Retrospective Study of CIPP Liners used for Rehabilitation in Columbus, Ohio and Denver, Colorado

Cured-in-place pipe (CIPP) has been successfully used for the rehabilitation of deteriorating wastewater pipes for nearly 30 years in the U.S. However, little quantitative data is available regarding the performance of these liners that can confirm their estimated design life. With more than 70 million feet of CIPP liners installed worldwide, utilities and municipalities seek verification that these rehabilitation systems will be performing up to their design service life of 50 years. As part of the U.S. Environmental Protection Agency (EPA) 's Aging Water Infrastructure Research Program, one of the key areas of research being pursued in collaboration with water utilities is a CIPP retrospective evaluation. The purpose of this research is to (1) determine the engineering properties of aged in-service CIPP liners and compare them with original design values; (2) identify and provide insight into degradation mechanisms and deterioration rates of CIPP liners; and, (3) attempt to provide a more reliable estimate of the service life of CIPP liners.This paper describes the testing of two CIPP liners installed in 8 in. vitrified clay pipe (VCP) host pipes, one in Denver, CO in 1984, and the other in Columbus, OH in 2005. Specimens prepared from the exhumed samples were subjected to a series of tests including ASTM D638, ASTM D790, hardness, hydrostatic buckling, Raman spectroscopy, and measurement of ovality. Results were compared with design values as well as with controlled specimens prepared in the laboratory. This project is the first known attempt in the U.S. to study the properties of CIPP liners which have been operating under field conditions for nearly 30 years. Results of the study will provide insight into the longevity of in-service CIPP liners, thus enhancing confidence in current design procedures and specifications of these rehabilitation systems.