The utilization of traditional open-cut methods for the installation of underground utilities has been common practice in the construction industry for many years. Today, engineers are being tasked with the requirement of selecting a suitable construction method that not only offers the most economical solution, but also minimizes impact to the environment. Trenchless construction methods offer such solutions for installing new utilities and rehabilitating existing infrastructure. The use of multiple construction equipment during open-cut construction, along with extended project schedule, invariably results in considerably more emitted emissions into the atmosphere compared to employing trenchless methods, which have minimal on-site equipment requirements. Pollutants such as carbon dioxide (CO 2), carbon monoxide (CO), nitrogen oxide (NO X), particulate matter (PM), and sulfur oxide (SO X) are identified by the United States Environmental Protection Agency (US EPA) as emissions emitted from equipment engines. This paper describes a methodology developed for quantifying the carbon footprint of a typical underground utility project. Case studies of trenchless pipe replacement, horizontal directional drilling, trenchers, and traditional open-cut are used to demonstrate the reduction in emissions by adopting trenchless technologies. Reducing emissions into the atmosphere is a vital step in developing sustainable solutions for infrastructure construction. Copyright ASCE 2009.