Editor’s note: This article has been updated to include a statement from Gov. Bill Walker. It has also been edited to correct a reference to the leaking pipeline’s diameter.

Crude oil is now leaking from one of Hilcorp’s platforms in Cook Inlet.

The leak was discovered around 11:20 a.m. Saturday on the Anna Platform, northeast of Trading Bay on Cook Inlet’s west side. The oil is leaking from an 8-inch crude oil pipeline, according to a situation report issued by the Alaska Department of Environmental Conservation on Saturday night.

Staff on the platform felt an impact to the platform Saturday morning before the oil sheen was discovered, according to the report. Hilcorp reported the spill to DEC at 12:05 p.m. the same day.

“In looking over the side of the platform to see what was going on, personnel observed sheen and bubbles coming up from near one of the platform legs where the 8 inch line is located,” the report stated. “Personnel confirm that the bubbles or sheen were not observed the day prior.”

On a flyover conducted at 12:30 p.m., Hilcorp staff observed six sheens, the furthest approximately 3.5 miles south of the Anna Platform. The largest was 10 feet by 12 feet and two were 3-4 feet by 25-25 feet, according to DEC’s report. An hour later, during another flyover, no sheens were observed.

After discovering the sheens, the company shut-in the Anna Platform and a neighboring platform, the Bruce Platform, and reduced the line pressure from 70 psi to 5 psi, according to the report. The company’s response contractor, Cook Inlet Spill Prevention and Response, Inc., sent a ship out to the Anna Platform by 12:45 p.m. and looked for oil sheens but didn’t spot any. CISPRI is also serving as the Incident Command Post for a Unified Command in response to the spill, with representatives from Hilcorp, the U.S. Coast Guard and DEC, according to the report.

“Hilcorp has hired a diving contractor to investigate the line and conduct repairs,” the report stated. “It is anticipated that this work can be conducted late next week.”

The report of the oil leak comes in the midst of an ongoing natural gas leak from one of Hilcorp’s seafloor pipelines serving the Middle Ground Shoal, a formation northwest of Nikiski’s East Forelands. The Anna and Bruce platforms are in the Granite Point Unit, northeast of the Middle Ground Shoal. After more than a month of leaking, the company announced last week it would half the pipeline pressure to the Middle Ground Shoal platform, as reported by the Clarion.

The leak may be the fault of a flange located within the first 50 feet of the 8-inch line coming off the platform, according to the DEC report. The company planned to send a foam pig through the line past the flange point, essentially plunging out the line, to isolate any leak location.

“It should be noted that the crude oil line leak involving the Anna Platform is unrelated and unconnected to the Hilcorp natural gas leak in Cook Inlet between Platform A and Nikiski,” the DEC report stated.

The Anna Platform was originally constructed in 1965 and operated by Amoco, according to a fact sheet from the Cook Inlet Regional Citizens Advisory Council. It’s changed hands multiple times over the years as oil companies have come and gone in Cook Inlet; Chevron was the last owner before Hilcorp took over.

Infrastructure on and supporting the platform has also failed multiple times over the years. When BP forced air into a pipeline to the Anna platform in 2002, it sprung several leaks, causing crude oil to leak and create sheens as large as 200 yards wide and five miles long. Eight years later, in 2010, Chevron chose to suspend crude oil operations from the Anna platform after the U.S. Pipeline and Hazardous Material Safety Administration refused a waiver to allow a corrosion-damaged pipeline to be used. The company planned to curtail production until the pipe could be repaired.

Hilcorp took over the platform in 2011 after Chevron exited operations in Cook Inlet. The company rapidly bought up aging infrastructure in Cook Inlet as other companies withdrew and rejuvenated production on both oil and natural gas fields. In a little over five years, Hilcorp has become Cook Inlet’s dominant producer and is currently expanding operations at its natural gas Kalotsa pad near Ninilchik and completed an on-land exploration program called Greystone south of Ninilchik this summer.

Environmental groups have been critical of Hilcorp as the gas leak has continued. On Feb. 27, Tucson-based environmental group the Center for Biological Diversity sent Hilcorp a 60-day notice of its intent to sue over the ongoing gas leak and will monitor the oil leak “to determine whether legal action is warranted,” according to a news release from the organization. Homer-based conservation nonprofit Cook Inletkeeper also announced its intention to sue Hilcorp on Feb. 15, as reported by the Clarion.

On Sunday, Gov. Bill Walker issued a statement saying the DEC was keeping him updated on the situation.

“It has been less than a week since Hilcorp agreed to temporarily shut down oil and gas production as part of its respnose to a leaking gas supply line,” Walker said in the statement. “Now, Hilcorp has reported a separate leaking oil line — which is significantly more harmful than natural gas. I am deeply concerned about the potential impact to the environment.”

This is a developing story.

Reach Elizabeth Earl at elizabeth.earl@peninsulaclarion.com.