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A retrospective evaluation of the performance of liner systems used to rehabilitate municipal gravity sewers
Citation:
Alam, S., R. Sterling, E. Allouche, W. Condit, J. Matthews, A. Selvakumar, AND J. Simicevic. A retrospective evaluation of the performance of liner systems used to rehabilitate municipal gravity sewers. Tunnelling and Underground Space Technology. Elsevier BV, AMSTERDAM, Netherlands, 50:451-464, (2015).
Impact/Purpose:
In the U.S., there are approximately 16,000 wastewater systems incorporating approximately 740,000 miles (1,190,660 km) of public sewers plus 500,000 miles (804,500 km) of private lateral sewers. Some components of the U.S. wastewater infrastructure are well over 100 years old. The combination of age, neglect, and mishaps gives rise to approximately 50,000 sanitary sewer overflows (SSOs) per year, along with the resulting illnesses and environmental degradation and as much as 10 billion gallons of raw sewage released yearly (EPA, 2004). The latest 2013 infrastructure report card issued by the American Society of Civil Engineers (ASCE) provides a “D” grade for wastewater infrastructure (ASCE, 2013). ASCE estimates that nearly $300 billion is needed for capital investments over the next 20 years (ASCE, 2013). Use of pipe rehabilitation and trenchless pipe replacement technologies has increased over the past 30 to 40 years and represents an increasing proportion of the approximately $25 billion annual expenditure on the operation and maintenance of the nation’s water and wastewater infrastructure (EPA, 2002). Despite the massive public investment represented by the use of these technologies, little formal and quantitative evaluation has been conducted on whether they are performing as expected and whether rehabilitation is indeed cost-effective compared to replacement.
Description:
This paper provides new results gathered as part of a 6-year project funded by the U.S. Environmental Protection Agency (USEPA) to document the in-service performance of trenchless pipe rehabilitation techniques. The results from a pilot study focusing on cured-in-place pipe (CIPP) rehabilitation technologies were previously reported and the research program was extended to allow collection of additional CIPP samples and also to extend the study to other rehabilitation technologies (specifically included in this Phase 2 research were fold-and-form, deform-reform, and sliplining technologies). The establishment of a database to house performance evaluation data for rehabilitation technologies used in the water and wastewater sectors is also described. The additional retrospective data for CIPP and other rehabilitation technologies are reported and an overall assessment of CIPP life cycle performance is provided. The examination of CIPP liners with up to 34 years in service and other rehabilitation technologies with up to 19 years of service has shown that all of the rehabilitation technologies are showing little evidence of deterioration in service. The test results for 18 CIPP samples from nine cities across North America indicate that properly designed and installed CIPP liners should meet and likely exceed the typical 50-year expected design life. For the fold-and-form, deform-reform, and sliplining technologies, there are only two to three samples per rehabilitation technology and hence less can be said about overall performance. Nevertheless, all of the samples tested still met the material property requirements at installations after 14 to 19 years of service. In summary, the results provide an excellent prognosis for the rehabilitation technologies evaluated.
