Quake-resistant beauty

Dec. 28, 2000

California's El Camino Real (royal road) took Spanish missionaries along the Pacific coastline where they founded the Santa Barbara Mission in 1786, one of the 21 original California missions. To this day, a major thoroughfare, State Route 101, crosses the picturesque city, and the citizens adamantly cling to the architectural style of the mission. It's what makes Santa Barbara extraordinary.

In 1989, Santa Barbara County taxpayers passed Measure D. They agreed to pay a half-cent sales tax to raise about $17 million a year to pay for transportation projects. At the top of the list was the highly congested La Cumbre Road Interchange at the El Camino Real Freeway, or S.R. 101. It needed to be rebuilt.

But how do you embellish a freeway overpass with mission architecture, while making it strong enough to withstand earthquakes and alleviate traffic, but keep the small-town look?

Patrick Connally, the district division chief for construction for the state DOT (Caltrans), said, "It's a point of entry into a community that cares about appearance for travelers passing through as well as for visitors and residents. There's extra effort put into the project to enhance the community. Details are important.

"The project is a good example of partnering involving the community, the local government, the designer and Caltrans all working together to satisfy a transportation need in Santa Barbara that we can take pride and pleasure in."

The project has involved coordination among several agencies and citizens groups, including the Santa Barbara County Association of Governments (SBCAG), which funded the project through Measure D; Caltrans, which owns and operates the highway and the interchanges that connect to it; the city and county, both of which own rights-of-way; the city of Santa Barbara's Architectural Board of Review (ABR), the Southern Pacific Transportation Co., which owns the railroad tracks and right-of-way; and private groups with important issues.

By raising the money itself, the county will be able to complete construction projects that the state may make a lower priority. The county also can contract with private firms that can meet unique challenges under tight schedules and still be cost conscious. SBCAG selected the firm of Daniel, Mann, Johnson, & Mendenhall (DMJM) to prepare plans, specifications, and construction-cost estimates to reconstruct the present interchange.

The old 37-ft-wide two-lane bridge will be replaced by a new bridge 76 ft wide that will accommodate five lanes of traffic, and bicycle lanes and pedestrian sidewalks on both sides. The adjacent two-lane Southern Pacific Transportation Co. overhead bridge will be replaced with a three-lane bridge.

The southbound entrance ramp to the 101 will be widened to two lanes and the southbound exit ramp to three lanes. The intersections of the La Cumbre Road southbound ramps and La Cumbre Road/Calle Real will be signalized and an auxiliary/acceleration lane will be added to each direction of Route 101. Several local roads also will be widened, retaining walls constructed, several utility facilities relocated and the interchange will be landscaped in a style befitting this jewel of a city.

Widening La Cumbre Road will allow for a better flow of through traffic and traffic generated from La Cumbre Plaza, a large regional outdoor shopping mall of more than 65 stores. Vehicles entering the freeway from La Cumbre Road will be able to pick up speed before merging into the flow of high-speed traffic on the freeway. Meanwhile, freeway traffic will flow through as vehicles can easily enter and exit.

The interchange is located in a seismically active area. Three mapped earthquake faults (the More Ranch Fault, the Mission Ridge-Arroyo Parida Fault and the Mesa Fault) intersect the site, or are less than a mile away; each is capable of magnitude 7.5 earthquakes.

The design of the bridges was in the early stages when the Northridge Earthquake shook the Los Angeles area in January 1994. Caltrans revised its design standards based on data collected on seismic characteristics experienced during that earthquake and its aftershocks.

DMJM incorporated special seismic detailing in the bridges to meet the new safety standards. The bridges are designed with pile foundations beneath the columns and abutments that support the bridge. Reinforcing steel will wrap around each column core in tight configuration like a spiral cage to keep the concrete confined and prevent the column from breaking.

Each structure is designed to ride out a large movement caused by ground rupture. To accomplish this, the superstructure is not joined to the columns and bent cap but is free to slide on rubber bearings. The abutments, in turn, are designed with a wider-than-usual seat to accommodate potential shifting. The superstructure also is strengthened to withstand a vertical displacement of 16 in. at the abutments.

The bridges at the La Cumbre interchange are a gateway to Santa Barbara, and the community is particular about visual impacts of public works projects. Any approved design has to preserve the consistent Santa Barbara style of architecture and protect the character of the city. The Santa Barbara County Association of Governments was willing to pay the additional cost of special architectural treatments of the bridges, barriers and retaining walls.

The design staff incorporated recommendations from the Santa Barbara Architectural Board of Review (ABR) in combination with Caltrans standards to create a design that was safe, constructible, low maintenance and aesthetically pleasing.

For the bridge railing, the ABR wanted as open a style as possible but Caltrans standards require solid barriers for safety. DMJM proposed a solution of an arched indentation and pilaster design of a contrasting texture to give the railing a more open look. The outside of the bridge railing has a 2-in. deep indentation and the inside has a 1-in. indentation so any vehicle hitting the railing won't snag the bumper and possibly spin.

Other architectural features include arches underneath the bridge and arches between the columns. The protective chain-link fencing along the pedestrian walkway has a tapered-post design topped with a ball. Retaining walls will be poured into form liners that will make the walls look like local sandstone.

To provide the ABR with attractive landscaping, DMJM landscape designers planned for palm trees and flowering plants alongside the surface streets and intersections. Seedlings of oak trees and other native species will be planted in a formerly barren area to create a small woodland and plantings along the freeway will match existing flowering ground cover.

The bridge will be constructed in two halves to minimize impact on traffic, always maintaining the existing number of lanes. To accommodate local business owners, construction will not prevent shoppers from getting in or out of La Cumbre Plaza and work adjacent to the mall is to be stopped entirely during the holidays. Construction of the project is scheduled to be completed spring 1997.

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