Argonne National Laboratory-East (ANL-E) has begun production-scale testing of a low-level and mixed radioactive waste solidification system. This system will be used to treat low-level and mixed radioactive waste to meet land burial requirements. The system can use any of several types of solidification media, including a chemically-bonded phosphate ceramic developed by ANL-E scientists. The final waste product will consist of a solidified mass in a standard 208-L drum. The system uses commercial equipment and incorporates several process control features to ensure proper treatment. This paper will discuss the waste types requiring treatment, the system configuration, and operation results for these waste streams.

An approach is presented for evaluating site-specific or multisite alternative environmental remedies that involve nonmonetary benefits. After discussing problems that currently preclude the use of benefit-cost analysis for such evaluation, the analytical approaches of cost effectiveness and incremental cost analyses are presented, including discussion of data requirements, procedures for application, and guidelines for interpreting results to inform decision making. The analyses and interpretation of their results are illustrated with a hypothetical application, based on data from an actual case study involving the cleanup of contaminated underground storage tanks, using a software program called ECO-EASY.

The principal objective of this paper is to introduce strategies for modeling, designing, and operating landfills with leachate recirculation. A numerical model capable of predicting leachate quantity and quality, as well as biogas generation at solid wastes is presented for both single-pass leaching and leachate recirculation. The model, PITTLEACH, is based on fundamental relationships among hydrologic, hydraulic, physical/chemical, and biological processes of landfill leaching and stabilization. The principles of unsaturated flow and contaminant transport in porous media were used to predict leachate movement and landfill stabilization in three general areas: moisture distribution and flow, leachate organic characteristics, and overall methane gas production. The microbially mediated processes of solid waste decomposition in landfills were simulated in terms of solublization of solid organic constituents (hydrolysis), acid formation (acidogenesis), and methane fermentation (methanogenesis). The design code and configurations of landfill leachate recirculation were based on the fundamentals of fluid dynamics and applications of Darcy's law, with the leachate recirculation simulation including a surfacial cascade-type distribution network of perforated pipes and a system of vertical recharge wells with horizontal interconnectors. The operational strategy of the leachate recirculation is also presented and discussed.

The purpose of this article is to acquaint the practicing engineer with the principles that underlie the health risk assessment process and provide an orientation to emerging techniques for dealing with the effects of contamination events. In the past decision makers were forced to rely on rudimentary methods of analysis that incorporated large safety factors to offset gaps in our knowledge base. Improvements in computational methods now allow for a more precise description of risk levels by incorporating inherent variability and uncertainty of the data into the analysis. This paper describes the elements of the risk assessment process and presents Probabilistic Health Risk Assessment (PHRA) as a tool for modeling the fate of contaminants. The common means of evaluating carcinogenic and noncarcinogenic materials are presented along with a brief discussion of the toxicological principles that underlie the methods. A guide to data sources and procedural references is provided along with suggestions of how to use PHRA in current practice.

Expedited site characterization (ESC) is an environmental investigation approach that focuses on using nonintrusive and minimally intrusive investigative techniques synergistically to efficiently and thoroughly characterize hazardous waste sites. Unlike traditional approaches, ESC uses a dynamic (i.e., flexible) work plan with an on-site decision-making team of senior-level technical staff. Another key feature of the ESC process is the emphasis on understanding site geology and hydrogeology at a high level of detail before searching for the contaminants. Geophysical techniques were successfully incorporated into an ESC project at an oil seepage basin site on the U.S. Department of Energy's Savannah River site to define the limits of buried wastes, to detect and map an inorganic plume emanating from the waste trenches, and to define the approximate depth and lateral continuity of major stratigraphic units across the site. The geophysical techniques, integrated with minimally intrusive direct push technologies, provided the framework for the development of the conceptual site model. The refined conceptual site model was then successfully used to guide ground water contaminant sampling to define the spatial extent of the inorganic and organic plume emanating from the waste trenches.