After a multi-week cleanup effort and investigation, a Washington Department of Ecology spokesperson said the agency is not sure how much it will cost to clean and contain a cooking oil spill in the Black River, nor do they have any leads as to who could be responsible for the illegal dumping.

Agustina Cartagena-Mclean, spill responder at the Department of Ecology, said responders were notified of an apparent oil spill in the Black River near a King County pumping station near 550 Monster Road SW on Aug. 31.

She said at first, the oil spill did not seem particularly large, but an oily sheen was soon noticed spanning roughly a half-mile upstream into the wetland.

According to Ecology spokesperson Ty Keltner, it was originally estimated by responders that about 200 gallons of oil were in the wetland, but after closer inspection and initial response efforts, that estimation was expanded to be somewhere between 400 and 500 gallons of oil.

After analysis and testing of the pollutants, Cartagena-Mclean said that safflower oil, soybean oil and peanut oil were among the primarily identified pollutants, leading investigators to believe it was a “deliberate dumping” of waste cooking oil.

But with no obvious truck access to the waterway, and few leads, investigators are not sure how the oil got there and who is responsible.

“We don’t have a source,” Cartagena-Mclean said in an interview with the Renton Reporter on Sept. 13. “We are kind of at a loss.”

According to Cartagena-Mclean, oil spills such as this one can cause immense harm to a wetland ecosystem, even though cooking oils are not as chemically toxic as other types of oil spills. She explained that oil slicks at the top of the water can prevent the proper oxygenation of the water, effectively suffocating fish and other marine wildlife.

“We found dead fish every other day,” Cartagena-Mclean said as responders already reported finding dead trout and young salmon.

She said the sticky, “goopy,” quality of the oil can damage the feathers of waterfowl and impact their ability to function and survive. Responders found an oil heron that was “emaciated,” as it was not able to hunt for its own food with oily feathers and wings. Cartagena-Mclean said responders tried to take the heron to receive medical care, but the bird died of starvation while being transported.

She said this cooking oil spill is “one of the biggest incidents [she has] ever had to manage,” and estimated that a response and cleanup like this could cost hundreds of thousands of dollars to manage.

“With costs, we won’t have those numbers until the operation is completed, so I can’t speculate on that right now,” Keltner said in a Sept. 20 email when asked about the expected cost of the cleanup operation.

Keltner said an oil spill cleanup company called Clean Harbors was contracted to help clean the wetland with floating booms and other methods over the past couple of weeks.

As of Sept. 20, Keltner said that most of the oil around the pump station had been collected. However, he said a drone used to survey parts of the river inaccessible by foot may have identified more oil upriver.

According to Keltner, representatives of Washington DFW, NOAA, NMFS and Ecology met on Sept. 19 to discuss reopening the fish ladder that had been closed in response to the spill.

“If cleanup continues to progress as it has over the last several days, we may be able to open the fish ladder,” Keltner said in an email on Sept. 20.

While the Dept. of Ecology continued to investigate this incident for clues to who could be responsible, they urge anyone who may have information about it to call 360-790-6899 and report it.