The 500-gallon oil spill on the North Slope of the Uinta Mountains probably had a minimal impact on the stream in the area, according to a state expert.

Mark Holden, aquatic resource analyst for the Utah Division of Wildlife Resources, said two division biologists inspected the scene of the spill, which was discovered at Phillips Petroleum's Bridger Lake Unit Tuesday morning.A long vent pipe on top of a holding tank was spewing out crude oil as it was pumped from a new well. The accident was tentatively blamed on a clogged equalizer pipe, which was supposed to let oil flow from one tank to another.

About 300 gallons were captured by an earthen berm around the leaking tank, while 200 gallons went into a wetlands and 20 gallons of that seeped into the Henrys Fork Creek. Workers immediately shut off the flow, erected booms across the stream and began cleaning up the spill.

Division biologists took water samples from three locations, both upstream and downstream from the spill. Laboratory ana-lyses aren't complete on the samples, but the indications so far are that the spill had little impact on the fishery.

Holden said he wasn't sure what the effect would be on the marsh, about half an acre of which was flooded with oil.

"Wetlands are critical areas in the state," he said. "They're valuable for most wildlife."

The DWR will be discussing with Phillips officials what mitigation may be required, as well as measures to prevent future spills.

The spill happened on land leased by Phillips from Wasatch National Forest. Wasatch National Forest spokesman Dick Cline said a federal fishery biologist examined the site.

"He indicated that they were not able to find any problem with fish kills or any problem with damage to the fisheries environment there," he said.

However, Kline does not know the extent of damage to the wetlands.

Phillips' public information officer in Bartlesville, Okla., Dan Harrision, said the cleanup is essentially complete.