Dry Barriers for Waste Containment

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9800255 Craig Composite caps consisting of a geomembrane and compacted clay layer are often used for closure of landfills and for isolation of contaminated soil and waste because they are very effective at minimizing percolation. However, composite caps are expensive. As a result, interest has developed in less costly and equally effective alternative caps constructed almost entirely with earthen materials. The objective of the proposed study is to investigate fundamental factors affecting the behavior of a new alternative earthen cap called a "dry barrier," a special type of earthen cover where airflow is used to remove intruding water. This design permits the use of thinner layers while still preventing percolation, even during the most stressful periods, such as snowmelt and heavy winter rainfalls. As a result, thinner layers are required and the cost of the cap is lower. Designing dry barriers requires an understanding of the "in situ evaporation" process and flow of air laden with water vapor in porous media. Moreover, models need to be developed for use in design. This study addresses these issues through experimental work and development of computer models. Experiments will be conducted to characterize the "in situ evaporation process" as a function of soil type, water content, air stream velocity, and humidity of the air stream. Models will be developed based on the experimental work and verified using large-scale laboratory tests and a field experiment. Results of this study will demonstrate the benefits of using dry barriers and provide analytical tools and data for their design. ***