BRIDGE HISTORY
The San Diego-Coronado Bridge built with an eye to appearance
as well as transportation service, has become a symbol of the
San Diego area-just as the Golden Gate and San Francisco-Oakland
Bay Bridges symbolize that area around the world. Its distinctive
towers and graceful curve are a striking landmark in the harbor
area. In 1970, it received the Most Beautiful Bridge Award of
Merit from the American Institute of Steel Construction. The
bridge was financed by a California Toll Bridge Authority $47.6
million bond issue which has since been repaid from toll revenue.
It is one of nine State-owned toll bridges. Construction started
in February 1967, and the bridge was opened to traffic on August
3, 1969 during the celebration of the 200th anniversary of the
founding of San Diego. It is notable among the world's great
bridges for the number and size of its concrete towers. There
are 30 towers and over the channel they reach a height of 200
feet. They were designed with a curved cap to echo the mission
arch shape associated historically with regional architecture.
The towers rest on 487 prestressed reinforced concrete piles.
The piles, 54 inches in diameter and with walls 5 inches thick,
were driven and jetted into the sand and clay of the bay bottom
up to lengths of 100 feet. The mud was removed from inside the
piles, which were then filled with concrete. Clusters of up to
44 piles were used under some towers. Girders of the steel superstructure
are painted blue to harmonize with the predominant color of the
sky and bay. Beginning at the toll plaza in Coronado, traffic
ascends at a 4.67% grade, curving gracefully 90 degrees toward
San Diego. This 2,850-foot section is the longest in the U.S.
using curved steel plate girders. The shipping channels are spanned
by the world's longest continuous three-span box girder, 1,880
feet. The roadway is of orthotropic steel plate design and serves
as the top flange of the box girder. Its spans are third longest
of their kind in the country. This design saves steel and provides
a slender superstructure with a smooth exterior, all braces and
stiffeners being inside the box girder. The steel superstructure
was fabricated and erected in the San Francisco Bay Area. Girders
were barged down the Pacific Coast and lifted into place by the
largest barge crane in the West, the "Marine Boss."Precast
prestressed concrete girders of up to 165-feet in length were
manufactured in Long Beach. These are among the longest of their
kind in use in the country. The roadway has five lanes. The center
lane is a switch lane with a moveable center divider, which is
used to provide three lanes for peak-hour traffic when demand
warrants. The 34-inch-high concrete barrier railings are low
enough to permit an unobstructed view from vehicles on the roadway.
Wide at the bottom and narrow at the top, the railings are safety-designed
to redirect the wheels of a vehicle back to the roadway with
little or no damage. The 7-lane toll plaza, with an architecturally
designed canopy on sculptured pedestals, received special landscape
attention, including extensive lighting to enhance the appearance.
Traffic volume on the bridge has grown at a healthy rate, permitting
several toll reductions. The basic auto toll is $1 for westbound
passage. Commute books cost $24, to provide a reduced toll of
60 cents to the regular commuter. The California Department of
Transportation employs a force of 65 persons to operate and maintain
the bridge. The total traffic volume in 1971 was 8,631,436 vehicles.
In the year 1996, the average daily traffic was 66,000. During
the summer, volumes increase to over 69,000 vehicles a day.
OVERALL GOALS
- Strengthen the bridge to resist seismic forces in the event
of a major earthquake.
- Improve safety in the communities in Barrio Logan and Coronado,
and the traveling public.
- Minimize environmental impacts of the project
BACKGROUND
The San Diego - Coronado Bridge was opened to traffic on August
1969. In 1973, modern seismic bridge design practices were introduced
that incorporated lessons of bridge performance learned from
the 1971 San Fernando earthquake. As a direct result of the earthquake,
the San Diego- Coronado bridge was retrofitted in 1977. Results
of the 1989 Loma Prieta Quake in the San Francisco Bay area,
identified a need for more strengthening than was implemented
in the 1970's retrofitting project. As of December 1996, the
retrofit strategy has been finalized. The strategy does not adversely
impact the aesthetics of the bridge and manages to preserve the
important murals in Chicano Park.
THE PROJECT
At this time, studies to determine the structural integrity of
the bridge are completed. Caltrans is now finalizing the contract
plans for the last three contracts. The project is scheduled
to be completed in four stages. The first contract was awarded
to American Bridge Company of Long Beach, California for $3.1
million.
COMMUNITY INVOLVEMENT
Beginning late October 1995, Caltrans began meeting with artists,
community representatives, agencies, and elected officials to
keep them appraised of the status of this important retrofit
project. Caltrans will continue to share information as it is
received and solicit assistance from the community throughout
the retrofitting process.
TIMELINES
October 1995 begin environmental studies, community meetings
May 1996 open-house public meeting
December 1996 announcement of strategy decision
Winter 1997 begin construction
Fall 1999 complete final design of the project
