Repair halts natural gas spew from Alaska undersea pipeline
Posted April 14
ANCHORAGE, Alaska — Divers have placed a clamp over a hole in an underwater Alaska pipeline, stopping the flow of millions of cubic feet of natural gas into Cook Inlet, home to endangered beluga whales.
Hilcorp Alaska LLC, a subsidiary of Houston-based Hilcorp, announced Friday that divers Thursday night covered a gash at the bottom of the 8-inch (20-centimeter) diameter line in 80 feet (24 meters) of water. They measured the hole at less than 0.5 square inches (32 sq. centimeters).
"A total of 12 dives were completed on the fuel gas line in order to locate the leak, then properly position, stabilize and prepare the pipeline for repair," said Hilcorp spokeswoman Lori Nelson by email.
Cook Inlet covers 180 miles (290 kilometers) from the Gulf of Alaska to Anchorage. A Hilcorp helicopter crew spotted gas bubbling from the line Feb. 7 about 4 miles (6.4 kilometers) off shore.
The pipeline carries processed natural gas to four production platforms, where it's burned to generate electricity. Analysis of gas flow indicated the pipeline probably started leaking in mid-December and initially spewed up to 310,000 cubic feet (8,780 cubic meters) of natural gas per day.
Hilcorp lowered pressure in the line to reduce the daily flow to 85,000 to 115,000 cubic feet (2,407 to 3,257 cubic meters).
The inlet is notorious for extreme tides that produce strong currents. Hilcorp held off on repairs until the additional threat to divers of floating ice had diminished.
Divers found the leak where the pipeline rested on a boulder in the seafloor.
"After proper cleaning and preparation, a steel and rubber clamp was installed over the leak," Nelson said. "The clamp assures a gas tight, liquid tight seal that will reinforce the pipeline."
The federal Pipeline and Hazardous Materials Safety Administration had ordered repairs to be completed by May 1 or shut down. The agency later called for inspection of a nearby crude oil line subject to the same stresses as the natural gas line.
As weather permits, more inspection and stabilization of both lines will be completed, Nelson said.
"Neither pipeline will be returned to regular service until Hilcorp, along with state and federal regulators, agree it is safe to do so," Nelson said.
Hilcorp owns 15 of the 17 production platforms in Cook Inlet. Fourteen platforms were built in 1968 or before.
The Center for Biological Diversity has formally petitioned the Pipeline and Hazardous Materials Safety Administration for state and federal inspections of the aging infrastructure. Kristen Monsell, an attorney for the organization, said Thursday that the gas leak shows that self-policing does not work.