Seven volunteer to sample toxics at home Seven volunteer to sample toxics at home (July 09, 2004)

EPA wants more data about vapor risk

By Jon Wiener

Seven more residents of northeast Mountain View have volunteered to let the U.S. Environmental Protection Agency (EPA) sample their homes for toxic gas, and the EPA is hoping more will come forward before its July 22 deadline.

EPA project manager Alana Lee has been going door-to-door on the west side of Whisman Road to find volunteers for the indoor air sampling and conduct a survey of the nearly 100 homes in the area. Sampling involves placing several steel canisters on a table or in the corner of a room for a 24-hour period.

The EPA is hoping to gather enough data to draw some conclusions about a process known as vapor intrusion, in which toxic chemical vapors accumulate in buildings, elevating potential health risks.

The homes the EPA is targeting now sit on top of ground water polluted with trichloroethene (TCE), a cancer-causing solvent. TCE contamination garnered national attention as the cause of a cancer cluster in Woburn, Mass., highlighted in the book "A Civil Action" and movie by the same name.

Water to air correlation unclear

TCE has been found in indoor and outdoor air in and around many of Mountain View's seven Superfund sites. The area bounded by Middlefield Road, Ellis Street and Whisman Road (known as MEW) has generated concern because the proximity of a residential neighborhood means people may face increased long-term exposure to contamination.

The technology companies responsible for the plume of groundwater contamination estimate that it extends approximately 100 feet to the west of Whisman. The plume's "boundary," essentially an approximation of where groundwater concentrations drop below five parts per billion, is serving as a guideline for initial air sampling.

"We don't know what the contaminant level is that means you have vapor intrusion," said Lenny Siegel, director of the Center for Public Environmental Oversight and board member of the Northeast Mountain View Advisory Council (NMAC). TCE vapor turned up outside of the plume boundaries at an outdoor sampling station at Slater School originally intended as a control point last fall and again this past winter.

Preliminary tests in March examined four homes over the plume boundary. Results showed the chemical had made its way through the soil into at least one home with an earthen cellar in levels above the EPA's provisional standard for one increased cancer case per one million people.

Jane Horton has lived in the house that tested positive for almost thirty years. An NMAC board member like Siegel, Horton had always wanted to have her house tested. Only when redrawn maps of the plume boundary showed it going directly under her house did she feel confident enough to ask to have it done.

"When you live across the street from a Superfund site ... you think things are taken care of. But without testing your own location, you don't have a way to know," said Horton.

Foundation types may have impact

Another goal of the EPA's survey efforts is to gather information about the foundations of the buildings, in order to help determine the types of foundations that are most and least susceptible to vapor intrusion. According to Lee, the vast majority of homes surveyed have crawl spaces beneath them, and no other than Horton's has an earthen cellar.

The EPA will also analyze foundations at volunteer residences for "preferential pathways," like cracks or electrical conduits through which TCE vapor could travel. Siegel likened these pathways to a puncture hole in a bicycle tube.

"All of the air comes out, not just what's next to the hole," he said. Likewise, TCE vapor in soil can remain below ground due to a pressure gradient, but a change in that gradient might suck chemical vapor into a building, he added.

Both community activists and the EPA's own recently published Five-Year Review draft report said that clean-up efforts at the MEW site need to focus more on protecting residents from vapor intrusion. The report is available online on the NMAC Web site at www.nmac.whisman.net. The public can provide comments on it through July 16.

E-mail Jon Wiener at jwiener@mv-voice.com.

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