Alaska underwater pipeline leaking for months: regulator
ANCHORAGE — A pipeline spewing natural gas into Alaska’s Cook Inlet may have started leaking in December, two months before the leak was spotted from the air, according to a federal pipeline safety office.
The estimate of when gas started leaking into winter habitat for the endangered Cook Inlet beluga whales was issued in a proposed safety order last week by the U.S. Pipeline and Hazardous Materials Safety Administration that the agency confirmed on Tuesday.
Processed natural gas continues to leak from a Hilcorp Alaska LLC pipeline that supplies four oil platforms in the inlet south of Anchorage — at a rate estimated by the company of 210,000 to 310,000 cubic feet of gas daily.
A Hilcorp helicopter crew spotted gas bubbling to the surface about six kilometres off shore on Feb. 7. However, the company reported it had detected increased gas flow through the pipeline in January and started looking for a leak, according pipeline safety office’s report.
A subsequent analysis of gas flow indicated the pipeline likely began leaking in December, the agency said. It issued the proposed safety order requiring the line to be repaired by May 1 or shut down.
Hilcorp has 30 days to respond. In a statement, spokeswoman Lori Nelson said the safety of response personnel is the company’s top priority. She said Hilcorp is pleased that the proposed safety order recognizes immediate repair is not viable.
The pipeline is in 25 metres of water. Repairs by divers cannot be made in current winter conditions that include sea ice, severe weather and extreme tides, according to Hilcorp.
The company told the federal pipeline office safe diving operations cannot start until late March at the earliest.
Shutting the gas pipeline down is not an option, Hilcorp said. Before the pipeline carried natural gas, it moved crude oil. Without pressure in the line, seawater could enter and allow residual crude oil to leak, the company said.
Hilcorp purchased the pipeline and other oil and gas facilities from XTO Energy, Inc., in September 2015. The 20-centimetre line also leaked in June and August 2014. The leaks were 20 metres apart about a kilometre from the current leak. They were repaired with clamps.
XTO Energy concluded that previous leaks were caused by rocks contacting the pipe in locations where the line was not continuously supported by seabed.
Besides endangered beluga whales, Cook Inlet is home to salmon and other fish.