A tank at a Prudhoe Bay processing center operated by BP overflowed Monday, spilling an estimated 4,200 gallons of crude oil and oily water, the state Department of Environmental Conservation said in a report Tuesday.
The spilled oil and water were contained in the area by an impermeable liner and didn't leach out, and the overflow has stopped, the DEC said. The mishap happened at Flow Station 2, a BP processing facility on the North Slope to separate oil, natural gas and water.
Instruments and valves used to control the level of fluids in the tank malfunctioned somehow. An alarm went off, and a BP worker checking it discovered the spill, said BP spokesman Steve Rinehart.
Production was not affected, he said.
"This was an isolated, contained incident," Rinehart said.