Underwater assessments of the sunken World War II tanker Montebello have found no oil onboard.
The announcement follows 11 days of surveys and sampling by a remotely operated dive vehicle at the wreck site more than six miles off the coast of Cambria. Samples of cargo and fuel tanks found no quantifiable amount of oil onboard.
“After careful evaluation of the data, we have concluded with a high level of confidence that there is no oil threat from the S.S. Montebello,” said Coast Guard Capt. Roger Laferriere, one of two on-scene commanders of the expedition.
Although it will never be known exactly what happened to the more than 3 million gallons of crude oil that were onboard the tanker when it was sunk in December 1941, computer modeling by the National Oceanic and Atmospheric Administration indicates that the oil leaked gradually from the wreck over a long period of time.
“Such modeling indicates that most of the oil remained offshore and headed south. Some would have evaporated within the first few days, and the remainder may have washed ashore but may have been so widely scattered that it went unnoticed,” said Jordan Stout, NOAA scientific support coordinator.
The dive vehicle took a variety of samples from the ship’s tanks, from sediment around the wreck and from the hull. Ultrasonic testing of the hull indicates that it is structurally sound, and metallurgic sampling will help determine its corrosion status.
The final report on the Montebello assessment is expected to be released next spring. Tank and sediment samples are being sent to laboratories for further analysis. However there was no visual evidence of contamination in the sediment.
The Montebello assessment was a joint operation between the Coast Guard and the state Department of Fish and Game Office of Oil Spill Prevention and Response. State Sen. Sam Blakeslee, R-San Luis Obispo, praised the multijurisdictional cooperation and described the results as a huge relief.
Officials feared that if large amounts of oil remained on the wreck, it could leak catastrophically, causing a widespread oil spill along the coast.
“The U.S. Coast Guard and OSPR deserve enormous credit for leading this complex and technically challenging project,” Blakeslee said. “The team brought to bear the best minds and most advanced tools to ascertain the condition of this 70-year-old shipwreck.”
Capt. Chris Graff, the state’s on-scene commander of the mission, said researchers used new technology that gave them surgically precise control over the dive vehicle and research vessels. Those techniques could be used to assess the ecological danger of other sunken vessels.
Cost of the operation is estimated to be $5 million. It was funded by the Oil Spill Liability Trust Fund, using fees paid by the oil industry and not general taxpayers.