Flow reduced in leaking underwater Alaska gas pipeline

Natural gas spewing into Alaska's Cook Inlet from a ruptured underwater pipeline has been reduced by about half after owners lowered pressure in the line.

The pipeline carries gas from onshore to four production platforms owned by Hilcorp Alaska LLC. The platforms burn natural gas for power. Only two platforms were producing oil.

Hilcorp over the weekend temporarily shut down production, reducing the platforms' need for energy and allowing the company to reduce pressure in the leaking line.

The 20 cm pipeline has been leaking since mid-December in habitat used by endangered Cook Inlet beluga whales, other marine mammals and fish.

Hilcorp already had reduced pressure in the line twice. Hilcorp estimates the pipeline will continue to leak 2,400 to 3,200 cubic metres of gas per day, down from 5,400 to 6,000 cubic metres daily, said company spokeswoman Lori Nelson in an announcement.

The company hopes to repair the line after floating ice is gone and divers can safely reach the leak.

"Based on current weather forecasts and ice conditions Hilcorp expects to mobilize equipment and deploy divers to begin repair operations within the next 10 days," Nelson said.

Governor asked for shutdown

Hilcorp has said it has detected no harm to wildlife or the environment from the leak.

However, Alaska Gov. Bill Walker asked the company to temporarily shut down production to reduce safety risks and environmental impact. Alaskans, Walker said in an announcement Saturday, want peace of mind that their waters are protected.

The platforms continue to need fuel to operate equipment, Nelson said.

"Shutting in wells and idling lines and equipment in very cold temperatures create a known risk of freeze-up and potential rupture," she said.

Alaska's warming temperatures have reduced the risk, Nelson said.

The U.S. Pipeline and Hazardous Materials Safety Administration on March 3 issued a proposed safety order requiring the natural gas line to be repaired by May 1 or shut down.

Environmental groups have called for an immediate shutdown. Two groups have given required 60-days' notice that they intend to sue. A leak of processed natural gas creates a low-oxygen dead zone threatening marine mammals and fish, according to the groups.