New methods might speed up toxic cleanup
New Google office site one of several affected by TCE groundwater plume
Without new cleanup methods, efforts to remove remaining toxics from the groundwater in Mountain View will soon slow to a crawl, according to the Environmental Protection Agency, which is now studying alternatives.
A toxic groundwater plume a mile and a half long and 2,000 feet wide in northeastern Mountain View is the result of the early computer component manufacturing operations of Intel, Fairchild Semiconductor and Raytheon
The EPA first found trichloroethylene (TCE), a solvent commonly used to clean metal parts, in soil and groundwater near North Whisman Road in 1981. It had leaked from underground basins at each site. The plume migrated north of Highway 101 and "co-mingled" with sources of TCE at the former Naval Air Station at Moffett Field, said Penny Ready, project manager for the EPA.
The area is now home to major tech companies including Symantec, Nokia and soon, Google.
To their credit, the three companies and the U.S. Navy have been filtering the groundwater with "pump and treat" systems to clean up the majority of the toxics. But those systems are now losing effectiveness and are not expected to reduce the plume much over the next 10 years, according to Ready in a presentation to the Moffett Field Restoration Advisory Board last week.
Ready reported that an EPA study is underway to evaluate new ways to clean up the Middlefield-Ellis-Whisman (MEW) area, including the use of microbes injected into the ground that turn the TCE into organic ethane and ethene gasses (neither are greenhouse gases).
Lenny Siegel, Mountain View's resident expert on superfund sights as director of the Center for Public Environmental Oversight, called the EPA's feasibility study "a national model of how you go back to a site where 'pump and treat' has lost its effectiveness."
Unacceptable levels of TCE vapors have been measured in buildings in the area of Middlefield, Ellis and Whisman streets, but Siegel says he is unaware of any buildings in use that don't have ventilation systems to keep out the vapors that emanate from below their foundations. TCE is a known carcinogen, and human health effects include kidney and liver cancer, lymphoma and various other reproductive, developmental and neurological impacts, the EPA has reported. Exposure can come through the skin or by inhaling the vapors.
Google's new offices
Google has recently signed a 10-year lease for seven buildings on Ellis Street (see story page 1) It also happens to be the Fairchild Superfund site, a portion of which apparently contains the largest concentration of toxics in the MEW plume. The 450,000 square foot campus was built in 1997, before special "depressurization" systems vented TCE vapors from underneath building foundations. But Siegel says the buildings are safe so long as their heating, ventilation and air conditioning systems are working to keep the vapors out.
Siegel wanted to make it clear that community members have been working on the cleanup for a long time. He founded CPEO in 1992.
"To the people who are going to be working there, we feel we've already addressed short-term and long-term risks, or were in the process of addressing them," Siegel said of the Fairchild site.
Thanks to a recent EPA decision, property owners are now able to have responsible parties fund the retrofit of buildings with sub slab depressurization systems. It saves owners the cost of running HVAC systems at all hours, Siegel said.
The presence of eco-friendly Google, also known as "the hottest company in the world," might make it more likely that a new sub-slab depressurization system would be installed, even if it costs as much as an EPA estimated $200,000 for a 20,000 square foot building. But Google's presence may not make much difference in how quickly the underground mess is cleaned up, Siegel said.
"There's a good chance we would be using (new cleanup technologies) even if Google wasn't moving in," Siegel said.
At last week's Moffett Field Restoration Advisory Board meeting, Dan Leigh of Shaw Environmental presented the results of a test. Microbes were injected into the ground next to the Moffett Field Museum, where indoor TCE vapors had been measured at levels unacceptable to the EPA. Leigh said he was pleased to report that the microbes completely removed the TCE from the upper aquifer (the area that creates indoor vapors) within a 4-foot radius of each injection.
Leigh said the microbes eat a lactate that is also injected into the ground, while breathing in the TCE and breathing out ethane and ethene.
But the challenge with "bioremediation" is getting the microbes under the museum, or any building. Leigh says creating a vacuum in the aquifer can draw the microbes and lactate underneath buildings.
"Theoretically it's possible," Siegel said. "If you are doing a small area it's fairly practical. But in a large developed area it becomes more and more difficult." When drilling into the ground "you have to worry about running into infrastructure," such as pipes and electrical lines.
Other alternatives being studied for the MEW include the use of permeable underground barriers made of iron filings that break down TCE as the plume moves toward the bay, an option that has found success at an older Sunnyvale site. And "natural attenuation," would leave naturally occurring microbes to slowly break down the TCE. The drawback of using the iron barriers is that they leave behind small amounts of vinyl chloride, another toxin.
Siegel said all of the alternatives have their place. "Each remedy works for a certain purpose. You combine them and you can get a good overall cleanup."
The EPA passed on three other methods that would extract TCE from the ground using heat, suction or compressed air to force vapors to the surface for collection.
The advantage of alternatives to pump and treat is that they don't move the problem elsewhere. The charcoal filters used are trucked away and burned, often exposing impoverished communities to toxins. As the Voice reported in a series of 2003 articles, filters from Mountain View sites were being burned on an Indian reservation in Arizona, exposing the tribe there to dioxins, a substance more harmful than TCE.
E-mail Daniel DeBolt at email@example.com