Comparative Analysis of Environmental and Social Costs of Trenchless Cured-in-Place Pipe Renewal Method with Open-Cut Pipeline Replacement for Sanitary Sewers

Abstract

The development of underground infrastructure, environmental concerns, and economic trends is influencing society, resulting in the advancement of technology for more efficient, environment-friendly, and cost-effective pipeline installation and renewal. A comparison of environmental and social (E and S) costs of a pipeline renewal and replacement (R and R) is an essential element when considering sustainable development of underground infrastructure. Project owners, decision-makers, design consultants, and contractors commonly take into consideration the construction costs only and overlook the E and S cost aspects while making a choice between trenchless renewal and open-cut pipeline replacement (OCPR). Trenchless cured-in-place pipes (CIPP) involve a liquid thermoset resin saturated material that is inserted into the existing pipeline by hydrostatic or air inversion or by mechanically pulling-in and inflating. The liner material is cured-in-place using hot water, steam, or light cured using ultraviolet (UV) light, resulting in the CIPP product. The objective of this paper is to provide a comparative analysis of E and S costs of a trenchless CIPP renewal method (CIPPRM) with OCPR for small diameter sanitary sewers (SDSS) and to identify influencing factors impacting costs. An actual case study based on a river basin in Pasadena, CA, was used for this research to evaluate the E and S costs implication of a small-diameter CIPPRM and OCPR. The results show that the total E and S costs of a trenchless CIPP method is 90% less as compared to OCPR for SDSS, such as 203–305 mm (8–12 in.) diameters. It was determined that the environmental impacts of the CIPP will be more than its social impacts. For open-cut, the social impacts are found to be more than environmental impacts. CIPP renewal caused less ozone depletion, global warming, smog, acidification, eutrophication, noncarcinogenics, respiratory effects, ecotoxicity effects, and fossil fuel depletion. The liner, felt, and resin influenced the environmental cost the most for CIPP compared to open-cut in which power consumption of construction equipment and pipe material drove the environmental cost. The cost of fuel for detour roads, detour delays, and pavement restoration were negligible for CIPPRM as compared with OCPR, which contributed a major social cost factor (approximately 75%). A similar approach can be applied for larger pipe diameters and other locations to develop a decision tool.