BP now estimates as much as 100 gallons of crude oil may have spilled in an area around a well house where a pipe broke in the Prudhoe Bay oil field, Alaska officials said Tuesday. BP's initial estimate was 3 gallons of oil.
The spill, discovered Dec. 21, came from a 6-inch line carrying a mixture of crude oil, water and natural gas, said spokesman Weld Royal of the state Department of Environmental Conservation. As of Tuesday, BP's updated estimate is that 300 to 700 gallons of liquid spilled, with as much as 100 gallons of that being crude oil. Last week, BP spokesman Steve Rinehart said the release involved an estimated 3 gallons of oil and 131 gallons of water.
Environmental Conservation officials acknowledge it's difficult to accurately assess spill volume where several liquids are involved, Royal said.
Royal said about six acres of snow-covered tundra, gravel pad and reserve pit have been affected. About 386 cubic yards of contaminated snow have been removed and stockpiled for transport to a temporary staging area.
The spill was discovered by a BP oil field operator doing a routine inspection. The break in the 6-inch line occurred where the production line left the well house.
Tom DeRuyter, the state's on-scene spill coordinator, said an investigation continues into why the line separated.
Cleanup workers will continue to remove contaminated snow near the well house using hand tools, Royal said. A skid loader will be used to clean a more heavily oiled area near the well house and reserve pit. Also, the well house will be removed to allow heavy equipment access to the more heavily contaminated area.
BP operates the Prudhoe Bay oil field -- North America's largest oil field.
Last month, one of the North Slope's biggest spills -- 46,000 gallons of oil, water and natural gas -- was reported at the Lisburne oil field, another BP-operated site. That spill occurred when an 18-inch line split on Nov. 29. The cause of that spill is believed to be ice buildup in the line.
Lois Epstein, an Anchorage consultant on pipeline safety, said the recent spills highlight a long-standing problem on the North Slope in certain pipelines that carry oil, gas and water. For decades those lines, unlike transit lines that carry oil after processing, have been unregulated by the federal government, she said. The flow lines were placed under state regulation only recently.