1. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of Maryland, College Park, MD 20742.
2. Professor Emeritus, Dept. of Environmental Science and Technology, Univ. of Maryland, College Park, MD 20742.
3. Professor and Charles A. Irish, Sr. Chair in Civil Engineering, Dept. of Civil and Environmental Engineering, Univ. of Maryland, College Park, MD 20742 (corresponding author).