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For town made famous by 'Erin Brockovich,' a toxic sequel?

Hinkley, Calif., battled pollution of its ground water by chromium 6 in the 1990s – a case that inspired 'Erin Brockovich.' Now the substance has escaped its containment barrier.

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Meanwhile, a California Cancer Registry survey for the census tract that includes Hinkley failed to find a disproportionately high disease rate. But George Alexeeff, deputy director for scientific affairs at California’s Office of Environmental Health Hazard Assessment (OEHHA), says Hinkley’s population is too small for a cancer survey to yield meaningful results.

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In August 2009, OEHHA proposed a “public-health goal,” or ideal standard, of 0.06 parts per billion for chromium 6 in water. On Dec. 31, it revised the draft public-health goal to 0.02 p.p.b., in response to research that raised concerns about risks for young children and other sensitive populations.

The California Department of Public Health will consider that goal, as well as cost and feasibility of remediation, in determining whether to set a drinking-water standard for chromium 6.

What Hinkley is doing about it

In Hinkley, state water officials already have set a cutoff for human consumption of 3.1 p.p.b., and PG&E has been trucking in water for residents whose wells exceed that level.

State officials have issued a series of formal orders requiring PG&E to clean up the pollution. They're studying new remediation options and will decide on additional steps in May.

According to Lauri Kemper, assistant executive officer at the Lahontan Regional Water Quality Control Board, PG&E has sought to break up Hinkley's pollution by pumping millions of gallons of tainted water from deep underground, then using it to irrigate alfalfa fields.

As the chromium 6 filters through the soil, it interacts with micro­organisms that convert it to healthful chromium 3. The company also is pumping in ethanol to stimulate the bacteria and injecting water back into the ground around the plume as a buffer, Ms. Kemper says.

Still, the plume is more than half a mile past PG&E's containment perimeter. And it's spreading at least a foot a day as heavy ground-water pumping by nearby farms sucks the contamination into previously untainted areas. PG&E's own pumping – part of the current remediation effort – may have accelerated the northern flow of the plume as well, Kemper says. Further, water-board records show that hexavalent chromium has penetrated a subterranean layer of clay that PG&E's remediation experts thought would protect a deeper aquifer.

With traces of naturally occurring chromium 6 in Hinkley's soil, says company spokesman Jeff Smith, it's difficult to determine whether a spike in test readings means the plume is growing. The boundaries of such plumes often shift with ground-water flows, expanding in one area while drawing back in another, Mr. Smith says.

"PG&E has worked very hard on a cleanup in the Hinkley area," he says. "We did use chromium in the 1950s and '60s in the way that's been described, and we've discontinued that. We're committed to a cleanup. But with some of what's going on, it will take study to determine the causes."

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