SEWER REHABILITATION RESULTS, TEN YEARS LATER

While many sewer collection systems owners have invested millions of dollars in sanitary sewer rehabilitation in the last twenty-five years, few have gone back to the rehabilitated areas to identify which techniques worked and which did not. This paper presents the results of one area where the City of Fayetteville, Arkansas, returned to an area that was rehabilitated ten years earlier to determine what worked, what failed, and what events occurred in that time period to cause additional failures in the collection system.Spurred by a 1989 Environmental Protection Agency (EPA) Administrative Order (AO), Fayetteville initiated a sanitary sewer rehabilitation program to eliminate sanitary sewer overflows (SSOs). The focus was on the hundreds of wet weather SSOs the City experienced each year. Concentrating on wet weather SSOs, in 1991, the City completed a thorough Sanitary Sewer Evaluation Study (SSES) and initiated several construction projects. The first all encompassing sewer rehabilitation project was constructed in 1993. The project had incorporated numerous lessons learned through several earlier SSES efforts and several smaller rehabilitation construction projects, and employed the latest standards and techniques available at the time. These lessons and standards applied to the SSES, collection system analysis, design, construction, construction inspection, and post-rehabilitation evaluation.Ten years later, the City returned to this area to reevaluate the results of that sewer rehabilitation project. All of the sewer lines in the basin were smoke tested, and the defects were evaluated to determine if the defect was related to the earlier rehabilitation work. If it was not, then we strove to determine what action occurred in the last ten years to cause the defect. Since few defects were found on pipe segments that had been repaired in the earlier rehabilitation project, the results were very satisfying. There are, however, some major lessons to be learned from the evaluation. This paper identifies these lessons learned, and describes those techniques that were most successful in the rehabilitation process.