Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
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ABSTRACT<br />
<strong>Pipe</strong> rehabilitation and trenchless replacement technologies have seen a steadily <strong>in</strong>creas<strong>in</strong>g use and<br />
represent an <strong>in</strong>creas<strong>in</strong>g proportion <strong>of</strong> the annual expenditure on operations and ma<strong>in</strong>tenance <strong>of</strong> the<br />
nation’s water and wastewater <strong>in</strong>frastructure. Despite public <strong>in</strong>vestment <strong>in</strong> use <strong>of</strong> these technologies,<br />
there has been little quantitative evaluation <strong>of</strong> how these technologies are perform<strong>in</strong>g. The major reasons<br />
for retrospective evaluation <strong>of</strong> rehabilitation systems are needed <strong>in</strong>clude: data gaps <strong>in</strong> predict<strong>in</strong>g<br />
rema<strong>in</strong><strong>in</strong>g asset life <strong>of</strong> pipes and how long rehabilitation techniques can extend that life; and to assess<br />
whether the orig<strong>in</strong>ally planned lifetime is reasonable based on current condition. The goals <strong>of</strong> this project<br />
were to draw attention to the need for this type <strong>of</strong> evaluation and to develop evaluation protocols that are<br />
technically and f<strong>in</strong>ancially feasible for carry<strong>in</strong>g out these evaluations.<br />
The <strong>in</strong>itial project focuses on cured-<strong>in</strong>-place pipe (CIPP) l<strong>in</strong>ers because they were the first trenchless<br />
l<strong>in</strong>ers (other than conventional slipl<strong>in</strong>ers) to be used <strong>in</strong> pipe rehabilitation and they hold the largest market<br />
share. The pilot test<strong>in</strong>g used CIPP samples from both large and small diameter sewers <strong>in</strong> two cities that<br />
were <strong>in</strong> excellent condition after be<strong>in</strong>g <strong>in</strong> use for 25, 23, 21, and 5 years, respectively. Test<strong>in</strong>g on the<br />
l<strong>in</strong>ers <strong>in</strong>cluded thickness, annular gap, ovality, density, specific gravity, porosity, flexural strength,<br />
flexural modulus, tensile strength, tensile modulus, surface hardness, glass transition temperature, and<br />
Raman spectroscopy. In addition, environmental data was gathered as appropriate <strong>in</strong>clud<strong>in</strong>g: external soil<br />
conditions and pH, and <strong>in</strong>ternal waste stream pH. Three <strong>of</strong> the l<strong>in</strong>ers had already been <strong>in</strong> service for<br />
nearly half <strong>of</strong> their orig<strong>in</strong>ally expected service life, but overall, there is no reason to anticipate that the<br />
l<strong>in</strong>ers evaluated will not last for their <strong>in</strong>tended lifetime <strong>of</strong> 50 years and perhaps beyond.<br />
Given the <strong>in</strong>sights provided by the pilot studies, an expansion <strong>of</strong> the retrospective study is recommended<br />
to create a broader database to better def<strong>in</strong>e the expected life <strong>of</strong> sewer rehabilitation technologies.<br />
Specifically, it is recommended that the retrospective program be extended to: cover additional CIPP<br />
sample retrieval <strong>in</strong> other cities, pilot studies <strong>of</strong> other rehabilitation technologies; capture locally<br />
<strong>in</strong>terpreted data from other cities; encourage sewer agencies to keep as-<strong>in</strong>stalled material test data for later<br />
comparison with follow-up test<strong>in</strong>g; and adapt, develop, and/or calibrate non-destructive test<strong>in</strong>g (NDT)<br />
methods that could use small physical samples that are easily retrieved robotically from <strong>in</strong>side the pipe.<br />
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