LOS ANGELES — Underwater dumps off the coast of Los Angeles contain munitions from World War II, including anti-submarine weapons and smoke devices, marine researchers announced Friday.
A survey of the known offshore sites in April managed to identify munitions using high-definition video covering a limited portion of the sites, said the Scripps Institution of Oceanography at the University of California, San Diego, which conducted the investigation led, in an email.
The study, which used unmanned deep-water vehicles equipped with sonar and a video camera, was a high-tech follow-up study in a region known as the dumping ground for industrial and chemical waste from the 1930s to the 1970s.
A 2021 survey using sonar had uncovered more than 25,000 'barrel-like objects' on the seabed that may contain DDT and other toxic chemicals. High levels of the toxic chemical have previously been found in sediments and marine mammals in the region, and DDT has been linked to cancer in sea lions.
However, later research, including from the US Environmental Protection Agency, suggested that much of the contamination could have come from acid waste containing DDT, which had been stored in above-ground tanks and then dumped into the sea in bulk from barges instead of in barrels.
The April survey involved recording some 300 hours of high-definition video in part of that area, allowing researchers to identify some of the mysterious boxes and barrels located on the seabed in the lines thousands of meters below the surface between the mainland and Santa Catalina. Island, Scripps said.
“In each debris line video sampled, the majority of targets appeared to be munitions,” the Scripps email said. “According to scientist Eric Terrill, 'we started finding dozens, if not hundreds, of the same objects.'”
Sonar scanned a much larger area of the dumps, but was not accurate enough to distinguish the nature of the thousands of previously mentioned objects, because ammunition and barrels are similar in size, meaning video was the only way to spot the objects on the seabed can be positively identified. Scripps said.
Researchers concluded that most of those identified objects were “multiple types of discarded military munitions and pyrotechnics,” according to an earlier statement from Scripps.
They included anti-submarine depth charges and smoke rafts used to provide cover for warships.
The United States. The Navy said the munitions were likely dumped during World War II as ships returned to port, which was considered a safe and government-approved disposal method at the time.
In a statement, the Navy said it is reviewing the findings to determine “the best path forward to ensure the risk to human health and the environment is appropriately managed.”
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This story has been corrected to remove a reference to thousands of seabed objects identified as World War II munitions through an investigation of a known industrial waste dump in California. A clarifying statement from the research institution that led the study says that although sonar was used over an area containing thousands of objects, high-definition video – the only way to identify the objects as munitions – was only used in a limited part of the study . area.