Kenai River watchers raised an alarm Tuesday afternoon when a rainbow sheen appeared in the water.
For about six hours, an unidentified oily substance leached into the river from the storm drain outfall near the Sterling Highway bridge in downtown Soldotna.
"It didn't seem like anything that would be normal to me," said Gary Folley.
Folley, an environmental specialist with the Alaska Department of Environmental Conservation, reported to the scene about 3 p.m. His office got a call at about 2:30 p.m. from a concerned citizen, who said the slick had appeared about 12:30 p.m.
"It was sheening pretty much all afternoon with the heavy rains," Folley said. "I've never seen one that extensive from that outfall. It was a pretty bright rainbow sheen."
Folley placed boom around the outfall, but the current and rain made it difficult to intercept much of the product. He also took samples, which he described as smelling like diesel.
The flow stopped about 6 p.m.
"It has dissipated," he said Wednesday afternoon. "I looked this morning. But, of course, it is not raining today."
His plan, he said, is to leave the boom in place, recheck the area next time it rains and to consult with the Alaska Department of Transportation and Public Facilities, which builds and maintains the storm drains.
Bill Pool, the station foreman at the DOT's Soldotna road maintenance shop, said he is working with DEC on the investigation of the incident.
His theory is that the oily substance was a result of the road work in downtown Soldotna.
Crews are finishing up a rebuild and resurfacing of the Sterling Highway. In the process, they cleaned out the existing storm drains, which should have reduced runoff.
But one ingredient in the new road surface is a water-soluble tar product, called a tack coat, used to fuse pavement layers together.
"I guess some of the tack coat went down the drain," he said. "It's basically just a glue for asphalt."
Pool speculated that the tar exposed along the edges of the new road surface dissolved in the rain, the first heavy rain since the road was resurfaced.
"We haven't had this problem before. ... It should be just a one-time thing. But we are monitoring it," he said. "It looks bad, but I don't think it was anything as substantial as a pollutant."
Pool and Folley said rumors linking the sheen with a fuel spill at a gas station were incorrect. In the Monday incident, a motorist at the Tesoro service station on the Sterling Highway in downtown Soldotna filled a vehicle with diesel, realized it was the wrong fuel, and attempted to dump the diesel on the ground. About 23 or 24 gallons were involved.
Pool said the women who worked at the station intervened, carried out a thorough cleanup and minimized any spill loss.
Folley explained that even if fuel from the Tesoro station had entered the storm drains, it would not have shown up at the outfall into the river.
The drains on the gas station's side of Binkley Street drain into the new sedimentation basin built this year behind the Soldotna Arby's restaurant. The state-of-the-art basins have oil separators and are designed to intercept contaminants before they get in the river.
Folley said that when the bridge is rebuilt, now scheduled to take place in 2003, the project will include a sedimentation basin for the other side of town as well. So in a few years the problem of polluting runoff getting from the streets into the Kenai River will have a permanent solution.
"It's in the works," he said.
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