The bridge is arched to provide an up to 24-ft clearance over the swamp.
Protecting the ecosystem
In 2013, shortly before design work began on the parkway, 3,520 acres of Reedy Creek Swamp were reclaimed as a mitigation bank. The preserve is a rich and diverse natural habitat consisting of woods, low-lying wetlands, swamps and marshes that provide a home to many species such as bears, panthers and alligators; a wide variety of fish and birds, including a blue heron rookery; and native flora ranging from old-growth cypresses to butterfly orchids. Reedy Creek also serves as one of the northernmost sources of water for the Everglades. The swamp is a popular destination for nature lovers who enjoy the visitor center and the network of trails in the area.
Dewberry addressed many environmental concerns during the design, permitting and construction process for the parkway. The team assessed a variety of aspects including the roadways, bridges, drainage, utilities and fiber networks to determine the extent of impacts on the local ecosystem, including the swamp. While an earlier proposal had suggested two 2,000-ft-long bridges separated by a long earthen causeway through the swamp, Dewberry engineers proposed a single 6,169-ft-long bridge over the environmentally sensitive area, eliminating the earthen plug. This approach maximized hydraulic flows and expanded the wildlife corridor.
The bridge is arched to provide a minimum 8-ft and maximum 24-ft clearance over the swamp to allow wildlife to walk or swim underneath. The arched profile facilitates the collection of storm-water runoff from the roadway into a scupper system that discharges into storm-water treatment ponds at both ends, eliminating direct discharge into the sensitive wetlands.
The Jr. Davis Construction/United Infrastructure team, with an extensive background in local projects and a strong working knowledge of soil and drainage conditions in the area, also focused on minimizing environmental disturbances during construction. One critical measure involved the use of low-pressure segmented barges to facilitate access as the bridge was constructed over the swamp. The barges served as material staging platforms, equipment work platforms and marsh mats for the areas of soft soils and inadequate flotation.
The use of the barges enabled the team to remove existing trees from the ground up, while preserving the natural vegetative root mat, which allowed for rapid regrowth and added stability to the work site. Rather than sinking into the root mat and wet soil, the sectional barges floated when necessary, barely leaving a footprint behind.
The bridge was constructed using driven concrete piles with precast beams. The choice of precast allowed for longer, nearly 100-ft spans, reducing the number of bents in the swamp. The spans were still short enough to allow for easy delivery and were light enough to handle from the cranes set on the barges. The superstructure required 7,700 cu yd of concrete, with an additional 1,000 cu yd for the substructure. The abutments and interior bents were constructed with piles driven from the ground topped by cast-in-place concrete cap beams. The girders were Florida-I 45 beams at 45 in. deep and 99.25 ft long.
Numerous agencies and stakeholders were involved in the effort, with Dewberry coordinating with OCX as well as the Florida Department of Transportation-Turnpike Enterprise, the Central Florida Expressway Authority, the Florida Department of Transportation-District One, the Florida Department of Environmental Protection, the U.S. Army Corps of Engineers, the South Florida Water Management District, Osceola County, Polk County, the Reedy Creek Mitigation Bank and numerous utility companies. The first phase opened in April 2016 and the entire $68.8 million project was completed in January 2017—three months ahead of schedule.
About The Author: Knudsen is a vice president in the Orlando, Fla., office of Dewberry.
