A Framework for Evaluation of Social Costs of Open-Cut Pipeline Replacement for Sanitary Sewers

Sanitary sewer pipelines, like any other assets, have deteriorated over time and require renewal and replacement (R and R). U.S. Environmental Protection Agency (USEPA) estimates that $271 billion is needed for wastewater infrastructure over the next 25 years. Conventional replacement of underground utilities, especially sanitary sewers, uses open-cut excavation methods, which involves social costs, particularly in urban areas. The social costs include inconvenience to the general public and damage to surrounding existing structures. These costs become more important as the public awareness grows with needs to conserve and protect our environment and maintaining quality of life. The open-cut pipeline replacement (OCPR) process includes selection for a new route, surface and subsurface survey, engineering, planning and analysis, trench excavation, foundation and bedding, placing a new pipe, embedment, and backfill with compaction with select soil, and reinstatement of the ground surface The objective of this paper is to present a framework for evaluation of social costs of OCPR and to identify the influencing factors impacting these costs. A case study is used to study and identify the potential social cost factors. It was found that cost of fuel for detour roads, detour delay, and pavement restoration costs were the major cost driving factors. It can be concluded that social costs’ evaluation is an essential element when considering sustainable R and R of underground infrastructure. Project owners, decision makers, and contractors commonly take into consideration the construction costs only, and sometimes overlook the social cost aspects while calculating the total project costs. This framework can be utilized to analyze social costs of OCPR in sanitary sewers for different project and site conditions.