In the wake of November’s San Francisco Bay oil spill, much media and scientific attention has been given to the cleanup process. But for Civil and Environmental Engineering Prof. Richard Luthy, controlling aqueous contaminants is not a new problem.

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Hunters Point Naval Shipyard, which used potentially cancer-causing chemical PCBs until they were banned in 1979, is where Prof. Richard Luthy hopes to use his new cleanup method. #gallery http://daily.stanford.edu/image/full/8286
Cristina Bautista

Hunters Point Naval Shipyard, which used potentially cancer-causing chemical PCBs until they were banned in 1979, is where Prof. Richard Luthy hopes to use his new cleanup method.

For more than two years, Luthy has been spearheading a pilot test, which so far appears to partially mitigate the environmental damage of industrial chemicals called polychlorinated biphenyls (PCBs) in Bay Area sediment.

“The idea is that by adding activated carbon to sediment, you can bind up certain harmful chemicals,” Luthy said. “The process absorbs the toxic chemicals and it prevents them from getting into the aquatic food chain.”

PCBs, which the Environmental Protection Agency has labeled as possible carcinogens, were widely used before their 1979 ban. But traces of the toxin still haunt aqueous sediments near former industrial sites like the naval shipyard by Hunters Point in San Francisco, the site for Luthy’s study.

In the past, some efforts have been made to remove harmful sediment through dredging, but this process merely transplants toxic waste, contaminating dumping sites on land. In fact, Luthy said that dredging the top layers of sediment may be more harmful than doing nothing at all, because it risks exposing older layers that have higher PCB concentrations.

Luthy claimed that his activated carbon method is not only more cost-effective than dredging, but it more thoroughly addresses the contamination problem. So far, tests on four muddy plots, each about “the size of a large office,” have delivered promising results.

“There’s been a reduction in aqueous concentration,” he said, “the process seems to be working.”

His work has found that clams left in mesh cages on treated sediment had 50 percent less PCB concentration than their counterparts left on untreated sediment. Luthy’s team will be continuing to monitor the site for a year, and a second test in New York’s Grasse River is currently underway.

“We have demonstrated what is possible,” Luthy said. “What’s needed now is a larger field test so that we can improve our engineering and scientific understanding.”