Hinkley groundwater contamination
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The town of Hinkley, California, located in the Mojave Desert, had its groundwater contaminated with hexavalent chromium, resulting in a legal case and a multi-million-dollar settlement. Samples taken in August 2010 showed that the plume of contaminated water had started to migrate into the lower aquifer. The legal case was dramatized in the film Erin Brockovich, released in 2000.
Pacific Gas & Electric operates a compressor station in the town for natural gas transmission pipelines. The natural gas has to be re-compressed approximately every 350 miles (560 km), and the station uses large cooling towers to cool the compressors. Between 1952 and 1966, the water used in these cooling towers contained hexavalent chromium to prevent rust in the machinery. Since the water was stored between uses in unlined ponds, it ultimately severely contaminated the groundwater in the town.
Pollution of groundwater 
The wastewater dissolved the hexavalent chromium from the cooling towers and was discharged to unlined ponds at the site. Some of the wastewater percolated into the groundwater, affecting an area near the plant approximately two miles long and nearly a mile wide.
After many arguments, the case had finally led to arbitration with maximum damages of $400 million. After the first 40 people received about $110 million, PG&E reassessed its position and decided arbitration was a bad idea. The case was settled in 1996 for $333 million, the largest settlement ever paid in a direct-action lawsuit in U.S. history.
Erin Brockovich, a legal clerk to lawyer Edward L. Masry, investigated illnesses in the community linked to hexavalent chromium, now recognized as a carcinogen. Her successful fight against PG&E became well known in the public's mind, as did Hinkley, when the film Erin Brockovich was released in 2000.
In 2006, PG&E agreed to pay $295 million to settle cases involving another 1,100 people statewide for chromium (VI) related claims. In 2008, PG&E settled the last of the cases involved with the Hinkley claims for $20 million. Ongoing cleanup documentation is maintained at California EPA's page regarding Hinkley.
A study released in 2010 by the California Cancer Registry showed that cancer rates in Hinkley "remained unremarkable from 1988 to 2008." An epidemiologist involved in the study said that "the 196 cases of cancer reported during the most recent survey of 1996 through 2008 were less than what he would expect based on demographics and the regional rate of cancer."
Average hexavalent chromium levels in Hinkley were recorded as 1.19 ppb with an estimated peak of 20 ppb. The PG&E Topock Compressor Station averaged 7.8 ppb and peaks at 31.8 ppb based on the PG&E Background Study. The proposed California health goal for hexavalent chromium is 0.02 ppb.
Chromium-6-contaminated water supply is apparently a widespread problem, and is not isolated to Hinkley.
See also 
- A decade after "Erin Brockovich," contamination spreads in Hinkley, Victorville Daily Press, 2010-11-09, accessed 2010-11-17.
- PG&E Hinkley Chromium Cleanup California Environmental Protection Agency, 9/10/08
- Baes, Michael (July 29, 2011). "Final Technical Support Document on Public Health Goal for Hexavalent Chromium in Drinking Water". Water. Oakland, CA: California Environmental Protection Agency. Retrieved April 23, 2012. "The health-protective level is based on avoidance of potential carcinogenic effects."
- "PG&E settles last chromium(VI) case". Los Angeles Times. April 8, 2008. pp. B2
- Schwartz, Naoki (2010-12-13) Survey shows unremarkable cancer rate in CA town, Boston Globe; J.W. Morgan and M.E. Reeves, Cancer in Hinkley: What was the real problem?
- Carrie Kahn (2010-12-13). "Erin Brockovich II? Activist Returns To Aid Town". NPR.
- PG&E Background Study
- Baes, Michael (July 29, 2011). "Final Technical Support Document on Public Health Goal for Hexavalent Chromium in Drinking Water". Water. Oakland, CA: California Environmental Protection Agency. Retrieved April 23, 2012. "The PHG [Public Health Goal] for hexavalent chromium is established at 0.02 parts per billion (ppb)."
- Chromium-6 Is Widespread in US Tap Water, Environmental Working Group, 2010