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Geotechnical Services for the Bryant Patton Bridge Replacement Project

Client: Florida Department of Transportation
Location: St. George Island, Florida
Project Cost: $72 Million

Williams Geotechnical Group, a business unit of Gannett Fleming, provided services for the St. George Island Bridge replacement project, one of the largest design-build efforts undertaken by the Florida Department of Transportation. The bridge replacement occurred near Apalachicola, Florida, in some of the most environmentally sensitive waters in North America.

As the geotechnical consultant, our firm performed all of the subsurface exploration and provided foundation recommendations. Using a barge-mounted drill rig, 49 borings were performed over water, along with 128 cone penetrometer soundings. Our firm provided all pile driving analysis and inspection of both test and production piles during construction; this included reviewing 56 test piles and 520 production piles. Additionally, our firm monitored all static load tests, including six statnamic load tests.

This project featured a 21,615-foot long bridge (4.1 miles or 166 spans). The old bridge was a primary evacuation route that needed substantial repair due to several structural deficiencies. The new design provides a wider bridge deck with two 12-foot wide travel lanes and two 10-foot wide safety lanes.

A key element of the design was the use of new, high capacity, 54-inch diameter, precast cylinder piles with precast concrete caps. These piles are expected to last more than 100 years in a harsh saltwater environment, and they offered the best foundation alternative with fewer piles and the least environmental disturbance. Apalachicola Bay accounts for 90 percent of the oyster harvest in Florida and is home to several endangered species.