Lab Studies and Site Characterization for Permeable Reactive Barrier Walls
Beyond general hydrologic factors, the stratigraphy and lithology of the site will often dictate the type of barrier design chosen. It is desirable to "key" the barrier into a low-permeability clay layer to prevent contaminant underflow, for example. If such a layer is not available at a reasonable depth, then a "hanging" design might be necessary. This type of system must be engineered to prevent contaminant underflow.
Understanding the vertical variation in stratigraphy is also important for choosing the zone(s) that the barrier will intersect. Clearly if the contaminant is moving though a highly permeable layer amidst less permeable layers, the barrier must be placed vertically to encompass this layer. Therefore a careful evaluation of the stratigraphic variability at the location of the reactive wall, and the continuity of this stratigraphy with respect to the upgradient plume, is necessary for having confidence in the installation.