The American Society for Quality defines quality assurance as “all the planned and systematic activities implemented within the quality system that can be demonstrated to provide confidence that a product or service will fulfill requirements for quality”. Requirements for quality in sewer CIPP projects typically revolve around achieving a minimum design life of 50 years and are defined within the Owners construction specification or tender documentation.

Research has demonstrated that the physical properties of installed sewer CIPP liners measured in laboratory tests can vary to a greater degree than more traditional pipe materials. To incorporate this characteristic of sewer CIPP installations, many owner’s quality requirements have been evolving to ensure that their CIPP projects achieve design life with an acceptable degree of confidence. Unlike the ASTM and ISO standards and specifications which are incorporated within owner specifications, there are no industry-wide universal approaches employed by owners to define their sewer CIPP quality assurance best practices.

This paper examines the quality assurance tests and the sewer CIPP quality assurance best practices employed by four Canadian municipalities, Edmonton, Montreal, Toronto and Winnipeg in current sewer CIPP projects and describes the quality assurance outcomes of the different approaches.

While CIPP lining for sewers and watermains have the same basic objective, containing the contents of the pipe within the pipe, the material properties required to achieve this are quite different in the two types of systems. The bulk of CIPP lining in North America consists of non-reinforced needle-felt based systems. Consequently, owners and installers are more familiar with the methods available to evaluate the installed properties of gravity sewer CIPP liners. Watermain CIPP installations require a different set of installed properties and subsequently require different laboratory test methods to evaluate for installed structural properties.

Structural watermain CIPP lining has a shorter history than its sewer lining sibling, a much smaller installed base and fewer systems to choose from. Canadian municipalities were early adopters of this technology and consequently have developed extensive experience in the use of this rehabilitation technology.

This paper describes the lessons learned over fifteen years of evaluating this rapidly evolving rehabilitation system.

Cured in place pipe has become ubiquitous as a rehabilitation process for underground infrastructure. While the technology has become widely accepted as an effective rehabilitation method, the strategies for ensuring the quality of an installation are still evolving. Research has shown high quality rehabilitations can be achieved with CIPP when it is deployed with sufficient oversight.

The two primary metrics for determining whether a CIPP installation will be effective are the short term flexural modulus and the installed thickness. Other industry research has shown that even with a rigorous QA process in place, short term flexural modulus and installed thickness can exhibit significant variability, exposing the Owner to the risk that non-conforming liners are being installed.

This paper identifies the shortcomings of the traditional QC sampling approach used in many heat cured CIPP projects and demonstrates the innovative QA/QC process used by Toronto Water to reduce the risk that nonconforming CIPP liners are installed in their sewer rehabilitation program.

Building on the pioneering work reported in our 2010 and 2014 NoDig papers, we continue to refine the understanding of the impact of machining the inner and outer surfaces of Cured-in-Place Pipe (CIPP ) flexural test specimens. Many CIPP flexural tests are performed on rough, unmachined test specimens which retain the existing outside and inside diameter surfaces of the CIPP liner as well as the inherent errors caused by the non-rectangular test specimen cross-section.

Machining material from the outer and inner diameter surfaces provides the required rectangular cross section, but can also preferentially bias flexural results because of the through thickness variation in properties exhibited by thermally cured CIPP materials. To isolate the effect of changing specimen geometry, the authors conducted an extensive experimental program on CIPP flat plate differentially cured test plates to isolate the impact of removing material as opposed to modifying test specimen geometry. This paper demonstrates the impact of machining material from the inside and outside surfaces of CIPP flexural test specimens, while excluding the impact of pipe wall geometry.

The determination of the flexural modulus and strength of a CIPP field sample is the standard test used to determine the short term physical properties of a CIPP installation. In our 2010 paper “Factors Affecting the Quality of Flexural Properties” we demonstrated with experimental data, the significant variability present in flexural data determined using the existing CIPP standard methods. While we identified the factors and the extent to which they affect flexural test data, we did not determine the underlying causes. Test variability makes it difficult for owners and installers to confidently use flexural test data to confirm contract compliance.

This paper closes the book on our original 2010 paper by determining the specific root causes of the factors we originally defined. Using the results of further experiments as well as theoretical and numerical analyses of test specimen geometry and stress distribution, test deflection artifacts and the effect of through thickness degree of cure, we successfully define the underlying reasons for this flexural testing data variation. The paper also describes the specific test specimen preparation and testing techniques which should be implemented to reduce this variability.