ANCHORAGE - Crews are slowly making progress cleaning up crude oil that spilled from a leaking pipeline in Alaska's Prudhoe Bay field, industry and regulatory officials said Saturday.
Crews working in 12-hours shifts have recovered 26,250 gallons - or 625 barrels - of crude and snowmelt. But they still have not found the breach in the 34-inch line leading from a processing plant toward the trans-Alaska oil pipeline, said an official with BP Exploration (Alaska) Inc.
"We know where it isn't, not where it is," Maureen Johnson, BP manager of the Prudhoe Bay unit, said during a teleconference briefing with reporters.
The leaked oil, discovered Thursday morning by a BP operator, has affected slightly less than two acres, Johnson said.
After the spill was found, the company shut down the processing plant, depressurized the line and blocked off both ends. Existing and manmade snow berms contained the spread, according to state environmental regulators.
The actual origin of the leak is difficult to detect because oil can seep into insulation and the sheath surrounding the line, exiting at a distance from it started, according to officials.
Until workers can pinpoint the breach, repairs can't begin. Finding it also will help point to a cause.
Crews have stripped insulation from possible areas and have narrowed the search to sections at a vertical support and a low-lying area that's covered by gravel to let caribou pass.
"We haven't ruled either of those locations out," Johnson said.
Meanwhile, minimal production was initiated, she said. A six-inch pipeline was pressed into service to begin production of 5,000 barrels daily. The plant usually processes 100,000 barrels of oil daily - slightly less than 10 percent of the daily flow through the 800-mile trans-Alaska pipeline.
Johnson said it's too early to say when full production will resume at the plant, located more than 200 miles east of Barrow.
Also unknown is the volume of oil released, said Leslie Pearson, an on-scene coordinator with the Alaska Department of Environmental Conservation.
Much of the spill is not visible in the area, which is covered with snow. Hot oil under a leak melts snow but then spreads horizontally when it reaches frozen ground beneath the snow.
The aboveground line, built in 1976, runs from Gathering Center 2 about 7.5 miles to Pump Station 1 of the trans-Alaska pipeline. A line from a second gathering center feeds into the pipe. The leak was between the two gathering centers.
The cleanup work is continuing and involves using equipment and crews to vacuum and scoop the oil.