ABSTRACT

Programs that protect ground-water supplies from potential contamination and which identify and define alternate sources of ground water are known as Wellhead Protection Programs. An important requirement in developing a viable program is a thorough understanding of an area's geology. Since the coastal plain of eastern Alabama is structurally uncomplicated, the occurrence of ground water, its direction and rate of flow, its production potential, and to some extent its quality, is primarily controlled by the stratigraphy and lithologic properties of the sediments.

Geological assessments conducted for wellhead protection programs in southeastern Alabama have led to some unsuspected results. In some areas, high topographic relief results in the nearby surface exposure of otherwise moderately to deeply buried aquifers. The high susceptibility of these aquifers to nearby surface contamination is critical in developing effective wellhead protection programs. Of even greater concern is disorder in the shallow subsurface stratigraphy resulting from inadequate drillers' descriptions of penetrated lithologies, the nonrecognition of facies change along strike and dip, and the lack of regional paleoenvironmental interpretations. This has led to the misidentification of aquifer and confining units resulting in confusion in the definition, delineation, and correlation of hydrologic and geologic data.

Case examples from southeastern Alabama demonstrate how detailed sedimentological analysis and local and regional interpretation of stratigraphy is essential in the preparation of effective wellhead protection programs and in the identification of alternate sources of ground water.