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The Assess-and-Fix Approach: Using Non-Destructive Evaluations to Help Select Pipe Renewal Methods (WaterRF Report 4473)
Citation:
Ellison, D., S. Ariaratnam, AND E. Allouche. The Assess-and-Fix Approach: Using Non-Destructive Evaluations to Help Select Pipe Renewal Methods (WaterRF Report 4473). Water Research Foundation, Denver, CO, 2015.
Impact/Purpose:
If non-destructive evaluation (NDE) were applied to water mains prior to rehabilitation, utilities would have greater confidence in the final, rehabilitated product. Non-structural methods could be applied where mains show little external corrosion and ample residual strength; where structural impairment is evident, a semi-structural or fully-structural rehabilitation method would be appropriate. Through the application of well-crafted specifications, an owner would have reasonable confidence that the rehabilitated mains would provide satisfactory service for many decades, without wasting money on unnecessary pipe strengthening. To achieve this marriage between NDE and water main rehabilitation, technical questions need to be addressed, including: • How can the remaining integrity of a water main be determined from NDE inspection data? • How can the future conditions of water mains be forecast based on existing conditions? • What types of rehabilitation are appropriate for different pipe conditions? • How should the lining be designed? • How can a utility assure the selected method meets the needs of the pipe? • Can NDE results be provided quickly enough to support an assess-and-fix model of delivery? This study answers each of these questions. Applying the criteria and methods set forth in this report, a utility will be able to employ assess-and-fix rehabilitation today. Benefits should include lower infrastructure renewal costs and reduced community impacts.
Description:
Nondestructive examinations (NDE) can be easily performed as part of a typical water main rehabilitation project. Once a bypass water system has been installed and the water main has been cleaned, pulling a scanning tool through the main is very straightforward. An engineer can then select and design a lining that is appropriate for the actual condition of the main. Performing a detailed condition assessment before lining a water main would allow utilities to optimize renewal, facilitating the use of semi-structural linings, in addition to non-structural and fully structural methods. This assess-and-fix approach is feasible today—the impediments to its adoption are more institutional than technical. Guidelines are needed to help utility owners select lining systems based on assessed pipe condition. These must be coupled with a delivery method, where the rehabilitation method is adjustable. This research project provides the bases to overcome both of these impediments, and shows how an assess-and-fix project can be accomplished. By following the guidelines outlined in this report, utilities can implement assess-and-fix rehabilitation immediately.
