When the San Luis Rey Bridge was built in 1925, its architect could not have known that the 21-foot-wide structure--also known as the Bonsall Bridge for its proximity to Bonsall--would see the density of traffic that it does today.
The northern San Diego County bridge, which with its graceful arches allows California 76 to span the San Luis Rey River, is structurally sound but dangerously narrow, say Caltrans engineers. Caltrans officials finally decided in March, 1983, that it was time to expand the perilous bridge, but met with a series of obstacles that would take them six long years to hurdle.
Construction of the new Bonsall Bridge began in March and, barring any more unforeseen obstacles, should be completed by August, 1990, Caltrans officials say.
The new Bonsall Bridge will be 40 feet wide and 1,220 feet long, and will have one lane and a shoulder lane going in each direction, said Roy Riesgo, engineering coordinator with Caltrans. Instead of the abrupt, 90-degree turns leading to and from the old bridge, the new bridge will have "nice, smooth, sweeping curves," he added.
It was the 90-degree swerves that contributed to 76 accidents from 1986 through 1988 at the old bridge, and raised concern at Caltrans about its safety. "We looked at the accident rate and looked at how it ranks with other state highways. The accident rate was higher at the bridge than other highways of the same nature," Riesgo said.
Bridge engineer Victor Lindamood agreed: "Structurally, the bridge is still quite adequate, but the bends just don't take care of the modern-day traffic through here. It was OK for cars 40 to 50 years ago, but nowadays, it's just too narrow and almost impossible to widen. . . . It doesn't meet the needs of the growing community."
But as plans to rebuild the Bonsall Bridge got under way, Caltrans met with two dilemmas that threatened to halt the construction.
First, northern San Diego County residents balked about the destruction of the historic bridge, saying that it should be preserved for posterity. Caltrans had announced earlier that, in order to receive federal funds for the construction of the $6.7-million bridge, it had to relinquish ownership of the old one. If no one adopted the bridge, it would have to be destroyed.
Although the Bonsall Bridge is one of only two of its kind within a five-county area, Don Rosbaugh, project engineer for Caltrans, could not understand at first why the bridge should be saved. The Bonsall Bridge is "not my kind of bridge," he told a Times reporter in 1985. "I like the Golden Gate Bridge and the George Washington Bridge, and those old steel truss bridges you find back in Pennsylvania. . . . Now, those are bridges."
But many residents disagreed vehemently with Rosbaugh. To calm the furor, the county stepped in and agreed to maintain the bridge as a historic pedestrian/equestrian crossing, and Caltrans agreed to build the new Bonsall Bridge 500 feet upstream from the current location.
But then a bigger problem, in the form of a little gray songbird, reared its head.
Environmentalists discovered that the planned site for the new bridge would destroy the home of the endangered least Bell's vireo, which nests in riparian habitats. The San Luis Rey River has been designated as one of the proposed protected habitat areas for the bird, said Brooks Harper, acting field office supervisor for the Southern California Office of the U.S. Fish and Wildlife Service.
The tiny bird was listed on the federal register as an endangered species in 1986 when only 300 pairs were found nationwide. Although there is no count for 1989, there were an estimated 400-500 pairs existing in 1988. The birds have become endangered chiefly because of habitat encroachment and the brown-headed cowbird, a nest parasite which often displaces vireo eggs to lay its own, said Art Davenport, wildlife biologist with the Fish and Wildlife Service.
Before allowing construction to proceed, Fish and Wildlife officials met with Caltrans biologists to develop a mitigation plan that would create three times the amount of vireo habitat for each acre disrupted by the bridge building. The new habitat, about a mile upstream, is still in the growing stage, but Caltrans biologists are pleased with the development thus far, Riesgo said.
"The habitat is in place. It's being developed and we're waiting for the trees to grow," he said. "We re-created the same natural setting in an area that was similar to what we've taken away at the bridge site." The habitat was completed in March, about same time construction of the new bridge began, he said.
While Caltrans officials wait for some of the sapling willows and cottonwoods to grow in the new vireo habitat, they are finally forging ahead with construction plans.
"Everybody's just elated that we're actually getting this done" after years of delays, Riesgo said. "It's been a long process with a lot of input from the community and the state to get where we are."