1. Assoc. Prof., Envir. Engrg. Program, Asian Inst. of Technol., P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand. E-mail: ajit@ait.ac.th
2. Grad. Student, Dept. of Civ. Engrg., Univ. of Calgary, 2500 University Dr. N.W., Calgary, AB, Canada T2N 1N4.