Last updated at 10:15 a.m. on Monday, April 3

Late Sunday night, Hilcorp confirmed that the leak stopped.

In a statement Monday morning, the company said all oil had been removed from the affected pipe.

“Based on standard calculations for the number and size of the initial oil sheens and the amount of oil recovered from the line, Hilcorp estimates the total volume of this spill to be less than three gallons of oil,” Hilcorp wrote.

The company said it has not seen any further oil sheen since the original April 1 discovery, but it will continue to fly over the area.

The Unified Command stood down Monday morning.

Updated at 5:45 p.m. on Sunday, April 2

Several large oil sheens were discovered Saturday near Hilcorp Alaska’s Anna Platform in Cook Inlet. By Sunday afternoon, efforts were underway to stop a leak under the supervision of the Alaska Department of Environmental Conservation (DEC).

Crews first noticed a sheen, as well as bubbling from underwater, shortly after 11:20 a.m., according to a statement from the DEC. The DEC was contacted by 12:05 p.m. the same day. The U.S. Coast Guard was also notified and has responded to assist.

It is unknown when the leak began. Workers on the Anna Platform reported an “impact” on the platform shortly before the oil sheen was discovered. The leak appears to be coming from an 8-inch pipe located southwest of Tyonek at a depth of about 75 feet underwater, according to the DEC situation report.

“At this time, we have a pipeline that is carrying crude oil between two platforms – the Anna platform and the Bruce platform – that is leaking oil,” said Kristin Ryan, the director of the DEC’s spill prevention and response unit. “Our number one goal is to stop the release of oil into the environment, and this is the company’s number one goal as well, and were overseeing their response efforts to accomplish that.”

(Map courtesy of Alaska Dept. of Environmental Conservation)

Ryan said roughly 461 barrels of crude oil can be held in the pipeline, which was cut off at either end once the leak was discovered, stopping the flow of oil. She said Hilcorp estimates roughly 10 gallons was released into the water, but until they flush out the pipe and see what’s missing, they won’t know for sure.

“In order to reduce the risk of a further spill, platform crews are displacing the existing oil in the pipeline with seawater,” a joint statement explained Sunday afternoon.

“The crude oil pipeline between the Anna and Bruce platforms has been shut-in and the pressure to the line has been reduced to zero pounds per square inch,” a second DEC situation report said Sunday. “A polyurethane pig has been deployed to remove the remaining crude oil from the line.”

The situation report said pigging operations should be done by 8 p.m. Sunday.

During a flight over the area at 12:30 p.m. Saturday, Hilcorp officials discovered six oil sheens near the Anna Platform — the largest was 10 feet by 12 feet in size. Ryan said no sheens were seen during the most recent observation flights over the area.

“Hilcorp has hired a diving contactor to investigate the line and conduct repairs. It is anticipated that this work can be conducted late next week,” the DEC wrote in its release.

The exact cause of the leak is unknown, and is being investigated.

This leak is not related to the company’s natural gas leak off the coast near Nikiski.

Gov. Bill Walker, whose office has been in contact with Hilcorp during the response to the first reported leak, said he is “deeply concerned about the potential impact to the environment” this newer leak poses. 

“It has been less than a week since Hilcorp agreed to temporarily shut down oil and gas production as part of its response to a leaking gas supply line. Now, Hilcorp has reported a separate leaking oil line — which is significantly more harmful than natural gas,” he said in a statement Sunday. “This oil line has been shut in. Our Spill Prevention and Response Team has immediately responded, and is keeping me apprised of developments.”

Bob Shavelson, the director of advocacy for the Alaska environmental protection group Cook Inletkeeper, said Hilcorp’s maintenance of its facilities needs to be reviewed.

“What we’d like to see is a comprehensive audit of all the pipelines Hilcorp is operating right now and also look at the bonding amounts,” he said. “Because we looked at bonding issues in 2013 and we found out there’s literally pennies on the dollar being put into this infrastructure that needs to be replaced or removed.”

He called the situatation “frustrating for all Alaskans.”

“Under our constitution, Alaskans own the public resources in Cook Inlet. So when you see a bad actor like Hilcorp come in and disregard our water and our fisheries, that’s not good,” Shavelson said.

As plans for repair and cleanup efforts unfold, Ryan said the DEC would continue to monitor the company’s response to the situation.

“The state of Alaska has a zero tolerance for oil being released into the environment and we’ll ensure that this company does what they need to do to stop this release and clean up what has been spilled,” Ryan added.

This is a developing story; please check back for updates.