Repairs on a leaking undersea natural gas pipeline in Alaska’s Cook Inlet cannot begin until mid-March because of sea ice, tides and other conditions, pipeline operator Hilcorp Alaska LLC has told a state regulator.

The leak was discovered Feb. 7. “Since its discovery, Hilcorp has diligently evaluated options for repairing the leak on an eight-inch fuel gas line located in Middle Ground Shoal oil field,” Hilcorp said in a statement Friday. “The line provides natural gas fuel for power generation to four offshore platforms. Potential response efforts need to address the leak while maintaining the safety of the public and our personnel and protecting the environment.”

In a Feb. 20 letter to the Alaska Department of Environmental Conservation (DEC), which was obtained and released by Alaska Dispatch News, the company said, “With respect to repair, the conditions in Cook Inlet — the broken ice, exacerbated by high tidal flows and limited daylight — prevent the immediate dispatch of divers to inspect and contain the leak in the Pipeline. Given the typical weather patterns affecting ice formation and dissipation in Cook Inlet, we currently anticipate that the earliest that conditions will allow diving will be in mid-to-late March.”

In its Friday update, Hilcorp said it has minimized the use of natural gas and lowered the line pressure by shutting down a water flood process used for oil production as well as other non-essential equipment and activities. It has also maintained positive pressure on the line to prevent infiltration of seawater and possible crude oil discharge. Years ago the pipeline was used to carry oil, residue of which could leak if pressure is not maintained, the company said.

Hilcorp said divers are the “best available option” to safely repair the leak; equipment has been mobilized and personnel have been briefed.

“Hilcorp continues to assess other ways in which it may further safely reduce pressure on the fuel gas line. However, at this time it is essential to maintain positive pressure to mitigate the risk of environmental and safety issues,” the company said.

“Current ice conditions prevent divers from accessing and repairing the line safely. Hilcorp is ready to proceed once ice conditions allow for safe repair operations to begin.”

In a Feb. 10 letter, the state of Alaska told the company that the leaking natural gas is considered to be a “hazardous substance” as defined by state law. The letter advised that company response actions must be approved in advance by the state. If they are deemed to be unsatisfactory, Alaska DEC could assume the lead role in the investigation and cleanup efforts, the letter advised.

More recently, on Feb. 15, environmental group Cook Inletkeeper told Hilcorp it intended to sue the company under the Clean Water Act. “…for illegal discharges to Cook Inlet which threaten water quality, fish and Beluga whales,” the group said in a blog post on its website.

“Inletkeeper’s notice of intent to sue is meant to provide a back-stop in the event Hilcorp opts to continue to put profits over fish, wildlife and water quality in Cook Inlet, and to press Hilcorp to address the larger issue of relying on antiquated infrastructure as part of its Cook Inlet business model,” the group said.

“Hilcorp has put forth various excuses why it cannot shut down the leaking pipeline — including that water would infiltrate the gas line and other reasons — but the fact remains Hilcorp simply wants to maintain production and profits without interruption.”