1. Consultant, Trinity Consultants, 12801 North Central Expressway, Ste. 1200, Dallas, TX 75243.
2. Asst. Prof., Dept. of Civ. Engrg., The Univ. of Texas at Austin, Austin, TX 78712 (corresponding author).
3. Res. Engr., Separations Research Program, The Univ. of Texas at Austin, Austin, TX.
4. Assoc. Prof., Dept. of Civ. Engrg., The Univ. of Texas at Austin, Austin, TX.