The Sunnyvale Sun
News
Contamination at Superfund site in shallow groundwater
Expert says pollution plume has crossed border into Sunnyvale
By HUGH BIGGAR
A recent report on a widespread industrial contaminant has a range of implications for a toxic waste site on the Cupertino/Sunnyvale border and for Santa Clara County, authorities say.
The report, published in July by the National Academy of Sciences, said the contaminant trichloroethlyne, or TCE, is up to 40 percent more hazardous to human health than previously thought.
The findings could lead to stricter cleanups at polluted sites and at military bases such as Sunnyvale's Moffett Field. The study also said evidence has grown that TCE causes cancer, which could lead to changes in drinking water standards.
"It's a pretty serious issue since Santa Clara County has the most Superfund sites in the country, and most are contaminated with TCE," Ted Smith, director of the Silicon Valley Toxics Coalition, said. "It's a concern for groundwater and drinking water."
About half the drinking water in the Santa Clara Valley Water District, which serves Cupertino and Sunnyvale, comes from deep aquifers, district spokesman Mike Di Marco said. Water in the deep aquifers, according to DiMarco, is not tainted with TCE. "We don't have TCE in our drinking water," he said, but added it did have TCE contamination in the 1980s.
At that time, officials discovered underground storage tanks containing TCE had leaked or spilled into the ground. As a result, officials designated several sites in Santa Clara County as Superfund sites-- including the Cupertino site on North Tantau Avenue. Many of the companies, such as Intersil and Siemens in Cupertino, had used TCE--a degreasing solvent--in their work manufacturing semiconductors.
Exposure from TCE retroactively could present a problem said, Dr. Gina Solomon, who served on the review committee of an initial draft of the NAS study in 2001.
"Exposure from decades ago could still lead to developing forms of cancer," Solomon, an occupational physician at UC Medical Center in San Francisco, said. She cautioned, though, that not every person exposed gets sick and sickness depends on things not entirely understood, such as genetics.
Since the discovery of contamination at the Cupertino sites in 1982, the San Francisco Bay Regional Water Quality Control Board has overseen cleanup. The water board has also conducted site reviews every five years, with the most recent in the fall of 2005. As a part of that r review, the water board's report said, "the deeper groundwater has been cleaned up to [current] drinking water standards."
The report also said chemical contamination was limited to two upper groundwater aquifers that are 50 to 150 feet deep, and was present in a groundwater plume. That plume now extends north across Homestead Avenue to a Sunnyvale residential neighborhood, and slightly west of the Tantau Avenue site.
Overall, the water board said 20 years of cleanup efforts including removing water and soil and sealing wells had been successful, though it cautioned the process could take up 300 years. The water board also said the groundwater plume is not believed to be advancing.
Di Marco said the water district tests hundreds of samples for contaminants each year and is about to open a new laboratory to help with that process.
In the meantime, both soil and air testing are recommended.
Ellis Wallenberg, a senior scientist for an environmental consulting firm, said sites directly over groundwater contamination plumes as well as soil up to 100 feet from the plume should be tested.
"The good news is soil testing of TCE is fairly cheap, about a dollar per square foot," Wallenberg said. "It's not routine and a phase one environmental review does not include soil vapor testing but you better get that done since it's an issue new to developers."
Ted Smith of the Silicon Valley Toxics Coalition said there was also a need for soil testing.
"There is evidence it is seeping up back through the aquifers and coming out of the ground," Smith said, comparing it to a candle flame drawing vapor up a wick.
UCSF's Solomon also recommended air tests, especially for buildings and homes above contaminated sites such as those in Sunnyvale.
"TCE can evaporate into the air and migrate to adjacent areas," she said, adding that state and federal agencies such as the EPA are responsible for checking for such accumulations inside buildings. While acknowledging not much could be done about past exposure, Solomon said keeping aware of the issue is important. "It important to do something about limiting exposure before it occurs," she said, " because there is a surprising amount of TCE still out there."
