1. Program of Interdisciplinary Research in Contaminant Hydrogeology, Department of Civil Engineering and Applied Mechanics, University of Virginia, Charlottesville, Virginia 22903-2442, IT Corporation, 1250 Capital of Texas Highway South, Building 3, Suite 200, Austin, Texas 78746, and Klohn-Crippen, 10200 Shell Bridge Way, Richmond, British Columbia V6X 2W7, Canada