DEC reports natural gas leak from Hilcorp pipeline near Nikiski

Hilcorp Platform A as seen in the distance from the air on Sunday, April 4, 2021.
Hilcorp Platform A as seen in the distance from the air on Sunday, April 4, 2021.(Photo provided by Hilcorp via Alaska Department of Environmental Conservation)
Published: Apr. 5, 2021 at 5:23 PM AKDT
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ANCHORAGE, Alaska (KTUU) - The Alaska Department of Environmental Conservation is investigating the cause of a natural gas leak from a Hilcorp pipeline in Cook Inlet near Nikiski, according to a situation report released Monday.

An unknown amount of gas has leaked from an 8-inch pipeline into Cook Inlet waters between Hilcorp’s Platform A and the unincorporated community of Nikiski. It’s not known what day the leak actually began, but it was reported by Hilcorp at 5:30 p.m. last Thursday, April 1, according to the report.

“... A helicopter pilot identified bubbles on the surface of the water during supply delivery,” the report states.

The gas is a processed, dry natural gas that is more than 98% methane, according to the report. It is not natural gas produced from the platform.

Following discovery of the leak, Hilcorp shut-in both Platform A and C. According to the report, the line’s pressure was 190 pounds per square inch prior to the release of natural gas. In response to the leak, the line’s pressure was reduced to 70 psi.

The department reported that source control was achieved at approximately 1:30 p.m. on April 3 — two days after the leak was reported — by activating block valves. That means that the block valves were closed on the pipe, and there is no more gas moving into the pipe, said Acting Central Region Manager Anna Carey.

The cause of the leak is not yet known and is being investigated. Hilcorp is expected to start sonar scans on Tuesday, according to the report, and diving operations to identify the reason for the release of natural gas will happen “as soon as ice conditions safely warrant.”

This same 8-inch pipeline had a weekslong natural gas leak in 2017. After waiting several weeks for weather and ice conditions to improve, Hilcorp eventually repaired the breach in the pipeline.

The pipeline is approximately 80 feet below Cook Inlet waters.

Hilcorp will continue to monitor the pressure on the line, according to the report, and staff will observe for wildlife in the area.

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