Caltrans is getting ready for the next major step in removing the big concrete piers that used to anchor the old eastern span of the Bay Bridge.
The agency conducted a test blast at midday Friday -- a dress rehearsal for a pair of implosions planned later this month to demolish and remove piers near Yerba Buena Island.
Caltrans spokeswoman Leah Robinson-Leach said the exercise was designed to check out all the safety and monitoring systems that will be in place when demolition crews implode Piers E4 and E5, located adjacent to the point where the new span curves east of Yerba Buena Island.
"We'll ensure that all our mechanisms are in place, our safety systems and all of our equipment and personnel are ready to go," Robinson-Leach said.
Those systems are virtually identical to those employed when the first of the old bridge piers was demolished last November. They include a bubble-curtain system designed to contain the effects of the underwater blast -- actually a series of hundreds of small explosions timed just milliseconds apart -- and limit the impact on marine mammal and fish species.
Other measures include sound cannons to scare off birds in the area, debris containment systems and on-the-water monitoring crews watching for nearby marine mammals.
Caltrans is planning to implode Pier E5 on Saturday, Oct. 15. In order to contain the spread of debris and sediment from the implosion, demolition charges would be set off about 11:30 a.m., a period of slack water immediately after high tide.
The California Highway Patrol will impose a brief "rolling stop" on the Bay Bridge -- motorists will be slowed down so that the area adjacent to the blast site is clear of traffic at the time of the blast.
"It's not so much for safety on the bridge itself," Robinson-Leach said. "It really is to ensure that if drivers are not paying attention and they happen to hear a sound, they won't be shocked by that sound."
Robinson-Leach said the U.S. Coast Guard will enforce a perimeter to keep boaters away from the blast site, and the eastern span's bike and pedestrian path will be closed at the time of the implosion.
As it did last fall, Caltrans plans to live-stream video of the implosion on its Bay Bridge website.
Caltrans plans to implode Pier E4 on Saturday, Oct. 29 -- an event also scheduled for midday. The implosions are designed to collapse the pier structures into their mostly hollow interiors below the bay floor. Caltrans says natural sedimentation will eventually restore the bay floor's original contours.
After this month's blasts, the agency plans to implode another 13 pier structures. Half a dozen of those are scheduled for demolition next fall, with the rest to be removed in autumn 2018.