1. Doctorial Student, Center for Biofilm Engineering, P.O. Box 178980, Montana State Univ., Bozeman, MT 59717-3980.
2. Graduate Student, Dept. of Civil Engineering, Dalhousie Univ., 1360 Barrington St., Halifax NS, Canada B3J 2X4.
3. Associate Professor, Dept. of Civil Engineering, Dalhousie Univ., 1360 Barrington St., Halifax NS, Canada B3J 2X4 (corresponding author). E-mail: graham.gagnon@dal.ca