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US pipeline regulator orders action over leaking Alaska gas pipeline

20 March 2017

The US Pipeline and Hazardous Materials Safety Administration (PHMSA) has issued a proposed order that operator Hilcorp fix a leaking gas pipeline in the Cook Inlet off Nikiski in Alaska by May 1 or shut it down. The PHMSA also ordered the company to conduct inspections of a "substantially similar" underwater pipeline that carries crude oil to shore from two offshore production platforms. 

Cook Inlet, Alaska - Image: Shutterstock
Cook Inlet, Alaska - Image: Shutterstock

The regulator said the crude oil pipeline was of the same vintage and size as the company's leaking gas line in Cook Inlet and could be threatened by the same forces that ruptured the gas line and cause a far more dangerous leak. Both of the 8-inch steel pipelines were installed in the mid-1960s.

PHMSA said the gas line leaked twice in 2014 in summer, but repairs were made before Hilcorp acquired the facilities from the previous operator. The leaks were caused by abrasion from rocks in areas where the pipeline is not supported by the seabed, according to the agency.

Although the cause of the ongoing leak on the (gas pipeline) is unknown, past leaks on the pipeline have occurred due to outside forces, such as pipe vibration or rock damage, the order said.

Hilcorp detected the gas leak in February when a helicopter flying above the pipeline route spotted water disturbance. The company indicated the leak began in December, according to PHMSA.

Hilcorp said pan ice and strong tides in Cook Inlet present dangers for repair divers. The company does not expect to begin finding and fixing the leak — about 80 feet underwater — until the ice clears. That is not expected to happen until at least late March, the agency said.

The notice said environmental harm from an oil leak could be "significantly greater" than from the gas leak, while the company's ability to respond could be severely hampered in winter, and could have a serious impact on the 340 endangered Cook Inlet beluga whales, as well as birds and fish.

The PHMSA said Hilcorp needed to introduce “smart pig” internal inspections of the pipelines on top of the side-scan sonar, multibeam echo-sounder surveys and diver inspections it currently undertakes.

After a final order is issued, Hilcorp will have 21 days to externally inspect the pipeline or shut it down and purge it, the agency said.

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