1. U.S. Environmental Protection Agency; National Risk Management Research Lab.; 26 W. Martin Luther King Dr., MS 421 Cincinnati OH 45268
2. USDA-ARS; National Soil Tilth Lab.; 2150 Pammel Dr. Ames IA 50011
3. Dep. of Civil, Construction, and Environ. Eng.; 486 Town Engineering Bldg., Iowa State Univ. Ames IA 50011