Alternative Use of MULTIMED Model for Subtitle D Landfill Applications

Abstract

To justify a performance-based landfill design or suspension of ground-water monitoring requirements under the federal criteria for municipal solid waste landfills, the characteristics, generation, and migration of landfill leachate must be assessed and/or predicted. In this study, alternative use of the Multimedia Exposure Assessment Model (MULTIMED) model for Subtitle D landfill applications is investigated. The primary objective is to develop a useable transient source term alternative to the standard steady-state assumption. To accomplish this objective, a hypothetical scenario is developed, using values for model input from statistical databases and other references. The hypothetical scenario is then used to conduct steady-state, transient, and unsaturated zone analyses. An alternate source term boundary condition, consisting of a combination of a pulse source and exponentially decreasing source, was found to be a reasonable alternative to the steady-state source term assumption. A supplementary finding was that consideration of the effects of the unsaturated zone can result in significant attenuation of leachate migration, particularly for those cases involving transport decay, and can be used to help evaluate ground-water monitoring requirements for a solid waste landfill.