State Limits on Water Contaminant May Be Tough On Desert Water Agencies

Not this kind of chrome | Photo: RW Sinclair/Flickr/Creative Commons License

California's Department of Public Health (DPH) has proposed a maximum safe level of the drinking water contaminant made famous by the movie "Erin Brockovich," and if they're enacted, some drinking water providers in the desert are going to have to work to clean up their water.

DPH announced Thursday it's proposing a legal limit on the metal hexavalent chromium (chromium 6) of 10 parts per billion in drinking water in the state. This would be the nation's first limit on chromium 6 which was the toxic contaminant at the center of the lawsuit surrounding groundwater in Hinkley, California that propelled Brockovich's rise to prominence. The announcement came after a state Superior Court ruling in July by Judge Evelio Grillo ordering DPH to set a draft standard for chromium 6 by the end of August.

Chromium 6 is a known carcinogen when inhaled, and standards for the metal as an air pollutant have existed for some time. The level of risk from exposure to chromium 6 in drinking water is less well-established, but there are discouraging reports of unusual cancers in lab animals that have ingested chromium 6. DPH's proposed Maximum Contaminant Level (MCL) is higher than levels previously proposed by the California Environmental Protection Agency (CalEPA) and environmental groups, but significantly lower than levels currently found in much of California's tap water.

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Water agencies were quick to respond to Thursday's announcement, with some boasting they already met the standard and others warning that compliance would cause an increase in monthly water bills. DPH explicitly took costs to consumers into account in setting the draft MCL, which isn't sitting well with environmental and public health groups. For instance, plaintiffs in the suit in the California Superior Court of Alameda that forced the release of the draft standard say the proposed MCL is far too high.

"The proposed standard is 500 times higher than the safe levels established by the state," said attorney Avinash Kar, who represented the Natural Resources Defense Council (NRDC) in the lawsuit. "That's an enormous departure and needs to change."

NRDC was joined in suing DPH by the Environmental Working Group, which has long been campaigning on the issue of chromium 6 in drinking water. Kar's mention of "safe levels established by the state" is a reference to CalEPA's "Public Health Goal" of 20 parts per trillion for chromium 6 in drinking water, which that agency set in July 2011.

Chromium 6 is a form of the common element that is highly oxidized. Oxidation is the technical term for the loss of electrons from an atom. Chromium 6 has six "empty spaces" in its electron orbital shell, making it highly reactive. Current drinking water standards have lumped chromium 6 in with its cousin trivalent chromium, which is far more benign -- in fact, it's a necessary nutrient in small amounts. The current total state MCL for all chromium in drinking water is 50 parts per billion.

For a real-world point of reference on the proposed MCL for chromium 6, 10 parts per billion is about equivalent to a tablespoon and a half of chromium 6 in an Olympic-sized swimming pool.

Erin Brockovich famously took on the utility PG&E over its contribution to chromium 6 in the groundwater of the Mojave Desert town of Hinkley. The utility used chromium 6 as an anti-rust additive in the water in its nearby coling towers, then allowed the water to run into unlined ponds, creating a plume of chromium 6 in the local aquifer. But as I reported here last year, many water companies in the California desert have problems with chromium 6, and much of it isn't from industrial pollution. Hexavalent chromium is a naturally occurring feature in the serpentine soils found throughout California, and in arid regions or closed hydrologiic basins where rainfall doesn't flush the accumulated contaminant to the ocean, the level of naturally occurring chromium 6 in groundwater can climb well past the DPH's proposed limit. According to a report by Ian James in the Palm Springs Desert Sun, a third of the wells that would be affected by a 10 parts per billion MCL for chromium 6 are in the Coachella Valley, with some supply wells delivering water containing the metal at two and a half times the MCL.

Technology exists to remove some of the toxic metal from drinking water, including filtration and chemical treatment: raising the acidity of water contaminated with chromium 6 can convert much of the contaminat to the more benign trivalent chromium. The question is how much said treatment will cost. In a press statement on the utility's website, the Coachella Valley Water District says the new standard could cost its ratepayers more than $40 per month:

Treatment technologies effective at removing chromium-6 from local groundwater will be CVWD's most expensive water treatment plants to build and maintain. Early estimates indicate the monthly service charge could increase from $7 per month to more than $50 per month, if the draft MCL of 10 ppb is adopted.

Meanwhile, other California water companies were quick to point out that their water already meets the proposed standard. For instance, Burbank Water and Power reports that as a result of directives in 2000 by Burbank's city council to address industrial pollution in the San Fernando Valley's groundwater, the city already exceeds the proposed chromium 6 standard. Glendale offered a similar prognosis for that city's taps, pointing to Glendale Water and Power's ongoing study of water purification methods intended to get chromium 6 levels down to a city-mandated level of five parts per billion, half the DPH's proposed standard.

Public comment will be accepted on DPH's draft chromium 6 standard until October 11. By law, DPH must enact a final MCL within 12 months, though the agency says it probably won't take that long.

About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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