Underwater pier detonated on old Bay Bridge early Saturday

Video of the #E3Implosion. Free to use and distribute. pic.twitter.com/HbmFIRyetV — TransportationAgency (@ca_trans_agency) November 14, 2015

Caltrans imploded an underwater pier of the old Bay Bridge eastern span at 7:17 a.m. Saturday, triggering 22,000 pounds of dynamite to pulverize the upper portion of the structure.

Spouts of water shot skyward from the force of the blast, but the explosives detonated mostly below the waters of the bay. Caltrans had placed a wooden and steel mat on top of the 80-by-140-foot concrete pier to contain the 20 million pounds of debris.

Spectators hoping to see a towering explosion may have been disappointed — the blast heaved water about 100 feet above the pier, but little debris was visible other than the remains of the mat that had covered the structure. Spectators sat on the hoods of their cars on the southeastern part of Treasure Island, and one man in a red kayak watched from the water. The roar of helicopters filled the air as several aircraft circled overhead.

The six-second implosion was timed to take advantage of slack tide, limited wildlife activity and, Caltrans hoped, light traffic.

The demolition, which cost $20 million, went off without a hitch, officials said. And traffic on the Bay Bridge was shut down for only five to seven minutes, causing few delays. BART briefly suspended service through the Transbay Tube but resumed running trains shortly after the implosion.

“As far as we know, everything went according to plan,” said Leah Robinson-Leach, a Caltrans spokeswoman. “We can't know everything at this point. It could take days or weeks to survey the environmental ramifications on air quality, water quality and animals. We want to create the best methodology moving forward.”

Robinson-Leach said implosions may be used to remove the dozen other remaining piers. She estimated it would cost around $190 million.

Pier E3 of the old Bay Bridge is imploded below the surface of the bay in San Francisco, Calif. on Saturday, Nov. 14, 2015. Pier E3 of the old Bay Bridge is imploded below the surface of the bay in San Francisco, Calif. on Saturday, Nov. 14, 2015. Photo: Paul Chinn, The Chronicle Buy photo Photo: Paul Chinn, The Chronicle Image 1 of / 40 Caption Close Underwater pier detonated on old Bay Bridge early Saturday 1 / 40 Back to Gallery

The pier demolished Saturday morning was the largest remaining piece of the old eastern span of the bridge, which was completed in 1936. That section was damaged in the 1989 earthquake and replaced in 2013.

The plan was to demolish the top 50 feet of the pier and bury the debris at the base of the 225-foot-deep remainder of the structure. Caltrans had hoped to limit harm to marine life, but before the blast officials said as many as 1,775 endangered longfin smelt, and possibly other fish, could be killed. A wall of bubbles was sprayed onto the underwater portion of the pier to help contain the shock wave.

Traffic was running smoothly following the implosion, said Officer Vu Williams, a spokesman for the California Highway Patrol.

“Any time you're stopping traffic it is challenging,” Williams said. “But early mornings are light. There were no incidences or issues related to the closure.”

Lizzie Johnson is a San Francisco Chronicle staff writer. E-mail: ljohnson@sfchronicle.com Twitter: @lizziejohnsonnn