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I-85 Interchange Design-Build Project Using Prefabricated Bridge Elements in West Point, GA
Project Overview and Lessons Learned
This project, which includes a new interchange on Interstate 85 in Troup County in west central Georgia, is the State's first to use prefabricated substructure elements and D-B contracting. The innovative contract also required the D-B contractor to propose state-of-the-art methods to achieve specified performance goals. Construction time was reduced, impact to traffic was minimized, and worker and work zone safety was increased with the use of prefabricated columns and pier caps, an innovative approach that had never been used in Georgia to construct a bridge substructure. Further project enhancements were realized with real-time speed band monitoring and D-B contracting procedures recently approved for use by the Georgia General Assembly.
The bridge was planned to provide access to I-85 for a Kia Motors manufacturing plant and training facility being built on an adjacent tract of land, which will generate thousands of daily auto and truck trips. This project, the cornerstone of a larger economic development plan for west central Georgia, is critical to implementing safe, convenient, and efficient access to the region.
Hfl Performance Goals
Safety, construction congestion, quality, and user satisfaction data were collected before, during, or after construction to demonstrate that innovations can be deployed while simultaneously meeting the HfL performance goals in these areas.
The costs and benefits of this innovative project approach were compared with those of a project of similar size and scope delivered using a more traditional approach. GDOT supplied most of the cost figures for the as-built project. The cost assumptions for the traditional approach were determined from discussions with GDOT employees and national literature.
The economic analysis revealed that GDOT's approach realized a cost savings of about $1.98 million or 45 percent of the interchange cost if built with conventional construction practices1. A significant amount of the cost savings was from not building temporary pavement to handle detour traffic associated with conventional construction.
Overall, the bridge construction went smoothly, resulting in a quality project completed ahead of schedule and in nearly half the time needed for conventional construction methods.
1. These costs were estimated in consultation with GDOT engineers and from publicly available traffic data for Georgia highways.
Working under a D–B delivery method brought about a GDOT paradigm shift in communication from the old way of sculpting a project with separate departments working independently to working as a team and conducting regular meetings (often onsite) among the D–B project managers, construction project managers, and D–B contractor. The focus had to change from solely a design perspective to ownership of each design element and an emphasis on overall project delivery. It was also important to assign well-defined roles and responsibilities to GDOT staff to facilitate efficient project administration. The bottom line was teamwork because the D–B process requires staff continuity from preconstruction to construction, and teamwork was the key to fostering acceptance of the new D–B concept. Moreover, utility coordination was much more efficient with the D–B method because of constant communication with all stakeholders.
Because this project plays a major role in the regional economic development plan, it involved the interests of many parties, which most certainly increased the complexity level. The Georgia Department of Economic Development helped simplify things by seeing to it that Kia Motors' needs were met as much as possible. A lesson for future D–B projects is that heavy third–party involvement should be kept to a minimum.
From the contractor's point of view, one issue to consider in future bridge projects is starting the approval process for prefabricated bridge elements well in advance of the scheduled delivery dates to allow the DOT extra time to review and approve "shop drawings" for the new components. At the beginning of the project, the contractor experienced delay in getting approval because it was the first time these elements were used in a GDOT project. The delay was more than compensated in the schedule by time saved in the erection process. Nevertheless, early approval of prefabricated bridge elements (or any new technology) on future projects will help to ensure the construction schedule stays on track. From GDOT's perspective, prefabricated elements, while used with success in this project's rural setting, may be best applied in urban locations in the future. The specified 0.25 in tolerance for precast elements was able to be achieved and provided for satisfactory field assembly of the elements.
Using RCC was good for quick installation of shoulders and was demonstrated on this project to be a timesaver. However, a smooth surface profile was difficult to obtain with RCC. As constructed, it was suitable for shoulder–type work, but not necessarily for high–speed traffic lanes. RCC had the added benefit of a slightly different color than the adjacent travel lanes, which increased the delineation between the shoulders and mainline pavement. GDOT gained experience with RCC through this project and learned that RCC will be good for specific applications on future projects.
Close observation of traffic volume via real–time speed band monitoring through the work zone led to changes in the original lane closure plan from traditional nonpeak hours in the evenings, nights, and weekends to a new schedule from 8 p.m. Sunday to Tuesday evening. The speed band monitoring allowed GDOT and the contractor to see in real time an increase in traffic volume during Sunday commuting, so the contractor moved the lane closures to later in the evening to ensure less disruption to work zone traffic.
Lessons learned in the wording of customer survey questions can be applied to large projects encompassing multiple construction activities or separate active projects in close proximity. The lesson is to be specific in asking about the level of satisfaction on the approach used to construct the project. It was determined during this project that the public associated the new Kia Motors plant construction with the I–85 interchange project and scored the 25 percent project completion survey questionnaire poorly on traffic impact, even though the interchange construction had not involved any lane closures by that point in the schedule. This had a negative effect on the survey results. After the survey question was reworded to specifically reference the I–85 interchange, later surveys generated more representative—and favorable—responses. Moreover, survey results should target frequent travelers through the work zone to get a true assessment of the construction's impact on travelers. Furthermore, the survey revealed that those respondents who were well informed by PR campaign of the project specifics were much more satisfied with the project results. The responses gave the project team a good idea of who the real stakeholders were in this project.
This project achieved a high level of quality and was brought to completion quickly and safely as a direct result of innovative contracting and construction methods. The success of this project will serve as a vehicle for GDOT to advance the integration of D–B contracting and the use of prefabricated substructure elements on future bridge projects. The innovations were validated as a result of the many experiences gained through this project and have been shown to be valuable tools for future GDOT projects.
This page last modified on 04/04/11