1. Post-Doctoral Research Associate, Division of Engineering, Brown Univ., 182 Hope St., Box D, Providence, RI 02912.
2. Environmental Engineer, CDM, One Cambridge Pl., 50 Hampshire St., Cambridge, MA 02139.
3. Professor, School of Civil Engineering, Purdue Univ., 550 Stadium Mall Dr., West Lafayette, IN 47907 (corresponding author). E-mail: blatch@purdue.edu