1. Professor, School of Civil Engineering, Purdue Univ., 550 Stadium Mall Dr., West Lafayette, IN 47907-2051 (corresponding author).
2. Intercommunale Ontwikkelingsmaatschappij der Kempen, Antwerpseweg 1, 2440 Geel, Belgium; formerly, Graduate Student, School of Civil Engineering, Purdue Univ., 550 Stadium Mall Dr., West Lafayette, IN 47907-2051.
3. Professor, Dept. of Biological Sciences, Purdue Univ., West Lafayette, IN 47907.
4. Student, Dept. of Biological Sciences, Purdue Univ., West Lafayette, IN 47907.