1. Graduate Student, Dept. of Civil and Environmental Engineering, Univ. of Maryland, College Park, MD 20742; formerly, Graduate Student, Dept. of Civil Engineering, Univ. of Nebraska-Lincoln, Omaha, NE 68182 (corresponding author).
2. Professor, Dept. of Civil Engineering, Univ. of Nebraska-Lincoln, Omaha, NE 68182.
3. Associate Professor, Dept. of Civil Engineering, Univ. of Nebraska-Lincoln, Omaha, NE 68182.
4. Engineer, Water Supply and Water Resources Division, USEPA, Cincinnati, OH 45268.
5. Associate Professor, School of Environmental Science and Technology, Huazhong Univ. of Science and Technology, Wuhan, Hubei 430074, P. R. China.