Abstract: The Pinellas County landfill site is on a flat, coastal area characterized by a nearsurface water table. Part of the site is subject to tidal flooding; altitudes within the study area range from 8 to 12 feet above sea level. Three geohydrologic units underlie the landfill site. In descending order, these are: a surficial aquifer about 19 feet thick composed of sand and shell, a confining bed about 35 feet thick composed of marl and clay, and the Floridan aquifer composed of limestone. Landfill operations have not altered surface-water quality. Although leachate movement downward into the Floridan _aquifer is not indicated, vertical movement through the confining bed is about 0.005 foot per year. The rate of lateral movement of ground-water away from the site is about 1.2 feet per year; . however, the rate of movement along the boundary from the oldest section of the landfill through the surficial aquifer is about 20 feet per year. Peaks in concentration of selected chemical parameters and flow-rate analysis of water from trenches indicate the possibility of intermittent release of leachate from the landfill.