"State environmental officials are investigating why a pipeline on Alaska's North Slope operated by BP ruptured early Saturday during a pressure test.
Workers in nearby buildings felt the ground shake from the force of the underground line break, Tom DeRuyter, on-scene coordinator for the state Department of Environmental Conservation, said Sunday.
BP Exploration (Alaska) Inc. estimated the size of the spill at 2,100 to 4,200 gallons of fluid, mainly methanol and other fluids along with an undetermined amount of crude oil. It spilled onto a gravel pad and into a small tundra pond, DEC said.
The trans-Alaska oil pipeline is shut down for planned annual maintenance, and oil field operators were taking the opportunity to work on equipment as well, DeRuyter said."
Lisa Demer reports for the Anchorage Daily News July 17, 2011.