How It Works: Water Quality Forensics Traces Contamination to Its Source
How It Works: Water Quality Forensics Traces Contamination to Its Source
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How It Works: Water Quality Forensics Traces Contamination to Its Source
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Investigating the source of water contamination allows cleanup efforts to be more targeted.

If Steve Gruber's job were a TV show, it would be called "CSI: Water." Gruber, a project manager in the San Diego office of Burns & McDonnell, specializes in water quality forensics, an emerging field dedicated to tracking down sources of stormwater contamination by studying the DNA of the offending bacteria. The findings can save substantial time and money on environmental cleanup.

Consider Poche Beach in San Clemente, California, which for decades had the worst contamination record among Orange County beaches. "The beach regularly exceeded water quality standards for fecal coliform bacteria, resulting in beach closures," Gruber says. "Our job was to identify where it was coming from."

That involved investigating everything from the watershed that drains onto the beach to the DNA of the bacteria found there.  "By going to the molecular level, we discovered there were several contributing factors," he says. The worst offenders — and the easiest to address — were gulls that congregated at the beach.

"We discovered that the birds' migration pattern led them to feed in a landfill and then move to the beach, where they drank fresh water and left their waste," he says.

Burns & McDonnell advised the city to retain a falconer — a professional who comes to the beach several times a week each summer to fly falcons that frighten away the gulls. The result: a precipitous drop in contamination, and the removal of beach closure signs.

"DNA markers aren't a magic bullet," Gruber says. "It's important to understand the whole watershed, and the DNA findings must be supported by other parts of the study. In the case of Poche Beach, over-irrigation in the watershed, bacteria regrowth in storm drains and a 15-foot-deep scour pond on the beach also contribute to the contamination."

Source identification studies allow cleanup efforts to be more targeted. "If you identify the source of bacteria, you can pinpoint the best management practices for removing it," Gruber says. "It's just a smarter way to go."

For more information, contact Steve Gruber, 858-320-2946.

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