A Decision Tree Approach to Illustrate Trenchless versus Open-Cut Construction Methods for the Southern Nevada Water Authority’s Horizon Lateral Program

Risk-based models have long been used by the Southern Nevada Water Authority to achieve consensus decision making among its project stakeholders. For the Horizon Lateral Program, risk modeling was applied during the feasibility phase to identify two viable pipeline corridors for this new $1.6 billion water transmission facility. As the project has advanced into preliminary design, the risk factors primarily related to traffic impacts, utility conflicts, constructability, and cost were further considered as part of an alignment refinement process that included evaluations of applicable open-cut and trenchless construction methods. These evaluations have been extremely beneficial where new transmission pipelines will cross major streets and highways within the city of Henderson and surrounding developments in the southern Las Vegas Valley. This paper presents the Horizon Lateral Program and a decision tree approach that has been applied to identify and screen nearly 30 trenchless crossing locations, providing decision makers with a visual tool to balance construction risks and costs while ensuring minimal impacts to community traffic patterns.