A robotic submersible from the Monterey Bay Aquarium Research Institute spent three days this month gathering sonar images of the historic wreck Montebello.
The expedition was part of a research project to assess the oil pollution threat posed by the World War II-era wreck, which sits seven miles off Cambria. Two more submersible visits to the wreck are planned for next year.
During the three-day expedition, an autonomous underwater vehicle or AUV was used to gather three types of sonar images of the ship and the surrounding seafloor. The vehicle emitted brief pulses of sound and the intensities of the sounds’ reflections were measured to build the images.
They will be used to determine the full extent and overall layout of the wreckage. They also indicate the nature and stability of the seafloor.
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The Montebello was torpedoed by a Japanese submarine on Dec. 23, 1941, during the opening days of World War II. It sank to a depth of 900 feet carrying three million gallons of Santa Maria crude oil.
It is unknown how much of that oil remains in the ship. Remaining oil could escape all at once if the wreck collapsed or it could leak out gradually if a pipe or valve ruptured.
At the cold depths of the ocean floor, the oil is the consistency of peanut butter. However, it is still buoyant, and would float to the surface, warm up and form a slick.
“We are taking proactive steps to determine if there is a pollution threat and, if so, to prevent an oil release that could impact California’s coastal areas,” said Steve Edinger, administrator of the state Office of Oil Spill Prevention and Response.
The multi-agency effort, called the Montebello Assessment Task Force, was begun in 2008 by then Assemblyman Sam Blakeslee, R-San Luis Obispo. The state is spending $100,000 on the effort and is looking for additional funding from federal agencies.
Two more expeditions are planned for next summer and fall. In one, a remotely operated vehicle will be sent down to videotape the wreck.
This video will be used to assess the condition of the wreck. These newer videos can be compared to video taken in 1996 and 2003. During the last dive, samples of the cargo tanks will be taken to determine if oil remains on board.
“This is an opportunity to work proactively and collaboratively to protect our coast from a potential environmental threat,” Blakeslee said.