Studying the Life-cycle Performance of Gravity Sewer Rehabilitation Liners in North America

Pipe rehabilitation and trenchless replacement technologies have seen a steadily increasing use and represent an increasing proportion of the annual expenditure on operations and maintenance of the water and wastewater infrastructure around the world. Despite the large public investment in use of these technologies, there has been little quantitative evaluation of how these technologies are performing. A retrospective study conducted by the U.S. Environmental Protection Agency collected 25 samples between 2009 and 2013 of in-service gravity sewer liners from 11 cities in North America. Testing of the various liners included thickness, annular gap, ovality, specific gravity, porosity, flexural strength, flexural modulus, tensile strength, tensile modulus, surface hardness, glass transition temperature, Raman spectroscopy, environmental stress crack resistance and pipe stiffness as appropriate to the liner type and condition. Cured-in-place pipe (CIPP) liners comprised 18 of the 25 samples. Other liners included were PVC fold-and-form, HDPE deform-reform and sliplining. The samples had seen from 5 years to 34 years in service. A number of areas where the QA/QC of liner installation should improve were noted in the studies but, overall, the liners were in excellent condition and the physical test results indicated that these liners are expected to last their 50-year design life and probably well beyond.