Hilcorp Alaska told a state regulator in a letter on Monday that it does not anticipate deploying repair divers to fix a Cook Inlet natural gas leak until at least "mid-to-late March," due to sea ice and other conditions.
Also, in a written update sent to reporters Friday, the company said it has worked with environmental experts and consultants who have determined the leak's risks to humans and wildlife to be low.
The update on the gas leak involving Hilcorp's 8-inch undersea pipeline did not provide information about the leak rate, which was pegged last week at between 210,000 and 310,000 cubic feet of gas a day. The leak, discovered Feb. 7 when a Hilcorp helicopter spotted roiling water, is located in the Middle Ground Shoal oil field northwest of Kenai.
Based on that number and average household consumption rates made public by Enstar Natural Gas Co., the amount of wasted gas would have been enough to fuel about 370 homes a day in December.
Hilcorp has said it can't shut down the gas line, which carries a fuel supply to generate heat, light and power on four offshore platforms in Cook Inlet. The pipeline is about 80 feet below the water, the Alaska Department of Environmental Conservation has said.
"With respect to repair, the conditions in the 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," Hilcorp Alaska said in a 10-page letter on Monday to a DEC official.
"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," the company said in the letter, obtained Friday by watchdog group Cook Inletkeeper, following a public records request to the state agency.
On Feb. 10, DEC had sent a letter to Hilcorp seeking information such as options for reducing and assessing the leak's environmental impact.
Hilcorp has said it needs to keep the line pressurized. Without a minimum pressure, the line could fill with water, allowing residual crude to escape from what was previously used as a crude oil pipeline.
Hilcorp's letter said the "choice is between the current methane release" and "one or more oil spills, along with other potential damage and additional risks," such as power loss on platforms that could put crews in danger and possibly damage platforms and other infrastructure.
The company has taken steps to reduce the amount of gas flowing through the line, in turn reducing the amount of leaking methane, by reducing a variety of platform operations.
In its update to reporters, Hilcorp did not provide its anticipated repair period but said it had "mobilized equipment and briefed personnel for repairs." The statement was issued by Lori Nelson, external affairs manager at Hilcorp Alaska, who did not return a phone call Friday afternoon.
Cook Inletkeeper last week issued a notice of intent to sue to Hilcorp, citing concerns under the Clean Water Act, including over methane that could reduce oxygen levels in the water column, posing a threat to animals.
In its statement to reporters, Hilcorp said consultants have conducted preliminary modeling of the amount of methane dissolving in the water column. They have estimated that "concentrations would likely be approximately 1/500th of the concentration level that may be harmful to fish," based on a standard provided by DEC.
The consultants are still refining their evaluation, the company said.
Experts working with Hilcorp have also reviewed several environmental studies, including some performed by federal agencies, to determine that "potential impact to marine life is minimal based on the volume of gas being leaked," the company said.
Hilcorp said the National Oceanic and Atmospheric Administration has performed calculations indicating "that the volume of gas being released to the atmosphere likely poses a low risk to humans."
Bob Shavelson of Cook Inletkeeper said on Friday the company could take steps to address the problem, like hiring an ice-management vessel to maintain ice-free conditions, so a remote-operated vehicle can be sent underwater to begin inspections.
"They're saying we can't do anything until the ice clears," he said. "So they admit they can't respond to an event in Cook Inlet in winter. If they can't do that, they shouldn't be doing business here."