Atlas Copco Compressed Air Protects Environment in Historic San Francisco Bay Implosion

In November, demolition crews in San Francisco Bay leveled Pier E3 – the largest remaining in a system of 21 piers that supported the old Bay Bridge. Thanks to the construction of a new Skyway between San Francisco and Oakland, the Bay Bridge is scheduled for removal by 2018.

Atlas Copco compressors helped protect the bay’s sensitive underwater ecological habitat throughout the historic event.

“California’s San Francisco Bay represents a significant natural habitat,” said Blake Gearhart, vice president of operations west for Atlas Copco Rental North America. “This operation represented a fusion of engineering prowess and environmental protection, and we were confident our compressors could get the job done.”

Planning for the implosion spanned two years, and environmental groups and the public expressed concern for how the blast would affect the bay’s wildlife. But the problem was solved by an innovative curtain bubble strategy, a method that places a curtain of air bubbles around the site in order to protect marine life.

General contractor Kiewit/Manson used Atlas Copco 1,600 cfm oil-free compressors to supply air at full capacity to the blast-buffering bubble curtain. The diesel-powered air compressors are California Air Resource Board (CARB) permitted and were an obvious choice for Kiewit/Manson, known for its socially responsible practices.

The San Francisco Bay project presented a unique challenge because of the sheer number of 1,600 cfm compressors required to bring down Pier E3 – the equivalent of a five-story concrete building. But Atlas Copco Rental has the largest fleet of 100 percent oil-free air compressors that are both diesel-powered and CARB-permitted in North America. The high-volume models were particularly well suited to an environmentally sensitive project, because they are designed to introduce 100 percent oil-free air into the water. As an added measure of safety, each compressor’s base provides fluid containment.

At 7:17 a.m. on Nov. 14, a series of blasts from 600 explosive charges rumbled through the 80-by-140-foot pier structure for a total of six seconds. The blasts fractured the reinforced concrete, which collapsed into the pier’s own honeycomb-like base below the bay floor.

Spectators gathered in the area had been hoping for an exciting show but were likely let down by the blast, which was largely limited to beneath the water’s surface. The compressors maintained the curtain created by sending compressed air through a unique design of holes drilled into underwater pipes. The curtain effectively absorbed shock and protected marine plants and animals throughout the short blast; in addition, a blast mat contained dust and flying rock particles, and a hollow structure on the bay floor collected debris.

The California Department of Transportation conducted extensive studies following the implosion and reported that there had been no apparent injuries or deaths to aquatic wildlife.

“This pier implosion was the culmination of years of collaborative preparation and planning,” said Leah Robinson-Leach, Bay Bridge spokesperson for the California Department of Transportation. “The combination of science, technology and engineering with environmental stewardship is historical.”

This successful demonstration of blasting in the bay may now be implemented on the remaining piers.