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Public Radio's Environmental News Magazine (follow us on Google News)

Meals for Microbes

Air Date: Week of

In many places, leaking fuel from gas station underground fuel storage tanks is an environmental hazard threatening groundwater. In California, where clean-up has been a priority, use of a new cleaning method is starting to move ahead and it's called bio-remediation. In bioremediation, microbes already existing in the soil go to work on the fuel so people don't have to. Cheryl Colopy reports on the technique and if it will actually do the job.


CURWOOD: It's Living on Earth. I'm Steve Curwood. In the early 1980s it was discovered that many underground tanks at gasoline stations have been leaking fuel. After decades in the ground they were corroded, and some were polluting groundwater especially in older urban areas. The Federal Government and the states went to work. California, for example, required a cleanup of all sites where groundwater was contaminated or threatened. But a new study has led California's water agency to recommend shutting down some of the cleanup sites. Instead, they say the state should just let nature take its course, as naturally occurring microbes in the earth slowly eat the fuel up. But as Cheryl Colopy reports, some critics say the state is moving too fast.

(Sound of a vacuum)

COLOPY: On a street corner in downtown Oakland, beneath the side of a former Chevron service station, an underground vacuum sucks up gas fumes day and night. The process is called soil vapor extraction. It's one of the latest and most expensive methods of mopping up fuel that's leaked from old storage tanks.

(Vacuuming sounds continue)

COLOPY: The Federal Environmental Protection Agency says there are 300,000 sites like this nationwide and that cleaning them all up could cost $32 billion. But here in California, scientists say there may be a cheaper way to do the job. David Rice calls it bioremediation: letting microorganisms already present in the soil eat up the fuel.

RICE: We had a spill of about 12,000 gallons. We found that the microbes could digest that 12,000 gallons in about 6 days under ideal conditions.

COLOPY: The kind of ideal conditions that exist here at Lawrence Livermore Laboratory, near San Francisco. David Rice, who directed a bioremediation study for Lawrence Livermore, says fuel is just another meal for the microbes. They've been consuming the byproducts of decaying plants and animals for millions of years. They're greedy and they're free.

RICE: And what we found was that there are a whole variety of microbes and there's a very rich population, and if one doesn't like a certain condition another one takes over. So it's not just one microbe. There are a very rich ecology in the subsurface which acts to chew apart the carbons.

COLOPY: David Rice, along with scientists from the University of California, studied 1,500 leaking underground storage tank, or LUST sites, throughout the state. They found that at 80% of them the fuel doesn't travel very far or very fast, partly because microbes keep it in check.

KOLB: These fuel sites don't pose big threats to major public water supplies.

COLOPY: Larry Kolb of the San Francisco Bay Regional Water Quality Control Board urged the state water board to take a close look at the Lawrence Livermore study and loosen up its regulations for cleaning up leaky storage tanks.

KOLB: Because these fuel sites, the old gas stations, typically are local, they're only shallow aquifers that are affected. In most cases the gas has only gone 100 feet or a couple hundred feet.

COLOPY: The state water board agreed, and now allows regional water quality districts to use bioremediation at low risk sites. Even though microbes may take up to 10 years to digest a spill, the most common alternative, pumping water out of the ground, then treating it, could cost $3 billion. Many cleanups are paid for by a surcharge on gasoline, and John Marshak of the Central Valley Regional Water Board says maybe the state should raise that tax instead of lowering its cleanup standards. He's worried that using microbes to save money is putting California's drinking water supplies at risk.

MARSHAK: And that's really what this entire Lawrence Livermore debate has done. It's put the regulators in the position of having to prove that there is a problem.

COLOPY: The Sierra Club's legislative director in Sacramento. Bonnie Holmes, agrees. She says that based on the Lawrence Livermore report, more than half the cleanup operations in California are being shut down in favor of bioremediation: a trend she warns other states not to follow.

HOLMES: I would be very concerned that other states not take this report and use it prematurely to shut down soil remediation at soil only and shallow aquifers. It's far too premature, that we see a lot of flaws in the report. The report has not been peer reviewed.

COLOPY: The Environmental Protection Agency says that sites where bioremediation is used have to be watched carefully to make sure the spills are really shrinking, and the EPA is providing states money for the monitoring effort.

(Office sounds. A phone rings. A woman answers: "Good afternoon, Weiss Associates. Hi.")

COLOPY: Weiss Associates of Emeryville was one of the first California firms to get into groundwater cleanup. You'd expect its president, Richard Weiss, to be worried about losing business now that so many groundwater cleanup sites are being shut down. But he says regulatory change is long overdue.

WEISS: In my opinion, what really happened is there were some very bad contaminated sites that did have really adverse effects. And what happened is that the public then generalized from these really bad cases to anything that has to do with contamination or toxicity in sand and basically use the big hammer, and it's like indiscriminate, anything that has to do with contamination we're going to treat it like it's the blight on the earth.

COLOPY: A hydrogeologist himself, Weiss says leaking fuel shouldn't be confused with leaking solvents such as those used in dry cleaning and computer chip manufacturing. They're much more carcinogenic, he says, travel farther and faster than fuels, and have fewer natural enemies in the soil. But at Stanford University, researchers are experimenting with microbes that may someday consume solvents, too. For Living on Earth, I'm Cheryl Colopy reporting.



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