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Los Osos water basin contains chromium 

Los Osos residents received a mix of good and bad news about the status of the Los Osos Valley Groundwater Basin during an annual report presented at the Los Osos Basin Management Committee meeting on May 25.

The bad news: Los Osos water purveyors recently detected the presence of hexavalent chromium—the chemical contamination famously uncovered by Erin Brockovich in Hinkley, Calif.—in the basin at levels higher than allowed by state law.

Hexavalent chromium can cause cancer, reproductive problems, respiratory irritation, and numerous other physical maladies when ingested at unsafe levels. The Los Osos Community Services District (LOCSD) has stopped pulling water from the 3rd Street well where higher levels of chromium were detected, according to LOCSD General Manager Peter Kampa.

In 2014, California upped its standards for an allowable hexavalent chromium presence in drinking water, to 10 parts per billion (ppb). The compound was detected in Los Osos groundwater at levels around 11 ppb, according to Rob Miller, executive director for the Los Osos Basin Management Committee.

“[Hexavalent chromium] occurs in both the upper and lower aquifers, it does crop up at various areas, and it is not tied to any single area,” Miller told the management committee. “It is both naturally occurring and man-made, so it’s very difficult to nail down what the source of this is. It’s something that we’ll be monitoring closely.”

Miller also warned the committee that seawater intrusion is still coming hard and fast into the basin at 200 feet per year and that nitrate levels continue to be detected at higher amounts than allowed.

But despite those developments, Miller gave reasons to be cautiously optimistic about the long-term prospects for the basin.

Data from the report demonstrated that water levels in the lower aquifer are showing signs of recovery. And while the El Niño winter didn’t bring nearly as much rain as hoped for, the Los Osos community countered that by conserving more water than it has since 1978. 

Officials hope that water production drops even further. Prior to 2014, the basin was being overdrawn.

“Because of the drop in production, we hit 89 percent [of maximum possible production],” Miller said. “If we can then implement some basin plan projects and continue water conservation, then we’ll be well below 80 percent and expect to recover the basin.”

Miller emphasized that the Los Osos basin still has a long road to recovery.

“It’s a good start that says we’re on the right path,” he said. “It doesn’t imply that we’re out of the woods by any stretch. [Seawater intrusion] is still a primary concern. We still need to implement everything we’ve talked about in the basin plan.”

The annual report will be submitted to SLO Superior Court in June as required by the Basin Management Plan approved by the court in September 2015. 

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