Quake Underscores Need to Fix Overpasses, Caltrans Says

The earthquake on Wednesday “underscores the need and importance to move ahead” with strengthening of highway overpasses throughout the state, according to a top Caltrans official.

There are dozens of highway overpasses vulnerable to earthquake damage in the area of Wednesday’s tremor, according to Jim Drago, chief of public information for Caltrans. Inspectors found that only one of the structures suffered any damage Wednesday, and that was termed “very, very minor cracking.”

Caltrans officials found cracks in the highway overpass at the intersection of Interstate 10 and Verbania Avenue in Riverside County, but the damage was so slight that the structure was not closed, Drago said in a telephone interview from Sacramento.

There are another 33 overpasses in San Bernardino and Riverside Counties in addition to several such highway structures in eastern Los Angeles County that have been placed on a Caltrans priority list for earthquake-resistance strengthening, called “retrofitting,” Drago said. Those structures apparently suffered no damage in Wednesday’s magnitude 5.5 quake.

Drago said that, despite the need to strengthen such overpasses, the earthquake showed that “we can sustain a pretty severe jolt and the system performs as it was intended.” More than 200 Caltrans workers rushed to the area to inspect overpasses following the temblor. They were to report any suspected damage to agency engineers for follow-up inspections, Drago said.

The bridges are among nearly 400 overpasses in the state that employ a single-column support system and are scheduled to be strengthened for earthquake resistance by the end of 1991 in a program estimated to cost more than $100 million. Of the total, 130 of the overpasses are in Los Angeles County, Drago said.

Drago said the Upland quake would probably not affect the pace of the retrofitting program “because we’ve accelerated it anyway.”

The acceleration in retrofitting came after the Oct. 17 Bay Area earthquake that collapsed the Nimitz Freeway in Oakland, killing 42 people. Despite the acceleration, only two single-column overpasses are scheduled for strengthening work in the near future. No contracts have yet been let on the nearly 400 other such structures, Drago said.

The Nimitz Freeway was supported by a multiple-column system that Caltrans officials acknowledged was not then scheduled for retrofitting. A program to strengthen that type of structure is now being formulated by Caltrans, Drago said.