State officials say an abandoned natural gas pipeline is the likely source of an oil slick spotted Tuesday on Cook Inlet.
Leslie Pearson, on-scene coordinator for the Alaska Department of Environmental Conservation, said a commercial airline pilot first spotted the slick about a mile and a half north of Unocal's Baker Platform at about 10 a.m. Tuesday.
"It was real silvery, with just a little bit of rainbow mixed in," she said.
The Baker Platform is near the west shore of the upper inlet near Granite Point. The slick was still visible later Tuesday morning when Unocal workers flew over, and again at 5:30 p.m. on Tuesday when Unocal, DEC and U.S. Coast Guard officials flew out to check.
Pearson said Cook Inlet Oil Spill Prevention and Response Inc. collected samples from the slick on Wednesday, and those have been sent to an Anchorage lab for analysis. By Friday afternoon, though, she had not seen the results.
The slick -- a mile long and 30 feet wide -- is in the area of two abandoned pipelines originally owned by Amoco, Pearson said, but Unocal inherited the lines in the early 1980s when it bought Amoco's Cook Inlet assets. She said state law makes both Unocal and Amoco potentially responsible for the spill.
On Wednesday, Unocal sent a boat equipped with side-scan sonar to survey the bottom. Pearson said the survey confirmed the presence of the two abandoned lines and found no other likely sources for the spill.
One of the abandoned lines carried crude oil. However, that has been severed and is now filled with sea water, she said. The other carried natural gas from the Unocal's Anna Platform and had been charged to a pressure of 50 pounds per square inch.
That is the most likely source for the spill, she said.
Unocal spokesperson Roxanne Sinz disagreed that Unocal is responsible for the two abandoned pipelines.
"Unocal's position on those lines is that we're not in the chain of title on those. We never operated those lines. I think we have to be clear that we don't know that those lines are the cause of the sheen at this point," Sinz said.
"Until we determine exactly what (the source of the sheen) is, Unocal is indicating that there is no evidence that it is a spill from Unocal operations."
Pearson said Unocal was bleeding the pressure from the abandoned gas line Friday, and officials planned an aerial survey after the pressure was bled. On Saturday, Pearson said she had not been notified of Unocal's findings.
"We're hoping that once the pressure is bled, the sheen will go away. Then, we'll know the source," she said. "If the gas line is the source, they'll have to formulate a plan to insure that no more oil comes out of it."
Several recent spills in the Cook Inlet area have been traced to aging pipelines, many of which date to the 1960s heyday of Cook Inlet oil development. In January 1999, a leaking pipeline in Unocal's Swanson River field spilled an estimated 11,424 gallons of crude oil and 217,224 gallons of produced water in the Kenai National Wildlife Refuge. In October 1999, a leaky pipeline from Unocal's Dillon Platform spilled an estimated 400 to 500 gallons of crude oil into Cook Inlet.
In May 2001, crude oil and produced water leaking from a corroded outfall pipeline at the Cross Timbers Oil Co. facility in Nikiski were the apparent source of a sheen found on the beach below the plant. Last week, a leak was discovered in the pipeline that carries refined fuels from the Tesoro Alaska refinery in Nikiski to Anchorage.
"We've been busy. There's no doubt about it," Pearson said. "We need to take a hard look at how to prevent these spills from occurring on what's becoming a regular basis."
She said she would like to see increased testing to ensure the pipelines are working properly and a program to map the locations of all existing lines, including those that have been abandoned.
"I haven't seen a good map yet. I'm sure that if all the operators started collaborating ... we could paint a pretty good picture of what we have here in Cook Inlet," she said.
Sinz said Unocal has a pipeline integrity program in place and has been feeding smart pigs -- tools to measure the integrity of pipeline walls -- through its system. Tesoro recently used smart pigs to assess its line to Anchorage and has a schedule for checking anomalies the pigs detected.
"We're trying to make sure everything is where it needs to be," Sinz said. "These lines will take a lot. They were over-engineered at the time."
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