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County begins search for source of TCE contamination near SLO airport

How experts are searching for TCE near the SLO airport

Jon Rohrer, principal hydrogeologist with Roux Associates, describes the process for TCE testing near Buckley Road and the airport in San Luis Obispo.
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Jon Rohrer, principal hydrogeologist with Roux Associates, describes the process for TCE testing near Buckley Road and the airport in San Luis Obispo.

San Luis Obispo County has begun an investigation into the source of a toxic solvent that contaminated 12 wells on private property around the San Luis Obispo County Regional Airport.

At the direction of the Central Coast Regional Water Quality Control Board, the county will take six water samples and collect soil gas samples at 93 sites in the Buckley Road area in an effort to determine where the pollutant trichloroethylene, or TCE, is coming from.

Starting this week, the county will take groundwater samples at six locations along Buckley Road and test them for the presence of TCE. Additional groundwater samples could be taken north of the airport’s runway, depending on the results from the first six locations, said Thea Tryon with the water board.

Preliminary test results are due to the water board Aug. 10.

The county also will collect 33 soil gas samples from locations along Buckley Road and another 60 samples from locations northeast and along the airport runway, Tryon said. Soil gas sampling is a technique for detecting TCE by the vapors it gives off.

Passive soil gas samples are obtained by inserting a probe that contains granulated charcoal 3 feet into the ground and allowing it to collect vapor that emanates from the soil, said Jon Rohrer with Roux Associates, the company hired to do the sampling. Additional sampling may be performed depending on the results of the initial soil gas sampling.

State water officials have said the airport is a likely source of the TCE contamination, but the county disagrees. The county has searched its records and cannot find any evidence that TCE was used at the airport.

“To date, we have yet to find anything to indicate that the source of TCE found in the groundwater along Buckley Road is coming from airport property,” said Guy Savage, assistant county administrative officer. “Regardless, we will continue searching until we are satisfied that airport property is not the source.”

State water officials will hold a public meeting in the fall to announce the results of the sampling. In all, 67 wells in the Buckley Road area were sampled, and 12 were found to have TCE levels that exceeded state standards.

The sampling is expected to cost the county at least $100,000, Savage said.

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