Ignore Fault -- "Salt Palace Work Can Continue"

Salt Lake County, owner of Salt Palace hires own consultants. Consultants say these are merely "liquefaction-induced faults." Utah State and Salt Lake County geologists not invited to review or challenge the decision to resume building.

February 3, 1999

Consultant Says Salt Palace Work Can Resume

BY LEE SIEGEL THE SALT LAKE TRIBUNE

A major earthquake fault does not run beneath the $47.5 million expansion of the Salt Palace Convention Center, so the suspended construction project should proceed, geologists hired by Salt Lake County said Tuesday.

They said the building's foundation should be built stronger because it will sit atop two sets of small faults created when the ground turned to quicksand and spread apart during a prehistoric quake on another fault.

A third underground feature just outside the expansion's southeast corner may or may not be a minor quake fault, and requires more testing, which will start today, the geologists added. So county commissioners decided to wait until next week before allowing construction to resume.

If it is a quake fault, the county might move or eliminate a planned 50-foot-tall tower at the expansion's southeast entrance, project manager Ken Ament said.

Nevertheless, "we have determined the site is safe," he said. "The site is buildable with some modifications to the foundation."

Geologists from Simon-Bymaster Inc. and Kleinfelder -- geotechnical consulting firms -- appeared before commissioners Tuesday to outline their two Salt Palace studies and recommend construction resume.

Former Salt Lake County Geologist Craig Nelson said he had not reviewed the studies. But if the commissioners proceed based on those studies, it is "an inherent conflict of interest" that will set "a real bad precedent for private developers," he said.

When developers hire consultants to determine if property is seismically safe, the county geologist reviews those studies, said Nelson, who quit the post last year to take a higher-paying job with Dames & Moore engineers.

The county is the developer of the Salt Palace, so a decision to allow construction should be made by independent geologists from the Utah Geological Survey (UGS), "not by the politicians," Nelson said.

"He's full of beans," Commissioner Brent Overson replied. He said there was no effort to influence outcome of the studies, and no other downtown construction site has been studied so carefully.

"I'm unaware Salt Lake City has any technical expertise to review that kind of study," said Lee Allison, director of the UGS.

He said his agency's geologists, who have visited the Salt Palace site, would be happy to review the studies, but "we haven't been asked."

The small faults on the Salt Palace site are not tectonic faults -- the kind that cause earthquakes, said Les Youd, a Kleinfelder consultant and chairman of civil and environmental engineering at Brigham Young University.

He said they are small, "liquefaction-induced faults" created when strong shaking caused waterlogged ground to liquefy and spread apart during a big earthquake on another fault sometime during the past 10,000 years.

As the ground was pulled apart, small faults or fissures opened up, and ground between them sank three to five feet, creating two trough-like "grabens" that run beneath the existing Salt Palace and the expansion site.

The water table is lower now, so liquefaction in a major quake today would cause only a few inches of vertical or horizontal ground movement at the site, said Edward Rinne, senior geotechnical consultant at Kleinfelder's Oakland, Calif., office.

He said the Salt Palace expansion should be redesigned to resist such movement by linking foundation footings together with horizontal beams. With such reinforcement, "the chance of loss of life, in our opinion, is nil," and damage would be reduced but not eliminated, Rinne said.

In December, David Simon of Simon-Bymaster discovered one of the grabens and prehistoric geyser-like "sand boils," prompting the county's Jan. 6 decision to suspend construction 30 days.

At the time, Simon said it appeared the graben in City Creek sediments was an active fault. The other graben and possible fault at the site's southeast corner were found later.

It is illegal to build on an active fault line -- the place where a fault intersects the surface and can rip apart overlying buildings.

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Page Modified February 4, 1999