The change is necessary because the oil line, which stretches across the Alaska wilderness from Prudhoe Bay to Valdez, is running at only about half capacity. North Slope oil production peaked at 2 million barrels per day (bpd) in 1988, but the maturation of major oil fields has cut that to under 1 million bpd.

Even without the throughput drop, automation is necessary to modernize the pipeline, said Alyeska spokesman Curtis Thomas. Comparable North American oil pipelines, including those in cold climates like Canada, operate under similar automation, he said.

"New technology was available and it was a perfect opportunity to take advantage of it," Thomas said.

Alyeska's owner companies dominated by BP (BP.L: Quote, Profile, Research) , ConocoPhillips (COP.N: Quote, Profile, Research) and Exxon Mobil (XOM.N: Quote, Profile, Research) earlier this month gave their approval to spend $250 million on the automation plan, which aims for completion of the changes by the end of 2005.

The investment, which Alyeska says is one of the biggest since the line was constructed in the 1970s, is expected to reduce operating costs by 10 percent a year. It will also end the outlays for maintenance for soon-to-be obsolete equipment and facilities, such as employee housing. In all, 350 workers are expected to lose jobs over the next couple of years.

Critics fear the changes will compromise environmental protection.

Automating the line is fine, said Walt Parker, a longtime environmental planner and board member of the Alaska Forum for Environmental Responsibility, a watchdog group. But getting rid of so many employees and backup protection is risky, he said.

"It was skimping that caused the Exxon Valdez (oil spill) to happen, and the bad response to happen," Parker said.

Alyeska insists the changes will enhance environmental protection. "Our oil-spill-response effectiveness will actually increase," Thomas said.

The plan calls for spill equipment to be stockpiled in strategic locations, rather than at pump stations, and the company is considering buying a fleet of fast-traveling helicopters so that workers will be able to respond quickly to any problem, he said. But those strategies offer Parker and others little comfort. New helicopters will do little good, he said, if Alaska's famously volatile weather conditions preclude flying.

He is most concerned about the areas where the pipeline crosses major rivers. "A major oil spill at any of these is kind of on the order of the Exxon Valdez," he said.

Although government agencies have given conditional approval to Alyeska's plans, regulators still have some concerns, said Rhea DoBosh, a spokeswoman for the Joint Pipeline Office, the consortium of state and federal agencies that oversee the pipeline.

Agencies have called for some changes to the plans for oil-spill equipment stockpiles, as well as the dedication of helicopters for emergency response.