The LaSalle Street Drainage Improvements Design-Build Case Study

Flooding in the historic San Marco neighborhood of Jacksonville, Florida, often occurs during relatively minor storm events that coincide with high tides due to the minimal head difference between street catch basin inlets and the water elevation of the St. Johns River. The City of Jacksonville's LaSalle Street Drainage Improvements project aimed to address this issue by repairing, replacing, and installing a new primary stormwater collection system (6,197 linear feet), a pump station with a capacity of 112 cubic feet per second (cfs), and a 650-ft force main discharge into the river. The project's primary goal was to reduce flooding in the LaSalle Street Basin, eliminate tidal influences on the stormwater system, and ensure floodwaters remain below the finished floor elevations of existing buildings during a 50-year, 24-h storm event. Additionally, the system was designed to handle mean-year, 24-h, and 5-year, 24-h storm events, while maintaining acceptable flood depths and recovery times. The pump station's design also accounted for resilience during a 500-year, 24-h storm event, incorporating value engineering to protect equipment elevations. This Design-Build project utilized innovative construction techniques, such as secant piles, for the wet well construction in a space-constrained residential area. Moreover, construction was completed, while the existing storm sewer system remained operational, navigating a historically significant neighborhood with a highly congested right-of-way. This presentation will showcase the achievements and challenges faced by the design-build team during both the design and construction phases of the project.