April Flowers for redOrbit.com – Your Universe Online
Between San Francisco and the Mexican border, US nautical charts have shown seven “chemical munitions dumping areas” along the Pacific Coast since World War II. Little to no information is available, however, about the amount, location or nature of the materials dumped at most of these sites.
Researchers from the Monterey Bay Aquarium Research Institute (MBARI) described a survey of one supposed deep-water dump site off the coast of Southern California at the American Geophysical Union (AGU) Conference earlier this week. The survey found 55-gallon drums and trash, but no chemical munitions. The findings suggest that not all marked sites contain chemical munitions, and also demonstrate the usefulness of underwater robots in surveying such sites to identify areas of concern.
In nautical charts of the US waters, there are a total of 32 chemical munitions dumping areas, seven of which lie between San Francisco and the Mexican border along the California coastline. Some of the marked areas off the coast of California are huge, encompassing more than 1500 square miles of seafloor. Only the area off the coast of San Francisco has been studied in any detail.
MBARI chemical oceanographer Peter Brewer is concerned by the lack of available information. Chemical munitions dumped at these sites could pose hazards to fishers and researchers studying the seafloor. Hundreds of fishermen in Japan, the Baltic Sea, and off the east coast of the United States have been injured by chemical munitions caught in their nets over the last 50 years. Brewer suspects, however, that some of the sites off the coast of California may not contain such munitions. Some of the sites might contain munitions, but the affected areas are likely to be much smaller than the marked off areas of the charts.
To perform a preliminary survey of a marked dump site in the Santa Cruz Basin, about 70 miles southwest of Los Angeles, Brewer and his team used two different types of underwater robots. The site Brewer and colleagues studied is approximately 6,300 feet deep.
MBARI’s seafloor‐mapping autonomous underwater vehicle (AUV) spent 18 hours in March 2013, surveying a portion of the Santa Cruz Basin using side‐scan sonar. The AUV followed a preprogrammed zig-zag path approximately 82 feet above the ocean bottom, surveying almost 10 square miles of seafloor. The survey site included areas both inside and outside the marked dump site. The researchers counted 754 “targets,” or objects sticking up from the seafloor, within the surveyed areas.
The AUV sonar surveys allowed the research team to locate hard objects on the bottom of the ocean, however, they did not provide enough detail so that these objects could be positively identified. In May 2013, Brewer and his team returned to the Santa Cruz Basin to videotape the seafloor using one of MBARI’s remotely operated vehicles, the ROV Doc Ricketts.
The ROV captured video showing 55-gallon drums in and on the muddy seafloor. The majority of these rusting barrels were covered with anemones, sponges, crabs and other animals. Other targets discovered by the AUV turned out to be garbage such as canned goods and cases of bottled water. Two small, unarmed drones used by the military for target practice, along with a 98-foot long steel mast from a ship, were also found. The ROV survey found no chemical weapons.
The findings of this partial survey suggest that not all sites marked as chemical munitions dumps may actually have been used for this purpose. The work does demonstrate the usefulness of modern undersea robots, such as MBARI’s seafloor‐mapping AUV, for surveying such marked dump areas relatively quickly. Cartographers will be able to redraw the lines around these areas, based on such surveys, to more accurately reflect what’s on the seafloor.