When oil began flowing south from Alaska's North Slope to the port at Valdez nearly 30 years ago, it was a new era for US energy production and distribution. From the start, it was a technologically daring and politically controversial project. As evidenced by this week's shutdown of a portion of pipeline in the Prudhoe Bay oil field due to a spill, it remains so today.
Despite what industry supporters say are more environmentally friendly ways of detecting and extracting oil from the North Slope today, the means of transporting the liquid gold south is old and – critics say – becoming dangerously decrepit. In some places pipeline walls have lost as much as 80 percent of their thickness as a result of corrosion, industry officials say.
Meanwhile, environmental, economic, and legal fallout continues from the 1989 oil spill, which dumped at least 11 million gallons of oil onto 1,200 miles of shoreline in Prince William Sound after the tanker Exxon Valdez had filled up at the pipeline's southern terminal.
All of this adds urgency to the long-running debate over whether to allow drilling in the Arctic National Wildlife Refuge.
Though most oil pipelines in Alaska have exceeded their 25-year design life they're generally safe and secure, industry officials say. Corrosion expert Bill Hedges, who works for BP, the company whose pipeline recently sprung a leak, says many lines are in "excellent condition."
The corrosion detection and control program in the 800-mile Trans-Alaska Pipeline system (TAPS) is "world class," says BP America chief executive Bob Malone. The pipeline is operated by Alyeska Pipeline Service Co, which Mr. Malone used to head.
But at a news conference Monday in Anchorage, Alaska, BP officials acknowledged that the company's method of testing the thickness of Prudhoe Bay transit pipelines connecting to the trans-Alaska system had proved inadequate.
"Clearly, we are already in the process of adjusting considerably our corrosion program," said Steve Marshall, president of BP Exploration (Alaska).
The pipeline system presents major environmental and design challenges. It crosses more than 800 rivers and streams, three mountain ranges, and three major active faults. Three-quarters of it traverses fragile permafrost. It is built in zigzag fashion to allow for expansion and contraction during temperature changes as well as movement from possible earthquakes.
Maintenance in the oil fields and along the TAPS includes sending mechanical devices known as "smart pigs" through portions of the pipeline to check for corrosion that can cause leaks. BP also uses ultrasound imaging to check pipeline integrity, as it did in the portion where a leak was discovered Sunday. Mr. Marshall now acknowledges that ultrasound is not a foolproof safety device.
In recent years, about 500 oil spills have occurred in the Prudhoe Bay oil fields and along the 800-mile pipeline each year, according to the Alaska Department of Environmental Conservation, even though the daily "throughput" of oil has declined from about 2 million barrels a day in 1987 to less than half that today. Most leaks are minor, quickly detected, and remedied.
But in March, the largest leak in North Slope production history – as many as 267,000 gallons – poured out of a corroded pipeline at the Prudhoe Bay complex for five days before being discovered. Since then, US EPA investigators have been seeking to determine whether BP violated the federal Clean Water Act by failing to prevent corrosion in the ruptured line. If it did, criminal charges could follow.
By comparison, the most recent oil spill was about 200 gallons. The consequent shutdown came after inspection tests found 16 thin spots from what BP officials said was "unexpectedly severe corrosion." The last time a "smart pig" had been used to check that line was in 1992.
"We knew it was a problem that would get worse over time," said former Alaska Gov. Tony Knowles (D) Monday. He's running this fall to regain his old seat.
BP expects to replace 16 miles of pipeline, which could take months.
Meanwhile, federal and state agencies say the damage to wildlife and habitat in Prince William Sound continues from the Exxon Valdez spill.
Under a 1991 settlement agreement, Exxon (now Exxon Mobil) was required to pay $900 million over 10 years for environmental restoration. But the settlement included a "Reopener for Unknown Injury" provision extending until 2006.
Last month, the US Justice Department and the Alaska Department of Law invoked that provision to seek another $92 million from Exxon Mobil for bioremediation and other technologies used to remove the larger patches of remaining oil that US scientists say continue to harm ducks, sea otters, shellfish, and other marine life.
• Yereth Rosen in Anchorage, Alaska, contributed to this report.