Alternative Boundaries in Solid Waste Management

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Abstract
Recent trends in solid waste management seem to favor the establishment of minimum performance criteria for waste facilities, as opposed to case by case detailed operational requirements. This implies some generally acceptable upper limit of contamination, say as provided by the primary and secondary Maximum Concentration Level (MCL's) developed by the Environmental Protection Agency. Not so easily defined is the compliance point at which the MCL's may be applied, which can range from the solid waste boundary (a containment option) to some alternative boundary outside the actual waste facility (a retardation option). In either case, it follows that any contaminant migration into the public domain beyond the acceptable boundary must enter below the MCL. The containment option would appear to be strictly a matter of engineering design of the waste facility. With the retardation option, however, there is need for a simplified procedure for assessment of the hydrogeologic environment responsible for retardation and attenuation of the contaminant stream. These are largely dilution and reaction processes. In this paper, some mechanisms of dilution are examined, including geometrical spreading of a contaminant plume, recharge from precipitation, and mixing with surface‐water bodies. This analysis focuses on average value calculations that constitute a semiquantitative measure of the dilution potential of waste sites prior to intensive investigations. For compliance and regulatory purposes, a simple model for maximum concentration predictions is developed for one‐dimensional steady flow and dispersion in directions perpendicular to the flow path. This model is reasonably operational with a minimum of data in that it avoids chemical reaction and the inherent fitted parameter known as longitudinal dispersion, and employs the actual measured concentration at the solid waste boundary as a boundary condition. The model thus provides a conservative estimate of whether or not minimum performance standards will be achieved at an alternative boundary.