HollyFrontier Corp. has been cleaning up after the Aug. 30 explosion that spewed 8,000 gallons of oil into the air for more than a mile southeast of the plant over cars, homes and yards.
The company has yet to say exactly what happened, although it is believed that water got into a holding tank containing refined waxy crude oil that was heated to keep from solidifying. Pressure built up and ruptured a seam in the tank.
Mike Astin, the plant's environmental manager, said the company will not be able to do its in-depth investigation of the cause for a week or two. Meanwhile, his office has fielded more than 260 calls from the plant's concerned neighbors, and Holly's insurance adjusters are receiving claims from affected residents and businesses.
Astin said the waxy crude is nonhazardous and low in volatile organic compounds.
The oil that splattered is much like spray from a can of motor oil, he said, only "this is gooier and stickier."
Dave Spence, environmental director for the Davis County Health Department, said his agency is also testing. A few affected residents have asked to have their indoor air quality sampled to see if the petroleum fumes have drifted indoors, and the health department has equipment to check that and will do it for free.
"They are real-time monitors," Spence said, "so they don't have to wait for the results."
The Utah Division of Water Quality, which has a Web page that discusses the health risks associated with the spatter, took samples of the oil with a special focus on Davis County's Mill Creek. It was dry Friday, when the initial samples were taken, and the tests were repeated after thundershowers had the stream flowing again, said Whitehead.
Results from more in-depth analysis of the oil are days or weeks away, he added.