1. Environmental Engineer, Barr Engineering Company, 4700 West 77th St., Minneapolis, MN 55435. E-mail: dkolstad@barr.com
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin, Madison, WI 53706. E-mail: benson@engr.wisc.edu
3. Professor, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin, Madison, WI 53706. E-mail: edil@engr.wisc.edu