2-6 Designing the Coastal Subsurface Monitoring System for Southeast Florida

Session: Coastal Hydrogeology in an Age of Rising Seas

Presenting Author:

Authors:

Abstract:

Southeast Florida is a low-lying coastal area underlain primarily by limestone of the exceptionally transmissive Biscayne Aquifer — the region's principal water supply source.  Saltwater intrusion is a major concern, and the location of the toe of the regional saltwater intrusion wedge, which usually lies several kilometers inland, is well monitored for water supply protection. However the configuration of the saltwater wedge near the highly developed shoreline is largely unknown. Near-shore groundwater is subject to tidal fluctuation and groundwater inundation is becoming more common, particularly during King tide season. Since the collapse of the Surfside, Florida, Champlain condominium tower in 2021, there has been increased interest in understanding near-shore groundwater and its possible interactions with infrastructure.

A $10M Coastal Subsurface Monitoring project was funded to help to fill the data gaps and advance understanding of the near-shore groundwater system and the corrosivity of the subsurface. The system design currently calls for as many as 7 transects each consisting of up to 10 monitoring stations within 1 kilometer of the shoreline and on adjacent barrier islands. Each station will have 5 boreholes. A shallow 3-m hole will be constructed as a conventional monitoring well designed to monitor the water table position and will be fitted with a conductivity, depth, and  temperature logger. The other 4 holes will be 30 m deep. Soil and limestone core will be collected from one of these holes. Three of these holes will be primarily dedicated to corrosion measurements including Wenner-array Electrical Resistivity, Linear Polarization Resistance (LPR), and Open-Circut Potential (OCP). One of these holes will contain silver/silver chloride reference electrodes, one will contain metallic working electrodes, and the third will leverage stainless steel screens associated with intakes on a multichannel tubing multilevel groundwater sampling well as counter electrodes. An access port for an Electromagnetic Induction (EMI) logging tool will be constructed in the last hole.

Design challenges include balancing a desire for real-time public data availability (useful for impending storm impact prediction) and research/practical data value against system complexity and cost.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6370

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