The New Carquinez Bridge (Alfred Zampa Memorial Bridge)—San Francisco, CA

In 2003, we designed the replacement bridge for the I-80 Carquinez Strait Bridge. The original bridge, designed by D.B. Steinman, opened to traffic in 1927. To accommodate the ever-increasing traffic flow on I-80, in 1958 the California Department of Transportation constructed a parallel bridge. This parallel bridge functioned as the eastbound span. Parsons designed the replacement bridge using current seismic criteria and incorporating current safety standards. The design life is 150 years and includes the benefits of low-maintenance materials. The two existing steel truss bridges connected the city of Vallejo in Solano County with the community of Crockett in Contra Costa County.

The California Department of Transportation (Caltrans) initially considered four different structural types for the new bridge. To help refine the selection process, Caltrans commissioned Parsons to prepare initial designs for cable-stayed and suspension bridge types. With Parsons’ assistance, Caltrans chose the suspension bridge as its final design.

In addition to the type studies, Caltrans retained Parsons to perform final design and engineering support during construction. Parsons developed detailed design criteria that encompassed state-of-the-art design of suspension bridges. The design also addressed demanding site conditions, including three active earthquake faults. It also looked at the significant risk for river scour and a history of strong winds.

Bridge Specs

The New Carquinez Strait Bridge has an overall length of 3,464 feet (1,056 meters), with a main span of 2,388 feet (728 meters). It incorporates state-of-the-art advancements in the design of orthotropic steel box girders. The suspended structure’s closed steel box girder is 10 feet deep and 95 feet wide. This is the first of its type in the United States.

Its floor system has the rigidity and strength to carry traffic and to resist torsion from wind, seismic, and other asymmetrical loads. Each of the main towers is founded on 12 deep-water drilled shafts, each measuring 9.84 feet in diameter. The north tower reaches 420 feet (128 meters) high. The south tower reaches 403 feet (123 meters) high.

As is typical of the elegant silhouette of suspension bridges, two hollow-shaft reinforced concrete towers soar 395 feet (120 meters) above the pile caps. They bear the load of the twin 20-inch-diameter main cables.

Our Scope

We provided environmental services, bridge-type studies, initial design, final design, and construction support services. Design management included type studies and final design of deep-water drilled shaft foundations, reinforced concrete towers, an orthotropic still box girder superstructure, and air spun suspension cables. Site-specific seismic criteria were developed for the 2,500-year return period ground motions, soil structure interaction, river scour, and performance-based design parameters. Wind studies included section model testing and full-bridge aeroelastic testing for site-specific wind speeds.

Support Services

We also provided a full range of support services during construction. Our scope of services for construction support included:

• Bid evaluation
• Field and shop engineering support throughout manufacture and fabrication
• Review of contractor submittals
• Review of shop drawings
• Evaluation of contractor means and methods
• Review of contractor request for proposed changes
• Review of as-built drawings

Construction support services and construction engineering services included detailed steel fabrication procedures. They also included sea-transport of fabricated box girders from Japan. In addition, wind performance during construction and erection engineering for temporary and permanent structures were addressed.