Naturally occurring level of chromium 6 in Hinkley may never be known

Source: San Bernardino County Sun, June 14, 2012
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How much of the cancer-causing chemical chromium 6 is naturally occurring in the Hinkley Valley?
Board members of the water agency which is overseeing the cleanup of Hinkley’s contaminated groundwater are beginning to see that the answer to that question may never be known.
And they want Lahontan Regional Water Quality Control Board officials to pursue finding out if a new study can reasonably be expected to determine how much chromium 6 was in the water before San Francisco-based Pacific Gas & Electric Co. began dumping it into unlined ponds, where it seeped in the groundwater, creating a plume that is thought to be more than 5 miles long and nearly 2 miles wide.
The question is important because it sets up what level PG & E needs to reach in order to return to the Hinkley Valley to its natural state.
For a time, water board officials and others thought they had that number.
A study PG & E commissioned at the request of the water board in 2007 found that upper end of the naturally occurring chromium 6 was 3.1 parts per billion.
But that study first came under fire by Hinkley residents and last year was discredited on several fronts by three scientists hired by the state to review its methodology. In a presentation to the water board Wednesday night in Barstow, Anne Holden, an engineering geologist on the staff of the Lahontan water agency, summarized those criticisms:
– The quality of laboratory sample analysis procedures.
– The types of wells used for the majority of the background study sampling.
– Statistical methods used to summarize groundwater sample results.
– Uncertainty in determining past chromium plume migration.
Holden said that all the criticisms can be corrected in a new study except one — determining the past chromium plume migration.
And that will be difficult because there are not records going back to the 1950s which can shed any light on the water use patterns going back some 60 years, she said.
Amy Horne was among several board members to advise the water board staff to pursue whether or not there can be a satisfactory way to uncover past plume migration so that pursuit of a new study would produce results that could be accepted by all.
“I don’t want us spending all kinds of money on a study which ultimately will produce nothing. We should be spending our money on the cleanup,” she said.
The board took no formal vote on the matter because they lacked a quorum.

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