It's long been a mystery as to how high levels of dangerous trichloroethylene (TCE) were found in the Silva family's well on Sherland Avenue in the 1970s, but now there's a new explanation.
The Silva family had used the 465-foot deep well for farming the area and had been drinking from it since 1949 until they received notice that the well water was found to be toxic in 1982. The carcinogen TCE -- a solvent once heavily used by local silicon chip makers -- was found in the Silva's well at 14 times the level the state considers safe for drinking.
"I love water, because I know what the value of water is," a 77-year-old Joe Silva told a reporter in 1982. "It is my life savings. It is the way I make my living. I love that well as much as I love my wife and my family."
Sewer lines spreading TCE?
It was originally thought the well may have been contaminated by a leaking underground storage tank at the Intel semiconductor manufacturing plant at 365 Middlefield Road the leak was discovered in 1981. But the connection never proved true, and Environmental Protection Agency officials found that the 1.5-mile-long plume of TCE-contaminated ground water that Intel and others left behind fell short of the Silva's well by half a block. The plume -- now mostly cleaned up -- doesn't reach much farther west than Whisman Road.
Now there's a new theory. Leaky sewer lines may have carried toxics to the well. Lenny Siegel, a longtime local expert on toxics in northeastern Mountain View and director of the Center for Public Environmental Oversight, is asking the EPA to do more soil and groundwater sampling around the Silva well to find out.
"If they were to find a hot spot on Murlagan or Sherland that they haven't found yet, that would reinforce this hypothesis," Siegel said. "It seems hard to believe there would be more of these but it was hard to believe they found these hot spots (on Evandale Avenue) at such high levels."
The well has long since been been sealed off. It sits in the backyard of a home on the north side of Sherland Avenue, its cleanup system visible from the Hetch-Hetchy trail.
Residents of the area have been suspicious for years that the area's TCE contamination has caused some of their health problems. Now there a local watchdog group is calling for soil and groundwater sampling around the well site to see if it was just the tip of a larger "hot spot" created by a sewer line leaking TCE solvent, which was dumped down the drain by semiconductor manufacturers, according to news reports from the late 1970s.
Link to new hot spots
In recent months EPA officials said sewer line and storm drain leaks were the only plausible explanation for four other recently discovered "hot spots" in the area: two among homes on Evandale Avenue, one in a hotel parking lot on Leong Drive. A city report blamed the same sewer line for another nearby hot spot on a piece of vacant city property known as the Moffett Gateway on Moffett Boulevard near Stevens Creek.
The danger is that residents of the homes in the area around the well may have been breathing unsafe levels of TCE vapors, which come out of the ground and get trapped indoors. At high enough levels, even short-term exposure to TCE vapors can cause birth defects, and a host of other diseases when breathed in over many years. In late 2012, the EPA discovered two homes on Evandale Avenue with TCE vapors above EPA limits, and since then, 95 homes on Evandale Avenue and Leong Drive have been tested. Four others were found with only trace amounts of TCE vapors inside.
"People investigating other sites are finding the sewer lines and other horizontal conduits are significant sources of indoor vapors," said Siegel, noting what he had heard at a recent Defense Department seminar on toxic cleanups. "In some locations, such as Hill Air Force Base, contaminated groundwater infiltrates sewer lines, moves horizontally, and releases vapors into buildings away from the groundwater plume."
After many years of being a complete mystery, sewer line leaks are also now suspected as the cause of the Orion Park TCE plume just out side the main gate at Moffett Field, where hundreds of apartments for military families existed for decades before being torn down in 2009. The Army now has new offices and training facilities on the site, and has refused to clean up the TCE. The Army contends that the toxics at Orion Park had to have come from an off-site source, as nothing other than a farm had existed on the site before the apartments were built in 1968.
Now there's potentially a new explanation for the Orion Park TCE plume: Siegel recently found a map showing a large city sewer line running along the east side of Orion Park, a line which also once served Fairchild Semiconductor's manufacturing plants along Whisman Road.