Last week, we posted about some of the information our engineers gathered during their tour of the new San Francisco – Oakland Bay Bridge. Here is part two of our post, with more stories about the construction process.
Great care has been taken to help protect the environment in the planning and construction of the bridge. When driving up to the Yerba Buena Transition structure, there was a section of water near the island that was blocked off by buoys. These buoys designated a zone with eelgrass, a protected marine plant that provides food and shelter to many fish and other local species. This shows just part of the great effort being made to conserve the environment around the bay bridge, even during construction.
The bay bridge is also home to the largest colony of double-crested Cormorants; these birds make their nests in the underside of the old east span. This means, that along with all of the other construction, special platforms have been added to the underside of the new bridge, so that the birds can make a new home once the old bridge has been taken down. These “cormorant condos” are an effort to protect this species of special concern, and cost around $550,000 to implement. You can read more about these structures and birds in this San Francisco Chronicle article.
As a final step in environmental protection, the old east span will be demolished in a different way. There will be no explosions or collapsing bridges, because the original east span was not only built with asbestos, but much of the paint contains lead, and it would be very damaging for those materials to end up in the water. So the old bridge will be cut down piece-by-piece, to ensure that it is disposed of properly, and to keep the environment safe.
One of the many challenges that the design faced was its proximity to historical landmarks and sites on Yerba Buena Island. For example, a torpedo warehouse from World War II is located under the transition structure, and the workers must take extra precautions when working there, being extra careful not to drop any tools, bolts etc. In order to help them remember, the falsework under the bridge is painted grey in that section. However, a real challenge came when it was discovered that the designed bridge would cast a shadow over Nimitz mansion, which belonged to respected admiral Chester W. Nimitz. This was considered disrespectful to the admiral and the historic site, and the Yerba Buena transition had to be shifted so that the mansion would remain always in the sun during the day.
While touring the new bridge, there was also ample opportunity to examine the old east span as well. As part of the tour, a “secret” protective troll that is welded onto the bridge was pointed out. It stands on the replacement section of the upper deck; the original section fell during the 1989 Loma Prieta Earthquake. This troll was created by local artist Bill Roan and then welded by ironworkers, without permission, onto the replacement deck. Trolls are commonly known as protectors of bridges, and the industrial troll seems to have done its part since then to protect the east span. It is unclear what will happen to the troll after the demolition of the old east span.
We look forward to the opening of the Bay Bridge in the fall of 2013!
Click here to learn more about the San Francisco – Oakland Bay Bridge.