Potential of soil and groundwater contamination due to mine subsidence under a landfill

Results of a study to evaluate the effects of mine subsidence on the integrity of a clay liner and potential for soil and groundwater contamination below a previously mined landfill are presented The results show that for the existing site conditions, surface subsidence features are expected to be similar to subsidence troughs and the site has minimal potential of being contaminated due to deep-sited subsidence in the mine. To further reduce potential for soil and groundwater contamination at the site, it is recommended that the minimum thickness of the compacted clay liner be 4 ft instead of the 2 to 3 ft generally used. Discussion is presented indicating that further study is required to develop an adequate design procedure to determine the effects of nonuniform settlement of foundation soils or refuse on the hydraulic conductivity of landfill clay barriers.