By Bart Ney, Caltrans Public Information Officer
Halfway though its reconstruction, the San Francisco-Oakland Bay Bridge — a visual icon in the region — has attracted an entirely new audience and form of recognition: from the global Internet community.
The series of mind-boggling construction and engineering feats to retrofit and replace the entire eight-mile bridge represents the largest — and most challenging — public works effort in California history. This monumental undertaking requires a massive mobilization of resources and resolve.
The determination of the vast workforce — from construction crews to designers — is unprecedented. It can be seen in every element of this endeavor, from herculean feats such as replacing a 6,700-ton slab of roadway ahead of schedule, to the smallest details, such as the art deco touches on the support columns of the west approach.
In addition to innovative architectural and engineering plans, Caltrans had a new outreach plan for this monumental project.
The Department had the Bay Bridge construction rendered on a three-dimensional model for large communications efforts and was looking for a bit more cachet with the electronically savvy online community. The Department negotiated directly with Google to make this happen.
Originally, Google Earth would not show buildings or structures under construction on its Web site. But Caltrans staff took their computer illustration of the bridge and offered to provide a model that showed the completed parts of the new bridge as solid imagery and the parts of the bridge that were under construction as transparent. Department staff promised to update the image as major construction milestones occur. Google management liked the idea and the model, and approved and posted it for public use. The Bay Bridge is now the first construction project in history to be represented on Google Earth.
Now people from around the world will discover the Bay Bridge reconstruction projects unexpectedly while searching Google Earth for restaurants or other items of interest in the Bay Area. They can virtually fly all around it and view it from any angle. As Caltrans staff update the model, the world can follow the bridge’s construction virtually and in three dimensions.
This accomplishes a lot for Caltrans, the Bay Area Toll Authority and the California Transportation Commission in their collaborative effort to communicate to the public. This additional communications path can be used when there are major messages to get out — like bridge closures. Google Earth’s structure information bubble links viewers to the Caltrans Web site, which contains the latest lane closure and construction information.
The Department also plans to use Google Earth as a teaching tool for its educational outreach program. The self-anchored suspension model in Google Earth will help students understand the geometry and the proximity of the structure to other Bay Area locations.
In addition to the Bay Bridge earning the title of the first construction project to be featured on Google Earth, the BayBridge360.org Web site has garnered Adobe’s “site of the day” award. These accomplishments have increased the Bay Bridge project’s cool cachet with folks in the online community.
The Bay Bridge retrofit and replacement efforts were jolted into life by the 1989 Loma Prieta earthquake. During the historical 7.1-magnitude event, a 250-ton section of the upper deck collapsed on the east span. The bridge closed temporarily for repairs. Crews quickly reopened the east span within a month, but critical questions lingered:
How could the Bay Bridge — an important regional lifeline structure — be strengthened to withstand the next major earthquake? Should the bridge be rebuilt, repaired or both?
These were important decisions to ensure that the Bay Bridge would survive heavy seismic activity, and provide access for emergency services and rebuilding efforts afterward.
Seismic experts from around the world performed an exhaustive study. They determined that to make each element seismically safe on a bridge of this size, the work must be divided into numerous projects. Each project presented unique issues, and each component needed to contend with one common challenge — the more than 280,000 vehicles that cross the bridge each day.
Keeping traffic flowing on one of the nation’s busiest bridges in the midst of this work demands new levels of innovation, from complex traffic shifts and the staging of crews and equipment, to unique approaches to demolition and construction. Caltrans has celebrated several milestones already: Traffic is now flowing smoothly on the permanent east-bound and westbound decks of the west approach in San Francisco. The 1.2-mile-long skyway, with its stunning panoramic bay views, is now complete. And all retrofit work is finished on the west span between San Francisco and Yerba Buena Island.
The twin suspension bridges of the west span (near San Francisco) required extensive retrofit work, which was completed in 2004. It involved bolstering the span with massive amounts of steel, concrete, bolts and new seismic safety technology.
The west approach is a one-mile stretch of Interstate 80 in San Francisco. It was demolished and rebuilt, one section at a time, as traffic continued to flow. Much of this work occured within inches of residential and commercial buildings.
The two-mile-long east span is being completely rebuilt. When finished, the new bridge will consist of several sections, but will appear as a single streamlined span. The new structure will feature the world’s longest self-anchored suspension (SAS) span, connected to an elegant roadway supported by piers (skyway), which will gradually slope down toward the Oakland shoreline to make its “touchdown.”
The SAS will be the first bridge of its kind constructed with a single tower. The innovative design features state-of-the-art seismic safety elements. It will also give the east span a graceful, modern, streamlined appearance that will fit well into a region recognized for its breathtaking skylines and bridges.
The traffic lanes of the east span will no longer include upper and lower decks. Instead the lanes
will be parallel, providing motorists with expansive views of the bay. A new path on the south side of the bridge, extending to Yerba Buena Island, will also allow bicyclists and pedestrians to enjoy the view.
The new span will be aligned north of the existing bridge to allow traffic to continue flowing on the existing bridge as crews build the new span. A new transition structure on Yerba Buena Island (YBI) will connect the SAS to the YBI tunnel, and will transition the east span’s side-by-side traffic to the upper and lower decks of the tunnel and west span.
When construction of the new east span is complete, and vehicles have been safely rerouted to it, the original east span will be demolished.
To view the current status of the construction, download the latest version of Google Earth and turn on the three-dimensional buildings listed in the left-hand toolbar. Then just “fly” down into the Bay Area.
You can’t miss it.