1. a Department of Environmental Health Sciences , University of South Carolina , Columbia, SC, 20208
2. b Department of Civil and Environmental Engineering , University of South Carolina , Columbia, SC, 20208
3. c Department of Civil and Environmental Engineering , Virginia Polytechnic Institute and State University , Blacksburg, VA, 24061–0105
4. d Department of Civil Engineering , Northwestern University , Evanston, IL, 60208