ANCHORAGE (AP) -- An oily sheen that appeared on the Colville River on Alaska's North Slope alarmed biologists and triggered an overnight investigation by government and industry.
But what the inspectors from Fairbanks, Barrow and Prudhoe Bay found a few miles downstream from Umiat last week was not a spill, but a natural oil seep percolating from the riverbed.
''It was almost like Mother Nature burped this oil,'' said Amanda Stark, an environmental specialist with the state Department of Environmental Conservation in Fairbanks. ''For some reason, this seep may have become active, bubbled up a little bit of oil, and stopped.''
Two biologists conducting bird studies for the U.S. Fish and Wildlife Service floated through the oil along an uninhabited stretch of the Colville Friday. They returned to Umiat and notified the state environmental agency in Fairbanks, Stark said. The alarm went out.
The responders included a crew from the North Slope Borough in a helicopter on Friday night, followed by a plane with Stark and two federal representatives, and a helicopter from Phillips Alaska on Saturday morning.
''What we did was make sure we didn't have any (spills) in our operations, and then continued south on the river,'' Phillips spokeswoman Natalie Knox said.
Stark finally found the source that afternoon while hovering in a helicopter about 15 feet above the river surface four to five miles downstream of Umiat. A few miles farther, some weathered oil had coated rocks in an eddy.
''There was no exact location where the sheen was coming up,'' Stark said. But out in the middle of the river, she saw a light purplish color coming to the surface.
With about 100 million barrels of proven oil reserves, the Umiat area has long been known for shallow deposits and a few surface seeps. Stark figured that this oil -- too little to recover -- had emerged from one of those deposits.
''To me, it's very interesting just seeing this oil bubble up out of the ground,'' she said. ''Honestly, this may happen more often than we realize.''
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