Mass Stabilization for Environmentally Sensitive Projects in Florida

US-1 is a two-lane highway and the main route to and from the Florida Keys. A hurricane preparedness and public safety plan included the Florida Department of Transportation's replacement of the drawbridge over Jewfish Creek with a fixed bridge and widening of the roadway north of the bridge. Before construction, the widening program included mass stabilization to improve the soft underlying soils, which consisted of 5 ft of granular fill placed over 10 to 15 ft of soft organic silt overlying limestone. The bridge approach embankments reached up to 20 ft in height. Safety was critical because the work took place adjacent to an active highway. The entire project was environmentally sensitive and required attention to spoil controls because the work was performed adjacent to water and wildlife. In another environmentally sensitive area, a new two-lane bridge was planned for construction on driven piling over a waterway in Port Everglades, Florida. The subsurface consisted of 3 to 4 ft of sand followed by 8 to 10 ft of peat, then limestone. The peat layer was unsuitable to support the mechanically stabilized earth (MSE) walls planned for the abutments. A mass stabilization program was conducted to improve the bearing capacity and limit settlement and to ensure global stability of the MSE walls. Considerations included the existing condition of soils contaminated by petroleum hydrocarbon and environmentally sensitive adjacent properties, including a manatee mating area. The mass stabilization construction methods and procedures, design considerations, quality control, equipment, and performance monitoring of these two environmentally sensitive bridge projects are discussed.