1. a Government of Makueni County, Department of infrastructure, Transport, Public Works and Energy, P.O. Box 78-90300, Makueni, Kenya
2. b Department of Civil, Construction and Environmental Engineering, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya
3. c Soil, Water and Environmental Engineering Department (SWEED), Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya