Rippling Effect

Al Stewart, P.E., and Chip Messenkopf, P.W.S. / August 06, 2008

Improvements to I-75 in southwest Florida have been planned for years. Originally slated for traditional design-bid-build, the Florida Department of Transportation (FDOT) decided to instead utilize a design-build-finance public-private partnership approach for this project. At that time, the I-75 widening project was divided into four separate projects prepared by four consulting firms, and plans were between 30-60% complete. This article focuses on designing and acquiring the environmental permits for the revised design-build-finance project.

The I-75 design-build-finance project, known locally as iROX (I-75 Roadway Expansion Project), involves widening I-75 from four to six lanes for 30.5 miles in Collier and Lee counties in Florida. The $430.5 million project will be constructed in a little over three years. The Anderson Columbia and Ajax Paving (ACCI/API) joint venture is financing the project as well as constructing it and will accept payments from FDOT over five years, which establishes the public-private partnership component.

Slippery slope

Two new lanes were to be added in the median of the existing four-lane highway and were to match the cross-slope of the existing roadway. This would drain the runoff from the new inside lanes along with the existing lanes to roadside ditches. Storm-water detention ponds were sized and designed to provide storm-water management for not only the widening to six lanes, but to accommodate future widening to eight and 10 lanes as well.

For the design-build-finance project, the new lanes are still added in the median of the existing highway; however, instead of sloping to the outside like the existing, the new lanes slope inward toward the median. For the most part, this keeps the area of new pavement separate from the existing pavement, offering several advantages:

  • Reduced area is needed for storm-water detention ponds due to smaller contributing drainage area;
  • Storm-water management (treatment and attenuation) is required only for the median area and new lanes rather than entire right-of-way;
  • Because the project traverses a significant amount of wetlands, confining the roadway and drainage improvements to the median significantly reduced wetland impacts by minimizing outside ditch work; and
  • A smaller drainage area of the median requires smaller conveyance ditch widths and storm drain pipe sizes.

The proper permits

FDOT committed to having most, but not all, of the identified pond sites available for the project. The request for proposals (RFP) indicated that the selected contractor was free to use those pond sites either in their entirety or in part. FDOT continued acquiring pond sites throughout the proposal, selection and early design phases of the project. This required flexibility during the drainage design as some of the easements and takings were modified during the acquisition process. It should be noted that FDOT’s right-of-way acquisition for storm-water ponds occurred during the peak housing boom in one of the most rapidly developing areas of the country. Very few parcels of land were available, and what was available was extremely expensive. As a result, some of the ponds were located in wetland areas, others in wetland conservation areas and some were joint-use facilities with other public roadway projects or with private developments.

The project faced numerous environmental challenges throughout the design and permitting phases. Critical issues such as a wetland-dominated project corridor, limited mitigation options, threatened and endangered species and coordination with multiple state and federal regulatory agencies were in turn heightened by the project’s aggressive construction schedule. In a design-build project, challenges such as these translate directly to risk. With increased risk there is the potential for substantially increased costs. To manage this risk, HDR formulated a unique approach to permitting this fast-tracked design-build project. On a typical design-bid-build project, there would be an 18- to 24-month schedule for design plans and permitting, followed by a two- to three-year construction period. The aggressive project schedule for I-75 required obtaining environmental resource permits (ERPs) for the first three segments of the project in eight months as opposed to a normal permitting schedule of nine to 12 months. Meeting this permit schedule required an equally aggressive design and plans production effort, particularly with the project drainage design. The project involves 24 storm-water ponds, including wet and dry detention facilities, along with new and widened bridges, cross drains, storm drains and conveyance ditches.

The joint-venture contractor, ACCI/API, has 1,150 days to complete the project. Construction started Oct. 28, 2007. This period includes completion of design plans and obtaining environmental permits along with completion of roadway construction. The contractor can achieve incentives of up to $15 million for finishing early, or face a $100,000 penalty for each day that it is late.

The substantial monetary disincentive resulting from a late project finish meant that construction had to start at the earliest possible time. Intensive negotiations with regulatory agency staff were initiated before the project was awarded to identify permitting strategies that would ensure the joint venture’s ability to complete the construction within the 1,150-day timeframe.

Environmental and drainage task leaders met with agency staff to identify work elements that could be conducted without state and federal permits and those work elements that would require a minimal permitting effort. The product of these negotiations was the ability to begin major work elements such as milling and resurfacing without state or federal permits. Fast-tracked permitting efforts allowed demolition and pile installation at key bridge sites shortly after the joint venture received notice-to-proceed from FDOT. These efforts enabled the joint venture to mobilize early and get started on construction.

During the RFP process, ACCI/API and the competing contractors expressed concerns with the projected schedule, particularly since it included obtaining environmental permits for the entire project. FDOT committed to obtaining permits for the southernmost segment of the project in Collier County (Segment A) in time for the project to begin construction. The winning contractor would have the option of building that segment of the project as originally designed and permitted, with the new lanes sloping to the outside, or modifying the permit to build something different.

This would allow the contractor to begin work on part of the project while awaiting receipt of permits for subsequent segments. FDOT submitted the application for the ERP for the Segment A based on the original design in August 2006 and received the permit in August 2007. During the permitting process, consultants were provided copies of the South Florida Water Management District (SFWMD) requests for information and allowed to attend (but not participate in) meetings between FDOT, the original design consultant and SFWMD.

Intensive negotiations with regulatory agency staff were initiated before the project was awarded to identify permitting strategies. This, along with monitoring FDOT’s pursuit of the permit for the southern section of the project, paved the way for developing a comprehensive approach to designing the drainage and obtaining permits. This approach was taken to ensure the joint venture’s ability to complete construction within the 1,150-day time frame. The following strategies contributed to this effort:

  • Designing, permitting and constructing the project in four segments with similar limits as the original design. This included obtaining a modification of the FDOT-obtained permit for Segment A. Permitting the project in segments minimized the risk that the entire project could be held up due to issues in one particular segment, allowing the joint venture to begin the actual widening construction work as soon as possible;
  • Utilizing multiple design teams, including teams from other offices, to work on the project segments simultaneously;
  • Using a uniform format for calculations, drainage design and environmental documentation, including summary tables with information that SFWMD staff specifically looks for when reviewing permit applications;
  • Continuous coordination with staff of the permitting agencies throughout the design and permitting process;
  • Keeping FDOT and the contractor advised of permitting issues with the potential to delay receipt of permits and impact the project schedule;
  • Understanding and using SFWMD’s permitting structure to get the contractor started on activities for which no permits are required. For example, the contractor was able to start milling, resurfacing and building up the outside shoulder in anticipation of traffic shifts during lane construction before the ERP was obtained;
  • Obtaining general permits (with less stringent documentation requirements and review times) for additional early construction activities such as partial bridge demolition and pile driving in upland (non-wetland) areas, and construction of accident investigation sites at interchange exit ramps;
  • Committing to a 14-day turnaround to address SFWMD requests for information on permit applications; and
  • Coordinating with the contractor and drainage subcontractor throughout the proposal and plans production phases on construction methods and materials to minimize the number of questions that come up during construction.

Going with the flow

Design of the drainage and storm-water management for I-75 posed several challenges. Physically, the project area is characterized by flat terrain, high water table elevations and shallow rock layers. Although the new lanes sloping toward the median facilitate collection of runoff from the new pavement, the majority of the storm-water ponds are located outside the limited-access right-of-way, requiring storm-water to be piped under existing travel lanes. Since four lanes of traffic must be maintained, jacking and boring is the preferred method of getting pipes under the roadway. Roadway runoff also has to be conveyed considerable distances by ditches and storm drains to get to storm-water ponds. Several of the storm-water ponds are located entirely or partially in wetlands, which increases the amount of required wetland mitigation.

The most significant challenge with storm-water management design and permitting dealt with differences in design parameter assumptions made during the identification and selection of pond sites versus design parameters required by SFWMD to get permits. In design of wet detention ponds, the required treatment and attenuation water volumes are “stacked” above the pond control elevation, which is normally taken as the wet season high water table. For some of the ponds, the permitted pond-control elevations were higher than what was originally assumed, resulting in the lower storage volume capabilities in those ponds. SFWMD also limited the ponds’ discharge from their respective control structures to approximately 1 cu ft per second per acre based on the size of the contributing pre-developed drainage area. Permitted pond discharges were significantly less than originally assumed, again resulting in lower storage volume capabilities in the ponds.

Fortunately, these differences surfaced during FDOT’s pursuit of the permit for the original design of Segment A, so HDR was able to incorporate the revised design parameters in the design of the ponds for the remaining segments as well as in the modifications to Segment A. By coordinating closely with the SFWMD, the design and permitting remained on schedule.

Dripping in wetland challenges

As construction began on the early work elements, environmental scientists were concurrently working to complete data collection for the environmentally sensitive portions of the project. Where wetland impacts occurred, a majority were remnant wetland areas that remained after the original construction of I-75 in the 1970s. To satisfy permitting criteria for SFWMD and the U.S. Army Corps of Engineers (USACE), approximately 30 miles of interstate right-of-way—including storm-water pond sites—required wetland jurisdictional determinations and subsequent reviews by both regulatory agencies. This task alone required jurisdictional and seasonal high-water determinations, functional assessments and plant community descriptions for approximately 200 wetland areas. In addition to the standard jurisdictional determinations and associated tasks, the decision by USACE to institute the new Rapanos criteria (United States v. Rapanos) toward the end of the permitting phase threatened to impact the project schedule.

From the onset of the project, the joint venture was committed to minimizing impacts to wetlands. Environmental scientists coordinated with project roadway and drainage engineers throughout the design phase to identify major wetland areas. Where avoidance was not feasible, efforts were undertaken to minimize impacts. In spite of the emphasis to avoid and minimize impacts, the project resulted in permanent impacts to approximately 105 acres of wetlands.

SFWMD and USACE require wetland mitigation to compensate for permanent wetland impacts. Traditional mitigation is accomplished by creating new wetlands, restoring areas that were formerly wetlands, enhancing existing wetlands or wetland preservation. All of these options require land acquisition which, due to the extreme costs involved, was not an option. It was decided to utilize regional wetland mitigation banks to provide the required mitigation.

Both SFWMD and USACE rely on functional assessment methodologies as tools to determine the quality of impacted wetlands and satisfactory mitigation. The two methodologies used for this project included the Wetland Rapid Assessment Procedure (WRAP) and the Uniform Wetland Assessment Method (UMAM). The WRAP and UMAM assessments enabled determination of the amount of mitigation credits needed to offset adverse impacts to wetlands. HDR acted as a liaison between the regulatory agencies and the mitigation banks to negotiate the number of mitigation credits required.

The presence of threatened and endangered wildlife species within the project limits posed additional challenges. A sampling of observed and potential listed species included the Florida panther, the bald eagle, the Big Cypress fox squirrel, the wood stork, the eastern indigo snake, the gopher tortoise, the Florida sandhill crane and the Florida black bear. Working with the Florida Fish and Wildlife Conservation Commission and the U.S. Fish and Wildlife Service to address this issue, the project team analyzed areas of panther and wood stork habitat to quantify future habitat loss. Mitigation for these impacts was provided through the purchase of habitat credits from mitigation banks that specialize in preserving species-specific habitat. For the remaining species, the project team produced a comprehensive wildlife management plan to ensure protection of listed species during construction. The team designed species-specific information pamphlets to be carried by construction personnel and conducted pre-construction information sessions to convey the importance of species protection.

The I-75 design-build-finance project is now under construction. At the time of the writing of this article, SFWMD ERPs and USACE permits have been received for three of the four project segments, with the ERP and USACE permits for the fourth segment anticipated in June.

About the Author

Stewart is a senior drainage engineer in HDR’s Tampa office. He can be reached at [email protected]<br />
Messenkopf is a senior environmental scientist in HDR’s Tampa Office. He can be reached at [email protected]

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