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If I Had This To Do Over… A Twelve Step Program to Successfully Measure Sewer Rehabilitation

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It has often been said that the best way to learn how to do a thing is to ask experienced people what mistakes they have made and what corrective steps they took in subsequent projects. The goal of this paper is to relay the top twelve issues in the sewer evaluation and rehabilitation process that the authors have identified by asking that question to themselves and others who have experienced both success and failure about their biggest mistakes and greatest triumphs in the measurement of effectiveness of sewer rehabilitation.

The sewer rehabilitation ‘industry’ has a long history of falling short of expected Infiltration Inflow (I/I) reduction. In the mid-1980s, the EPA Construction Grants Program would not award a grant to an applicant predicting that more than 30%of RDII will be removed from a collection system through rehabilitation. This limitation was established in the belief that higher removal rates were not possible. A grant applicant sizing a plant based on 60% RDII removal will end up with an undersized WWTP if only 30% is removed

Many practitioners assume the ineffectiveness lies in the rehabilitation technology used, the extent of rehabilitation or sources of I/I in private sewers that went unaddressed. While the rehabilitation work may contribute to the problem, it is evident to the authors that the approach to measuring I/I removal may contribute as much to the apparent ineffectiveness as the work itself.

WERF Project 99-WWF-8 studied I/I removal programs around the US and found that their efforts to acquire detailed analysis were unsuccessful for many utilities because information was not generated and archived suitably or that the data were incomplete or unreliable. The mismatch of methods and procedures for evaluating I/I created a lack of uniformity among agencies performing the sewer rehabilitation.

The paper will contain specific recommendations and graphic examples of successful and unsuccessful practices for the measurement of RDII effectiveness. This paper is intended to be useful to both the first-time and experienced I/I project managers who are establishing capital improvement programs for sewer rehabilitation and want to be able to answer the future question – “What have you accomplished with the money?”

Keywords: 10/20 Rule; Analysis; Basin Size; Forensic RDII; I/I; Infiltration/Inflow; Measurement; Potential I/I; Q vs. i plots; RDII; Rainfall Dependent I/I; Scattergraphs; Sewer Rehabilitation;

Document Type: Research Article


Publication date: January 1, 2011

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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