While working to map parts of Southern California’s deep-sea as part of a follow-up survey, an unexpected discovery was made when World War II munitions were found scattered across the seafloor. The munitions, which were found off the coast of Los Angeles, include anti-submarine weapons and smoke devices, marine researchers said on Friday.
The discovery was made during a survey of the known offshore site in April, in an area known to have been used as a dumping ground for industrial and chemical waste from the 1930s through the 1970s. The surveys are a part of an effort to better understand the impact of these industrial dumping sites, which has led to the presence of the pesticide DDT that is harming marine life and has been linked to cancer in sea lions.
The research is being led by UC San Diego’s Scripps Institution of Oceanography, and is a follow-up to the discovery of more than 25,000 “barrel-like” objects that were found using sonar in 2021. The barrels were believed to contain DDT, but further research suggested that the DDT contamination is actually linked to acid waste containing DDT that was stored in above-ground tanks that were then dumped into the sea from barges.
“Our analysis of sediments are showing that bulk dumping of DDT acid waste was the norm, that DDT immediately entered the environment and was likely not in barrels,” said David Valentine, a researcher with UC Santa Barbara.
Using hundreds of hours of high-definition video of the area, researchers were able to identify some of the mysterious objects and barrels thousands of feet below the surface. They concluded that most of the objects were “multiple types of discarded military munitions and pyrotechnics,” said Scripps researchers.
“In every debris line sampled with video, the majority of targets were found to be munitions,” Scripps said. “According to scientist Eric Terrill: ‘we started to find the same objects by the dozens, if not hundreds.”’
Among the discovered items were Hedgehog and Mark 9 depth charges which were typically used to attack submarines, and Mark 1 smoke floats which are chemical smoke munitions used by warships to conceal movements.
“This is a really interesting piece of work, because what it demonstrated or what it validated is that in fact there aren’t a huge, vast quantity of barrels down there — at least not what we were thinking,” said Brice Simmons, a marine biologist with Scripps, on Friday. “It turns out that a lot of the dumping was simply bulk material dumped off to the side.”
Officials from the US Navy told researchers at Scripps that the “disposal of munitions at sea at this location was approved at that time to ensure safe disposal when naval vessels returned to U.S. port.” But they added that they are reviewing the findings to determine “the best path forward to ensure that the risk to human health and the environment is managed appropriately.”