Hilcorp Energy has another Cook Inlet natural gas leak from an aged, submerged pipeline that has leaked before, the most recent for several months in 2016, the Alaska Department of Environmental Conservation said in a situation report issued April 5.

The leak was detected April 1 when a helicopter pilot noticed bubbles on the surface of Cook Inlet while making a supply delivery. Hilcorp Energy, the owner and operator of Cook Inlet oil and gas production, closed down the pipeline April 3 by closing block valves to isolate the leaking pipe section.

The 8-inch pipeline is in 80 feet of water and delivers dry natural gas for fuel to two oil production platforms, Platform A and C.

The state environmental conservation department will begin sonar scans April 6 to locate the source of the leak, and diving operations will begin as soon as ice conditions permit to determine the cause and to plan repairs.

The quantity of gas being leaked is unknown but the 8-inch pipeline operated at 190 pounds per square inch of pressure prior to the gas release, the state agency said.

Natural gas is defined as hazardous by the environmental conservation department, the agency’s April 5 statement said. An endangered population of beluga whales lives in Cook Inlet, but it is not known to what extent mammal who would be in the vicinity may be adversely affected by a natural gas release in the water.

Hilcorp dealt with problems with the same pipeline in 2017 that leaked gas for several months until ice and water conditions were safe enough to do repairs. Bob Shavelson, director of Cook Inlet Keeper, an environmental organization that monitors industry activity in the Inlet, said the same pipe had experienced leaks in 2014.

Most of Cook Inlet’s oil and gas production infrastructure, including offshore platforms and submarine pipelines, was built in the 1970s, and has now aged.

Operating companies do not have pressure-monitoring equipment in place to be able to detect and gas leak or oil spill, and rely mostly on observers like pilots, vessel operators or fishermen to report gas or oil in the water.

“We issued a report several years ago on the condition of offshore infrastructure in the Inlet, and there were several improvements that came from that,” Shavelson said in an interview. “However, there’s only do much you can do with a 55-year old undersea pipeline.”

“We’re dealing with dinosaur technology here,” he said.

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