Flexing City Hall

The $299-million seismic retrofitting of Los Angeles City Hall is near completion and the entire restoration project is on schedule to be completed next summer, according to an update from the project manager.

The retrofitting of the 1928 building will essentially make the structure more flexible during a major earthquake.

“It will withstand an 8.1 quake on the San Andreas Fault and a 6.8 on the Elysian Park Fault,” said Stan Morimoto, the project manager in the city’s Department of Public Works. “All current technology is being used to upgrade the building, and the quality of the project is second to none.”

In the event of a stronger earthquake, the building should still hold up with some exterior damage, he said.

Workers have put in 500 of 526 base isolators--laminated rubber and steel coils--that soften the movement of the earth under the building. Although the isolators are only 14 inches tall, the contractors had to excavate 5 to 7 feet under the entire building, removing 20,000 cubic yards of dirt.

Much like a rubber bumper, the isolators can reduce the energy absorbed by a building during an earthquake to one-third the normal amount, said Morimoto. They allow horizontal movement, while stopping most vertical movement.

To minimize rolling and oscillating, the city is installing devices that act like big shock absorbers. They are called viscous dampers, and 52 of them will be in the basement, along with the isolators. An additional 12 of the devices will be installed on the 26th floor.

Other reinforcement measures such as concrete shear walls also are being added.

City Hall is the tallest building ever to undergo base isolation for earthquakes. Morimoto said there are other ways to retrofit a building, including simply buttressing it with more concrete and steel.

But because City Hall is brittle, he said, such measures would only stiffen it during tremors and perhaps cause worse damage. “This high technology filters out some of that energy,” he said.

Morimoto said much of the remaining work involves the building’s “skin,” fallen terra cotta tile and painting.

The retrofitting began in spring 1998 as the last city staff moved out to surrounding buildings, including City Hall East. About 280 workers have been on the project, sometimes in double shifts.

Originally, the retrofitting costs were set at $153 million, but they but grew as fire safety, electrical and plumbing modernizations were added. Also, as the economy recovered, construction in the region boomed and costs went up.

A year ago it wasn’t clear whether the funds would be available to restore all the upper floors.

But over time the City Council voted to allocate more money for the project, and today it appears that the entire 28 floors will be available for use, said Morimoto.

As recently as March, the City Council approved an additional $26 million for the project. About $12 million of that was attributed to construction bids that were higher than expected, while the other costs were for interior improvements.

The city’s chief legislative analyst blamed some of the cost overruns on a blue-ribbon committee appointed by Mayor Richard Riordian, while the mayor countered that the City Council was responsible.

The mayor was forced to disqualify himself from direct decisions on the City Hall project because he has an outside business relationship with the City Hall architect.

On Monday, a member of the mayor’s staff said that he was still concerned about the cost overruns, but that most people in City Hall were excited about moving back to the fabled headquarters. “This is part of Los Angeles history,” said press deputy Carolina Guevara.