving & Salvage to clean up the spill.