Framework for multi-purpose utility tunnel lifecycle cost assessment and cost-sharing
Introduction
Utility networks (e.g. gas, water and sewer pipes, and electrical and telecommunication cables) are developed above and under the ground. Above ground utilities in urban areas can cause problems, such as aesthetic issues, occupation of limited urban space, limited accessibility space, safety issues related to utilities exposed to weather changes (e.g. hurricane, extreme high/low temperature, and accident). Therefore, the traditional method of buried utilities is common for the development of utility networks, especially in urban areas.
Different studies have reported that underground utilities infrastructure in developed countries has aged and almost reached their service lives (Gagnon et al., 2008, Ormsby, 2009). Therefore, to access aging buried utilities for repair, maintenance, and renewal activities, repeated excavation, and street cuts are needed. Urban areas have been experiencing many street closures and traffic disruptions because of excavation for maintaining underground utilities. These construction works have imposed major costs on public and private utility providers as well as on citizens and local businesses (i.e. social cost) (Oum, 2017). The Multi-purpose Utility Tunnel (MUT), is defined as “an underground utilidor containing one or more utility systems, permitting the installation, maintenance, and removal of the system without making street cuts or excavations” (Canto-Perello and Curiel-Esparza, 2013). Luo et al. (2020) provided a detailed review of the history and recent developments of MUT projects in the world.
Although MUT has numerous benefits, it is not widely used because of the need for high construction cost, the need for high level of safety and security, and coordination between utility companies. Despite the high initial investment needed, direct operational and social cost savings can make MUT Life Cycle Cost (LCC) less than conventional buried utilities. To investigate if MUT is an economically viable alternative for the traditional method of buried utilities in a specific project, different factors should be considered related to the specifications of utilities, the location of the project, and the construction method. The LCC of each method is a function of these factors. Therefore, there is a need for a systematic approach to estimate the LCC and find a breakeven point, where the cost of both methods is equal. MUT is the economic method when the estimated design and construction costs of MUT is lower than the breakeven point.
After deciding on a MUT project, the next challenge is financing and cost-sharing of the project (Canto-Perello and Curiel-Esparza, 2013). MUT should be more economical for each utility company compared with the buried utility option (organization level) and the MUT benefits should be distributed fairly, to convince utility companies to participate in the MUT project.
This paper aims to develop a comprehensive and systematic model for MUT and buried utilities LCC analysis by considering factors of utility specifications and location conditions, and construction methods. The output of this model determines the design and construction cost of MUT at the breakeven point. The result can help in decision making at the project level and can reveal in which conditions the MUT is an economic method. From the organization's point of view, this paper proposes a model of MUT cost-sharing to ensure the decision-makers of utility companies that MUT is the economic method for their company and that all the utility companies benefit from MUT fairly. This paper is an extension of the papers of Alaghbandrad and Hammad, 2018a, Alaghbandrad and Hammad, 2018b.
Section snippets
Literature review
Different aspects of MUT are discussed in the literature review. MUT advantages and disadvantages, classification, and construction methods are presented as the general aspects. Then economy, financing and cost-sharing of MUT are reviewed. Finally, game theory is introduced and its application to determine the contribution of each utility company to the benefit from MUT is explained.
Proposed method
The proposed method considers the MUT economy at the project level as well as the cost-sharing between stakeholders. Fig. 1 shows the method of economy assessment and cost-sharing of MUT.
Case study
The case study is considering MUT lifecycle economy assessment and cost-sharing for a segment of Ottawa Street (between Peel Street and De Montagne Street) in Montreal with the length of 250 m. The proposed method is implemented as follows.
Summary and conclusions
This paper proposed a comprehensive and systematic model for MUT and buried utilities LCC analysis by considering factors of utility specifications, location conditions, and construction/maintenance methods. The output of this model estimates the lifecycle cost of MUT and buried utilities. The proposed model can justify whether a MUT project is an economic alternative method for buried utilities. In addition, a MUT cost-sharing method is proposed to ensure the decision-makers of utility
CRediT authorship contribution statement
Ali Alaghbandrad: Conceptualization, Methodology, Data curation, Writing - original draft. Amin Hammad: Supervision, Methodology.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
The authors would like to thank Centre d'expertise et de recherche en infrastructures urbaines and City of Montreal for providing information related to the case study. This research is funded by MITACS project number IT12092.
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