Engineered barriers to isolate potentially harmful waste from humans and ecosystems have been used for over 35 years, and much has been written about them and their constituent components. However, few reports have provided an overall assessment of the performance of engineered barrier systems. The last broad assessment was conducted in 1995 (Rumer and Mitchell, 1995). Since that time, new materials and sensor technologies have been introduced and models to predict contaminant transport have improved. At the request of program managers at the Environmental Protection Agency, Nuclear Regulatory Commission, National Science Foundation, and Department of Energy, the National Research Council established a committee to assess the effectiveness of surface and subsurface engineered barriers over.
