Safety Fears Spur Bridge Inspections : Infrastructure: County will spend up to $400,000 to find ways to shore up seven spans over the Santa Ana River while flood-control work is done.

Concerned that flood-control work could pose potential structural problems for seven bridges over the Santa Ana River, county officials plan to spend $400,000 to find ways to shore them up.

They want to know whether planned work in the river channel will mean trouble for the bridges, especially during an earthquake.

Specifically, county engineers said they are concerned that the bridges might become vulnerable due to the effects of lowering the river bed up to four feet in coming years, as planned during the flood-control project.

County supervisors are expected to award a $414,000 contract next Tuesday to the engineering firm of Robert Bein, William Frost & Associates, based in Irvine, to analyze bridge deficiencies and report back on possible remedies.

The bridges under study are: Talbert Avenue-MacArthur Boulevard; Slater-Segerstrom avenues; Edinger Avenue; McFadden Avenue; Bolsa Avenue-1st Street, 5th Street and Fairview Street. All carry street traffic over the river channel in Santa Ana or Fountain Valley.

The seven bridges run over a strip of the channel between the San Diego Freeway and Fairview Street. The Army Corps of Engineers is reviewing final plans for channel work along that stretch.

Some foundation pilings are already exposed on the bridges as a result of normal aging, officials say.

An engineering report given to the supervisors in advance of next week’s vote warns that “the lowering of the grade line . . . may reduce the stability of the bridges” even further during an earthquake. More of the bridges’ foundations will be exposed out of the ground, “and there’ll be a lot more opportunity (for the bridges) to move and flex,” explained Richard Hart, Orange County’s senior civil engineer for bridge design.

“The whole purpose of what we’re trying to do is prevent collapse of the structure” during a major earthquake, said Paul Young, Bein’s senior director of structural engineering. “We’re looking at a worst-case scenario.”

Even apart from the lowering of the channel, Hart said, he has questions about the stability of some of the seven bridges because of their age. The McFadden Avenue bridge, for instance, was built in the 1930s, he said.

“There is a potential that some of the bridges may collapse today (during an earthquake) just because of their age,” Hart said.

The corps has identified the Santa Ana River as the greatest flood threat west of the Mississippi. In response, Congress has given the go-ahead for the flood project--including a new Seven Oaks Dam in San Bernardino County, an enlarged Prado Dam in Riverside County, and major channel improvements along a 31-mile stretch of river from the Prado Dam through Orange County.

The federal government has agreed to spend $975 million on the project. Orange County is to pick up $427 million of the tab, Riverside County $28 million and San Bernardino County $18 million, under the present plan. The project is due for completion by the early 21st Century.

The bridge study is to be completed by November. Hart predicted that more than half of the bridges analyzed may need major improvements. These could include adding concrete at the base, placing restraining cables, encasing exposed pilings or other remedies, Hart and Young said.

Bridge Trouble The county is going to spend $414,000 to study potential problems with seven bridges that span the Santa Ana River in Santa Ana and Fountain Valley. Officials are concerned that the future expansion and deepening of the river channel as part of a massive flood-control project could make the bridges ore vulnerable to damage. The bridges to be studied are shown here.