A salvage tug was expected to drag the carcass of the New Carissa about 200 miles into the Pacific Ocean Wednesday afternoon.
The Coast Guard said at a news conference that an assessment team had been checking the condition of the ship and weather conditions in preparation for the move.
With the bow still containing about 135,000 gallons of oil, Navy officials believe sinking the 440-foot front section will help contain the sticky liquid.
"This oil is already thick and viscous. If you get it down to these depths, about 5,000 feet, it will be very cold and under pressure, which will help immobilize it and contain it," Coast Guard Lt. Commander Ed Parsons said.
Officials initially believed less than 40,000 gallons of fuel oil had spilled.
Between the oil still aboard the Japanese-owned ship and the oil that spilled, less than half of the nearly 400,000 gallons that on the New Carissa was burned off in fires ignited by a Navy explosives team last week.
The ship broke into two pieces after the crews used napalm and explosives to try to burn off its fuel cargo. The burning, the first such attempt in the continental United States, was considered the best hope of averting an environmental disaster along the south Oregon coastline. The beaches are home to rich marine life and rare bird species.
A memo cited in today's edition of The Oregonian says the Environmental Protection Agency has waived all environmental permits required for scuttling the ship because the Coast Guard has declared a state of emergency.
Plans to move the fractured ship's smaller stern portion had not yet been made as of Wednesday.
The New Carissa ran aground off the north entrance to Coos Bay on Feb. 4 while the crew was trying to wait out a storm. After a week of pounding surf, officials decided that torching the ship was the only way to save beaches from a disastrous spill.
The nearby beach is home to the Western snowy plover, a small shorebird protected as a threatened species under the Endangered Species Act. Only about 100 breeding pairs can be found in Oregon.
"Their nesting season is due to start mid-March. A long-term removal project in the area where they're due to be nesting is a great consideration," Parsons said.
Teams have found 42 dead birds, 20 with obvious signs of oil. None were snowy plovers. Twelve birds, including nine snowy plovers, are in rehabilitation.
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