This digital product contains gridded estimates of the elevation of the base of the unconfined portion of the Columbia aquifer for Sussex County, Delaware. Mapping was supported by the Delaware Department of Natural Resources and Environmental Control and the Delaware Geological Survey. These grids were produced with the methods described in Andres and Klingbeil (2006). Additional analyses of the hydrogeologic framework and grids are also contained in that report. Briefly, the method to determine the elevation of the base of the aquifer includes assessing the elevation of subsurface materials in descriptive and geophysical logs and using computer-based interpolation to estimate elevation across the study area. Separate grids were determined for eastern and western Sussex County and were merged and smoothed to minimize edge effects. The elevation grids has 30-m horizontal and 1-ft vertical resolutions. REFERENCES CITED Andres, A. S., and Klingbeil, A. D., 2006, Thickness and transmissivity of the unconfined aquifer, eastern Sussex County, Delaware: Delaware Geological Survey Report of Investigations No. 70, 19 p., 1 plate.

This digital product contains gridded estimates of the elevation of the base of the unconfined portion of the Columbia aquifer for Sussex County, Delaware. Mapping was supported by the Delaware Department of Natural Resources and Environmental Control and the Delaware Geological Survey. These grids were produced with the methods described in Andres and Klingbeil (2006). Additional analyses of the hydrogeologic framework and grids are also contained in that report. Briefly, the method to determine the elevation of the base of the aquifer includes assessing the elevation of subsurface materials in descriptive and geophysical logs and using computer-based interpolation to estimate elevation across the study area. Separate grids were determined for eastern and western Sussex County and were merged and smoothed to minimize edge effects. The elevation grids has 30-m horizontal and 1-ft vertical resolutions. REFERENCES CITED Andres, A. S., and Klingbeil, A. D., 2006, Thickness and transmissivity of the unconfined aquifer, eastern Sussex County, Delaware: Delaware Geological Survey Report of Investigations No. 70, 19 p., 1 plate.