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Tower to start with a 'boom'

Explosives will be used Wednesday and Thursday evening to test the soil for Signature Place's foundation.

By PAUL SWIDER
Published September 24, 2006

ST. PETERSBURG - Don't be alarmed if you're downtown this week and hear a boom in the early evening.

Construction is about to begin on Signature Place, and workers are testing the soil before starting the foundation for what could become Pinellas County's tallest building.

"It's loud, but it's not dangerous," said John Bowden of Bovis Lend Lease, the London firm that will be blowing up two concrete test pilings to see how deep it should sink supports for the 36-story mixed-use tower at 100 First Ave. S. "But no matter what notices we give, people are going to ask."

Signature will eventually have more than 200 such "caissons" reaching more than 100 feet to lime rock underground to support the two buildings. The pillars, 3 to 5 feet in diameter, will uphold an 8-foot-thick concrete slab foundation.

The tests, scheduled for 6 p.m. Wednesday and Thursday, will place explosives on top of the columns to create 1,800 tons of force. Sensors will show how the surrounding soil reacts to what is about four times the actual load from the completed building, Bowden said.

"We know what the caisson will do - it will probably shear," he said. "Then we'll be able to determine how deep we have to drill into the rock."

The caissons will be poured in place, not pounded in, Bowden said. That and the other foundation work would be done in about four months, still on schedule for the complex's first residents to move in by 2008.

Bovis was recently named the construction manager and general contractor for the $200-million Signature project. The company built the Opera House in Sydney, Australia, and the AOL Time Warner headquarters complex in New York, and is building Donald Trump's 90-story project in Chicago.

[Last modified September 23, 2006, 21:58:06]