After months spent securing signatures from various marine and wildlife groups, Caltrans has the final permits necessary from the US Army Corps of Engine to demolish, via implosion, the largest pier of the old eastern span of the Bay Bridge. Bay City News and the SF Chronicle report that the bridge section known as Pier E3 will be demolished on the morning of November 7th.
The method: 600 small explosives, or micro-charges, to be detonated at a cost of $160 million. Their target: A 268-foot chunk of concrete buried 165 feet in soft mud. Implosion, says Caltrans, “significantly reduce[s] impacts to the environment” over an originally proposed $254 million demolition plan involving sawing and damming.
In just six seconds, the concrete debris from the destroyed pier will be buried down in its own cavities while a "bubble curtain" of compressed air contains the blast. Traffic on the new Bay Bridge eastern span will nonetheless be closed in both directions for about 15 minutes.
What could go wrong? Well, monitors will be watching the water to make sure no mammals such as seals, sea lions, or porpoises wander into blast zone. Baykeeper, an environmental watch group, says they'll be keeping a close eye on the implosion and have expressed concerns about the bubble curtains ability to contain pollution and debris.
Environmental watchdog group Baykeeper has raised concerns about whether the bubble curtain can in fact contain the concrete debris and prevent it from polluting the bay. They have said they will be closely watching November’s implosion.
But if you thought this meant the old Bay Bridge was finally behind us, think again. While Pier E3 is up first — the massive section has been partially dismantled in anticipation of the November demolition — there are 21 smaller piers still standing. Those might also be imploded — depending on how this all goes.
The Bay Bridge's 2-mile eastern span has stood for 77 years and has been taken down in roughly the reverse order of that in which it was built. When it's all over, more than 58,000 tons of steel and 245,000 tons of concrete will have been removed, according to Bay Bridge Seismic Safety Projects.