Clayey Barrier Systems for Waste Disposal Facilities

Abstract

Basic concepts. Introduction. Overview of barrier systems. Transport mechanisms and governing equations. Complicating factors. Modeling the finite mass of contaminant. Modeling a thin permeable layer as a boundary condition. Hand solutions so some simple problems. Summary. Design considerations. Introduction. Impact assessment. Waste and leachate composition. Leachate mounding and collection. Leakage through liners. Leak detection systems. Landfill capping and the control of infiltration. Choic of barrier system and service life considerations. Geotechnical considerations. Summary. Clayey barriers: compaction, hydraulic conductivity and clay mineralogy. Introduction. Methods of assessing hydraulic conductivity. Compaction-permeability relationships. Clay mineralogy. Clay colloid chemistry. Clay-leachate compatibility by measurement of hydraulic conductivity. Introduction. Soil- MSW leachate compatibility. Compatibility of clays with liquid hydrocarbon permeants. Summary and conclusions. Flow modeling. Introduction. One-dimensional flow models. Analysis of two-and three-dimensional flow. Finite difference approximation. Application of the finite element method to the analysis of plane flow. Boundary element methods. Chemical transfer by diffusion. Introduction. Free solution diffusion (Do). Diffusion through soil. Steady-state diffusion. Transient diffusion. Use of laboratory and field profiles to measure diffusion coefficient De. Diffusion during hydraulic conductivity testing for clay - leachate compatibility. Summary and conclusions. Contaminant transport modeling.Introduction. Analytical solutions. Application of Laplace transforms to develop a finite layer solution for a single layer. Contaminant transport into a single layer considering a landfill of finite mass and an underlying aquifer. Finite layer analysis. Contaminant migration in a regularly fractured medium. Determination of diffusion and distribution coefficients. Introduction. Obtaining diffusion and partitioning/distribution coefficients: basic concepts. Example tests for obtaining diffusion and distribution coefficients for inorganic contaminants. Dispersion at low velocities in clayey soils. Effective porosity. Distribution coefficients and nonlinearity. Effect of leachate composition, interaction and temperature. Diffusion and sorption of organic contaminants. Use of field profiles to estimate diffusion coefficients. Summary and conclusions. Field studies of diffusion and hydraulic conductivity. Introduction. Examples of long-term field diffusion. Examples of short-term diffusion. Hydraulic conductivity of contaminated clay liners. Contaminant migration in intact porous media: analysis and design considerations. Introduction. Mass of contaminant, the ref erence height of leachate, Hr, and the equivalent height of leachate, Hf. Development of a contaminant plume. Effect of base velocity. Effect of horizonta