A high volume of discarded military munitions dating back to World War II were found during a seafloor survey off the Palos Verdes Peninsula, researchers from UC San Diego’s Scripps Institution of Oceanography announced on Friday, Jan. 5.
The revelation was the latest in ongoing investigations into contaminants in the ocean off the Peninsula.
In its first survey in 2021, Scripps researchers discovered what they considered to be 27,000 barrels on the ocean floor that potentially could detain the insecticide DDT. That insecticide, which has been banned for years, had been dumped by a local company legally for decades.
At the time, Scripps researchers also noted tens of thousands of other unidentified objects they believed to be man-made.
A majority of the objects — surveyed in an April study led by Scripps oceanographers Sophia Merrifield and Eric Terrill — have now been identified. The results were announced during a Friday press conference.
And, it turns out, much of the debris is not barrells of DDT — though some of that still exists.
Rather, the objects are “multiple types of discarded military munitions and pyrotechnics” that were dumped by Navy ships on their way back to the Port of Long Beach during World War II — a standard practice at the time.
It is unknown whether any of the munitions contain explosives that could detonate. But, in a press release, the Navy said it is “reviewing the findings and determining the best path forward to ensure that the risk to human health and the environment is managed appropriately and within applicable federal and state laws and regulations.”
The Scripps survey, with support from the U.S. Navy’s Supervisor of Salvage and the Office of Naval Research, mapped 135 square miles of the San Pedro Basin, about halfway between the Palos Verdes Peninsula and Catalina Island.
Besides the munitions, researchers also found barrels from industrial dumping in smaller numbers than previously thought. Within the survey area, there are also whale carcasses and several old fishing vessels, according to a Friday press release.
Finer sonar resolution enabled researchers to get a better look at what was on the seabed, Terrill said at Friday’s virtual press conference. And, what they found, he said, is that most of the debris is Navy munitions, not barrels as previously believed.
“(There were) four categories of munition and pyrotechnic that were found,” Terrill said during the press conference. “We found these objects to be pervasive along the debris field.”
The sonar mapping technology used in 2021, Merrifield said, could not distinguish between what turned out to be munitions and barrels because the two were of the “same size and acoustic intensity.”
“There aren’t a huge, vast quantity of barrels down there, at least not what we were thinking,” said Brice Semmens, a marine biologist with Scripps. “And it turns out that a lot of the dumping was simply bulk material dumped off.”
With the undersea camera system, researchers found munition boxes and depth charges they believed were dumped during World War II.
“It wasn’t until we discovered them laying on their side,” Terrill said, “that we could actually piece them together with historical information to understand the composition of this type of ammunition.”
The Port of Long Beach had previously been the home of a U.S. Navy shipyard.
“Many ships had to return for repair during the war to get quickly back on the road,” Terrill said. “So the Navy’s president is reviewing the findings and they’re going to determine the best path forward to ensure that risks to human health and environments managed appropriately.”
“These munitions are likely a result of World War II-era disposal practices,” the Navy said in a statement.
“While disposal of munitions at sea at this location was approved at that time to ensure safe disposal when naval vessels returned to US ports,” the statement added, “the Navy follows Department of Defense guidance for the appropriate disposal of munitions that aligns with state and federal rules and regulations.”
As for the DDT barrels, while the actual amount is lower than previously thought, the Scripps scientists said, there is little doubt that DDT and other harmful chemicals were being dumped into the Pacific Ocean, though the extent of the damage to the environment has yet to be determined.
Researchers are also studying the impact on recreational fisheries.
“We’ve also been doing some deep ocean samples and surveys in order to look at how much of the DDT is transitioning from the sediments into that dumping site,” Semmens said, “into the those deep ocean ecosystems and communities.”
It looks like the “highest abundance” of DDT is “subsurface in the sediments,” Semmens said, and “that’s to be expected given that it was dumped 50 or more years ago.”
It’s also fairly clear that DDT is continuing to get into the food web of the deep ocean, Semmens added. And, depending upon where you are in the ocean, he said, the toxins may have impacted the upper ocean creatures we care a lot about.
The mapping also discovered seven sunken whale carcasses, which were confirmed by video.
But there is the potential for as many as 60 carcasses, based on sonar data.
Because the whale skeletons were found in low oxygen water, decomposition might have slowed down, said Scripps marine biologist Greg Rouse. So it is too early to know when or how the whales died.
Rouse said they are also documenting animal life on the ocean floor, which includes tiny mollusks and crabs to determine DDT and other chemical levels that could extend through the food chain.
Craig Smith, benthic ecologist at the University of Hawaii at Manoa, said it will take a radiometric dating technique to figure out how long the whales have been on the ocean floor.
“I would expect that can take years for a large whale to have its soft tissue disappear,” said Smith, indicating that only bones have been found.
The investigation into DDT dates back more than a decade.
David Valentine, a professor of microbiology and geochemistry at UC Santa Barbara, and a team of scientists initially discovered more than 60 barrels on the ocean floor in 2011 and 2013 while exploring the Peninsula seafloor with a remotely operated vehicle.
Valentine said in a 2022 interview that testing showed one area had 40 times the highest concentration of DDT surface sediment contamination compared to other areas in the vicinity.
In August 2022, the U.S. Environmental Protection Agency released a report stating that the hazardous materials dumped into the ocean by the defunct Montrose Chemical Corporation was not contained in the barrels but had been dumped directly into the ocean.
Because of that, according to the report, Montrose was not responsible for the barrels discovered by scientists in 2011 and 2013.
Valentine is “currently mapping DDT in sediments collected across the San Pedro Basin as part of the same project as the seafloor survey,” Friday’s Scripps press release said. He is working to “fingerprint” the “DDT sludge” found at a dumpsite.
“Our preliminary findings of our analysis of sediments are showing that bulk dumping of DDT acid waste was the norm,” Valentine said in a press release, “that DDT immediately entered the environment and was likely not in barrels.
“Once dumped, DDT spread at the seafloor, expanding its footprint to at least the base of the Catalina slope,” he added. “We are finding that original DDT remains abundant in the seafloor today, in both absolute and relative terms.”
Multiple companies and agencies, aside from Montrose, were allowed to dispose of chemicals off the California coast from the 1930s to the early 1970s. Among those chemicals was DDT, a synthetic insecticide banned in 1972 because of its detrimental impacts on humans and wildlife.
One of the legal dumping sites was the San Pedro Channel.
Starting in the late 1940s, Montrose manufactured, packaged and distributed DDT in an unincorporated area of Los Angeles County near Torrance and most of the acid waste, millions of gallons a year according to scientists, went into the ocean legally.
But in 1989, seven years after it closed for good, Montrose was named a Superfund site by the EPA, claiming the company was one of the nations’s most toxic collections of pollutants.
Montrose eventually reached a $140 million settlement in 2001 with federal agencies for dumping the chemicals and part of the settlement helped fund the Palos Verdes Reef Restoration Project.
A positive outcome of the ongoing research, Semmens said, is scientists have had the opportunity to explore the deep ocean.
“We’re seeing these really neat discoveries that are not necessarily part of the intended products,” Semmens said, “but are nonetheless gaining us some really key insights into how our deep oceans work off of our coast.”
