1. Assoc. Prof. and Dr. Engrg., Dept. of Urban Engrg. and Sanitary Engrg., Faculty of Engrg., The Univ. of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan
2. Master of Engrg., Planning Div., Dept. of Water Supply and Environment, Ministry of Health and Welfare, Tokyo, Japan