Publications Details
Assessment of dry barriers for containment of mobile constituents in the unsaturated zone
A dry barrier may be formed by circulating dry air through a soil layer above or below a waste disposal site, thus reducing the soil moisture content to very low values. Drying a horizontal soil layer creates a barrier to vertical water movement in three ways. First, the drying removes water from the system, intercepting water infiltrating down from the surface. Second, drying a soil layer increases its water storage capacity so the soil will tend to retain rather than transmit water. Third, as a soil layer dries, moisture is removed from progressively smaller interstitial pores so that the hydraulic conductivity of the formation (for liquid flow) decreases. For example, the hydraulic conductivity of a typical sand may decrease by three orders of magnitude as its moisture content is reduced from 20 to 10 percent. This study analyzed the technical and economic feasibility of the subsurface dry barrier concept for containment of a migrating contaminant plume in unsaturated soil. The concept was shown to be a viable option for limiting aqueous migration of pollutants through unsaturated media, with estimated capital costs of between $130,000 and $260,000 for a 1-hectare barrier, and annual operating costs of $10,000 per year.