Oil spill cleanup crews have removed crude that pooled in a containment area after a major spill last week at the trans-Alaska pipeline's Pump Station 9, state environmental officials said Tuesday.
The cleanup effort now is focusing on cleaning oil that saturated the gravel at the containment area. The pump station is a few miles from Delta Junction.
The Department of Environmental Conservation estimates about 210,000 gallons of oil spilled, the third-largest spill ever for the 33-year-old 800-mile pipeline. The spill shut down the pipeline for more than three days and forced North Slope producers to slash production during the shutdown so that oil field storage tanks wouldn't fill.
The DEC said about 56,000 gallons of oil had been recovered by Tuesday afternoon.
That recovered oil was sent to the tanker terminal in Valdez for recycling and return to the pipeline.
Spilled oil remaining in the gravel is being extracted through a sump-and-drain system being dug into the gravel, the DEC said.
"When all of the recoverable oil has been removed, it is then planned to begin soil removal," the DEC said.
The exact cause of what went wrong in the May 25 spill is under investigation by state and federal authorities.
The pipeline is run by Alyeska Pipeline Service Co., an oil company-owned consortium.
The spill occurred while the pipeline was shut down for routine maintenance, Alyeska said. The company had turned off its main power to test its battery-controlled backup system. But the batteries failed.
The power outage triggered valves to open and divert oil from the pipeline into a partially filled 2.3 million- gallon storage tank, Alyeska said. Those valves remained open for about 55 minutes before workers noticed the storage tank overflowing and got the valves closed.
The oil spilled into a large, lined and bermed containment area and doesn't appear to have escaped the site, company and state officials said. The saturated gravel lies above the liner.
The pipeline was turned back on Friday afternoon. It normally carries about 650,000 barrels a day, or 27 million gallons, of oil. That's about 10 percent of U.S. oil production.
Alyeska is owned by BP, Conoco Phillips, Exxon Mobil, Koch Industries and Chevron.