Federal pipeline safety authorities have ordered Hilcorp Alaska to inspect the underwater crude oil pipeline running adjacent and parallel to the leaking Hilcorp natural gas line that is presently releasing between 193,000 and 215,000 cubic feet of methane per day into Cook Inlet.

The Pipeline Safety and Hazardous Materials Administration, a pipeline-regulating division of the federal Department of Transportation, issued the notice to do so to Hilcorp on Friday.

The crude oil pipeline is approximately 14 miles long and transports oil produced at four Hilcorp platforms in the Middle Ground Shoal Region of Cook Inlet to an onshore Hilcorp facility on the East Forelands coastline of Nikiski. From the onshore facility, the crude is piped to the Tesoro refinery.

Hilcorp confirmed on Feb. 7 that the pipeline carrying methane fuel to the four platforms is leaking. Since that time, Hilcorp has maintained normal operation of the crude pipeline, which according to PHMSA’s notice transports about 3700 barrels of crude a day from the Middle Ground Shoal’s two active platforms.

The ongoing methane leak is the third to spring from that gas pipeline since 2014. The others, in June and August 2014, occurred during ice-free months and were repaired. Causes of past leaks include rock impact, vibrations, and seafloor erosion that leaves the pipeline unsupported and prone to bending, according to PHMSA.

PHMSA’s notice doesn’t report any previous known leaks from the crude pipeline. Because the two pipelines share the same environment, however, the factors that caused the gas leak may also affect it.

“Although the cause of the ongoing leak on the ‘A Pipeline’ (gas pipeline) is unknown, past leaks on the pipeline have occurred due to outside forces,” PHMSA Western Region Director Chris Hoidal wrote in the notice. “… Accordingly, it is reasonable to conclude that similar conditions are also present on the ‘B pipeline’ (crude oil pipeline).”

PHMSA notes that environmental damage from a leak in the crude pipeline would be much greater than the present gas leak, and repair would be just as difficult should a leak occur when the Inlet is iced over.

Like the leaking gasline, the crude pipeline is 8 inches in diameter and coated with an inch of concrete. According to the PHMSA report, Hilcorp successfully pressure-tested it in 2005, 2010 and 2015. The company also inspects it annually via sonar and echo-sounder, with diver inspections of areas determined by the sonar inspection. The sonar and echo-sounder inspections, however, “do not provide sufficient information” about certain kinds of damage, according to the PHMSA notice.

The measures in PHMSA’s Friday letter are proposals, subject to modification and negotiation with Hilcorp, which has 30 days to respond. They include new inspection requirements for the crude pipeline similar to those PHMSA proposed for the leaking gas line in a March 3 notice: using high-resolution sonar to find places where the pipe’s concrete is missing or the seabed beneath has eroded away, and inspecting those areas with divers.

If the inspection results lead PHMSA to determine that the pipeline “poses a risk to public safety, property or the environment,” it must be shut down and purged within seven days of PHMSA’s notice. Hilcorp must perform the inspections again in the summer of 2018.

The proposal also requires Hilcorp to revise its oil spill response plan by Nov. 1, 2017 to account for “environmental barriers and restraints” such as the ice that presently prevents it from repairing the gas leak.

The four Middle Ground Shoal platforms and their connecting pipeline system are among the oldest offshore oil and gas infrastructure in Cook Inlet, built in 1964 by Shell Oil Company and bought by Hilcorp in 2012 and 2015. Two of them, the A and C Platforms, are actively producing oil while two others, the Baker and Dillon Platforms, are inactive and unmanned.

Reach Ben Boettger at ben.boettger@peninsulaclarion.com.