1. Professor, Dept. of Civil and Environmental Engineering, Northwestern Univ., Evanston, IL 60208 (corresponding author).
2. Research Assistant, Dept. of Civil and Environmental Engineering, Northwestern Univ., Evanston, IL 60208.
3. Division Manager, Hayward Baker, Inc., 1350 W. Lake St., Roselle, IL 60172.
4. Field Engineer, Hayward Baker, Inc., 1350 W. Lake St., Roselle, IL 60172; formerly, Research Assistant, Dept. of Civil and Environmental Engineering, Northwestern Univ., Evanston, IL 60208.