Bay Bridge’s old supports to be imploded
Destruction of concrete foundations scheduled over several weekends
Thirteen little concrete islands that once helped hold up the old Bay Bridge east span will be blasted into history in a series of implosions over six weekend days beginning in September and concluding in November.
Caltrans officials will announce the demolition plans Monday for the bridge foundations, or piers. Five other foundations are expected to be spared. Tentative plans call for a large foundational pier near Treasure Island to be saved for conversion into public spaces. Four piers on the east end in Oakland would be saved for the same purpose.
Caltrans also wants to spare as much bay wildlife
as possible and has been working with natural resources agencies to come up with a suitable plan. The demolition work, which had been expected to extend through fall of 2018, will now be finished by the end of this year under the new plan that calls for imploding piers on certain weekends.
“We’ll be imploding piers every other weekend for the next three months,” said Brian Maroney, Caltrans’ chief bridge engineer. “We’ll be done before Thanksgiving.”
The plan is expected to save money, get demolition crews off the bay earlier and spare the bay and its marine residents by reducing the number of days imploding piers by seven, said Dan McElhinney, chief deputy district director for Caltrans.
“We expect at least $10 million in savings,” he said.
The series of demolitions will, however, come at a price for the bridge’s bicyclists and walkers, who have faced delays and frequent closures of the bridge path. For the week preceding each demolition, the bike and pedestrian path on the new Bay Bridge will be closed while crews load explosives then detonate them, McElhinney said.
The path, which stretches from Oakland to Yerba Buena Island, had just opened seven days a week in May, and made it all the way to the island, after keeping cyclists and walkers waiting for 3½ years.
Implosions are scheduled for these Saturdays: Sept. 2, Sept. 16, Sept. 30, Oct. 14, Oct. 28 and Nov. 11. Specific times will be announced later.
If tides, weather conditions or wandering wildlife get in the way, however, the implosions could be pushed to the immediately following Sundays, or Mondays if necessary.
“If a porpoise or a harbor seal goes into (an implosion) zone, we are not allowed to go ahead until specialists say the area is all clear,” Maroney said. “We cannot harm Flipper.”
To help protect bay wildlife, including the Pacific harbor seal, California sea lion, northern elephant seal, northern fur seal, harbor porpoise and bottlenose dolphin, demolition crews are limited to using implosions during September through November, when the creatures are less common in the area.
Implosions are also restricted to narrow time frames when the bay waters aren’t being pulled by tides. To diminish the spread of waves, crews employ contraptions that use pipes and compressed air to create a curtain of bubbles around the implosion sites.
When conditions are right, the bubbles are turned on, and crew members ask the CHP to start a rolling traffic break across the bridge to avoid distracting drivers. Then the master blaster detonates the explosives, which cause the concrete piers to collapse inward. When more than one pier is being imploded, Caltrans will wait about half of a second between detonations to avoid creating larger waves.
After each implosion, demolition crews will dig the concrete shards from the bay muck at the same time they’re preparing for the next implosion. Caltrans’ permits allow for the digging to continue through the end of the year, Maroney said.
The piers left intact may one day become places for people to stroll or hang out by the bay. The old span’s massive westernmost pier, near Yerba Buena Island, may become an observation deck, while the four piers on the Oakland side that resemble concrete goalposts might someday support a boardwalk or pier reaching 1,000 feet into the bay.
About $60 million that would have been used to demolish those foundations could help pay to transform them into public places, McElhinney said. The Toll Bridge Program Oversight Committee, which oversees the Bay Bridge project, is expected to decide on the future of those foundations at its Aug. 29 meeting.
“What a great asset that could be for the community.” Maroney said.
To diminish the spread of waves, crews employ contraptions that use pipes and compressed air to create a curtain of bubbles around the implosion sites.