An oil platform at dusk
Cook Inlet oil platforms are visible from shore near Kenai, Alaska. (Rashah McChesney/Alaska’s Energy Desk)

Energy company Hilcorp has been ordered to replace an undersea pipeline in Cook Inlet after it leaked gas last week, for the fifth time in the last several years.

In a corrective order dated April 6, the Pipeline and Hazardous Materials Safety Administration told Hilcorp it must temporarily repair the 55-year-old pipeline by April 17, permanently repair it by May 1 and submit a plan for the pipeline’s replacement within 45 days.

The last time the pipe leaked, in 2017, Hilcorp didn’t complete repairs for three months, citing danger from ice in the inlet.

Sea ice is again a problem.

Crystal Smith, an environmental program manager with the Alaska Department of Environmental Conservation, said Hilcorp is waiting for the weather to improve before sending divers down to inspect the pipeline.

She said Hilcorp has both temporary and permanent clamps and will determine which will work best. The line is seven miles long, eight inches wide and carries fuel gas, mostly containing methane, to two Hilcorp platforms in Cook Inlet.

An image of water and land shows the location of a spill site, in the Cook Inlet.
The spill site, near Nikiski in Cook Inlet. (Alaska Department of Environmental Conservation)

A pipeline administrator said in the order he thinks it’s dangerous to continue to operate the pipeline due to its history of leaks and the its age, plus the fact that the pipeline is under a critical habitat for endangered species, including the Cook Inlet beluga..

Smith said DEC has deployed state and federal agencies to provide input on resources that might be at risk.

“Hilcorp has actually had folks out there doing wildlife observations,” she said. “They have not seen any impacts to the wildlife at this time.”

RELATED: Hilcorp gas pipeline springs another leak in Cook Inlet

The leak occurred a mile from one of Hilcorp’s platforms and six miles offshore from Nikiski. It was first reported last Thursday by a helicopter pilot who spotted bubbles on the water’s surface.

Hilcorp reported the leak to state and federal authorities an hour later and immediately reduced pressure on the pipeline. When it could not sustain that amount of pressure, it changed course and shut in the line, the order said.

Hilcorp estimates the leak initially let out between 75,000 and 150,000 cubic feet of natural gas per day.

Authorities still don’t know what caused the leak. But the order gives Hilcorp four months to find out. Before restarting operations there, Hilcorp has to submit a plan to federal regulators.

The pipe was built in 1965 and had two reported leaks in 2014, a year before Hilcorp bought the pipeline. Leaks occurred again in 2017 and 2019, and all were repaired with clamps, the order said.

Hilcorp is known for buying and reinvigorating old infrastructure and is currently Cook Inlet’s biggest oil and gas producer.

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