Declaring in 2000 that the site poses “an unacceptable risk to human health and the environment,” the EPA has been planning to cover part of the Palos Verdes Shelf with a thick cap of clean sand at an estimated cost of $60 million.
But now there may be little need to build that controversial cap, which is unprecedented in deep ocean waters. The deposit not only has shrunk in size, but its peak concentrations, or hot spots, of DDT and PCBs have been dramatically reduced, according to the new EPA data and maps. The contaminant levels already are what the EPA had hoped to achieve with the cap.
“We’ve either achieved [our goal] without the cap, or close to it,” Huang said. “We have a lot better understanding now based on the 2009 data,” she said. But, “to me, this whole project is like a giant jigsaw puzzle.”
The 100 samples from 59 spots on the ocean floor were collected back in 2009. But then the EPA hired outside experts to review the unexpected findings, which were then confirmed last fall. The data, obtained by Environmental Health News, have not been made public until today.
There have been no major storms, earthquakes or landslides that could explain such a huge, rapid change.
“We’ve been seeing declines in fish tissues and surface sediments for the past 20 years. But this [new finding] was more than what we expected. It appears that the change has accelerated,” said Joseph Gully, supervising environmental scientist at the Los Angeles County Sanitation Districts, which operates the sewage outfall that discharged Montrose’s DDT into the ocean.
“DDTs don’t break down that quickly. I don’t see this as the bacteria all of a sudden eating up all this stuff. It’s a bit of a mystery,” added Steve Bay, head of toxicology at the Southern California Coastal Water Research Project, a government-funded institute that studies pollution off the coast of Southern California.
Christopher Sherwood, a USGS geological oceanographer who has studied the site's sediment since 1991, suspects that the new data may be a "statistical fluke" because there is nothing he can think of that would make DDT transform so quickly.
"If I were a betting man, I'd say that next time we look we'll see a higher inventory of DDE than we did in 2009," he said. "My personal hypothesis is that they just missed the places with the highest contamination." He acknowledged that such a huge error – missing 90 percent of the deposit – would be "really bad statistical luck."
Essentially, what really is happening on that deep ocean floor remains a mystery. "We're all just grasping at straws," Sherwood said.
A long, twisted saga
The vanishing act is the latest twist in the convoluted saga of the Palos Verdes Shelf, which is considered the most studied piece of ocean floor on Earth. Every day, hundreds of millions of gallons of the county’s treated sewage are discharged there.
The EPA declared the Palos Verdes Shelf a Superfund site in 1996. Two miles offshore in 200-foot deep ocean waters, it is one of the most unusual and challenging sites on the nation's list of the worst dumpsites.
It was the focal point of one of the largest court cases in U.S. history that has sought natural resource damages. The case, filed by the U.S. Justice Department in 1990, led to an acrimonious trial in federal court in 2000. About $140 million in settlement money was paid by Montrose, several other manufacturers and the county sanitation agency.
Ironically, at the time, Montrose company representatives had argued in court that the deposit would degrade naturally so there was no need for costly cleanup. But their key expert was thrown out by the judge when the government provided evidence that he was not a biodegradation expert and may have manipulated some data.