October 27, 2004

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Publication Date: Wednesday, October 27, 2004

Portola Valley: Dispute over Town Center earthquake reports

By David Boyce
Almanac Staff Writer

A showdown may be in the works between a small group of residents and the Portola Valley Town Council over plans to tear down the current complex of buildings at the Town Center -- buildings found to be sitting in a rupture zone on the San Andreas Fault -- and rebuilding at a cost of $13 million to $15 million in a location considered safe for construction.

Four residents -- former mayor Bob Brown, his brother Allan Brown, Charles Engles and Ed Wells -- recently signed a letter mailed to registered voters in town arguing that the council should find out whether the existing buildings can be economically upgraded to current building codes.

The mailer included a letter by a James A. Cheney, a University of California at Davis emeritus civil engineering professor, who argued in support of retrofitting the buildings.

Calling themselves the Portola Valley Committee for a Safe Town Center, the group's letter charges the council with pursuing its own agenda by not discussing the project's impact on town finances and by not investigating the retrofitting idea.

Mr. Cheney said he has accepted an invitation by Sheldon Breiner, who chairs the town's Geological Safety Committee, to speak to the committee at 10 a.m. Wednesday, November 3, in the Historic Schoolhouse. The town will also be inviting geologists to the meeting, said Councilman Ted Driscoll, who was involved in gauging the safety of the new site and who expressed concern about the wide distribution of the letter.

In his letter, Mr. Cheney argued that the "beautiful and well-built" Town Center buildings could be made relatively safe with "a few architectural changes" and that "living on top of the San Andreas fault is always risky."

Mr. Cheney told the Almanac that his support for retrofitting is based on a site visit, two existing geotechnical engineering reports paid for by the town, and a map from some 25 years ago that shows a fault crossing the proposed new location for the buildings.

"We have world-class geologists who are going to take this guy apart," Mr. Driscoll said in an interview, adding that he thinks Mr. Cheney is being lured into a controversy. "I feel sort of sad. I don't think he knows what he's walking into."

Mr. Cheney has a master's degree in soil science and a doctorate in mechanical engineering from Stanford University. He was director of the Center for Geotechnical Modeling at UC Davis from 1983 to 1989 and is a member of the Consortium of Universities for Research in Earthquake Engineering.

Clash of experts?

In a 1972 report, H.J. Degenkolb & Associates -- a San Francisco-based seismic engineering firm -- concluded that upgraded or new buildings at the current location between two fault traces would not reduce the danger of building collapse in the case of ground warping or if there were a fault-slip of 10 feet located directly under a building.

Mr. Cheney credits tree-root systems with "effectively reinforcing" a building site against earthquake faulting. A fault path to the surface will change with 100 years of changes to the topography, including tree roots, building foundations and compacted soil, he said. It is analogous to predicting the path of a hurricane, he added.

In 2002, the town commissioned a report from William Lettis & Associates, a Walnut Creek-based consultant in applied earth sciences. Trenches were dug and bore-holes drilled to look back 1,000 years for evidence of ruptures on a fault that breaks every 200 years or so. The report concluded that the area now containing buildings is within a rupture zone, but that the northwest corner of the 11.2-acre site, where new buildings are planned, is "free of active faulting and folding."

The 1980s-era map showing a fault under the northwest corner was a preliminary finding based on aerial photographs of what may have been a culvert, a fence line or a surface anomaly, said John Baldwin, a geologist and co-author of the report. "We determined, based on our trenching, that the fault did not exist," he said.

Mr. Cheney credits the map as determinative and said the report's conclusions are interpretations, not science. "They couldn't find (the fault), so they think it isn't there," he said. The trenches weren't deep enough, he said, adding that the area could succumb to liquefaction.

INFORMATION

Two geological reports on the Town Center site, which were commissioned by the town, are on the Web at portolavalley.net.

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