Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...

combining this broadly available information with additional detailed evaluations of selected liners. It
should be noted in this regard that selecting liners with more severe exposure conditions or other
circumstances likely to cause an accelerated deterioration may provide a greater understanding about
deterioration mechanisms, but may not be representative of the deterioration of liners in general use.
To get the best value from retrospective evaluation activities, it is recommended that a dual track be
followed in which aggregated experiential and condition assessment information on lined pipes be
collected from cities that are willing to participate together with continued intensive evaluation of liners
that have seen a variety of service conditions.
Municipalities have shown great interest in having better nationwide information on the experience with
the rehabilitation technologies that they are using or considering. It also appears from the discussions
with municipalities regarding the pilot studies described here that municipalities would be willing to
participate in providing data about their own experiences in return for being able to access the nationally
aggregated information. Some municipalities may have limited resources to assist in the dig up and
retrieval of host pipe samples or even liner coupons (from larger diameter pipes). As mentioned earlier,
being able to combine the sample retrieval with other needed work – either on the sewer, on neighboring
utilities, or on the pavement above the sewer – significantly eases the decision of the municipality to
participate.
7.4 Aggregating National Data on Liner Performance
Since the ultimate goal of carrying out retrospective evaluations is to be able to provide better guidance to
municipalities on the long-term performance of the various rehabilitation technologies available to them,
it is worth looking ahead as to how that data might be collected into a national database.
Table 7-3 provides a summary of an overall structure that could be used for such a database. The agency
or municipality will be the key provider of the information and the agency name, contact information for
the person providing the data, system size, and current extent of rehabilitation should be recorded.
Various agencies would have differences in the types of technologies used and the specifics of those
technology applications. It is suggested that the categorization of the city experiences be able to be as
detailed as the city data would allow, but would also allow information capture at a broader level when
only that level of information was available. For example, Agency A may be able to break down their
experiences with CIPP installations by whether they were hot-water or steam-cured, which type of resin
was used, etc. Agency B may only have retained sufficient records to be able to provide information on
the length of lines rehabilitated with CIPP and their general experiences with CIPP. The database should
be able to focus on or exclude specific variants if desired or to analyze all of the CIPP data in aggregate.
As discussed in Section 7.3, broad interpreted data from agency records, CCTV inspections, and
condition assessment databases needs to be able to be accessed in the database in addition to well
characterized, quantitative data from retrospective liner testing or the use of specific NDT approaches to
liner evaluation.
It is not intended that the database proposed would attempt to include all of the individual CCTV or
condition assessment data that cities are collecting. Rather, the database proposed would contain the
interpreted results from agencies of the performance of rehabilitation technologies plus specific physical
or NDT that addresses liner performance or degradation. The aggregation of all inspection and condition
assessment information would provide additional opportunities for understanding liner performance, but
is an effort that would require a larger level of resources to accomplish.
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