HYDROGEOLOGICAL STUDIES ON THE MECHANICAL-BEHAVIOR OF LANDFILL GASES AND LEACHATE OF THE NANJIDO LANDFILL IN SEOUL, KOREA

The Nanjido Landfill is the largest uncontrolled landfill in Korea and it causes various kinds of environmental problems. Landfill gases and leachate are recognized as the most serious environmental problems as sociated with the landfill. This study employs a series of numerical m odels and uses test data to interpret the distribution and flow of lan dfill gases and leachate. Leachate seepage appears about 40-60 m highe r than the estimated basal groundwater table. Thus, seepage data indic ate that perched or floating leachate layers are formed in the unsatur ated zone of the landfill. The leachate production rate is estimated u sing infiltration test data and a model for unsaturated groundwater no w. Geochemical data indicate that the landfill leachate degrades the b asal groundwater quality along the downgradient zone. The environmenta l impact of the leachate on river water is estimated.