The mission: to shoehorn three new 10.5-mile-long reversible toll lanes into the middle of a six-lane interstate highway—including work on 63 bridges and 2.5 miles of the Florida Turnpike—while minimizing disruptions to up to 200,000 daily vehicles in the Fort Lauderdale area of Broward County, Fla.
The method: a concessionaire agreement with a design-build construction contract, a first for the Florida Dept. of Transportation (FDOT). The $1.8-billion Interstate 595 widening project also came with plenty of complexity, including southern Florida's quirky geology, various stakeholders and an immovable canal that borders the project's alignment.
But four years after I-595 Express, the group led by the Spanish firm ACS's Coral Gables subsidiary, won the concessionaire agreement, most of the intricate realigning and ramping is complete. The design-build contractor Dragados USA, also owned by ACS, expects to complete construction as much three months ahead of the March 2014 deadline, says Rafael Molina, Dragados deputy project manager.
Going with a public-private partnership (P3) and design-build approach shaved at least 10 years off the project, say officials. "We originally planned to build it out in sections," says Gerry O'Reilly, FDOT district director of transportation. "There would have been disruption along this corridor for years and years."
Upon the toll lanes' opening, FDOT will pay I-595 Express $10 million for a total of $50 million on eight construction milestones. I-595 Express will maintain and operate the facility, but the state will own it and collect the tolls. Over the life of the 30-year contract, the state will pay the concessionaire a maximum of roughly $1.3 billion in availability payments, which are monthly fees awarded if the facility meets state performance requirements. The project marks the first use of availability payments in the U.S.
Braiding and Bridging
"This project consists of just about anything you can imagine," says Scott Case, project manager with HNTB Corp., the construction-engineering inspector (CEI) for I-595 Express. "We've got steel girders, tub girders, Florida I-beams—a mix of bridges. There are open cuts, jacking, horizontal bores, fire-suppression systems. You've got sound-barrier walls supported on auger-cast piles or ground-mounted or shoulder-mounted walls. You have all these different types of construction. You could search for 20 years and not find a job that has all of that."
In addition to building the three reversible toll lanes and pushing out the existing interstate lanes, Dragados and its subcontractors—at peak, about 2,500 on-site workers representing 160 firms—rebuilt state Route 84 frontage roads on either side of I-595 and built new auxiliary lanes, 13 sound-barrier walls up to 22 ft high and a seven-mile-long greenway for cyclists and pedestrians. FDOT also wanted new "braided" ramps, lanes that are grade-separated so vehicles don't have to merge directly into or out of interstate traffic.
The Dragados team divided the project into bite-size pieces: nine design zones and five construction segments, says Molina. "There was no typical cross-section," adds Juan Miguel Perez Rodriguez, Dragados executive vice president. Some new ramps allow Route 84 to connect directly to Route 7, which helps motorists avoid using the interstate for a short distance. Other locations have combined exit ramps, allowing motorists to access or bypass upcoming crossroads.
To push out the existing alignment, crews built a steel bulkhead, or seawall, along the canal that borders the highway on the north side. After dredging the canal, crews installed sheet piles as long as 45 ft, covered them with 15 ft of fill and topped the wall off with cap beams, says Richard Dun, then-construction manager with Dragados. The seawall eliminated the canal's sloping banks and provided room for a pushed-out westbound lane of state Route 84.
One of the most challenging intersections, at University Drive, involved jacking up and realigning an existing 700-ft-long flyover ramp to make room for the expanded interstate below. Last summer, after reinforcing bridge foundations with micropiles and installing temporary shoring, crews used 24 hydraulic jacks to elevate five million pounds of bridge about 18 inches during a 24-hour closure. Over the next several months, crews demolished and rebuilt the southern 251-ft-long section, says Molina.
In the original design, another flyover at the same intersection would have been demolished. But the contractor opted to change the alignment by building the new express lanes in the former eastbound lanes, rather than in the I-595 median, and shifting the eastbound lanes farther south, says Paul Lampley, FDOT project manager. That meant the flyover's foundations could stay where they were. The approaches to the two flyovers saved an estimated $100 million, says Molina.
Micropiles were used elsewhere on the project, especially where flyovers come very close together, says Case. "The original design had pipe piles in certain areas where we had headroom restrictions. The pipe-pile construction itself is very time-consuming because you have to insert the pipe piles in sections. Once you get it down, you have to weld the next section of pipe. A typical foundation with five to six pipe piles could take up to a month to install." The team implemented micropiles in some of the critical foundations that were impacting the schedule, Case adds. "Where you have a foundation that could have taken a month, the use of micropiles meant it was done in a week," he notes.
Stormwater drainage was a big challenge on the project because the groundwater is extremely shallow. FDOT purchased drainage rights on two golf courses and bought a third course, eventually sold to a local town. The majority of stormwater runoff is directed to the golf courses' lakes through microtunnels running under the road. The shared-use solution saved more than $60 million in rights-of-way purchases for drainage facilities.
The 14 microtunnels were needed due to the water table and the depth of drainage structures, notes Case. "Once you get past a certain depth, the typical jack-and-bore or directional bore methods are no longer applicable," he says. The microtunnels run as long as 600 ft and up to 72 in. in dia, Lampley adds.