The 800-mile trans-Alaska oil pipeline remained shut down late Saturday after crews discovered a leak at Pump Station 1 on the North Slope earlier in the morning.
North Slope oil producers have been asked to cut their production to 5 percent of normal, a level expected to be reached by 9 a.m. today, according to Alyeska Pipeline Service Co., which operates the line and its pump stations.
A station line -- not the main pipeline -- encased in concrete leaked an unknown quantity of crude oil just outside a booster pump building, according to Alyeska spokeswoman Michelle Egan.
The crude oil flowed from the line outside the building into a concrete sump and traveled into the building, according to a situation report released late Saturday by the Alaska Department of Environmental Conservation. The DEC thinks oil is still trapped in the space between the leaky pipe and the concrete around it.
A crew doing a routine inspection noticed the leak at about 8:15 a.m. Saturday, and Alyeska shut down the pipeline just before 8:50 a.m., Egan said.
"There's no visible oil on the tundra," Egan said. "We believe it's all inside that casing."
However, the DEC situation report indicates a gravel pad may have been affected along with the building. "We're expecting that there may be some release outside that concrete into the gravel pad," said the state's on-scene coordinator Tom DeRuyter from Alyeska's emergency operations center in Fairbanks late Saturday.
A DEC employee already on the North Slope, along with two more en route, will be monitoring Alyeska's response, said environmental program specialist Bob Mattson.
Vacuum trucks -- which resemble trucks used to pump septic tanks, DeRuyter said -- were at the scene.
Determining the approximate amount of oil spilled will likely involve Alyeska personnel checking meters on the lines, Mattson said.
Vapors from the oil were above safety and health levels, according to the DEC. Responders ventilated the building before oil removal could begin, according to the report.
The booster pumps near the leak were isolated by about 4 p.m. Saturday and crews had begun to recover the spilled oil, Egan said.
While Alyeska staff believe the leak is contained, Egan said, they won't know for sure if it had escaped that concrete structure until crews had a chance to excavate around the pipe. Crews are working to determine how to fix the line and get the pipeline running, Egan said.
Alyeska was unsure when the pipeline might be restarted, Egan said. Plans to engineer a plan for a temporary pipe were expected, according to the DEC.
"We want to make sure that we aren't going to make the situation worse by restarting, so we're being very careful and methodical about that," Egan said.
Any further leaks caused by the shutdown were a concern for the state responders, DeRuyter said.
"The state ramped up the response for the release at hand, but we're also looking for secondary releases," he said.
BP was in the process of cutting off production at the fields it operates late Saturday, said Steve Rinehart, Alaska spokesman for the oil company. It will take time for wells to be shut in and pipelines and other facilities to be freeze protected.
The temperature at the site was 10 below zero Saturday night, according to the DEC. Alyeska reported the temperature at 4 above.
Normal production from the North Slope fields averages around 630,000 barrels a day of oil. Cutting production by 95 percent would keep about 600,000 barrels a day in the ground -- or about $50 million a day worth of oil.
The oil fields have limited storage capacity, and the production that occurs -- about 30,000 barrels a day, if the full slowdown takes effect -- will go into storage while the trans-Alaska pipeline is shut off.
BP runs most of the oil fields on behalf of itself and the other leaseholders. Conoco Phillips and Pioneer Natural Resources also run fields. BP, Conoco and Exxon Mobil are the major producers on the North Slope.
Rinehart said it was unclear how long the pipeline shutdown will last.
The pipeline runs from the North Slope to a tanker port in Valdez. Pump Station 1 is at the beginning of the pipeline. Alyeska runs the pipeline for the five oil companies that own it: BP, Conoco, Exxon, Koch Industries and Chevron.
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By CASEY GROVE