Two decades after the Exxon Valdez disaster, a tugboat working to prevent another oil spill in Alaska's Prince William Sound ran aground on the same reef and left a three-mile sheen of fuel oil on the water.
The 136-foot tug Pathfinder had just finished checking for dangerous ice and was heading back to port in Valdez when it hit Bligh Reef.
The boat is part of the Ship Escort Response Vessel System that was created after the Exxon Valdez ran aground in 1989 and spilled nearly 11 million gallons of crude oil _ the worst ever U.S. spill.
U.S. Sen. Mark Begich of Alaska said it was troubling that a spill response vessel "managed to run aground on one of the most well-marked and well-known reefs in the Northern Hemisphere."
It wasn't immediately known how much spilled. The Coast Guard said Thursday that two of its tanks _ containing an estimated 33,500 gallons of diesel fuel _ were damaged and there was a fuel sheen on the water about 3 miles long and 30 yards wide.
The tug reported the grounding at 6:15 p.m. Wednesday and by Thursday an oil response vessel arrived and began skimming the water near the sheen.
Coast Guard Lt. Erin Christensen said an estimate on how much fuel spilled couldn't be done until the fuel was off-loaded to a barge Friday.
Alaska Gov. Governor Sean Parnell had sharp words for Alaska's oil industry, noting that there had been three "significant" recent spills in the Prudehoe Bay oil fields prior to Wednesday's spill in the sound.
"Frankly, when I saw so many spills in such a short time I was indignant that these spills would occur," Parnell said in a statement. "The spills harm both Alaska's environment and Alaska's reputation for responsible resource development. I let the companies know this was not acceptable."
The spills in the Prudehoe fields included one discovered Monday that contaminated several thousand square feet of snow-covered land. Last month, a spill of 46,000 gallons of oil, water and natural gas was reported. And officials also investigated another oil spill of about 7,100 gallons of water with oily residue.
Coast Guard Petty Office Jon-Paul Rios said the tug's six-member crew deployed 200 feet of fuel containment booms around the vessel after clearing the reef and continuing to deeper waters.
A dive team inspecting the Crowley Marine Services tug found damage to the hull and a 4-to-5 foot section of keel missing, Rios said.
The SERVS system provides two escort tugboats for each tanker traveling through the sound after leaving the Valdez Marine Terminal with North Slope crude delivered through the trans-Alaska pipeline.
Two tankers scheduled to depart the marine terminal when the accident occurred. One tanker was on its way and the other was soon to be, said Alyeska Pipeline Service Co. spokeswoman Michelle Egan. "We are assisting in the response."
Officials are investigating the cause of the grounding. The six crews members tested negative for alcohol use.
Rios stressed that the grounding of the tug was very different from the Exxon Valdez accident in which an enormous amount of black crude oil spilled.
The tug is carrying much lighter diesel fuel that will evaporate in time, Rios said. The Coast Guard estimates that for a small spill of between 500 and 5,000 gallons of diesel fuel it takes a day or less to evaporate. This spill will take somewhat longer, but will evaporate, he said.