State investigates after trans-Alaska pipeline operator discovers oil at old spill site

State regulators are investigating a report of crude oil discovered along the trans-Alaska pipeline north of Fairbanks, after the pipeline operator found oil in the ground that could be left over from a 2013 release, or tied to a new problem, a state official said Tuesday.

Alyeska Pipeline Service Co. has recovered 10 gallons of crude oil that was discovered Sunday following an excavation south of Atigun Pass, in a buried section at pipeline Milepost 194, Michelle Egan, Alyeska Pipeline spokeswoman, said Tuesday.

The excavation is continuing, Egan said.

The amount of oil recovered could turn out to be larger than 10 gallons, said Ashley Adamczak, environmental program specialist with Alaska Department of Environmental Conservation.

The discovered oil could be an overlooked portion of an oil release reported in 2013 at the same site, but was missed during a cleanup, Adamczak said. That release was tied to frost-jacking from soil movement as the tundra freezes and thaws, she said.

Twenty-one gallons of crude oil was discovered then, according to state records.

Crews inspecting the area had expected to find some trace of oil left from 2013, Adamczak said. But the amount discovered was more than expected.

"We're working through Alyeska to develop a cleanup plan, and to figure out if this is contamination left from the 2013 release or whether it is indicative of a new issue at the valve," Adamczak said.

The oil was discovered in soil north of Pump Station 5 on Sunday as crews inspected a mainline valve, leading to an excavation, Egan said.

"Engineering and field personnel are assessing the situation and developing plans to safely excavate the valve and to determine the cause of crude oil in the excavated area," Egan said in an emailed statement.