San Francisco, CA

Marine Foundation Dismantling

project info

Location:  San Francisco, CA

Project Contractor: CalTrans

Client: Kiewit / Manson, A Joint Venture

Project Date: 2018

Description: The New East Span of the San Francisco-Oakland Bay Bridge was opened to traffic in 2013. To fulfill environmental commitments and for the safety of marine traffic, the old bridge was dismantled and removed.

work carried out

The scope of work for this project consisted of removing the marine foundations from miles 0.5 miles east of Yerba Buena Tunnel to 0.8 miles west of the Toll Plaza. The old marine foundation piers were blast-imploded from the top down to an elevation of 3 feet below the natural San Francisco Bay mudline to provide sufficient clearance for ships passing through the San Francisco Bay Shipping Channel. The blast plans were designed to break the reinforced concrete structures into small enough pieces so that the majority of the concrete would fall into the caisson cells below the mudline of the bay.

From 2016 to 2018, Municon’s work on this phase of the project involved pre- and post-construction photo and video documentation, as well as vibration monitoring before and during the blast-implosion demolition.

For each of the eight blast-implosions, Municon deployed 2 to 3 seismographs to monitor the ground-borne vibrations produced by the blasts. A seismograph was also deployed at a nearby historical building, The Torpedo Building, when the blast-implosions were located close enough to potentially affect this building. The vibration monitoring was unique due to the fact that seismographs were deployed on the pier caps of the new San Francisco-Oakland Bay Bridge East Span. Ground-borne vibrations were measured as they traveled from the demolition of the old piers, through the San Francisco Bay and back up through the piles of the New San Francisco-Oakland Bay Bridge East Span. Real-time data was provided to the contractor as work proceeded.

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