Alyeska plans to again shut down pipeline for repairs 157 feet of new pipe scheduled to be installed over a 36-hour period starting tonight.

The trans-Alaska oil pipeline is scheduled to shut down again tonight to stop the leak that resulted in one of the longest-ever shutdowns of the 800-mile line.

Alyeska Pipeline Service Co. said the second shutdown will last 36 hours. During that period, workers will install 157 feet of new piping to bypass the leaky section.

The company had stopped the flow of oil on Saturday morning after discovering a leak in buried, concrete-encased piping at Pump Station 1, at the start of the pipeline, near the huge Prudhoe Bay oil field.

The 84-hour shutdown -- the second longest in pipeline history -- stopped production of about $50 million a day worth of oil.

Alyeska restarted the pipeline Tuesday night to allow the North Slope wells to begin producing oil again and to avoid the complex process of restarting a cold pipeline, among other issues. Oil in the pipeline was flowing at about half its normal rate at midday Thursday -- 320,000 barrels per day, company officials and regulators said.

Those restart procedures, which involve bringing in generators and other equipment to warm up the line, must be used if the pipeline is shut down for an extended period.

Alyeska said Thursday it may know as soon as today how much gunk accumulated in the line during the four-day emergency shutdown. The interior of the line is susceptible to waxy buildup and ice when the oil inside cools down.

Scraping devices called pigs clean the 800-mile line. Two of them were in the line during the shutdown. The one that created the most concern was expected to arrive at Pump Station 8, southeast of Fairbanks, on Thursday night.

"We fully expect (the pig) to bring along a good bit of wax," company spokeswoman Michelle Egan said.

The company and state and federal regulators said that they have recovered 7,854 gallons of oil from the leaking pipe at Pump Station 1 since Saturday. The leak rate has remained constant and no oil has escaped the building, Egan said.

Alyeska runs the pipeline and Valdez tanker port for the five oil companies that own them: BP, Conoco Phillips, Exxon Mobil, Koch Industries and Chevron.

Find Elizabeth Bluemink online at adn.com/contact/ebluemink or call 257-4317.

Fisherman's Choice Charters