The negative effects of greenhouse gas (GHG) emissions, such as climate change and global warming, have become major environmental concerns, especially for the construction industry, which is the third-highest source of GHG emissions among industrialized countries. Presently, underground utility projects are considered one of the most common types of construction, primarily due to aging infrastructure across North America and the subsequent rehabilitation of old pipelines and installation of new pipelines and facilities. Given the increasing demand being placed on the industry, the need to study airborne emissions associated with different underground construction technologies has risen, which will be helpful in selecting the most sustainable underground construction methods. This study investigates pollutant emission from two common trenchless methods used in underground construction, hand tunneling and pilot-tube method (PTM), through their varying GHG footprint sources and emissions measured by the United States Environmental Protection Agency (EPA). This paper analyzes a case from Edmonton, Canada, in which both PTM and hand tunneling were used by comparing the suggested indexes, including HC, CO, NOx, PM, CO2, and SO2. In this case study, both methods were used in the installation of a new 68-cm diameter (27 in.) clay sewer line with an overburden depth of 12.9 m (42 ft) and length of 60 m (197 ft). Results indicated that the amount of airborne emissions was reduced between 17% and 36% through the use of PTM compared to the traditional hand tunnelling method.

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