ANCHORAGE (AP) An oil spill at Prudhoe Bay is about 12 times larger than originally estimated, according to officials with the state Department of Environmental Conservation.
When oil company BP first reported the spill Tuesday, regulators and oil company workers believed about 500 gallons, or 12 barrels, of oil and other fluids including oily water had spilled from a ruptured pipeline.
The DEC on Friday revised the spill estimate to 1,500 gallons of crude oil and about 4,500 gallons of ''produced water,'' which flows out of Prudhoe Bay oil wells along with the crude.
As cleanup crews continued work Friday, wells producing up to 10,000 barrels of oil a day remained shut down pending repairs to the buried 24-inch pipeline. The line carried oil from well pads to a nearby processing center where oil, water and other fluids are separated.
The shutdown is interrupting the flow of oil worth close to $300,000 a day at current market prices, said Dave MacDowell, a spokesman for BP, which operates the Prudhoe Bay oil field.
He said he didn't know when the wells would begin producing again.
''At this point, our focus is on the cleanup,'' MacDowell said.
Even with the greatly increased volume estimate, the spill historically doesn't rank as particularly large for the Slope, said Ed Meggert, the DEC's on-scene emergency response coordinator in Fairbanks.
That the original estimate would change was to be expected, he said.
''A lot of the spill was under snow and ice, so the initial estimates were due to go one way or the other,'' he said.
The positive is that the area of tundra affected by the spill remains confined to well under an acre, Meggert said.
He praised BP for the speed and vigor of the cleanup. Much of the work is being done by Alaska Clean Seas, a North Slope industry spill-response cooperative.
Crews of 20 people are working two 12-hour shifts per day, with workers at times wearing respirators due to high benzene levels, according to a DEC report.
The buried pipe will be unearthed as part of an investigation by the DEC, BP and a North Slope oil workers union, BP officials said Friday.
Corrosion is the suspected cause, and the oil could have leaked from the pipe slowly, without being noticed, over the winter, Meggert said.
Cleanup workers hope to flush the spill site with warm water and then vacuum up the oil to minimize tundra disturbance. No wildlife has been affected, the DEC reported.
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