Analytical Decision Analysis for Construction Methodology Selection for a Water Transmission Main River Crossing

Abstract

The decisions made during the preproject planning and design stages are very crucial for infrastructure and underground projects due to the inherent risks and uncertainties in such projects. In the selection of a crossing method, the owner has to consider various factors, including cost, environmental impact, serviceability and maintenance, constructability, and schedule. Unfortunately, this decision is complex due to the numerous variables that need to be considered. When choosing a crossing methodology, the project manager must balance the likely capital cost of the project with the risks inherent in the chosen construction method. Ideally, a project manager would investigate numerous alternatives to fully explore the merits of various construction methods, including the level of risk, before making the final decision. This paper presents the results of an actual project workshop with the objective of selecting the most optimum construction method for the construction of a water transmission main beneath the North Saskatchewan River, in Edmonton, Alberta, Canada. The project used the analytical hierarchy process as a method to capture the risks, merits, and demerits of each construction method. Conventional open trench, horizontal directional drilling, microtunneling, and conventional tunneling were the four methods considered for the project. The paper includes the background information, workshop setting, methodology of the selection criteria, and the results of the workshop considered in selecting the most optimum method for the specific project circumstances. A summary of the design based on the recommended methodology is also presented along with a summary of the crossing construction completed in 2007.