Cold weather may have contributed to a crude oil spill of less than 200 gallons at the Valdez Marine Terminal over the weekend.
And while there's no direct evidence that oil sprayed into the waters of Prince William Sound, state regulators said they aren't ready to rule out that possibility.
The leak happened at an oil loading dock at Berth 5 at 7:30 a.m. Saturday.
Terminal operator Alyeska Pipeline Service Co. says the oil was captured within a containment area and did not reach the water.
"With the wind, we don't exclude the possibility that some reached the water, but have not found any in or on the water," said Alyeska spokeswoman Kate Dugan.
"We don't think it did" reach the water, she said.
Geoff Merrell, central region manager for the state Department of Environmental Conservation, said oil was captured in the containment area.
The containment area at the berth acts like "a big concrete pan, with a curb and lip," he said. "It's designed to hold oil if there's a spill, rather than have the oil run off into water. It did what it was supposed to do."
But Merrell said there's a good chance some oil sprayed onto the water.
By the time spill responders got a helicopter into the air, after daybreak Saturday, there was "no direct visual evidence" of oil on the water, Merrell said.
But if there had been a sheen, the strong waves that day could have broken it up, preventing them from spotting it, he said.
Looking at leak volumes, timelines and spray and wind patterns, "we think the chances are good (that) some of that oil probably landed on the water," he said.
Merrell said he could not say how much oil might have reached the water. He said Alyeska had initially reported on Saturday that less than five gallons of oil might have sprayed into the water. The incident is under investigation, he said.
Dugan said she is "not aware" of such a report from Alyeska, but acknowledged one could have been issued without her knowledge.
Merrell said it appears that a drain line at the berth may have frozen, causing oil to back up and leak from pipes, or loading arms, that deliver oil to tankers.
Oil leaked from the end caps of two of four loading arms, the state reported Sunday. Responders deployed skimming vessels and the berth was boomed, the state said. A tanker was not being loaded at the time. Valdez saw weekend temperatures in the single digits.
Merrell said the cleanup won't be completed Monday. The spill area on the berth is difficult to reach, because of a mix of industrial hardware such as valves, pipelines and conduits.
"They're having to build platforms and scaffolding and things so people can get to areas to clean some of this," he said.
Brooke Taylor, a spokeswoman for the Prince William Sound Regional Citizens' Advisory Council, said the spill prevention group believes the state's view is appropriate.
Strong winds and waves could have made it difficult to spot a sheen, if one existed, she said.