Three contaminated sites in Sunnyvale have until Sept. 2 to respond to a notice of deficiency from the U.S. Environmental Protection Agency.
The EPA delivered the letter to AMD at 901/902 Thompson Place, the Philips (formerly Signetics) site at 811 E. Arques Ave. and 444 N. Wolfe Road, and TRW Microwave Superfund Site earlier this month.
There are more than 100 residences and at least four schools within the 100-acre area that spans from E. Arques Avenue to Lakehaven Drive.
The EPA has been investigating the potential for vapor intrusion, a process by which vapors from groundwater contamination may migrate into the indoor air, particularly at schools and homes in the Duane and San Miguel avenues area.
The EPA reported indoor air sampling has been conducted every year at some school buildings, and results continue to meet EPA requirements; however, the agency recently strengthened its protective levels for trichloroethene (TCE).
“We’re still learning about vapor intrusion in California, and when we did a census review internally in the spring of groundwater sites that could have vapor intrusion, this particular set of sites really jumped out as high priority, given the number of houses and number of schools,” said John Lyons, acting assistant director of the sSuperfund Division Site Cleanup Branch.
“Vapor intrusion is one of the highest priorities for the region and division. We are continuing to learn about this problem, and we’re committed to being open and transparent and available to the community and getting sampling done to answer questions that are raised. We want to get it done expeditiously.”
TCE is a type of volatile organic chemical, which can move as vapors from groundwater through soil. If levels are high enough and prolonged enough, it may create a health risk.
According to the letter submitted to the companies on Aug. 11, several deficiencies in addressing potential subsurface-to-indoor air vapor intrusion included no sampling being proposed for San Miguel Elementary School and lack of historical background, including summary of vapor intrusion evaluation and mitigation work performed to date.
The volatile organic compounds (VOCs) were discovered in 1981 from leaking underground acid neutralization tanks on the former Advanced Micro Devices, Inc. property. Initial investigation at the Philips site began in February 1982 with the detection of a leak in an underground waste solvent storage tank.
“For more than 30 years, AMD has demonstrated an unwavering commitment to do what is right for the public in addressing the investigation and cleanup of former semiconductor manufacturing facilities in Silicon Valley,” AMD spokesman Andrew Fox said in an email. “AMD has and will continue to undertake our obligations regarding those sites in a manner that protects public health and the environment, in accordance with the best available science, and in coordination with state and federal regulators.”
According to the EPA’s superfund website, the removal of contaminated soils and tanks and the continued treatment of contaminated groundwater have reduced the potential for exposure to hazardous materials at the site, but investigations are ongoing. Drinking water is not affected by this contamination, as the neighborhood’s drinking water comes from the Hetch Hetchy Reservoir.
“Over the last 30 years there have been huge advancements in cleaning up groundwater in the South Bay,” Lyons said. “It is difficult to remove, it takes a lot of time and a lot of water needs to be removed.”
This past year alone, the companies treated 100 million gallons of water in the neighborhood next to Duane and San Miguel. AMD also first piloted a bacteria cleanup process, in which it saw a 90 percent reduction in concentration of TCE within six months.
“Those results are really encouraging,” said Melanie Morash, superfund project manager. “One of EPA’s goals is to focus in the near term on indoor air sampling.”
The majority of data the EPA has collected in the last year has shown no evidence of vapor intrusion, and sampling at some school buildings such as the Montessori School, which is over the highest concentrations in groundwater, has shown that levels of TCE are very low.
More testing will be done in the area this fall and winter to make sure that the new lower levels for TCE are not being exceeded.
For more information, visit epa.gov/region9/triplesite or contact EPA project manager Melanie Morash at 415.972.3050 or morash.melanie@epa.gov. EPA community involvement coordinator Alejandro Diaz can be contacted at 415.972.3242 or diaz.alejandro@epa.gov.
