AIR PERMEABILITY FROM PNEUMATIC TESTS IN OXIDIZED TILL

Soil vapor extraction (SVE) to remove volatile contaminants from conta minated soil in the unsaturated zone has been successful in sand and g ravel formations. In less permeable glacial till, the usefulness of SV E is unclear. Field experiments in the loam till of central Iowa were performed to determine air permeabilities. A radial and vertical, anis otropic, heterogeneous compressible-flow model coupled with an optimiz ation routine solved the inverse problem by using vacuum pressure and flow-rate data to estimate air permeabilities. Air-permeability anisot ropy was determined to be less important than depth variations. Using a four-layer description of the deposit to account for varying moistur e content with depth, the average predicted air permeability varied fr om 4 x 10(-8) cm2 in the deepest layer to 1 X 10(-5) cm2 in the layer nearest the ground surface.