1. Senior Geotechnical Engineer, Kiewit Engineering Co., Kiewit Plaza, 3555 Farnam St., Omaha, NE 68131 (corresponding author).
2. Professor, Dept. of Civil and Environmental Engineering, Univ. of Massachusetts at Amherst, Amherst, MA 01003-5205.
3. Designer, Kiewit Engineering Co., Kiewit Plaza, 3555 Farnam St., Omaha, NE 68131.
4. Staff Engineer, HDR Engineering, Inc., 8404 Indian Hills Dr., Omaha, NE 68114.