Hilcorp gas pipeline springs another leak in Cook Inlet

A map of the spill site, near Nikiski in Cook Inlet.
Credit Alaska DEC

Oil company Hilcorp is reporting another undersea natural gas leak near one of its platforms in Cook Inlet, about six miles offshore from Nikiski.

Authorities said they don’t yet know how much gas has leaked into the ocean or what caused the leak from the eight-inch-wide pipeline, located 80 feet underwater. The leak was first reported Thursday evening by a company helicopter pilot who spotted bubbles on the water’s surface, the company said.

Hilcorp reported the leak to state and federal authorities an hour later and immediately reduced pressure on the line, according to a report issued late Monday afternoon by the Alaska Department of Environmental Conservation. 

It said Hilcorp activated valves to control the leak on Saturday afternoon, and officials said there’s no longer gas running through it. 

This is not the first time the same pipeline has sprung a leak, according to local watchdogs. Four years ago, a rock on the ocean floor punctured the line and caused the loss of as much as 310,000 cubic feet of natural gas a day. 

The pipe also leaked twice in 2014, according to Bob Shavelson, the advocacy director of Homer-based watchdog group Cook Inletkeeper.

Ice in the inlet blocked Hilcorp from repairing the 2017 leak for three months. Cook Inletkeeper threatened to sue the privately-owned company over damage to the environment and local marine life.

The leaking pipeline is more than 55 years old, according to Cook Inletkeeper. Hilcorp is known for buying and reinvigorating old infrastructure and is currently Cook Inlet’s biggest oil and gas producer.

The gas that leaked isn’t produced from the platform. Instead, it’s dry natural gas that fuels nearby Hilcorp platforms. It’s almost entirely composed of methane.

Hilcorp will assess damage when ice conditions allow, the company said. A representative from the company also said divers will install a temporary clamp on the pipeline later this week.

The spill area is within the designated habitat for endangered Cook Inlet belugas. It’s also an essential fish habitat for several Pacific salmon species.