Stockpiles of oil from Alaska ’s North Slope have surged to a five-year seasonal high as tanker maintenance slows loadings, forcing the grade to trade at a discount to U.S. crude for the first time since 2010. Inventories at the Valdez terminal, the northernmost ice-free port in North America and the loading point for Alaskan oil, have averaged 4.38 million barrels this month, the most for October since 2009, data posted on the Alaska Revenue Department’s website show. Tanker repairs have shrunk the pool of vessels available, terminal operator Alyeska Pipeline Service Co. said. The trapped stocks threaten to further cut prices for oil from the North Slope, once the most prolific crude-producing region in the nation, as refiners on the U.S. West Coast turn elsewhere for supplies. California is bringing in a record volume of oil by rail from other states and the region has increased imports from […]