EPA begins toxic cleanup on Evandale Ave.

New gas analyzer can detect small amounts of TCE

The Environmental Protection Agency is investigating the theory that early computer chip manufacturers spread toxics into the residential neighborhood east of Whisman Road through sewers lines that were eaten through by a toxic cocktail of acids and solvents.

To help with the investigation, a sort of laboratory on wheels has been roaming around the area, helping to test air samples taken from under manhole covers, among other sites. Commissioned by the EPA and operated by Lockheed, it is called the TAGA, or trace atmospheric gas analyzer. The converted white passenger bus has an electronic nose so sensitive that it can sense TCE -- the toxic solvent that ended up polluting the groundwater and soil under much of northeastern Mountain View -- from inside a sealed jar. Operators say they can get an idea of where to look first just by driving it slowly down the street, although toxics deep in the ground may escape its detection.

The EPA is keeping silent on the results until they are finalized, but if the theory is proven, polluters such as Fairchild Semiconductor (now called Schlumberger), may be on the hook for cleaning up several "hot spots" -- underground concentrations of TCE that trace the path of a sewer line.

Following the path of the line are two hot spots recently discovered on Evandale Avenue, where a pair of homes have been found with TCE vapors coming through the floor at unsafe levels after polluted groundwater had spread onto the properties. Another hot spot has been discovered under a hotel parking lot on Leong Drive and yet another under a vacant city-owned property on Moffett Boulevard. All are located at similar depths and adjacent to the same sewer line.

The EPA has been examining the city's records and found that the line in question was used more heavily by silicon chip makers until the late 1960s, when the area's main sewer line was constructed just to the north along Fairchild Drive. "What we're evaluating is (lines built) prior to the late 1960s," said Alana Lee, vapor intrusion project manager for the EPA.

The EPA is also reporting success in testing the use of chemical oxidation to clean up the hot spots on Evandale Avenue with the financial help of the responsible companies. By injecting a substance called "permanganate" into the ground, the TCE is broken down into harmless carbon dioxide, manganese oxide and salts, said Penny Reddy, groundwater project manager for the EPA. A series of test injections have reduced concentrations from 100,000 micrograms per cubic liter to only 38 in one location, and from 9,600 microgams per cubic liter to 2,700 in another location.

The injections involve closing off one lane on Evandale and may resume in July in order to reach all of the contamination.

"What we see here are good, positive results," said Reddy at a May 7 neighborhood meeting with the EPA.

Many are waiting on results of the sewer line investigation, as there may be other hot spots that have contaminated soil underneath homes in the neighborhood, causing a threat to the health of residents. TCE vapors can cause cancer and other health problems from long term exposure, and birth defects if mothers are exposed to unsafe levels for just a matter of weeks, according the EPA.

"You lucked out in finding it on Evandale and Leong, but we don't know where else that risk might be," said Lenny Siegel, director of the Center for Public Environmental Oversight.

The EPA had found the hot spots by drilling into the street to see if the TCE plume's boundary along Whisman Road had moved.

When describing the effort to clean up the 2-mile-long TCE plume in northeastern Mountain View at a recent neighborhood meeting, Moffett Field Restoration Advisory Board co-chair Bill Berry said, "Frankly, it has been our experience that we've had surprises come up all the time, like on Evandale, an area we thought to be very well characterized, which I'm sure Alana would agree with, and then we get surprised. So we try and stay on top of it."


Like this comment
Posted by Martin Omander
a resident of Rex Manor
on May 15, 2014 at 4:35 pm

Great article summarizing an important issue for Mountain View! Silicon Valley's history is rich, but some history we'd prefer had not happened the way it did...

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