EPA officials said residents in the area should only be concerned about being exposed to toxic vapors trapped inside buildings, adding assurances that the city's water supply is safe, as well as the outdoor air in the area after tests of "hundreds of outdoor air samples."
Gardners don't need to worry either, the EPA said, noting that vegetables grown above the plume are safe to eat.
There is an ongoing effort to notify residents along Evandale Avenue, from Whisman Road to Tyrella Avenue, of free voluntary indoor air testing that is available to make sure homes are safe. So far 30 homes have been tested and two have been found with TCE (trichloroethylene) vapor levels above the EPA's limit of 1 microgram per cubic meter. Both homes are on the northern side of Evandale Avenue near Whisman Road, an area the EPA considers to be a "high priority" for indoor air testing.
The EPA still doesn't know how the toxics made their way under Evandale Avenue. The samples may be connected to the massive plume that was thought to exist mostly on the east side of Whisman Road. EPA officials said that throughout the 1960s, 1970s and into the 1980s, Silicon Valley's original chip manufacturers released chemicals into the ground, with the primary pollutant being TCE. The responsible parties include Intel, Raytheon and Schlumberger Corp., the descendant of the first chip manufacturer in the Valley, Fairchild Semiconductor. Along with the United States Navy and NASA on the other side of Highway 101, the companies left behind a 1.5-mile long, 1-mile wide plume of groundwater pollution.
The portion near Evandale Avenue is known as the "MEW" because it is roughly bordered by Middlefield Road, Ellis Street and Whisman Road.
On March 3 a group of about 100 residents assembled on a poolside patio at 114 Flynn Avenue after an electrical outlet caught fire as the meeting began in the housing complex's recreation room. Several EPA officials spoke, including EPA vapor intrusion project manager Alana Lee, toxicologist Dan Stralka and groundwater project manager Penny Reddy. Also chiming in from the audience was Lenny Siegel of Mountain View's Center for Public Environmental Oversight. He introduced himself as a Mountain View resident who has followed the massive plume of toxics in the area for 30 years.
Many residents were left with some uncertainty about whether their health had been affected. One woman was worried if her dog's rare case of Lupus wasn't a sign that she might also develop health issues soon.
"How do I know that it is not affecting my health or my pet's health or anybody that comes to my house?" said Brian David, a longtime resident of a home where TCE vapors were found at levels acceptable to the EPA (.44 micrograms per cubic meter) on Whisman Road near Evandale.
A woman asked if there was a way to be tested for exposure to TCE and Stralka said such tests are not readily available for humans. "What we are able to measure now are high levels in short-term exposure," he said. "We're concerned about levels that are so low in long-term exposure" that it can't be detected.
In 2011 the EPA issued its Final Health Assessment for TCE, calling it "carcinogenic to humans by all routes of exposure" and reporting that inhalation can cause "hepatic, renal, neurological, immunological, reproductive, and developmental effects." It is also linked with kidney and liver cancer as well as non-Hodgkin lymphoma.
The indoor air limits applied in Mountain View are intended to protect against birth defects from short-term exposures. Stralka said the concern was during a "21-day period when (the heart) is actually forming" in the first trimester of pregnancy.
Stralka addressed the Bay Area Cancer Registry report on cancer rates in the area, which looked at rates of kidney and liver cancer and non-Hodgkin lymphoma, finding nearly double the regional rate of NHL between 1996 and 2005. Some have questioned why other types of cancer were not studied, and Stralka said other types "are not directly associated with what we are seeing in lab animals." EPA officials also said they don't use such reports when considering where to test for toxics.
EPA officials said they were surprised to find extremely high concentrations of TCE late last year under Evandale Avenue. Whether it came from the larger "MEW" plume or another source is still under investigation, EPA officials said on Sunday.
"It could be dumping something down a drain or falling off a truck, we don't know what the source is at this point," Reddy said.
Contrary to some news reports, EPA officials said the MEW is not a "runaway plume." Evandale Avenue had simply not been tested before, and EPA officials said they did not know why. Every other street in the area had been.
Groundwater samples taken every 100 feet along Evandale Avenue had no logical pattern. The results "are puzzlingly curious," Reddy said.
One particular "hot spot" on the 200 block of Evandale Avenue had 130,000 parts per billion of TCE in the groundwater, "higher than any concentration we have in our plume right now," Reddy said.
The EPA's groundwater cleanup goal is 5 parts per billion.
She said the hot spot was found 13 feet down — the same depth as a sewer line running under the street, which could have a layer of gravel around it that could also be acting as a conduit to the rest of the plume. The EPA is also examining a video city workers took of the inside of the sewer line to see if it could also be a conduit.
An extraction well could soon be installed on such hot spots to pull the groundwater out and clean it, while also providing enough suction to keep it from spreading, Reddy said. There are several other extraction wells in the MEW that "contain the plume" and are checked three times a week to make sure they are operational.
Reddy said that TCE is heavier than water and sinks down to the layer of clay deep underground before dissolving into the water and evaporating, a volatile chemical "that can migrate up through conduits and preferential pathways," Lee told residents at the meeting.
EPA has not completed sampling the area's groundwater and is trying to get permission from private property owners to see how far the plume really goes. Reddy lamented not being able to do more testing just north of Evandale on Fairchild Drive. She said a number of utility lines in the street had blocked the necessary drilling.
Leong Drive residents
Some residents attending the meeting were surprised to learn of another area with elevated levels of TCE in the groundwater, but where indoor air testing isn't being done on nearby homes for lack of funds.
"We just found out it is not funded, that worries us," said Ben Longoria, a resident of Easy Street, as he pointed to an area on a map shown as the "Moffett study area."
"We are actively searching for responsible parties in this area" to fund cleanup and indoor air testing, Ready said. Siegel added that it was unlikely that a polluter would be found with "deep enough pockets" to help.
Lee said the EPA had not done any indoor air testing in the homes on Leong Drive closest to the hot spots on the site of a former Denny's and a motel, where the indoor air was found at acceptable levels. Groundwater samples from 2011 showed concentration as high as 12,000 parts per billion in two locations across the street from homes.
"Just because you are in that area doesn't mean you are on Leong where you should be particularly concerned," Siegel said at the meeting.
Concentrations as high as 440 parts per billion were found nearby on the west side of Moffett Boulevard on a property once home to the county's vector control yard, purchased a few years ago by the city, possibly for a shopping center.
After the meeting, Siegel said he wanted to make it clear to those in the Wagon Wheel neighborhood that it is unlikely most people are going to be affected by the contamination.
"They tested 30 homes and only came up with two. Even if they find something, they can install a system that protects you," Siegel said, referring to vapor control systems.
Officials said they were going to be going door-to-door in the neighborhood soon and would send out a new fact sheet that discusses the dangers of TCE over the following week.
"Everybody who moves into the area has to know that sampling is available," Siegel said. "If you've had your property sampled, it should be disclosed."
Not every new homeowner is notified. There might be a notice buried in paperwork for a home that "tells you about a Superfund area," Siegel said. "But they don't tell you about your specific house. I don't believe California requires that specific info. But I'm not an attorney so I can't guarantee that."
For homes with elevated levels, vapor control systems are installed by the polluters to draw the vapors out from under the home and exhaust the vapors above the roof-line, which Lee assured residents was safe.
Of the two homes with elevated levels on Evandale, one had a ventilation system installed in early February that still requires modification to clear up the air to levels to below the EPA limit. The other household is still having its system designed. The systems also protect homes from radon, a naturally occurring carcinogen that some consider more dangerous then TCE, said Peter Strauss of the Center for Public Environmental Oversight.
The EPA once estimated that it would take 300 years to clean the plume but more recently, the estimate was revised to 100 years, Siegel said. "Pump and treat" methods have pulled tons of TCE out of the ground and filtered it out, but the last little bit is proving very hard to remove. Intel has begun experimenting with cleanup methods that involve injecting TCE-eating bacteria into the ground, called "in-situ bioremediation" with promising results. But it is hard to cover large areas with it, or areas where buildings stand in the way of drilling into the ground, Siegel said.
"The question is, will it take forever?" Siegel of the cleanup. "The responsible parties are arguing that you can't totally clean it up, so why try?"
For more information, visit the EPA Region 9's MEW study area website at tinyurl.com/ofquyf. Or contact these EPA officials:
EPA Vapor Intrusion Project Manager
EPA Groundwater Project Manager
EPA Community Involvement Coordinator