1. Formerly, Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of Maryland, College Park, MD 20742.
2. Associate Professor, Dept. of Civil and Environmental Engineering, Michigan Technological Univ., 1400 Townsend Dr., Houghton, MI 49931.
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Maryland, 1173 Glenn Martin Hall, College Park, MD 20742 (corresponding author).
4. Research Microbiologist, U.S. Dept. of Agriculture, Agricultural Research Service, Beltsville, MD 20705.