Date of Award

Winter 2006

Project Type

Thesis

Program or Major

Earth Sciences - Geochemical Systems

Degree Name

Master of Science

First Advisor

Kevin H Gardner

Abstract

As of now, the beneficial-use (recycling) of secondary materials (e.g. coal-fly ash) in highway construction is limited. In 1998 and 1999, the Association of State and Territorial Solid Waste Management Officials (ASTSWMO) conducted a Beneficial-Use Survey to determine the issues that states face when evaluating potential beneficial-use applications for recycled/secondary materials. The report identified the largest obstacle as the lack of good information for use in evaluating potential risks to human health and the environment (i.e. soil and groundwater contamination) from beneficial-use applications. The absence of such data has resulted in reluctance in the beneficial-use of such materials causing them to be stockpiled indefinitely or disposed of in landfills. It is hypothesized that the USEPA's Industrial Waste Management Evaluation Model (IWEM) may aid in the evaluation of whether secondary materials are safe enough for beneficial use applications in the highway environment.

IWEM uses the EPA's Composite Model for Leachate Migration with Transformation Products (EPACMTP) to model the fate and transport of constituents through the subsurface. Specifically designed for simulating constituents leaching from waste management units, IWEM is able to solve the advection-dispersion equation in both the unsaturated and saturated zones while accounting for transport processes that include linear/nonlinear equilibrium sorption isotherms and first-order decay and zero-order production reactions. The objective of this research was to validate IWEM using data from field studies in Wisconsin, North Carolina, and Maryland and comparison with other solute fate-and-transport models (e.g. HYDRUS-2D). Use of these types of predictive tools should improve acceptance of the appropriate recycling of secondary industrial materials and help interpret leachate data, which can help to conserve natural aggregate and reduce unnecessary disposal.

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