A graphical approach for determining dilution-attenuation factors: Basic theory and approach for submerged sources

The dilution attenuation factor (DAF) is a quantity used to relate the conc entration of leachate leaving a source zone (e.g., landfill, impoundment, o r contaminated soils) to its impact on down-gradient ground water quality. The DAF is of importance because it plays a key role in U.S. Environmental Protection Agency (EPA)'s methodologies for developing soil cleanup goals a nd for managing hazardous wastes. In this work, a simplistic graphically-ba sed approach for determining site-specific and generic DAFs was developed. In this case the DAF is based on time- and vertically-averaged concentratio ns along the plume centerline, and the mathematical framework employs well- known analytical and semianalytical solutions for dissolved contaminant tra nsport. Finite sources with a range of decay characteristics are allowed fo r. One unique feature of this work is that the graphical approach allows fo r varying levels of site-specificity, and thus can be used when one has a l ittle, or a lot., of site-specific information. The graphs visually indicat e the sensitivity to various parameters, which is valuable information not easily gleaned from most numerical software simulators. This approach is, h owever, not applicable to very complex hydrogeologic settings (e.g., fractu red geology), or to ground water flows that cannot be reasonably approximat ed as one-dimensional.