GEOLOGICAL CHARACTERIZATION OF A HIGHLY URBANIZED AREA IN SOUTHEASTERN FLORIDA TO INFORM THE DESIGN OF A COASTAL SUBSURFACE MONITORING NETWORK TO ASSESS INFRASTRUCTURE RISK

Coastal cities in southeastern Florida have subsurface infrastructure that might be at risk from sea-level rise, saltwater intrusion, shallow water tables, frequent flooding caused by intense precipitation, storm surge, and high tide flooding events (e.g., King tides). To address these challenges, the U.S. Congress appropriated funds for a pilot project designed to develop a subsurface monitoring network in Broward and Miami-Dade counties. The program goal is to create a long-term vadose zone and groundwater monitoring network within a densely urbanized area that is capable of quantifying the hydrologic (e.g., salt water intrusion, water table dynamics) and environmental (e.g., corrosion potential) conditions at the scale needed to evaluate existing and future risks to building foundations, buried utilities, and other subsurface infrastructure.

During the preliminary design phase, a Monitoring Technology Advisory Panel was convened and consulted. The Panel emphasized the importance of collecting existing geological information (e.g., especially geotechnical lithologic data on the shallow subsurface, and other lithologic and geophysical data) to inform the selection of monitoring site locations, as well as the design and installation of instrumentation. These data are currently being assembled from federal, state, and local agencies including the Florida Department of Transportation and by request through relevant building departments. Preliminary evaluation of these data indicate the shallow subsurface (<10 m) is dominated by the Miami Limestone. However, the lithostratigraphy is locally complex and may consist of calcareous sand, peat, or fill. For example, the barrier islands generally appear to consist of a sand layer of variable thickness overlying limestone, and some thin peat layers on their mainland sides. The project will compile and synthesize the available data.

This presentation will provide an overview and preliminary analysis of existing geotechnical data in the context of coastal subsurface infrastructure.