The Gasparilla Island Bridge Authority learned the old South Bridge was much shakier than though during its demolition.
"We now know the South Bridge pilings were about 35 feet shorter than the old design plans had indicated, which was about 45 to 50 feet," said Jim Cooper, GIBA executive director. "We learned the pilings were not as deeply embedded in the ground to safely support the bridge as we originally suspected."
The worst piling at the second pier was supported by 38 inches of ground. The deepest piling was embedded roughly 9 feet in the ground.
The South Bridge was demolished just in time.
"That is for all 12 pilings," Cooper said. "No surprise we had far less less ground support coverage on the two piers and six pilings lying under the south side where the channel is far deeper than under the north side."
The depth of the fast-moving tidal area under the south side of the old South Bridge was perhaps 2 to 5 feet deeper than anticipated and the vulnerability and the risk factor was far higher than anticipated for extreme bridge damage.
Cooper said the South Bridge faced the possibility of severely reduced weight limits or temporary closing from a big storm-surge event that scoured the remaining ground supporting its pilings.
"GIBA's Board and Engineering Committee made the right decision to begin the priority for the replacement of our three bridges at the South Bridge," Cooper said.
The temporary steel deck South Bridge, which opened for two-lane island traffic June 8 a month ahead of schedule, provides Gasparilla Island with a far safer and more reliable bridge for access to and from the island during hurricane season, Cooper said.
The South Bridge deck can carry more than double the traffic weight at more than 50 tons than the 20-ton limit of the old South Bridge.