A new effort to clean the last vestiges of an underground plume of toxic chemicals known as TCE from beneath an area of Mountain View is under study, and could result in an accelerated cleanup campaign starting in 2009.

Maile Smith, project manager for Northgate Environmental, said new tactics and technologies for cleaning the plume, located in what is known as the MEW area, will be evaluated in a feasibility study released early next year.

Traditional "pump-and-treat" methods for cleaning up the groundwater have become gradually less effective, but will remain in place to keep the plume from migrating. Three quarters of the TCE has been cleaned up, Smith said Tuesday.

"It's that last 25 percent that's really challenging," Smith said. "It's a challenge across the entire country."

Under study on Intel's MEW property -- bordered by Middlefield, Ellis and Whisman roads and Highway 101 -- is a process where natural organisms break down the TCE. To feed the process, soybean oil is injected into the soil.

Smith said such "bioremediation" has shown significant success since it began in 2005. It is on a list along with 20 other possible technologies for MEW cleanup, including injecting chemicals like hydrogen peroxide, ozone or potassium permanganate into the ground to oxidize contaminants.

Once the study is approved by the EPA, renewed cleanup efforts can begin.

TCE is a known carcinogen that was used as an industrial solvent during the manufacture of circuit boards in the MEW in the early 1980s.

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