City of Casper, WY Phase II North Platte Sanitary Sewer Condition Assessment and Rehabilitation Analysis

摘要

The City of Casper operates an extensive wastewater conveyance system that includes the NorthPlatte Sanitary Sewer Interceptor (NPSSI). The NPSSI is a 30-year-old, 47,000-foot-long pipeline ranging indiameter from 24 to 54 inches which is constructed of unlined reinforced concrete pipe. Concerns regardinghydrogen sulfide corrosion prompted the City to undertake a risk-based condition assessment of this interceptor.The City and CH2M HILL developed a cost-saving tiered approach to assessing the NPSSI’s current condition. Thefirst phase of the study involved top-side camera inspections and was presented at the 2011 No-Dig (City of Casper,Wyoming’s Approach to Assessing a Large Diameter Sewer Interceptor). In the Phase II study, CCTV assessmentwas conducted of only the most-corroded pipeline segments as determined in the previous field work. Following theassessment phase, the risk levels and remaining service life of the alignment were determined, segment-by-segment,using CH2M HILL's SCREAM™ software from inspection information collected using the National Association ofSewer Service Companies' Pipeline Assessment Certification Program (PACP). Based on the data analysis, pipelinerehabilitation was prioritized for the various segments of the NPSSI. A corrosion control analysis was alsoperformed to determine the feasibility of implementing a corrosion control program to extend the service life forpipeline segments which did not warrant immediate rehabilitation.This paper will illustrate the results of a cost-saving, multi-faceted field investigation and planning study to manageand extend the remaining service life of this critical City asset and will highlight the field investigation approach andfinal recommendations for minimization of capital expense.