1. Professor, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO 80523 (corresponding author).
2. Independent General Engineer, P.O. Box 5592, Albuquerque, NM 87185.
3. Geotechnical Engineer, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO 80523.
4. Emeritus Professor, Dept. of Geosciences, Colorado State Univ., Fort Collins, CO 80523.