A sewer line that runs through the city's Moffett Gateway site leaked the Trichloroethylene (TCE) pollution found in the soil and groundwater there, the report concludes, and points to dumping into leaky sewer lines for causing other "hot spots" of TCE contamination in soil and groundwater on Leong Drive and Evandale Avenue.
"It's the most detailed information I've seen thus far" about the hypothesis that sewer lines created the mysterious hot spots located away from a 1.5-mile long regional plume left behind by early silicon chip makers along the east side of Whisman Road, said Lenny Siegel, director of the Center for Public Environmental Oversight.
The four hot spots include the one at the Moffett Gateway site and two recently found among homes on Evandale Avenue. Another had been discovered years prior in the parking lot of a hotel on Leong Drive, though recent sampling found surprisingly high levels there in the soil and groundwater. "It's a very plausible explanation for all four hot spots." Siegel said.
"What's really striking are the maps that show where the sewer lines are," Siegel said. "I had thought, 'Gee, wouldn't it be funny if (the sewer line) zig-zagged and went by the other two hot spots (at the hotel and Moffett Gateway site)?' That would be almost a smoking gun. And it does. It's not just in the general area — it's right there."
The city-commissioned report by Bureau Veritas concludes, "The direct correlation between distinct areas of high concentration of TCE in groundwater along the sanitary sewer line in areas of no known historical TCE use strongly suggests that historical discharges of TCE-containing wastes into the sanitary sewer may have occurred and then leaked at various locations both on the (Moffett Gateway) site and off-site, resulting in impacts to groundwater."
An ongoing investigation by the EPA has yet to come to a conclusion, but EPA project manager Alana Lee told residents on Nov. 12 that there was no other plausible explanation for the hot spots on Leong and Evandale. "It appears to be coming down the sewer," she said, adding that the dumping stopped years ago when semiconductor manufacturers left the area.
Fairchild Semiconductor had been caught by the city dumping acid and other toxics into the sewer and storm drains that run to Stevens Creek in the late 1970s, according to several news reports from the time. Fairchild's corporate descendant, Schlumberger Corp., is paying to clean up the two Evandale Avenue hot spots, along with the two Evandale Avenue homes where TCE vapors were found above EPA limits for risk of cancer and birth defects — but has refused to take legal responsibility for the contamination.
The EPA has sampled the indoor air in over 95 homes in the Evandale Avenue and Leong Drive area and a total of six were found with TCE vapors inside, though four were under EPA action levels.
Looking at a map of the numerous interconnected sewer lines under every street in the area, it's hard to not ask, as a resident did at the Nov. 12 meeting, "Are we sampling enough to know we haven't missed some (hot spots)?"
"He's not the first person to ask that question," Siegel said after the meeting.
A number of groundwater samples on far-flung residential streets — such as Easy Street and Tyrella Avenue — have turned up with low levels of TCE along sewer lines. Siegel and others wonder if those samples might just be the tip of the iceberg.
As for the Moffett gateway site, it could be developed with office space and a hotel within a year or two, with or without a site clean-up, said Dennis Drennan, property manager for the city. He said that unless a polluter is held accountable by the EPA, the city may end up paying for a toxic cleanup of the largest of two Moffett Gateway hot spots.
A smaller hot spot on the site appears to have come from the county's use of the site as a vector control yard.
"We have a very keen interest in having this plume cleaned up at some point," Drennan said. "In an ideal world we would find a responsible party and we would clean it up very quickly."