Construction work continues on Matlacha Bridge
Two weeks ago saw the largest concrete pour for the Matlacha Bridge project, even though it was delayed by about 90 minutes because of rain, putting it on course for an estimated completion in October 2013.
Exceptionally foul weather held off, the temperature remained less than 92 degrees needed and traffic was virtually unimpeded during the massive pour, which used 470 cubic square yards – about 532 tons – of concrete, said project manager Sarah Clarke, with the Lee County Department of Transportation. She added the amount of concrete was needed “to properly support the structure to be built above the footing.”
She said the one-time pour was needed “to minimize the amount of joints between concrete placements. This helps to keep the saltwater out of the structure.” It also helps prevent thermal cracking as the concrete “cured” to a hardened state.
The concrete mix used is a standard for Florida Department of Transportation structural concrete – a 5,500 psi mix. Included in the mix are additives to prevent chloride, or salt, intrusion into the concrete, Clarke said. The life expectancy is about 75 years.
The concrete was poured into forms which kept the saltwater from touching it.
“Concrete must be cured for seven days before being exposed to salt water,” she said. “Concrete actually cures for years after it is placed.”
Special machinery was used for the pour.
“A concrete pump sitting on a floating barge was used to deposit the concrete in the forms built by the contractor,” Clarke said. “Electric vibrators were used to consolidate the concrete once it was deposited in place.”
About 40 people worked on the project which took about 10 hours to complete. The roadway was down to one-lane during the 5 p.m. to 9:30 a.m. closure for trucks to deliver the needed concrete to the pump. The extra time was allotted in case weather affected the work.
“The placement was completed at night to minimize traffic interruptions to the public. No emergency services were affected,” Clarke said. “Traffic interruptions were minimal. Notice of the lane closure was provided on the project website, via a press release and on message boards approaching the project. No complaints were received from businesses, residents or motorists regarding the lane closure.”
Clarke explained the history of the project, dating to 1991 when the bridge was transferred to Lee County from the Florida Department of Transportation to operate and maintain. Annual inspections noted deterioration, some significant.
Ten years later, in 2001, Lee County had a structural review completed to determine the cost-effectiveness of continued repair versus replacement, and replacement was recommended.
“Repairs continued to maintain structural integrity until funding could be programmed to design, permit and construct the bridge replacement,” she said.
“Design and permitting began in 2005 and was completed in 2008. Funding to construct the replacement was programmed in 2008,” she said. “However, due to the economic downturn, the construction funding was moved out to 2010.
“The project was advertised for bids. Archer Western Contractors was the low bidder and was awarded the contract. Construction began in October 2011 and will take two years to complete.”