The pipes follow a winding north-south route across mountain ranges, rivers, streams, and miles of permafrost.
The entire structure, which turns 30 next year, cost $8 billion (U.S.) to construct.
On August 6 BP announced a shutdown of the oil field while they replaced 16 miles (25.7 kilometers) of damaged or suspect pipes.
More recently, BP has said it will be able to do a phased shutdown and maintain delivery of roughly a third of the normal supply. Company officials have said the oil field could return to full production by early 2007.
Meanwhile a press release on the Alyeska Web site says the pipeline remains open and ready for oil despite BP's shutdown at Prudhoe Bay.
But environmental groups, including the Wilderness Society, have been complaining for years about spills along the pipeline that have sent oil into the tundra (see photos of Alaskan wildlife).
Though EPA doesn't confirm such investigations, the Associated Press reports that the agency has been investigating BP's maintenance of its Prudhoe Bay infrastructure since 2004.
For its part, BP says it has been responding to leaks when they occur.
According to spokesperson Neil Chapman, workers routinely use a program of computer corrosion models and external testing to check the pipes.
And following the spill last March, BP used a more direct technique called pigging to investigate its pipes.
A robotic device known as an intelligent pig traveled through the pipes to measure wall thickness and other indicators of condition.
The results gave the company a surprise.
"What was happening didn't correlate with our models," said BP spokesperson Neil Chapman.
Based on data from the pigs, the company found 16 places where more than 70 percent of the steel wall had been eaten away, Chapman says.
Over the years, the amount of crude oil flowing through the Prudhoe Bay pipes has dropped in proportion to other materials, like water, that are corrosive.
Chapman says that the company routinely sends chemical corrosion inhibitors through the pipes to combat this problem.
But BP has told regulators that the March spill could have resulted from inadequate use of such chemicals.
Word From Washington
Alaska's transportation department, which is in charge of pipeline safety, has ordered BP to proceed quickly with its tests and repairs even as it cooperates with federal investigations.
Meanwhile, the Justice Department is pursuing possible criminal charges in connection with the March spill, and has ordered BP Alaska to cut out and send as evidence a 12-foot (3.6-meter) section of pipe where the leak occurred.
Huffines of the Wilderness Society says that no matter what action regulators take, she doesn't see much hope for a cleaner oil industry in Alaska.
"The oil business is a dirty business," she said. "They're going to cut costs on maintenance and they're going to allow these things to continue to happen."
Her organization isn't calling for an outright halt to Alaska's oil industry, she says, but it does want to see critical thought go into its expansion.
Huffines has been working with residents of Inupiat villages along Alaska's North Slope west of Prudhoe Bay.
Oil companies have been eyeing expansion opportunities in this region for years and have gotten recent green lights from legislators in Washington, D.C.
Recently Inupiat natives rallied against drilling in the Teshekpuk Lake region, a network of coastal lagoons, deep-water lakes, wet sedge grass meadows, and river deltas that the environmental group the Sierra Club has called unparalleled wildlife habitat.
(Read about Teshekpuk Lake in "Fall of the Wild," a National Geographic magazine feature about the battle for the North Slope [May 2006].)
Huffines especially hopes that Congress will continue to stave off drilling in the Arctic National Wildlife Refuge now that the risks are in the spotlight.
"My hope," she said, "is the American people will tell Congress, Don't do this."
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