Updated at 2:50 p.m. with PG&E response.

HINKLEY The Lahontan Regional Water Board recently released peer reviews that questioned the legitimacy of studies determining background levels of chromium 6, a toxic metal that has been found in Hinkley water wells.

In 2007 Pacific Gas and Electric was ordered by the water board to oversee conducting a study to determine background levels of chromium 6 in Hinkley water. That study showed background levels in Hinkley were at maximum 3.1 parts per billion. PG&E officials said this is the level to which they think they should be required to clean up water contaminated by chromium 6 released from cooling towers in the '60s.

Last week PG&E petitioned an order by the water board that required the company to clean the water to .02 parts per billion of chromium 6. PG&E's main argument was that they shouldn't have to clean up the water beyond the area's background level.

In May, the water board requested the State Water Resources Board's scientific peer review program conduct reviews of the 2007 study. The program employed three experts from varying backgrounds to conduct reviews.

In the peer review, the scientists outlined several key problems with where and how the original study gathered water samples to determine background levels of chromium. The main issue was gathering samples of water from wells used for agriculture or for use in homes.

James Jacobs, a geologist who specializes in water and also co-authored "The Chromium VI Handbook," was one of three scientists who reviewed the findings and methods of the study. Jacobs argued these wells do not necessarily isolate aquifers, meaning that waters from separate underground bodies of water could be mixed. As separate aquifers have varying levels of chromium, the samples obtained by PG&E are "not valid or relevant" to determine actual levels of chromium, Jacobs said.

Jacobs explains that while water samples from these wells can reflect the overall quality of the water in the area, it cannot be used to determine true background levels. In order to get a true reading of background concentrations, a study needs to to examine separate levels from individual aquifers in order to understand the migration of the chromium through the aquifers. Understanding the migration of the chromium is essential in determining true background levels, he said.

Jacobs recommended drilling new, more accurate sampling wells to get an accurate background level for the Hinkley area. He also recommended sampling in areas furthest away from the chromium 6 plume, in areas unaffected by historical water pumping.

Though the Water Board is evaluating the findings of the reviews, Lauri Kemper, executive director of the board, said the board is not sure what they're going to do with them. As of yet, the board is not ordering another background study.

"We don't want a new background study to delay any of those initial next steps in terms of ordering additional cleanup," Kemper said.

PG&E spokesperson Jeff Smith said that in light of the peer reviews the background levels do need to be examined.

"Clearly we do have some more work that needs to be done in order to determine the actual background levels in the Hinkley area," Smith said. "We are committed to working with the water board and the community to make sure that the correct background level is established."

PG&E will be holding a public meeting at 6:30 p.m. Wednesday, Nov. 2, at the Hinkley Elementary School, 37600 Hinkley Road.

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(760) 256-4123 or klucia@desertdispatch.com