AKA: Panama-California International Exposition, Cabrillo Bridge, Balboa Park, San Diego, CA; State of California Department of Transportation (Caltrans), Laurel Street Overcrossing, Balboa Park, San Diego, CA

Structure Type: built works - infrastructure - transportation structures - bridges

Designers: Allen, Frank Phillip, Jr., Architect (firm); Frank Phillip Allen Jr. (architect)

Dates: constructed 1912-1914

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El Prado
Balboa Park, San Diego, CA 92101

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Overview

Built to connect the main fair buildings of the Panama-California Exposition with the Bankers Hill neighborhood west of Balboa Park, the Cabrillo Bridge was erected between 12/1912 and 04/1914 at a cost of $195,653. In keeping with the fair's Spanish Colonial Revival architectural theme, the fair's organizers wanted an authentic old Spanish bridge to connect the Balboa Park site with the rest of the city. The Cabrillo Bridge spanned what had been known during the 19th century as "Pound Canyon," and, by the early 20th, "Cabrillo Canyon," through which a small stream flowed filling a man-made pond under the bridge, the Laguna de Puente. The bridge provided a grand entryway to the fair for those approaching either by foot or automobile, mostly the former. Thirty-thousand people attended on the exposition's first day alone, 01/01/1915.

Building History

Although the architect of the Panama-California Exposition, Bertram G. Goodhue (1869-1924) prepared a more elaborate, Spanish Colonial Revival design for this bridge, it was another designer, the fair's Director of Works, Frank P. Allen, Jr. (1880-1943), who designed the Cabrillo Bridge as built. Allen, who held a great deal of influence over fair officials and financiers, objected to the cost of Goodhue's design, a scheme based on the Alcantara Bridge in Toledo, Spain, which supposedly exceeded spending limits by $7,000. Ironically, Allen's bridge also went over budget, but by much more, $75,254.98. Harris, working with the San Francisco civil engineer, Thomas B. Hunter, produced a bridge design that outwardly resembled the Bridge at Alcantara, Spain, and the Aqueduct at Queretaro, Mexico, but possessed a different structural system. (See Richard W. Amero, sohosandiego.org, "The Cabrillo Bridge, Caltrans and Balboa Park," accessed 11/13/2017.) Although it utilized arched motifs commonly seen in Roman aqueducts and later Spanish bridges, the Cabrillo Bridge did not employ masonry arches. The Engineering News stated in 1915: "In fact this viaduct, known as the Cabrillo Bridge, is not a series of arches but rather a series of hollow, box-like pedestals with the upper parts cantilevering out form the arched openings. The bridge is 946 ft. long, and its main portion comprises seven semicircular 56-ft. arches, with a maximum height of above 120 ft. to the roadway." (See "The Cabrillo Bridge at the San Diego Exposition, Engineering News, vol. 73, no. 19, 05/20/1915, p. 926-928.)

As noted in the Engineering News, to build a bridge replicating the arched structures of old Spanish bridges would have been too costly. It wrote: "With few exceptions, (where Gothic pointed arches were used) all Spanish masonry bridges until modern times have been built with full semicircular arches of comparatively short spans. Semi-circular arches carried on tall and relatively slender piers will generate in the piers bending moments that will be expensive to deal with. When temperature stresses are added to these moments, for a bridge of this length the cost of the structure becomes almost prohibitive." (See "The Cabrillo Bridge at the San Diego Exposition, Engineering News, vol. 73, no. 19, 05/20/1915, p. 926-927.) Instead of masonry arches, Allen and Hunter employed a series of reinforced-concrete cantilevers in arched form to support the span. The Engineering News described this novel cantilevered design: "Each pier consists of a pair of hollow columns, with a width the same as that of the arch ribs, and the cantilever arms spring from the sides of these columns. The cross-section is proportioned to the distribution of loads, the inner sides (carrying the roadway cantilevers) being much heavier than the outer sides, which carry the sidewalk cantilevers. Along the springing line of the arches the columns are connected by curtain walls which extend between the arch ribs to the level of the roadway." (See "The Cabrillo Bridge at the San Diego Exposition, Engineering News, vol. 73, no. 19, 05/20/1915, p. 928.)

Assistant Secretary of the US Navy, Franklin Delano Roosevelt (1882-1945) attended the dedication of the Cabrillo Bridge along with San Diego Mayor Charles F. O'Neall ([1875-1929] a real estate agent who served as San Diego's Mayor from 1913-1915), Gilbert Aubrey Davidson (Southern Trust and Commerce Bank founder and President of the San Diego Chamber of Commerce), Colonel Fred Jewell (an executive with the United States National Bank of San Diego) and Lieutenant Commander G. C. Sweet (Special Duty Officer of the Machinery Division at the Navy Yard and Station, Mare Island, CA). The Panama-California Exposition lasted two years, 1915-1917, and consisted of four permanent buildings, by its end, the United States' entry into World War I necessitated that the fairgrounds be requisitioned by the military; during the 1917-1918 wartime period, Balboa Park played host to a U.S. Naval Training Center. During World War I, a guard house was set up on the Cabrillo Bridge's western frontier. The fairgrounds were recycled for use during the 1935 California Pacific International Exposition, also held over two years, 05/29/1935-11/11/1935 (Armistice Day), and 02/12/1936-09/09/1936. During the Second World War, portions of the Balboa Park grounds--El Prado and the Palisades--were utilized for a US Naval hospital.

In 1941, the voters of San Diego decided it prudent to approve the construction of a freeway bisecting Balboa Park on its north-south axis. Historian Amero has written: "In compliance with a City Charter provision that required a vote of the people to set aside Balboa Park land for other than park purposes, the people of San Diego had voted, by a margin of 8 to 1, March 25, 1941, to set aside a 200-feet right-of-way through Cabrillo Canyon to serve as a State highway. To allow access from State 163 north and from ramps, within Cabrillo Canyon changes were made to the contours and landscaping of the Canyon. The Freeway's four traffic lanes passed under Cabrillo Bridge , two between the third arch on the east and two between the third arch on the west. A landscaped median passed under the fourth or center arch. Wonderfully, the bridge's 56 feet openings were wide enough to permit an easy flow of traffic." (See Richard W. Amero, sohosandiego.org, "The Cabrillo Bridge, Caltrans and Balboa Park," accessed 11/13/2017.)

Building Notes

A variety of figures have been cited as measurements of the bridge's length. Many sources indicate that the Cabrillo Bridge stretched 450 feet and stood 120 feet high; this measurement described the bridge's span over the Cabrillo Canyon only.Another source indicated that the bridge stetched 1,500 feet, although this counted the roadway on either side of the bridge span itself. Contemporary reports in the Engineering News of 05/20/1915, stated the bridge to have been 946-feet long. (See "The Cabrillo Bridge at the San Diego Exposition, Engineering News, vol. 73, no. 19, 05/20/1915, p. 926-928.) Bridge historian Richard W. Amero, quoting thisEngineering News article said it was 916 feet long, which appears to have been a minor mistake.

The Cabrillo Bridge originally spanned a man-made pool called the Laguna del Puente. It appears that a creek wended its way through the canyon, which fair organizers widened under the bridge to form the ornamental, reflecting pond. As noted above, this canyon was reshaped and the stream replaced by a 7.1-mile freeway cutting a 200-foot-wide right-of-way through the natural depression in 1948.

Alteration

A number of people have committed suicide by jumping off the bridge since its completion in 1914. By 06/1950, a rash of eight during the first half of the year prompted the City of San Diego to install wrought iron fencing to prevent access to the span's sides. The rate of suicides at the Cabrillo Bridge did not decrease until the completion of the San Diego-Coronado Bridge in 1969.

Timber members that served as forms for the bridge's concrete piers caught fire on at least two occasions, necessitating repairs. The first came on 07/17/1951 and the second on 06/17/2004. The second fire was more serious and required that firefighters cut through the bridge's sidewalks to extinguish the flames fully. The damage caused by the 2004 blaze necessitated that the State of California Department of Transportation work with the City of San Diego to examine the bridge's state of repair, including its resilience to earthquakes.

Additional factors influencing the bridge's state of seismic resiliency included the presence of groundwater under the bridge's foundations (sunk to 23 feet at the deepest) and the corrosive effects of salt air on the bridge's reinforcing steel. The State of California Department of Transportation (Caltrans) completed a thorough seismic renovation of the bridge in 2015. A Caltrans web site indicated that the project maintained the bridge's historic integrity while strenghtening its resistance to sudden seismic events: "Caltrans today announced that the Laurel Street Overcrossing/Cabrillo Bridge Retrofit and Rehabilitation Project was awarded the 2017 Seismic Safety Award. The $38 million project brought the 100-year-old bridge up to current earthquake safety standards, all with almost no impact to the historic bridge's architecture. Rehabilitation and seismic retrofit of this historic structure was necessary to improve the structural integrity of the bridge and to help ensure the safety of the traveling public passing under the structure and across the bridge. Retrofitting, all concealed within the internal framework of the bridge, included horizontal post-tensioning in the superstructure and vertically post-tensioning the piers with new shear walls. Work also included the removal and replacement of unsound concrete and steel reinforcement. The project was completed in May 2015." This award was apparently an in-house honor bestowed by Caltrans for its own projects. (See State of California Department of Transportation (Caltrans), "Cabrillo Bridge Retrofit Project in San Diego's Balboa Park Wins Seismic Safety Award," published 11/06/2017, accessed 11/13/2017.)

New lights on the bridge were replaced in 2016. According to a local television station, "The project is designed to bring the lights along the bridge back to the way they looked in renderings from 1915. The lights that are damaged or missing ornamentation are being replaced with new LED drivers and globes; others are being repainted with the same color used for the 1935 California-Pacific International Exposition. In addition to improving aesthetics, the lighting upgrades are aimed at increasing public safety and reducing energy costs in order to comply with the City of San Diego’s Climate Action Plan." (See Monica Garske, KNSD Television.com, "Light Fixtures Restored Along Cabrillo Bridge," published 09/22/2016, accessed 11/13/2017.)

National Register of Historic Places: ID n/a

PCAD id: 5750