ABSTRACT
Sinkholes were commonly used for convenient waste disposal in the past, and many of these sites are now Superfund sites. Since sinkholes offer landfill leachate direct access to solution-enlarged subterranean conduits, there is a high risk of off-site contamination from these sites, and their remediation should be a priority. Complex karst ground water and surface water flow patterns make the detection and treatment of off-site contamination very difficult. Remedial options for landfills are limited and costly, but the suitability of closure-in-place, which entails leaving the waste in place permanently, should be questioned. Lemon Lane Landfill is a four hectare, 500,000 cubic yard hazardous waste landfill on the National Priorities List. It was built in a 10-meter deep compound sinkhole situated in the karst terrain of the Mitchell Plain in southern Indiana, and is currently a candidate for closure-in-place. The complex hydrogeology is described to illustrate the complex flow regimes that can accompany landfills built on sinkholes.
