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8-inch hole punched in oil tanker hull No spill reported from double-hull ship, which carries Alaska North Slope crude for BP; precise cause of breach remains unclear Wesley Loy For Petroleum News
A tanker carrying Alaska North Slope crude oil sustained a hole in the bottom of its hull while in California waters.
Exactly what caused the breach remains something of a mystery.
The double-hull tanker Alaskan Navigator was traveling from Long Beach, Calif., to Washington’s Puget Sound when seawater was discovered leaking into one of the ship’s segregated ballast tanks, says a summary of the Jan. 25 incident.
Only the outer hull was holed. The ship’s inner hull remained intact, meaning no cargo holds were breached. Thus, no oil escaped to the sea, the summary says.
The ship proceeded to Port Angeles, Wash., where a dive survey was conducted on Jan. 26. Representatives from the U.S. Coast Guard, the Washington State Department of Ecology and the American Bureau of Shipping were there.
Anchor to blame? Investigators found a gash in the hull measuring about 2 inches by 8 inches, Anil Mathur, president of Alaska Tanker Co., told Petroleum News on May 1.
The Beaverton, Ore., company carries Alaska crude for BP to West Coast refineries. The 941-foot Alaskan Navigator, launched new in 2005, is one of four matching double-hull tankers in the ATC fleet.
After ATC tankers pick up North Slope oil at the Valdez terminal, they typically deliver part of their load first to Long Beach and then head back north to supply refineries such as BP’s Cherry Point plant in Puget Sound. They follow that route because the tankers, with a capacity of 1.3 million barrels, are barred from taking an oil cargo that large into Puget Sound.
The Alaskan Navigator hull breach is believed to have happened while the ship was at anchor in the Long Beach harbor, Mathur said.
An investigative team has finished its work, but the results are inconclusive, he said.
“There’s circumstantial evidence that we ran over our anchor,” Mathur said.
That can happen if the anchor, designed to lay flat on the bottom, becomes fouled in the anchor chain, he said.
The problem is, the Alaskan Navigator’s anchor showed little to no damage, and the hull puncture doesn’t seem to match any part of the anchor, Mathur said.
A diver searched for objects in the harbor that could have caused the hole, but found nothing, he said.
Presentation in Valdez The Alaskan Navigator was carrying about 520,000 barrels of crude at the time the hull breach was discovered.
“The double hull did what it was supposed to do,” Mathur said, referring to no oil leakage from the ship.
Authorities allowed the tanker to proceed to Cherry Point to offload its oil. Repairs approved by the Coast Guard and the American Bureau of Shipping were made later, and the ship is now in service, Mathur said.
ATC’s Mike Meadors was scheduled to make a presentation on the incident to the Prince William Sound Regional Citizens’ Advisory Council during its May 3-4 board meeting in Valdez. The council is a congressionally sanctioned nonprofit that monitors the Valdez oil terminal and associated tanker operations.
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