Oakland, Calif. — Caltrans reported that initial analyses of the implosion of Pier E3 indicate that the “bubble curtain” was effective in protecting fish, that birds and wildlife were unharmed, and that the impact on water quality was less than what had been deemed acceptable.
The implosion of the old Bay Bridge’s largest culminated years of planning and coordination with permitting agencies. Hundreds of small charges did their job, causing the concrete-and-steel structure to collapse into the voids within the foundation below the bay floor.
"As we collect and organize information on the implosion, we are seeing more and more data that is building documentation that this method can be the best way to remove such large piers from the bay waters," says Chief Bridge Engineer, Brian Maroney. "I just cannot offer enough appreciation to all the resource agencies and particularly San Francisco Bay Conservation and Development Commission, for supporting this demonstration project. Project staff are working tirelessly to process massive amounts of complex data."
The Blast Attenuation System, better known as the "bubble curtain," worked as planned. A complex array sensors collected volumes of data that is still under review. But a simple test, in which fish were placed at various distances from the blast to measure its effect on them, showed encouraging signs. Preliminary review found that none of the fish, which were held as near as 150 feet, were killed by the implosion. Another study, which involved gathering free-swimming fish in trawling nets, found no harm to federal or state-listed species. The implosion was carried out in the month of November, a time of year that such species are less likely to be present.
A large team of scientists specializing in marine mammal identifications and behavior, including sea lions, harbor seals, harbor porpoises, elephant seals and whales, were successfully deployed prior to the blast at observation locations as far away as 5 miles from the E3 foundation. The team continued to monitor for three days in case of subsequent strandings. No injuries or strandings have been reported.
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.
Biological scientists specializing in avian (bird) behavior established observation stations on the water and on the bike path. No diving birds were observed in the designated bird safety zone area during the blast. An air cannon sounded, along with several blasts of local foghorns right before the blast.
Thorough findings will be released in the coming weeks.
For more information on the Pier E3 implosion, visit www.dot.ca.gov/e3implosion.