COOK INLET - Chevron Corp. says it has shut down oil production at an offshore platform in Cook Inlet after federal regulators rejected its request to continue using a corroded undersea pipeline there.
The company's Anna Platform had been producing about 900 barrels of oil a day.
Chevron had sought a waiver from federal rules that require pipelines in sensitive locations be repaired when corrosion has eaten away more than 50 percent of their wall thickness.
In one section of pipe near the sea floor, the line has lost more than 60 percent of its wall thickness. The corrosion attacked a 134-foot pipeline called a riser, which was installed in 1967. Offshore oil and gas operators use risers to link a platform to a subsea pipeline.
Instead of fixing it, Chevron asked a year ago to keep using the corroded pipeline indefinitely. Chevron proposed periodic inspections of the pipeline plus weekly inspections by air to look for an oil sheen.
Federal regulators asked for public comment on the company's proposal and got just one: from the state's Petroleum Systems Integrity Office.
In the letter, state officials raised several concerns about Chevron's proposal. For example, weekly air patrols to look for oil sheen were "both impractical and dangerous," the letter said.
"Aside from the regulatory matters, the political and environmental ramifications of a spill in Cook Inlet are grave and if oil is released the consequences will impact our entire oil and gas industry," the state's letter said.
On April 27, while the nation was hearing about a massive offshore oil spill in the Gulf of Mexico, the federal Pipeline and Hazardous Materials Safety Administration rejected Chevron's request for a special permit.
The agency didn't order Chevron to shut down the Anna Platform. But it said if Chevron continued to operate the corroded line, it would be "potentially subject to enforcement action."
Chevron said it shut down Anna last week, as soon as it received the letter.
The loss of the platform is another blow for the oil company, which has been producing less oil since the Redoubt volcano eruption prompted the shutdown last spring of one of its Cook Inlet oil storage terminals.
Chevron spokeswoman Margaret Cooper said the company's Unocal subsidiary is working with federal regulators on how to repair the corroded pipeline so that oil production at Anna can resume.
Anna Platform produced less than 1 percent of Cook Inlet's oil - 846 out of 6,771 barrels per day - in the first three months of this year, state records show.