Largest support pier of old San Francisco-Oakland Bay Bridge demolished

The largest of more than 20 in-water piers that supported the old eastern span of the San Francisco-Oakland Bay Bridge was demolished Saturday morning during a six-second underwater implosion.

Sprays of water shot into the air as workers set off 600 charges that had been placed in pre-drilled holes in Pier E-3, a hollow, reinforced concrete structure that stretched from the waterline to 175 feet beneath the bay floor.

The 6-second implosion was a test run of sorts for the California Department of Transportation.

“In the coming weeks, we’ll be exhaustively collecting extensive data and determining the effect the implosion had on the environment and fish nearby,” Brian Maroney, a Caltrans chief bridge engineer, said in a statement. “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.”

The piers are the remnants of the bridge’s old eastern span, which was replaced after it was severely damaged in the 1989 Loma Prieta earthquake. The much-delayed, over-budget new span opened two years ago. Planks were placed over E-3 to prevent debris from flying onto the bridge and Caltrans briefly stopped traffic during the demolition, which occurred about 7:15 a.m.

Caltrans said most of the pier pieces either fell into or will be placed in the pier’s hollow casing below the bay floor. The agency decided to demolish the pier with explosives rather than mechanically remove it because the latter method would have taken years and required construction of a wall of piles to create dry space for workers.

bettina.boxall@latimes.com