Caltrans Granted Clearance for Further Use of Implosion Technique to Demolish Old Bay Bridge
OAKLAND – Today, Caltrans was granted permission from the San Francisco Bay Conservation Development Commission (BCDC) to remove piers E4 and E5 of the old Bay Bridge using the same implosion technique that safely demolished E3, the largest underwater pier, in a matter of seconds last fall. The next implosion could take place as early as October. Approval was also granted to remove 13 additional remaining piers over the next two years, some by implosion and some by mechanical means.
"Caltrans should be commended for its engineering creativity and its proactive willingness to work with all of the resource agencies and partners to ensure that species and habitat are protected in such unique ways."
This approval that will allow for continuing the innovative demolition that began with the successful demonstration removal of pier E3 last fall. Caltrans plans to use the tightly choreographed sequential-charge implosion method to remove the piers E4 and E5 during the upcoming window months of October and November, during slack tide to minimize the transfer of energy and debris downstream. In addition, a heavy protective mat will be placed on top of the piers during each operation to prevent flying debris from being projected. Extensive monitoring efforts are being implemented pre-, during and post-blast. The following critical measures will ensure the least impact to the Bay during this necessary demolition:
- Blast Attenuation System (BAS) - Reduces the potential impact of shock waves by 80% to any fish in the area
- Timing - When the least number of species will be present in the area
- Small, highly controlled, sequential charges - Much lower impact than one large significant charge
"Hard technical data has indicated that all systems used during the implosion of Pier E3 were an overwhelming success. It was proven that bold research and scientific, biological innovation are the best approach as we continue the demolition of these piers"
Over the last several months, Caltrans met with the following environmental agencies to continue allowing controlled charges as the effective and environmentally sensitive method of safely removing the underwater piers:
- California Department of Fish & Wildlife (CDFW)
- Regional Water Quality Control Board
- U.S. Army Corps of Engineers
- U.S. Coast Guard
- U.S. Fish & Wildlife Service
- National Oceanic and Atmospheric Administration (NOAA)
The November 2015 implosion of Pier E3 proved that the implosion demolition was not only the most cost-effective option, but had an even lower environmental impact than expected. Before and after the blast, scientists specializing in water quality collected and monitored water conditions, measuring water clarity, pH, and temperature. Following the blast, there were no visible sign of change in turbidity. Increases in pH levels were less than expected and the duration of the effects on the water was shorter than expected. Analyses also indicated that the "bubble curtain" was effective in protecting fish and that birds and wildlife were unharmed.
Caltrans will once more utilize controlled charges that quickly dissipate and do not generate harmful chemicals. Controlled implosions mean that construction crews are not working underwater for many months, resulting in fewer disturbances to marine life.
The process will be a bit different, however, from that of pier E3 in that these two piers, E4 and E5, will be imploded within two weeks of each other. Although similar to Pier E3, the most massive of all the underwater piers, these two are not as extensive and will therefore require less explosives for each implosion. Moving eastward toward the Oakland shoreline, the piers are smaller in size and the waters become more shallow. As a result, the amount of explosives, when necessary, will be reduced as well.
These controlled charges will happen underwater and are unlikely to be heard or seen by nearby motorists. Caltrans will also provide a temporary rolling traffic stop strictly for sound to ensure motorists are not distracted.
Caltrans will remove seven underwater piers in the fall of 2017 and six underwater piers in the fall of 2018. The total demolition of the old Bay Bridge is expected to be complete by the end of 2018.
Here is a link to a video simulation showing highlights of the underwater removal: https://vimeo.com/179255514/790e4a57f3
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