No. 6 - S.R. 93 (I-75) Improvements

In the state of Florida, there are three primary hurricane evacuation routes—I-4, I-95, and I-75.

Running from Alligator Alley—the Naples/Ft. Myers region—all the way up to the Florida/Georgia line, I-75 is also a major freight corridor that handles, in the region of this particular project, 61,000 vehicles per day, a bulk of which are heavy trucks.

“Hurricane Irma was the first major mandatory evacuation in a long time,” Marlena Gore, CPM, interstate construction project manager, Florida DOT, told Roads & Bridges. “The last one was when Charlie came through, a decade before that. The trouble was that every other part of I-75 was six lanes except this portion, so when people were trying to travel north from the Naples/Ft. Myers area, they were getting bottlenecked down to two lanes, then going to three, and the width of the shoulders precluded their use over the bridges. It was a major traffic nightmare during those evacuations. Also there’s a lot of heavy truck traffic. There’s a way station just south of the project limits, which means lots of trucks go in and out of the interchange.”

The I-75 expansion project, from N. Jones Loop Road to just north of S.R. 35 (U.S. 17), involved the addition of a new 12-ft travel lane and paved shoulder in each direction of what was the last four-lane segment of I-75 in Florida. Its completion was a major milestone, as it increased, at last, all of I-75 to six lanes, improving capacity, safety, and overall efficiency. The existing interstate bridges over N. Jones Loop Road and Riverside Drive/Seminole Gulf Railroad (SGLR) were widened to accommodate the additional lanes, and a new underdeck drainage system was installed beneath the existing U.S. 17 overpass bridge. The N. Jones Loop Bridges involved steel I-girder superstructures founded upon steel HP 14 x 89 piling, while the Riverside Drive/SGLR Bridges involved 36-in. Florida I-beams founded upon 18-in. square pre-stressed concrete piling.

The project also included milling, resurfacing, and overbuilding the existing travel lanes and outside shoulders to correct the cross slopes, reconstruction of the access ramps, and median and shoulder improvements on N. Jones Loop Road, as well as painting of the new and existing bridge components. The added I-75 stormwater runoff was accommodated by construction of four new linear dry retention treatment swales and excavation of a floodplain compensation area at the southeast quadrant of the U.S. 17 Interchange.

When it was evident that the northbound Jones Loop Bridge was not scheduled to be completed in time for the start of the 2018 hurricane season, FDOT requested that contractor Ajax Paving Industries accelerate bridge work to have sufficient deck space to accommodate three lanes of traffic in an emergency or evacuation, a challenge Ajax ably met.

They redirected bridge crews from the two Seminole Gulf Railway bridges at the north end of the project and brought an additional bridge crew to the project so that work could continue day and night. Considering some work tasks fell during Florida’s rainy season where thunderstorms usually occur daily—and to offset production losses due to weather—the team created opportunities for advancing work within the accepted schedule by substituting materials that could increase their productivity by expediting the mainline widening at the roadway approaches by using asphalt in lieu of Type B Stabilization and lime-rock base. This work was performed using an added crew, which enabled the existing roadway base subcontractor to continue to simultaneously work on other critical areas. The accelerated bridge work was completed in 18 days.

Another challenge was to correct the existing mainline cross slopes without exposing or jeopardizing the existing base.

“We used survey data from FDOT to create our own 3-D model to figure out a better way to mill and resurface the roadway,” Felipe Jaramillo, alternative contracting project manager for Ajax, told R&B. “We did not go public with it; it was designed for our paving and milling guys to help direct that scope of work. We eliminated a phase at the end of the job as a result of it and could fast-track the job very quickly.”

The project scope had multiple milling depths and overbuild depths, which posed a further major challenge, but Ajax’s cost saving initiative and the 3-D model that resulted from it made it possible to eliminate much of that inherent risk.

“The original design had lots of milling depths,” Jason Prokopetz, project manager for Ajax, told R&B. “It was tricky that way. But we did a redesign of that, and we didn’t hit any base rock. We took the existing slopes and drew a best-fit milling line, and then came up from that for FDOT thickness requirements. As a result, we mitigated the risk, saved FDOT money, and earned our early completion incentive.” The job came in 143 days ahead of the contract’s allowable time, a 30% time savings.