Evaluation of Apparent Permeability and Field Assessment of Aged Asphalt Capping Systems

Abstract

An asphalt cap system physically isolates contaminated soil from surface runoff to reduce contaminant migration from soil to groundwater. It is one of the most frequently selected remedies for managing sites contaminated by hazardous materials. However, despite its wide usage, the apparent permeability of aging caps has rarely been studied. Based on hydraulic calculations for simplified crack models, this study found that the apparent permeability of an aging cap is primarily influenced by the intrinsic permeability of cap materials and the geometry of cracks. The distribution of crack width, a key indicator of cap integrity, was examined for the first time with four asphaltic caps, aged 3, 4, 12, and 15 years, respectively. The apparent permeability of a 15-year-old cap was estimated to range from