City says project needs TCE liner City says project needs TCE liner (September 03, 2004)

Developers interested in building in area near toxic plume

By Jon Wiener

Despite the site's proximity to carcinogenic chemicals in northeast Mountain View's ground water and toxics in the air, developers approached the city council on Tuesday to build a new condominium complex.

The city council responded by approving the project, with the condition that Palo Alto-based Mozart Development Company install a protective vapor barrier.

The site under discussion, 555 Clyde Ave., is a former agricultural site a few blocks from several toxic ground water plumes.

Mozart Development applied to the council for permission to create a unique style of development intended to provide independent-minded business owners with affordable office space. Its plans include six office-condominiums at the abandoned lot near the city boundary, where there is currently a large 55,000-square-foot building that has sat empty for three years.

Small concentrations of toxic organic compounds like trichloroethene (TCE) in nearby ground water prompted the city to recommend installation of a vapor barrier below the condos. A vapor barrier is an impermeable liner that lays underneath a foundation and protects it from gases rising from below ground.

City planners consulted with Alana Lee, a U.S. Environmental Protection Agency (EPA) official who works on a nearby Superfund site, before recommending the barrier. Lee said it was unlikely that any toxic gases would seep into the air at the proposed development.

"It sounded like it was of low potential concern, just based on the levels they were citing," Lee said.

According to the city's analyst, Kevin Woodhouse, Mountain View will hold informal discussions with the EPA and other agencies as plans for new developments near or on a Superfund site arise. The city has already recommended a similar barrier for the fourth phase of development at Whisman Station, which is located over a toxic plume. Lee said the EPA is planning to formalize the discussion process in the future.

The EPA is investigating the potential sources of so-called "vapor intrusion" in a residential area west of Whisman Road, but has no plans to issue formal guidelines on how to prevent it. Consequently, the city is taking up the mantle.

"It's up to the developer to come up with the specifications" for the vapor barrier, said Lee. "In general, the plumes in this area are either stable or shrinking, so the likelihood of vapor intrusion (outside of the plume boundaries) is on the low side."

Project architect Ken Rodrigues said there was no contamination under the Clyde Avenue site to be concerned about and that he had not started making plans about what kind of protective liner he might use.

Four heritage trees to be taken out

The council also gave the developer permission to remove four of the site's 13 protected heritage trees, which are designated as such because of their large trunks. Three of those, all ash trees, are in less than good condition.

But removing the fourth, a coast redwood 7.5 feet in circumference and more than 40 feet tall, was of some concern to council members. Mozart Development proposed removing it to make space for a driveway for the development.

"I know it's just one tree, but it's a beautiful tree," said Council member Rosemary Stasek, who voted against the project.

E-mail Jon Wiener at jwiener@mv-voice.com

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