On Saturday, the largest of the piers of the San Francisco-Oakland Bay Bridge’s old east span was removed from the bay through a careful and extensively planned implosion.
Early in the morning at slack tide, years of preparation, more than half-a-dozen permits and thousands of hours of labor culminated in the explosion conducted by local government body Caltrans.
In just six seconds, nearly 600 controlled charges weakened the 50-feet of Pier E3 which stood above the bay floor, allowing gravity to collapse the tower into its hallow casing below the mudline.
The pier is about as tall as a five-story building and has been outfitted with a wood and steel cage that will trap debris from the explosion that used 9,072kg of dynamite. Barges outfitted with air compressors created a “bubble curtain” to disperse the underwater shockwave.
“In the coming weeks, we’ll be exhaustively collecting extensive data and determining the effect the implosion had on the environment and fish nearby,” said Brian Maroney, Chief Bridge Engineer of Caltrans’ Toll Bridge Program. “We don’t know exactly what it looks like down there, not yet. The information will be critical for determining the best method for demolishing the remaining 21 piers.”
While there is much still to be analyzed, a number of goals were met by Caltrans, its contractors, and participating and permitting agencies:
• The implosion occurred during the target month of November, the month with the least environmental impact, including the fewest marine animals present.
• The blast attenuation system, or “bubble curtain,” which is estimated to cut down the pressure waves from the charges by about 80 percent, was successfully deployed.
• Dozens of environmental and biological experts carefully monitored areas surrounding the blast zone, verifying large animals were not nearby during the implosion.