Analysis of flow behavior in a landfill with cover soil of low hydraulic conductivity

This paper presents the results of field tests of hydrologic parameters in a landfill and the cy of the pumping method to reduce leachate levels in th e landfill. The field hydraulic conductivity and storativity of waste and b uried cover soils in the landfill are measured by pumping and slug tests. T he hydrologic condition inside the landfill is first calibrated using the d rawdown-time curve obtained from the pumping test, and the flow behavior of leachate during pumping in the landfill, when various layers of waste and buried cover soil exist, is analyzed through three-dimensional numerical si mulation of flow. The results of the field investigation show that the buri ed cover soil of low hydraulic conductivity forms an impermeable layer prev enting the downward flow of leachate and upward flow of landfill gas. The h ydraulic conductivities of the pumping test and slug tests were quite close on the same order of magnitude. It was also possible to match the drawdown -time data of the field tests with those of the model using input data clos e to the hydrologic property obtained from the field tests. The numerical f low analysis showed that pumping was possible up to 120 tons/day for a sing le well without a drain, while the pumping rate could be increased to 300 t ons/day for the same well with the drain. From the vertical section of the flow vector with a horizontal drain, the barrier role of buried cover soil is identified, which was proposed by examining thp water contents of the di sposed cover soil and waste in the field.