HYDROLOGIC MAPPING OF THE UNCONFINED AQUIFER IN SUSSEX COUNTY, DE, USA

Rapid growth in Sussex County, DE, has increased concern over the protection of the vulnerable unconfined aquifer. Maps of unconfined aquifer thickness and transmissivity (T) are being re-created utilizing a geographic information system (GIS) to provide state officials with modern digital products of high spatial resolution. Resultant thickness and T maps are being produced in grids of 30 and 90-m horizontal resolution, respectively, using lithologic data from thousands of well records countywide. To provide more complete data coverage, 51 test borings (50-220ft deep) have been drilled and logged geophysically in areas of poor data availability. The resulting maps will better aid management in decision making regarding permitting for wells, septic systems, wastewater disposal, and construction and in the delineation of wellhead protection areas for public supply wells.