Moffett Field Toxic Plume Subject of EPA Meeting with Mountain View Residents

What caused a spike in the readings of toxic chemicals in Mountain View? The Environmental Protection Agency is telling residents what – if anything – they’ve found.

NBC Bay Area’s Investigative Unit first broke the story of the expanding Superfund site.

MORE: EPA Superfund Sites Cause New Toxic Plume Concerns

In question is a toxic plume of chemicals a mile and a half long, and a half-mile wide. The plume is mostly TCE, a solvent that’s known to cause cancer and could harm unborn children.

As The Investigative Unit first reported in February, the EPA discovered new hot spots of the chemical TCE in Mountain View, outside the original boundaries of the MEW Superfund site situated in and around Moffett Field. Now, we have new levels to report: Recent tests show levels of up to 110,000 parts per billion in the ground water. And that leaves the question, How did the TCE get there?

The MEW Superfund site extends under the 101 and beneath Moffett Field. And, for decades, the EPA has monitored and extracted the toxic solvent trichloroethylene, or TCE, from the groundwater below.

TCE is a cleaning solvent once used by the budding semiconductor industry three decades ago. The chemical has since been linked to cancer and, when it evaporates, can collect in buildings in a process called vapor intrusion, which can cause heart deformities in unborn children during the first trimester of pregnancy.

MORE: Google Employees Face Health Risks, Superfund Toxic Vapors

Removing the contamination could take decades, even centuries. The EPA has removed tons of TCE from under the neighborhood and admits that there is plenty left to accomplish.

“We cleaned up over 5 1/4 billion gallons of contaminated water and over 110,000 pounds of toxic contaminant,” EPA Superfund site project manager Alana Lee said back in February.

The new areas of concern are along Evandale Avenue, according to the EPA. The most recent tests at Leong Drive and Evandale showed levels up to 110,000 parts per billion in the ground water. The EPA considers anything over 5 parts per billion unsafe.

Mountain View learned the EPA will start a pilot program called In-Situ Chemical Oxidation. The process injects chemicals underground and cause the TCE to be consumed, safely cleaning the ground water below.

Tuesday night, the EPA revealed to residents of Mountain View that the agency did not find new homes or buildings with vapor intrusion. But the EPA still does not know where these hot spots of TCE came from, and they will continue to investigate how the toxins got there.

MORE: Cancer Rates High Near Moffett Field Superfund Site

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