This study is an evaluation of Post Closure Care (PCC) duration of landfills using performance based methodology. The post closure care phase begins once the landfill is closed. As required by the Resource Conservation Recovery Act (RCRA) Subtitle D, PCC duration for municipal solid waste landfills is 30 years. During the PCC period, the landfill operator/owner is required to conduct monitoring for leachate, landfill gas, and ground-water and maintain the integrity of the cap so that the landfill does not impose a threat to surrounding human health and environment (HH&E). The duration of PCC can be reduced by the director of an approved State if an owner/operator of a landfill demonstrates that the landfill exhibits no threat to the surrounding HH&E or can be increased if the director of the approved State determines that an increased PCC period is required for the protection of HH&E. RCRA provides flexibility in optimizing PCC duration of landfills, although it does not identify the criteria/methodology which can be used in demonstrating the status of a landfill from the point of PCC. Researchers worldwide recognize that the threat imposed by a landfill after closure depends on the extent of degradation occurring inside the landfill. The increased functional stability of landfills reduces its risk to the surrounding HH&E. However, there is a wide range of opinions in defining functional stability of a landfill. The present thesis applies performance based methodology, developed by Environmental Research and Education Foundation (EREF), to making a decision on the PCC of landfills. Performance based methodology is a modular approach encompassing all four PCC components of landfills (Leachate, gas, groundwater and cap maintenance). This methodology was applied to Alachua County Southwest Landfill (ACSWLF) in Alachua County, Florida. Each module was analyzed individually and recommendations on the PCC monitoring at the landfill site were provided.