“Despite the dramatic drop in the sediment, we have not seen similar, commensurate drops in the fish. This recent result should lead to a much greater, more focused look at fish concentrations,” Gold said.
Tiedje said the fish – and consequently the eagles, seabirds and the rest of the food web – may remain contaminated for a long time, since fish are “good scavengers.”
“You have to have these sediments really cleaned up for it to have an effect on the fish,” he said.
Huang said the EPA now plans to do more sediment testing this fall to see what’s happened since 2009.
“We should go out and take another look because of the difference between 2009 and 2004,” she said. One lingering question: If it was 14 tons in 2009, what is it now? “We know it’s declining. It is getting smaller. How much smaller I do not know,” she said.
According to its 2000 plan, the EPA’s goal for capping the site was to “immediately bring” average DDT concentrations to 78 parts per million, down from the 150 ppm found in 2004. But the average is now calculated at 58 ppm. For PCBs, the goal was to reduce it to 7 ppm and the new data show it is now only 0.23 ppm.
"We’ve had concerns about capping it from day one,” Gully said. “The risks associated with putting a cap down are not insignificant. If it’s not done well, it can make a bad situation way worse.”
Nevertheless, at EPA, “capping is definitely still under consideration,” Huang said. But she added that other options now must be considered since it is so much smaller. One idea is to find ways to enrich the microbes so they work even faster.
More paralysis by analysis?
Gold worries that the shrinking deposit will lead to more paralysis at EPA. “The inaction of the last decade in a weird way is being rewarded,” he said. “But from my perspective, this project shouldn’t end.”
Sherwood said all eyes will be on the next round of sampling to see if it confirms the huge drop in contamination.
"If it does, there'd be reason to celebrate," he said. "But I'm not popping open the champagne yet."
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.