The Cupertino Courier

News

Agencies recommend vapor monitoring for waste sites

By Hugh Biggar

Cleanup efforts are progressing at two toxic waste sites in the North Vallco neighborhood on the Cupertino/Sunnyvale border, but, with the area up for redevelopment, authorities recommend further precautions.

The two sites at 10900 N. Tantau Ave. and 19000 Homestead Road are being treated to remove toxic waste, and have been since the 1980s.

The contaminants, generated by former computer chip manufacturers, are present in a shallow groundwater plume extending from the sites north to Inverness Way in Sunnyvale, slightly west of the sites and just south of Forge Drive.

Cupertino hopes to redevelop the area surrounding the sites. The neighborhood is primarily industrial, and the city is holding talks on redevelopment possibilities, including housing. Apple also plans to build a campus on 50 acres in North Vallco.

While authorities say the contaminants no longer affect drinking water, they also say continued monitoring of vapors--particularly from one of the contaminants, trichloroethlyne, or TCE--is necessary.

"The concentrations could change and is something we monitor every two years," Roger Papler, a geologist for San Francisco Bay Regional Water Quality Control Board, said.

Water board staff said soil samplings now show that concentrations in the shallow ground water do not exceed levels that would require indoor screening for Sunnyvale residences above the plume.

Even so, others suggest proactive screenings for vapors would be a good idea.

"If you are planning to build 100-200 feet horizontally from the plume, then there is an issue," Lenny Siegel, director of the Mountain View-based Center for Public Environmental Oversight, said. "The drinking water is basically protected. The key question is vapor intrusion into the air [from TCE]."

The water board, in its September 2005 report on the Cupertino sites, also said, "Vapor intrusion pathway is an emerging issue, for which the science continues to evolve."

That evaporated vapor could pose problems for buildings directly above the ground -water plume in adjacent areas as well.

In Cupertino, the affected sites formerly belonged to Intersil and Siemens Components. The companies used TCE, a nonflammable colorless liquid, as a degreaser in manufacturing semi-conductors. The chemical was then stored in underground tanks, which either leaked or spilled.

The Environmental Protection Agency designated both sites as national priorities for cleanup, or Superfund sites, after toxic waste was found in the early 1980s. Since that time, the water board has overseen removal of the contaminants. The work has included pumping out contaminated water, treating and vaporizing soil and sealing wells to contain contaminants. While making progress, the water board also cautioned the process could take up to 300 years.

In the meantime, in July of last year, the National Research Council published a report stating TCE is believed more hazardous than previously thought.

According to the report, evidence TCE causes cancer and other health problems has increased (though some agencies such as the Department of Defense have debated its level of lethality). On its website, the EPA lists possible health problems from chronic exposure to TCE through inhalation include dizziness, headache, sleepiness, nausea, confusion and blurred vision.

TCE is found in many sites in the United States including at the 29 Superfund sites in Santa Clara County and at former military bases such as Moffett Field.

The EPA has so far not said if the NRC report will lead to changes in its guidelines, though some experts say it could lead to changes in drinking water standards.

For now, Siegel and others stress the importance of ensuring the safety of the sites on the Cupertino/Sunnyvale border ahead of any development.

Siegel, while stressing that health problems from the vapors would require long-term exposure, said, "The sites need to be fully evaluated and it's easier to do that before anything gets built."

The next scheduled five-year review of the Cupertino/Sunnyvale Superfund sites is September 2010.