"If this has been going on for 20 years, how come nobody told me about this when I moved in?" asked one resident after EPA officials said the plume at Moffett has been monitored for decades.
The contamination comes from chemicals dumped or released over many years by the Navy, NASA and early silicon chip makers south of Highway 101.
EPA's Vicki Rosen explained that "there is no requirement" that renters be notified about proximity to Superfund sites like Moffett's TCE plume, though state law requires such information be disclosed when a home is sold.
The concern followed weeks of news about the recent discovery of toxics on Evandale Avenue, a residential street south of Highway 101. Residents of Wescoat were assured that the levels of TCE near their homes was much lower than what was found on Evandale Avenue, where levels were as high as 130,000 parts per billion in the shallow groundwater. Most of Wescoat's shallow groundwater is below 5 parts per billion, the level at which EPA will test a building for toxic vapor intrusion.
"There's potential for vapor intrusion into any of those buildings in the green area," said Alana Lee, EPA project manager, pointing to a map. She offered indoor air testing to residents living above portions of the plume where TCE levels in the shallow groundwater are higher than 5 parts per billion. A number of attendees signed up for indoor air tests after the meeting.
The homes at Wescoat were built in 2006 with "passive sub slab ventilation systems" that draw the vapors away before they can be drawn into the homes above. Lee said the homes were tested for TCE vapors after they were built and elevated levels were not found, but residents questioned whether the systems were properly installed and tested because the EPA didn't oversee the tests or the construction.
Lenny Siegel, director of the Center for Public Environmental Oversight, said it is "reasonable" to request indoor air sampling at Wescoat and he would do so "if I were in your position," he told the crowd. But he added that "chances are the air is is just as safe as the air I'm breathing in downtown Mountain View."
"I'd be concerned if I was going to be here a long time, but I'm a military guy, I'll be here three years, maybe longer," said one Wescoat resident.
EPA toxicologist Gerry Hiatt said EPA limits for TCE vapors — 1 microgram per cubic meter for residences and 5 for offices — are based on a long-term exposure of 25 years and are designed to confine cancer risks from TCE to a "risk range" of one cancer case per million people to 100 cases per million. He added that 35 percent of people get cancer in their lifetimes. The limits also protect against possible heart defects in a developing fetus if mothers are exposed during the first trimester.
"Can we get a test of the outdoor air or is that not possible?" said one woman.
She said that she wanted to know what the levels were at the playground in the Wescoat housing complex that a portion of the plume runs underneath. Lee said such tests are "not uncommon for us to do."
The groundwater is close to the surface at Moffett — within 5 to 10 feet — shallow enough to flood the basement of a 1937 Westcoat home where one attendee said she lives. While outside of the plume area, testing the indoor air of the cluster of historic homes is "something we'd consider," Lee said. She said the historic homes were tested in 2004 and no TCE was found.
Tap water still a concern
While EPA assured residents that the TCE contamination couldn't enter their pressurized water pipes, some residents are still wondering whether the brown tap water they began to see in early March is safe to use. The water comes from "municipal sources" and not the groundwater, EPA said, but "sediment" is apparently being picked up somewhere and making its way to Wescoat.
One woman said her tap water continues to run brown and has a "strong smell of fish." She held up a picture on her cell phone of brown water in a bathtub. A Wescoat resident had previously reported to the Voice
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