HYDROGEOLOGY OF FORT MORGAN PENINSULA, ALABAMA: METHODS OF GROUNDWATER MODELING AND CAPTURE ZONE ASSESSMENT

Fort Morgan Peninsula, measuring approximately 25 kilometers long and two to five kilometers wide, is an attached portion of a dynamic barrier complex in the northern Gulf of Mexico that is surrounded by Bon Secour Bay and Mobile Bay to the north and the Gulf of Mexico to the south. The hydrostratigraphy of the study area is characterized by three aquifer zones: Aquifer Zone A1, which is represented by a Pleistocene-Holocene interval, Aquifer Zone A2, which is represented by an interval of Pliocene-shallow Miocene silicilastics, and Aquifer Zone A3, which is represented by deep Miocene siliciclastic sediments that overlie the confining Pensacola Clay. By utilizing existing groundwater well data and previously calculated regional aquifer parameters, a conceptual model is being constructed to establish steady-state conditions of the groundwater system of Fort Morgan Peninsula. In subsequent phases of the project, test wells will be constructed in various locations on the peninsula to determine local hydrostratigraphic variations and to perform pumping and/or slug tests that will determine more resolute hydraulic conductivity values. Data calculated from these test wells, along with previously recorded data, will then be used to construct a detailed, calibrated numerical groundwater model of Fort Morgan Peninsula using USGS MODFLOW code. Additionally, 50-year capture zones will be delineated for existing groundwater wells, and this information will be used to construct a GIS dataset that will be used to compare the zones to previously determined capture zone data, where available.