Box culverts are fairly small structures, but their replacement can incur major costs and travel delays. This was the Florida Department of Transportation’s concern for a box culvert replacement along US 98, a 150-mile two-lane roadway that extends along Florida’s Gulf Coast.
This concrete box culvert located between the Mexico Beach and Port St. Joe communities had experienced significant deterioration due to saltwater exposure. It was at risk of falling into an unusable condition and causing that portion of the roadway to collapse. Repairing this box culvert before failure was a priority, but it required some out-of-the-box thinking to overcome obstacles.
An Innovative Solution
A complete road closure would have burdened travelers with a 59-mile detour or a costly on-site diversion. To avoid either of these undesirable outcomes, the project team resolved to repair the box culvert in mere days while maintaining a single travel lane.
The solution: utilize precast, prestressed concrete deck panels typically used in bridge construction. This innovative approach allowed the team to always maintain one lane of traffic. Half of the box culvert was exposed, and the panels placed were supported on the culvert walls. The structure was then backfilled and repaved. The panels would provide sufficient support, negating the need for a full replacement.
Extensive coordination took place between the design team and the construction engineering inspection team for contingency planning for unforeseen conditions.
A Short-Term Measure
While this type of repair doesn’t offer a long-term solution, it serves as a stop-gap measure for FDOT. The goal is a full replacement once a more viable detour becomes available within the next 10 years.
Calculating Cost Savings
Traditional box culvert replacements require approximately nine months of construction and cost an estimated $1.2 million. This repair project provided significant cost and time savings. Installing precast structural slabs into the existing box culvert totaled $431,500 in hard construction costs, and construction was completed within four days.
Additional “soft” savings can be calculated in terms of reduced carbon emissions, user delays, vehicle operations, and crash costs.
The design team’s innovative solution provided a safe work zone with minimal disruption to traffic. This installation method allowed major construction activities to be completed in only four days. As a result of the project, the culvert is no longer in danger, and larger emergency actions are not required. This project is a net win for FDOT and travelers alike.
