EPA considers new technology to remove TCE EPA considers new technology to remove TCE (March 26, 2004)

Biodegradation system would break down toxin underground

By Grace Rauh

Environmental Protection Agency officials may adopt a fast new removal system to break down the cancer-causing solvent tricholoroethene (TCE) in northeastern Mountain View.

The new biodegradation system is expected to significantly speed up removal of TCE in groundwater and would be implemented at the former Sobrato Properties on East Middlefield Road, which is currently owned by VeriSign, Inc., if approved by the EPA.

"As far as the idea of using a new technology to see if we can potentially remove contaminants more quickly - we are very supportive of that effort," said EPA project manager Alana Lee.

The new technology, known as enhanced reductive dechlorination, calls for a honey-like substance to be injected into the ground. The material releases a lactic acid that comes in contact with the groundwater. The combination produces hydrogen, which enhances the degradation process, according to Lee.

TCE breaks down first into cis-1,2-dichloroethylene, then vinyl chloride and finally ethane. "Once it makes it to ethane then it's non-toxic and it's non-harmful," Lee said.

The pump-and-treat system that is currently used to filter chlorinated solvents out of contaminated groundwater has successfully reduced TCE levels at the former-Sobrato site, but the new technology could save time and money.

"It is probably a good path to try," said local environmental advocate Lenny Siegel, who directs the Center for Public Environmental Oversight. "The problem with pump-and-treat is that it takes a long time to remove enough contaminated mass to reduce concentration."

The new system is likely to cost more up front than the current method, but it could save dollars down the line if it significantly reduces clean-up time as expected, Lee said.

The biodegradation method has worked well at other locations, but it is not entirely foolproof. The degradation process could stall out when TCE breaks down to vinyl chloride, which is toxic. However, if vinyl chloride somehow leaked into the air or nearby buildings it would still be less toxic than TCE, Lee said.

The EPA is still reviewing the plan put forth by PES Environmental, Inc., an environmental consulting firm working on behalf of SMI Holding LLC.

E-mail Grace Rauh at grauh@mv-voice.com

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