PHMSA proposes oil pipeline inspection
Agency wants Hilcorp to ensure the subsea crude oil pipeline from Middle Ground Shoal field to Nikiski does not develop a leak
The federal Pipeline and Hazardous Materials Safety Administration has sent a letter to Hilcorp Alaska proposing an order requiring Hilcorp to inspect the subsea pipeline that delivers oil from the Cook Inlet Middle Ground Shoal field to shore at Nikiski. The agency thinks that the oil line is subject to a damage risk similar to the risk associated with a subsea gas line that has ruptured, causing a gas leak in the waters of the Cook Inlet. The gas line delivers fuel gas to the field’s offshore platforms.
PHMSA’s concerns stem from the facts that, while the gas line (designated the A pipeline) and the oil line (designated the B pipeline) run across the seafloor close to each other and are of near identical design, the A pipeline has now suffered three leaks since June 2014. Both lines are eight inches in diameter, cased in concrete. The B pipeline was installed in 1965.
A leak from the oil line would be significantly more environmentally damaging than the gas line leak.
Inspection within 21 daysPHMSA has already proposed another order, requiring Hilcorp to repair the subsea gas line by May 1. The agency now proposes an order requiring Hilcorp to inspect the oil line within 21 days of the new order being issued, and to send the results of the inspection to PHMSA’s Western Region director within three days of the inspection being completed.
The inspection must involve a survey using high-resolution side-scan sonar or equivalent technology, to identify sections of the pipeline that are not adequately supported by the seabed. Areas of the line that are found not to be adequately supported over distances of 10 feet or more, with a gap of one foot or more from the sea floor, must be inspected by a diver, or by some equivalent means, to locate any unsupported pipeline sections that lack a protective concrete coating. And, where that concrete coating is missing, the line must be inspected for defects including dents, gouges and metal loss.
PHMSA says that abrasion of unsupported sections of the gas pipeline by rocks as a consequence of the vibration of the line in the Cook Inlet tidal currents has been identified as the likely cause of the previous gas pipeline leaks.
If Hilcorp is unable to conduct the required inspections of the line within the 21-day time limit, or if PHMSA determines that the inspection results indicate a pipeline integrity risk, Hilcorp must shut the pipeline down and purge its contents within seven days, PHMSA proposes.
A pipeline shutdown would presumably cause a shut-in of the Middle Ground Shoal field.
Modification and inspection planIn addition, PHMSA’s proposed order would require Hilcorp to develop a modification and inspection plan for the oil line and to submit that plan to the agency within 45 days of the issue of the order. The plan, which would require PHMSA approval, must include a plan for modifications to the pipeline to enable in-line inspections. Hilcorp must then conduct an in-line inspection and complete all necessary repairs to the line by Sept. 30, 2018.
The proposed order also says that Hilcorp must review and modify, as necessary, its oil spill response plan, in the light of the experience of responding to the leak in the gas pipeline. And Hilcorp must submit to PHMSA quarterly reports presenting analyses of the results of testing and evaluations mandated by the PHMSA order, and the progress of any resulting pipeline repairs and other remedial actions.
Hilcorp response“Hilcorp will work with PHMSA and other state and federal agencies to ensure a thorough and timely response to the concerns in the proposed order,” Hilcorp said in response to the letter from PHSMA. “Hilcorp continues to focus on addressing the natural gas pipeline leak and ensuring the safety of our responders in the field.”
Hilcorp said that the oil pipeline was pressure tested in September 2015 and that the line is operating normally.
The company is waiting for sea ice in Cook Inlet to clear before sending divers down to repair the gas line - the company has said that the use of divers in sea ice conditions would be unacceptably dangerous. Once the repairs are started they will likely take several day to complete, the company has said. Previous repairs to the pipeline involved installing bolt-on, split sleeve clamps.
PHMSA, in its letter to Hilcorp, said that the National Marine Fisheries Service has expressed concern about the potential impacts of the gas leak on marine mammals, especially the endangered Cook Inlet beluga whales. The U.S. Fish and Wildlife Service has indicated that the risk to birds, sea ducks and water fowl is currently low but will increase with the seasonal migration that typically starts in March. Hilcorp has said that no significant impacts to wildlife or the environment have been observed. The company is implementing an environmental monitoring and sampling plan.