Day 4 of the trans-Alaska oil pipeline shutdown:

The biggest operator on the North Slope was preparing to pump oil back into the ground.

Environmental officials were supporting a plan that allows some more oil to leak in order to prevent bigger problems.

And a whirlwind of activity was under way to make repairs and get oil pulsing through the pipeline again.

As temperatures dropped at Prudhoe Bay and the shutdown of the 800-mile pipeline continued Tuesday, federal and state regulators agreed to allow Alyeska Pipeline Service Co. to temporarily restart the flow of oil even though some will ooze out of a leaking secondary pipe.

The flow of oil back into the pipeline was to resume Tuesday night, said Alyeska spokeswoman Michelle Egan.

That was expected to raise the temperature of oil in pipelines and tanks, avoid a more complex cold restart, avoid expected problems with freezing and wax buildup and allow North Slope operators to resume higher levels of production, Alyeska said.

"We are in the middle of the restart process. We are opening valves," Egan said around 8:30 p.m. The pipeline was shut down for more than 80 hours, the second-longest period in the pipeline's 33-year history.

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