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Prudhoe Bay oil leak escaped monitor Field output down $6 million a day; spill one of largest in field’s history; BP will investigate whether detection system failed Wesley Loy Anchorage Daily News
The state four years ago fined BP $300,000 and ordered it to install an accurate leak-detection system on major Prudhoe Bay crude oil pipelines, including one that recently sent more than 21,000 gallons of oil oozing onto the tundra.
But the system didn’t alert oil-field workers to that leak along the pipeline. Rather, it was a worker who happened to be driving down a gravel road next to the line and smelled oil who sounded the alarm early March 2.
The spill is one of the largest in the 29-year history of production at Prudhoe Bay, the nation’s largest oil field, and a massive cleanup effort continues in subzero weather.
State pollution regulators found BP was behind schedule on installing leak-detection systems required by law and issued the company an order in May 2002 to hurry up the work.
BP complied, adding equipment designed to alert field workers whenever the daily flow of oil through a pipeline dips by 1 percent or more, suggesting a possible leak. Company tests showed the systems worked at that time.
Maureen Johnson, BP’s senior vice president for Prudhoe Bay, said the company will investigate whether the leak-detection system failed, or if field workers didn’t respond correctly to indications the pipeline was leaking. Responses might have included driving or flying along the 3-mile pipeline to check, she said.
Johnson added she expects the state to fine or otherwise punish BP for the spill.
“If you mess up, you expect to be penalized for that,” she said. Source of leak identified BP and pollution regulators with the state Department of Environmental Conservation jointly announced March 7 that they had pinpointed the source of the leak — a quarter-inch hole at the bottom of the steel pipe inside a culvert underneath a caribou crossing.
A caribou crossing is a gravel mound placed over pipelines to allow the migratory animals to walk over.
Internal corrosion is suspected of causing the hole, BP and DEC officials said.
Daren Beaudo, a BP spokesman, said the 34-inch pipeline — which carried oil from a processing plant known as Gathering Center 2 to the 800-mile trans-Alaska pipeline — has corroded spots that are regularly inspected and chemically treated to prevent the pipeline wall from thinning further or rupturing.
However, he said the section of pipe in the culvert was not a known trouble spot.
“Our people were genuinely surprised and did not anticipate a problem in this area,” Beaudo said.
But the many caribou crossings in the vast Prudhoe Bay field have caused worry.
In 2003, BP promised the state it would check all caribou crossings in search of standing water in the culverts or other problems. Water is a mortal enemy of pipelines, triggering corrosion that can quickly eat through steel. BP made the promise after three small holes developed in a 24-inch pipeline, allowing 1,500 gallons of crude oil and 4,500 gallons of oily water to leak, covering nearly an acre.
The spill discovered last week is much more serious.
At 21,000 gallons, the spill is the sixth-largest ever on the North Slope. The largest was 38,850 gallons in the Milne Point field in 1989. Two acres affected DEC officials say spilled oil from the Gathering Center 2 pipeline has affected close to 2 acres, reaching the edge of a frozen tundra lake. The volume of spilled oil is likely to grow larger as cleanup workers — 60 of them working day and night — continue to recover oil using vacuum trucks.
The agency said it expects to have a full estimate of the spill size by March 9.
BP workers glued a temporary rubber patch over the hole.
The line remains shut down indefinitely, pinching oil production by about 95,000 barrels per day or 12 percent of total North Slope output. The interrupted oil is worth close to $6 million a day at the March 7 closing price.
The leak-detection system relies on meters at either end of the pipeline to measure the amount of oil going in and coming out. The system is supposed to sound an alarm in a Prudhoe control room if the daily oil flow unexpectedly dips by 1 percent or more.
The Gathering Center 2 pipeline was among a handful of important “transit” or “sales” pipelines — lines that carry processed oil ready for market — covered under the state’s 2002 leak-detection order.
Less than a year after receiving the order, BP asked the state to lift it. The company provided test results showing the leak-detection systems worked, including that on the Gathering Center 2 pipeline.
BP testers had diverted some oil going through the line to simulate a leak, and an alarm sounded 13 hours later, according to a BP letter to DEC.
Sam Saengsudham, a DEC environmental engineer, reviewed the test results and concurred the leak-detection systems worked, according to an internal DEC e-mail the agency provided March 7. However, he also recommended that the pipelines be patrolled regularly “as an integral part” of detecting leaks. Smell of oil uncommon Although Prudhoe is a sprawling and highly productive field, the smell of oil like that noticed by the field worker March 2 is uncommon, Beaudo said. He said he didn’t know how often workers travel the road along the leaky pipeline.
It’s possible the pipeline’s leak-detection system wouldn’t notice a very small, low-volume leak that persisted for perhaps weeks from a tiny hole, slowly sending oil across the tundra where it could be concealed by heavy snow, Beaudo said.
Johnson also noted that the leak-detection systems are not fail-safe and can be affected by “noise” such as sediment accumulation in pipelines.
Many Prudhoe pipelines have no leak-detection system, but workers check all of them regularly by driving by or flying over with infrared equipment that can spot escaped oil, which comes out of the ground hot, Beaudo said.
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