Caltrans announced October 1 that it received environmental approval to use controlled underwater charges and implode Pier E3, the largest of the underwater piers on the Old Bay Bridge. Experts have analyzed this method of demolition and contend that it will significantly reduce impacts to the environment, say Caltrans.
Caltrans engineers and its environmental experts have spent years working with resource agencies to determine the best method for demolition of Pier E3 and they were granted permission from more than half a dozen regulatory bodies to use the implosion method.
The most recent permit from the United States Army Corps of Engineers is the final permit required to proceed with the implosion of Pier E3.
"We can take this pier out of the Bay using highly controlled, sequenced charges and have it down in seconds or we can spend years pounding piles with all kinds of construction equipment lining the Bay," said Chief Bridge Engineer, Dr. Brian Maroney in a recent press release. "This is clearly the least environmentally impacting method and we owe it to the Bay to do it.”
The estimated $160 million project will remove the equivalent of a five story concrete building from the bay. A simulation video created for Caltrans by Berkeley-based NorCal Structural, Inc shows an animated demolition concept for the E3 caisson.
The simulated construction process begins with an excavator on top of the old pier, methodically demoing the top area, section by section. As the machine breaks away chunks of the concrete, it moves onto makeshift platforms, while crews use ramps and a floating barge to catch debris from going into the water. After the dozer breaks away the top concrete, a crane is floated in to insert roughly 600 micro explosives on the underwater base of the pier, which sits in mud, nearly 170 ft below the surface of the water.
A perimeter is then set up with a large debris safety zone, surrounded by CHP boats, a marine mammal exclusion Zone to protect wildlife, as well as monitors to check water and air quality and noise disturbances. A blaster command center and a viewing area will then be established on the new Bay Bridge before setting off the implosion.
The controlled charges will be underwater and will likely not be easily heard or seen by nearby motorists, says Caltrans. But as a precaution, the public will be kept away from the area during the implosion. Caltrans says underwater controlled implosion technology has improved considerably over the past decade and that today there are controlled charges that quickly dissipate without harmful chemicals.
The implosion method has also received approval from California Regional Water Quality Control Board; California Department of Fish and Wildlife; National Oceanic and Atmospheric Administration; National Marine Fisheries Service; The San Francisco Bay Conservation and Development Commission; United States Fish and Wildlife Service; and United States Coast Guard.
Besides Pier E3, the Old Bay Bridge still has more than 20 other, smaller piers that need to be removed.
Crews began carefully dismantling the 77-year old East Span section-by-section, in roughly the reverse order of how it was built in the mid-1930s. Demolition of the nearly 2-mile long original East Span began two years ago and is taking place in three phases. Crews began at Yerba Buena Island, taking apart the cantilever section and demolishing the S-Curve, before moving east to dismantle the 504’ and the 288’ truss spans.
The demolition team is now aiming at the waterline to remove the piers, pilings and foundations that support the span. When the entire demolition project is complete, over 58,000 tons of steel and 245,000 tons of concrete will have been removed.
The implosion of Pier E3 is planned for November 7, 2015. Kiewit/Manson is the contractor for the project.