Purpose and scope: This reports presents the results of a 2-year investigation by the U.S. Geological Survey, in cooperation with the city of St. Petersburg, to evaluate geohydrologic conditions at a landfill in a coastal area. The report defines and describes the geologic and geohydrologic units underlying the landfill, and examines the controls these units exert on the flow and quality of surface and ground water in the area. The study increases the understanding of the geohydrologic aspects of landfill operations and will be helpful in the selection of future landfill sites in similar coastal areas.