The U.S. Environmental Protection Agency has shared its findings on vapor intrusion at three Sunnyvale sites.
The EPA held a public meeting on May 14 at San Miguel Elementary School to educate nearby residents on vapor intrusion in an area referred to as the “triple site,” which includes Advanced Micro Devices and 901-902 Thompson Place superfund site, the TRW Microwave superfund site and the Philips Semiconductors site, formerly Signetics Inc.
The EPA conducted a study during the winter months to gauge levels of possible vapor intrusion in homes and at San Miguel Elementary and three other campuses un the area: Rainbow Montessori School, The Kings Academy and Children’s Creative Learning Center.
The groundwater below the triple site was found to be contaminated in 1982 as a result of a leak in an underground waste solvent storage tank. The groundwater was found to be contaminated by various volatile organic compounds, the most notable of which is trichloroethene, or TCE.
TCE is a volatile chemical mainly used in cleaning products, some of which can even be found in household items. Vapor from the groundwater can seep into the soil and potentially into the homes and buildings atop the site.
According to Rusty Harris-Bishop, superfund project manager, TCE vapor can enter homes and buildings in different ways.
“Vapors can enter homes through basements, crawl spaces, cracks in foundations or utility access points, and levels can vary throughout the year,” he said.
Winter is the most vulnerable season for vapors to enter the home and be harmful because of little circulation of fresh air.
Out of the four schools and 54 homes sampled, three homes and one school showed evidence of TCE vapor intrusion, mostly in crawl spaces beneath the buildings. The 54 homes sampled are only one-eighth of the total homes located above the contaminated groundwater.
“The households that were sampled all met EPA’s requirements for being protective, with most showing either no vapor intrusion or very low-level vapor intrusion that regardless meets EPA’s most stringent health protection goals,” Harris-Bishop said.
Rainbow Montessori School showed evidence of vapor intrusion in the crawl space beneath the Building L auditorium. As a result of these findings, a crawl space venting system is being designed for the building, according to the EPA.
It was also discovered that a rooftop ventilation system was stuck in the closed position, so that was fixed to provide more air circulation and ventilation for the building.
Harmful effects of TCE exposure can include increased cancer risk from long-term exposure and heart defects in fetuses from short-term exposure to pregnant women.
Outreach
The EPA will be conducting door-to-door outreach in the 700 block of Duane Avenue and nearby streets, which is across from the Montessori school with elevated levels of TCE vapor, to encourage the households to participate in sampling efforts.
“We did not get many residents in this area signing up for sampling during our last outreach effort in the neighborhood,” Harris-Bishop said.
The sampling process is simple: A sampler is placed on a shelf or counter in the home for anywhere from 24 hours to a week.
“We want the community to know what activities are taking place in their neighborhood, what still needs to be done, and the risks posed by the site,” said Harris-Bishop. “We also want the community to know that while there is no immediate health risk posed by the site, our goal is to eliminate any potential risks, and that our efforts to more fully know the extent of vapor intrusion issues will help us in that goal.”
The three involved facilities are working to mitigate effects through cleanup efforts.
For more information, visit epa.gov/region09/triplesite or call Melanie Morash, EPA project manager, at 415.972.3050.
