It looks like Tesoro will have to excavate about an acre of contaminated soil to clean up a spill from the pipeline that carries refined fuels from its Nikiski refinery to Anchorage.
Just how deep workers will have to dig depends on the cleanup level Tesoro negotiates with the state, said Rod Cason, Tesoro Alaska vice president in charge of the refinery. It is necessary to negotiate the cleanup level partly because there are naturally occurring hydrocarbons in the peaty soil, he said.
"You could dig forever and ever and not get to the bottom of it," he said.
However, he said, Tesoro will have to return the area to its pre-spill condition.
The spill was discovered July 31 when Phillips Petroleum Co. workers found jet fuel on the ground near the buried Tesoro pipeline. The spill site is near Mile 35 Kenai Spur Highway -- about 13.75 pipeline miles from the refinery. It lies a couple hundred yards from the highway, between Bishop Creek and the Swanson River and inside Captain Cook State Recreation Area.
The 10-inch diameter pipeline, which carries jet fuel, diesel and gasoline, was shut down July 31-Aug. 3. It was back in service Aug. 4 after workers welded a sleeve over three pinhole leaks discovered at a weld in the original pipe. Workers dug two ditches to intercept contaminated runoff from the spill area. To facilitate the cleanup and minimize impact to the land, they also built a gravel road a half-mile long from the Spur Highway to the contaminated site.
Ron Noel, Tesoro Alaska vice president and general counsel, said cleanup workers have collected 35,000 gallons of contaminated water, from which Tesoro recovered 500 gallons of fuel. Workers also have stockpiled 120 cubic yards -- enough to fill 12 dump trucks -- of contaminated soil at the refinery. Most of that was excavated to find and repair the leaks in the pipeline.
Gary Folley, an environmental specialist with the Alaska Department of Environmental Conservation, said officials from Tesoro, DEC, the U.S. Coast Guard and Alaska State Parks agreed during a meeting last week that the best way to clean up the spill is to excavate the remaining contaminated area. Noel said that totals roughly 1.1 acres.
But how deep Tesoro must dig depends on what concentration of hydrocarbons the state agrees is acceptable in soil left in place at the site. Folley said state regulations set several complicated methods for determining acceptable cleanup levels.
"It gets into the contaminants of concern, tables in the regulations, the depth of groundwater, average rainfall," he said.
Noel said Tesoro expects to submit its remediation plan for state approval on Thursday. Then, there will be a seven-day public comment period through Alaska State Parks before the state can approve the plan and the cleanup can proceed.
Cason said the excavation probably will take a couple of weeks. The plan, once the cleanup is finished, is to remove the gravel access road, except for a portion 200 or 300 feet long that lies on private land, he said.
Folley said Tesoro also must submit a plan for treating the contaminated soil. Usually, that is done by heating it to burn off spilled fuels. That may be difficult in this case, since the soil is mostly peat, he said. Tesoro has sent samples to Alaska Soil Recycling in Anchorage to test the treatment. If it doesn't work, Tesoro will have to find another method, Folley said.
Cason said Tesoro probably will have to blend the contaminated soil with gravel.
"Then, we know it will burn. We're trying to get the right mix of gravel and peat," he said.
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