A third area of spilled crude oil has been discovered as part of an investigation into a 20-inch fill line that state regulators say was overpressurized during an operation this summer at the Drift River tank farm on the west side of Cook Inlet.
The spills by Hilcorp Alaska's Cook Inlet Pipeline Co. occurred in late June and were discovered by the company starting in early July, according to the the Alaska Department of Environmental Conservation.
The latest spill was discovered last Wednesday during an excavation of a buried flange, the agency said on Tuesday.
The agency said it did not know how much oil spilled in that area.
The first spill from the 20-inch line occurred June 25 as the company was emptying two tanks — and transferring the oil to another tank — to prepare for an internal inspection that takes place every 10 years.
The company properly followed procedures that have been in place since long before Hilcorp bought the aging Drift River facilities from Chevron in 2011, but the oil unexpectedly went to the wrong tank and the line became overpressurized, regulators have said.
Adding to the problem was that while oil still flowed, a valve to that tank was shut off at the end of the day as part of a safety measure instituted after the 7.1-magnitude earthquake in January, said Young Ha, the Inlet and Kodiak unit supervisor for DEC. The earthquake was centered 60 miles west of Homer.
The "misalignment" apparently existed for decades, but was only realized after the new safety procedure was put in place, Ha said.
State regulators have said in the first spill reported, 14 gallons of crude oil had collected inside a valve box. A gallon spilled on the ground.
In the second spill reported, the company on July 28 discovered a crude-oil stain between Tanks 1 and 4. The stain at the surface was triangular in shape, and measured 24 feet by 24 feet by 30 feet. The amount of this spill is unknown.
In the recently discovered spill, between Tanks 2 and 3, the "contamination extended only a few feet outside of the initial excavation area," state regulators said.
Cook Inlet Pipeline used about 60 sorbent pads to collect the oil, the state said.
Cook Inlet Pipeline "will submit a spill volume estimate based on waste generated as part of the final report," the agency said.