Large Diameter Sewer Assessment-Rehabilitation Alternatives Development Using Risk-Cost Analysis

Columbus, Ohio Division of Sewerage and Drainage (DOSD), concerned about the increasing age and possible structural defects of its critical large diameter assets, recently began a program to determine the condition of and rehabilitation prioritization for the large diameter sewers in its extensive system. This program consists of 20-year inspection cycles for each large diameter sewer. The goal of this program is to develop a methodology to facilitate decision making for type and timing of rehabilitation options. This assessment and analysis creates a better awareness of project cost compared to risk cost. The paper will describe how this approach helped DOSD optimize large diameter sewer interceptor rehabilitation and maintenance and how data collected from readily available sources, including GIS and CCTV inspection enabled cost saving decision making.This study compares five (5) rehabilitation alternatives applicable to the size and nature of the defects found for two sewers, the Scioto Main Trunk Sewer and the West Side Relief Sewer. The alternatives are: Do nothing, point repair only, point repair/CIPP lining hybrid, CIPP lining and slip lining.