State answers FERC questions about Cook Inlet pipeline crossing
http://www.alaskajournal.com/2019-06-05/state-answers-ferc-questions-about-cook-inlet-pipeline-crossingThe state-led gas line development team has told federal regulators it is confident the Alaska LNG project’s steel pipeline could withstand Cook Inlet’s strong currents, shifting seabed and traveling boulders along the 29-mile underwater route to the gas liquefaction plant in Nikiski, on the Kenai Peninsula.
The water-crossing information is among the remaining batches of answers the Alaska Gasline Development Corp. owes to the Federal Energy Regulatory Commission, which is scheduled to publish sometime this month its draft environmental impact statement for the proposed $43 billion project to pipe North Slope gas to the LNG terminal for export.
Federal regulators last October asked the state team for more information on the Cook Inlet pipeline crossing, including how the currents could affect the line’s stability on the seafloor and how the high-pressure steel pipe would be protected against boulders.
“The strong tidal currents of Cook Inlet could potentially move debris and boulders across the pipeline,†AGDC reported in a May 24 filing with FERC. The project team analyzed what would happen if boulders as large as 10 tonnes (22,000 pounds) fell on the 42-inch-diameter pipeline, which would be laid — not buried — on the seabed floor. The analysis also looked at the risk of 15-tonne boulders “traveling at the maximum identified Cook Inlet bottom current velocity of 4.8 knots.â€
The analysis showed that any hits by boulders of the size modeled “can be easily absorbed by the pipeline steel alone,†AGDC told FERC. For additional protection, the 1.25-inch-thick steel pipe would be coated with 3.5 inches of concrete before the lengths are welded together and lowered to the seafloor....
