Alaska Stops Oil Flow

Prudhoe Bay was already in trouble long before this latest crisis on the North Slope of Alaska.

The North Slope, discovered in the late 1960s and home to America's largest oil field, was gradually being pumped dry, supplying less and less of the nation's crude. As BP and other oil companies looked for other places to drill, environmental groups said the oil companies neglected the aging network of pipelines and drill pads in Alaska.

This weekend's shutdown has only made things worse.

"It's not unexpected that these things happen," said Athan Manual of the Sierra Club. "It's a 40-year-old oil field.

"It's such a huge area to police," he continued, "you don't see the problems because the area is so vast."

According to BP America, which runs the oil field, an internal sensing device, called a "smart pig," was being run through the network of pipelines at Prudhoe when it hit trouble. BP said it found 16 anomalies in 12 locations in an oil transit line on the eastern side of the field. Follow-up inspections found "corrosion-related wall thinning appeared to exceed BP criteria for continued operation," the company said in a release.

"We regret that it is necessary to take this action, and we apologize to the nation and the state of Alaska for the adverse impacts it will cause," BP America Chairman and President Bob Malone said in a statement. "However, the discovery of this leak and the unexpected results of this most recent "smart pig" run have called into question the condition of the oil transit lines at Prudhoe Bay. We will not resume operation of the field until we and government regulators are satisfied they can be operated safely and pose no threat to the environment."

It was BP's decision to shut down oil production, several sources agreed. Federal and state oversight at Prudhoe Bay has been the subject of continued debate. An oil spill in March -- 267,000 gallons -- raised accusations that regulators had been kept from doing their jobs.

The company has now promised to replace 73 percent of the feeder pipelines it has at Prudhoe Bay. It operates 22 miles of feeder lines, which send oil through the 800-mile-long Alaska Pipeline to the state's southern border.

BP, which has positioned itself as an environmentally-friendly company looking "beyond petroleum," has stopped counting on the dwindling reserves in Alaska for its future oil needs. Lord John Browne, the company's chief executive, has listed several "profit centers for the future": the western Gulf of Mexico, Trinidad, Angola, Azerbaijan, Russia and the Asian Pacific regions. Conspicuously missing from the list was Alaska.

Prudhoe Bay is a harsh place for oil workers. Buildings are mounted on stilts to ensure they don't sink in the permafrost. Workers go outdoors as little as possible; a swimming pool in one dormitory doubles as a water supply source in case of fire. The area is considered both a desert and a wetland -- a desert because there is surprisingly little precipitation; a wetland because what moisture there is never has a chance to evaporate.

Today, according to the National Weather Service, was a typical summer day for the North Slope, which is fewer than 1,500 miles from the North Pole: a high of 53 degrees Fahrenheit, and a low of 40. Daylight is constant for about two months during the area's brief, busy summer, but there are two months of nonstop darkness in midwinter to match.

And on this landscape, the difficulties of maintaining an oil field were obvious. Oil companies have pushed for decades to expand into the Arctic National Wildlife Refuge, about a hundred miles to the east. But Pam Miller, at the Northern Alaska Environmental Center in Fairbanks, said that campaign has taken another hit.

"This says the oil industry is not conducting business in the environmentally sound manner that they were claiming," she said.

"This accident," she concluded, "was industry's poor management."

The Associated Press contributed to this report, with additional reporting from ABCNews' Dan Arnall, Charles Herman and Lisa Stark.