SLO airport to be investigated as possible source of groundwater pollution

Officials at the San Luis Obispo County Regional Airport have until April 15 to submit a work plan explaining how they will search the airport property for possible sources for groundwater contamination in southern San Luis Obispo.

In a letter to airport manager Kevin Bumen, officials with the Central Coast Regional Water Quality Control Board said the county must conduct soil gas and groundwater assessments to determine whether the airport is the source of elevated levels of the chlorinated industrial solvent trichloroethylene, or TCE, in wells in the Buckley Road area near the airport.

Thea Tryon, enforcement coordinator with the regional water board, said 64 wells have been sampled in the Buckley Road area, with 12 of them having TCE levels that exceed the state’s allowable level of 5 micrograms per liter of water. TCE is a colorless, volatile nonflammable liquid that was used as a solvent in the aircraft industry.

In its letter to the county, state water officials said TCE could have been used and disposed of at the airport between 1938 and the 1970s, when the chemical was phased out of use because of its toxicity.

“Therefore, there is urgency in finding the source and starting cleanup activities to prevent further degradation of groundwater sources in the area,” the water board’s letter to the county stated.

Originally, state water officials wanted the information by Jan. 20 but granted the county an extension to April 15.

County officials did a previous evaluation of the airport property and preliminarily concluded that it is not the source of the pollution because it could find no historical records that indicated that TCE had ever been used at the facility. However, state water officials are not convinced and want the county to investigate further.

“There is just not enough evidence to make that determination,” Tryon said.

State water officials are requiring that airport managers take groundwater samples and soil gas samples. Soil gas sampling measures the vapors contained in soil.

In addition to the historic use of TCE at airports, the water board is concentrating on the regional airport because the southern portions of the facility are uphill from the contaminated wells, meaning that pollutants could flow down from the airport to the contaminated wells.

This story was originally published March 29, 2016 at 3:52 PM with the headline "SLO airport to be investigated as possible source of groundwater pollution."