Environmental Impacts of Conventional Open-Cut Pipeline Installation and Trenchless Technology Methods: State-of-the-Art Review

With growing concerns about global warming and greenhouse gases (GHG), there is an urgent need to quantify and reduce the environmental impact (EI) of pipeline installation (PI). The most common and popular criterion used to describe sustainability efforts from the environmental perspective is the concept of carbon footprint (CF). A CF is the total set of GHG emissions caused by an organization, event, or product. It is expressed in terms of the amount of carbon dioxide (${\mathrm{CO}}_2$), or its equivalent of other emitted GHGs. The open-cut pipeline installation (OCPI) method involves digging a trench along the length of the proposed pipeline, placing the pipe in the trench on suitable bedding materials and then embedding and backfilling. The trenchless method (TM) involves methods, materials, and equipment capable of the installation of new, replacing old, or renewing existing pipelines with minimal disruption to surface traffic, business, and subsurface. Choosing an appropriate low-carbon emission method to install or renew pipelines is an important task and may consider environmental concerns due to several energy-consuming activities, including material manufacturing, transportation, and installation. Because essentially, every PI and renewal project impacts the environment, it is of utmost importance for the pipeline project owner and the design engineer to evaluate this impact and take necessary actions to minimize any negative consequence. The objective of this paper is to present a literature review on progress acquired over the years in understanding GHG emissions from OCPI and TMs and to discuss a framework for CF estimation. Published papers were identified that reported GHG emissions and CF of the open-cut (OC) method and TM over a period from 1989 through 2019. This literature review suggests that for most of these PI and renewal projects, the material production phase consumes a large amount of energy and is a major contributor of GHG emissions. Higher GHG emissions in the OCPI method is a result of longer project durations and more equipment requirements compared with TMs where a smaller footprint or excavation area is used. Early phases of project planning should include appropriate ecological decisions consistent with the life cycle cost (LCC) and CF considerations. Pipe material and outside diameter should be considered during the installation phase by OC and TM to allow a detailed evaluation and comparison of their sustainability impacts. Incorporation of additional factors, such as cost and duration of the project, into the environmental analysis is recommended for the development of a comprehensive decision-making model to select the most environment-friendly PI method.