FLOW INVESTIGATION FOR LANDFILL LEACHATE (FILL)

A two-dimensional un-steady-state moisture flow model has been develop ed in order to describe the leachate flow process in a landfill. The u nsteady variation of leachate mound head has also been considered in t he saturated zone of the landfill to compute the time-varying leachate flow rates in both the lateral and vertical directions. The contribut ion of precipitation to the landfill leachate has been investigated by computing evapotranspiration and surface runoff due to side slope. Th e model was used to simulate the leachate flow rates in section 6/7 of Fresh Kills landfill, situated in Staten Island, New York. A comparis on of the results was made with the Hydrologic Evaluation of Landfill Performance (HELP) model, which is based on a quasi-two-dimensional ap proach. Comparisons were also made with the results obtained from prev ious studies using the Environmental Protection Agency (EPA) water-bal ance model and investigating the real field condition. An underestimat e of the surface runoff was observed in the case of the results obtain ed by the HELP model. The simulated leachate flow rates by the new mod el were found to be less than those obtained by other methods. The eff ects of the variation of the boundary condition, which depends on surf ace runoff and evapotranspiration, were examined to arrive at the bett er representation of the two-dimensional unsteady mechanism of leachat e flow process in a landfill.