Florida DOT Replaces Historic $100M Flagler Memorial Bridge
The $100 million Flagler Memorial Bridge project in Palm Beach County, Florida, replaces a 78-year-old bridge with a modern structure with wider lanes and shoulders and a sidewalk, making it vehicle and pedestrian friendly.
“Bridges have a finite life,” says Geoffrey Parker, P.E., Senior Project Manager with New Millennium Engineering in Miami, the owner’s representative. “It was functionally obsolete. After decades transpire, standards get upgraded. This bridge was at the end of its lifespan.”
Both the old and new bridges cross the Lake Worth Lagoon and the Intracoastal Waterway connecting the city of West Palm Beach with the town of Palm Beach. The new 0.66-mile bridge is immediately adjacent to the original, which will come down after the new one opens later this year. The final aspects will be paving the areas where the bridge meets the roads.
The original bridge, built in 1938, is old, but is not formally designated as an historic structure, although it has historical significance to the region and particularly to the town of Palm Beach, adds Tish Burgher, Public Information Officer for the project.
“There are a couple of features on the existing bridge that will be incorporated into the architecture of the new bridge,” Burgher says. These include two pylons and decorative lamps.
The bridge is named for Henry M. Flagler, who invested in building a rail line from Jacksonville to Miami and on to Key West. He built hotels to house his passengers, including The Breakers in Palm Beach. His home, now a museum, sits not far from his namesake bridge.
The New Structure
The Florida Department of Transportation (FDOT) conducted a Project Development and Environmental Study for the original bridge in 2006. At that time, the agency reviewed several alternatives, including maintaining or rehabilitating the existing bridge or replacing it. It also held public meetings to obtain suggestions from the citizens of the area. The department then moved forward with a replacement plan for the double-leaf rolling lift bascule bridge.
In order to meet current standards, vertical clearance will increase from 19 feet to 21 feet, and the width of the navigable channel, close to the west side of the waterway, will increase from 78 feet to 125 feet. While transportation officials often try to raise new bridges, so a bascule is no longer needed, this crossing was too short to accommodate a fixed bridge. The grade would have been too steep.
“The bridge joins two land masses that are somewhat close together,” Parker explains. “Because of that constraint we were limited by how high we could go up.”
The new bridge will have two 12-foot-wide travel lanes in each direction with an 8-foot-wide shoulder on each side and a 15.5-foot median. Concrete barrier walls will protect pedestrians on the two 8-foot-wide sidewalks. The new bridge also features four pedestrian outlooks, a tender house elevated above the bridge deck, new signage and signals and a drainage system. The tender house includes a series of rooms one atop of the other that house electrical and mechanical systems as well as space for the tender.
The flyover approach to the existing bridge will be permanently eliminated and replaced with a signalized at-grade intersection. In order to meet the new grade of this intersection, crews are reconstructing Flagler Drive on the West Palm Beach side of the bridge and raising the roadway.
“The existing flyover creates a visible barrier between the north and south sides of the bridge,” Burgher explains. “By removing the flyover, you enhance the view along this scenic roadway while enhancing traffic flow.”
Constructing Through Design-Build
FDOT selected PCL Civil Constructors and Hardesty & Hanover, both of Miami, as the design-build team in 2011. New Millennium Engineering serves as the consultant construction engineer and inspection firm overseeing the project.
“Design-build projects are typically done for the speed of construction,” Parker says. “It’s a more exacting set of plans, developed for actual site conditions. It’s a fast-track method of constructing a bridge.”
Work began in September 2012 and is expected to wrap up in spring of 2017. Crews focused on foundation work initially. To date, most work has taken place on barges in the water, Parker reports.
“Any construction in a marine environment has its challenges,” Parker says.
Drilled and poured concrete shafts support the new structure. This method was used because it is quieter than traditional pile-driven foundations and residential complexes flank the new bridge. Fewer piers support the newer bridge than the original.
“It’s more efficient,” Parker says. “The fewer piers you have, the fewer foundations, which reduces cost, and it enhances the aesthetics with longer distances between piers.”
The team used 12-foot-tall prestressed concrete haunch bulb-T beams and haunched fascia beams on the span substructure. The beams range in length from 136 feet to 150 feet, and it takes 12 beams for each of the 11 spans between piers. The approach spans are topped with an 8.5-foot concrete deck.
The movable bascule is constructed of structural steel beams, fabricated in Tampa, Florida, and topped with a concrete-filled exodermic decking to reduce the hum and traffic noise. That final section should be poured later this summer. Both the heel and toe of the bascule have been installed.
PCL used a Triple 8 Ringer crane, one of the largest available, with a spreader beam to erect the beams, which began in September 2015.
Conduits will carry electrical wires from the mainland to the piers and the equipment that powers the movable spans. Those plastic conduits are topped with concrete that becomes the sidewalk surface.
The construction has taken a great deal of coordination with the various agencies and municipalities involved, Burgher says. Fire rescue and police continue to use the existing bridge.
“This is a great example of cooperation and collaboration between the Florida Department of Transportation, the contractor and stakeholders,” Parker concludes. “We have all linked arms, and it has worked out very well.”