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

4.1 Introduction
4.0: CITY OF DENVER RETROSPECTIVE STUDY
The initial discussions were held with the City of Denver during August 2009 about the City’s
willingness to participate in the retrospective evaluation pilot studies. It was known that the City had
been one of the early adopters of CIPP lining in the U.S. The draft protocol outlined in Section 3 was
provided to the City so that they could understand the nature of the program and the requested role of the
City. After the City indicated its interest in participation on August 19, 2009, a face-to-face meeting was
organized and held in Denver on September 22, 2009.
At the meeting, the City identified a series of sewer mainlines in a residential area that had been relined
using CIPP in 1984. An additional advantage to the identified lines was that they were in alley locations
(low traffic) and that the alley pavement surface had areas that had been identified for replacement. The
City wished to complete the dig up of the 8-in. pipe and liner before winter and, hence, the field work was
organized for October 27, 2009. A CCTV inspection was made of several of the sewer lines that had
been relined in 1984 and the evaluations of liner defects seen from those inspections are given in
Section 4.2.17. However, the CCTV inspection was not used in this instance to pick a particular location
for the sample retrieval.
A second option for sample retrieval was identified as a brick sewer of 48-in. diameter that had a CIPP
liner installed in 1987. This liner had already had a physical sample removed for follow up testing in
1995 and, hence, another point of comparison for any degradation would be available. The retrieval work
and re-patching of the liner in this instance was carried out by one of the local CIPP contractors in the
Denver area (Wildcat Construction Co., Ltd.). The sample retrieval for this location was carried out on
May 20, 2010.
4.2 Site 1: 25-year Old CIPP Liner in an 8-in. Clay Pipe
4.2.1 Host Pipe and Liner Information
Location:
City of Denver, CO: Monroe Street and 1
Host pipe:
st Street
Circular, 8 in. diameter, vitrified clay pipe (VCP)
Burial depth:
5 ft (above crown)
Liner dimensions:
8 in. diameter; 6 mm thick
Resin: Reichhold 33-060; an isophthalic, polyester, unfilled resin
Primary catalyst:
Perkadox 16
Secondary catalyst: Trigonox C
Felt:
Unwoven fabric (similar to products used today)
Seal: Polyurethane, 0.015 in. thick (today CIPP liners use polyethylene coating)
Year liner installed: 1984
Liner vendor: Insituform
Resin supplier: Reichhold
Tube manufacturer: Insituform
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