1. Research Assistant Professor, Charles E. Via Dept. of Civil and Environmental Engineering and Dept. of Geological Sciences, Virginia Polytechnic Institute and State Univ., 5053 Derring Hall, Blacksburg, VA 24061.
2. Associate Professor, Dept. of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State Univ., 334B Smyth Hall, Blacksburg, VA 24061.
3. W. Curtis English Professor and Head, Charles E. Via Dept. of Civil and Environmental Engineering, Virginia Polytechnic Institute and State Univ., 200 Patton Hall, Blacksburg, VA 24061.