More Effective Front-End Decision-Making for Pipe Renewal Projects

Abstract

Access to clean, hygienic, and sufficient potable water is a concern in many countries. To ensure this, asset management, planning, and structured pipe renewal are crucial in providing an adequate level of service. However, there is a significant backlog in municipal pipe renewal, which needs to be addressed to raise the standard of potable water supply to an acceptable level in countries across most continents. Therefore, the objective of this research was to improve decision-making to reduce this backlog. Competent personnel are a scarce resource and not easily replaced. Standardized decision-making is considered an efficient approach to addressing the shortage of skilled personnel in pipe renewal. However, its effectiveness depends on its adaptability to the varying complexity and scale of such projects during implementation. This research is based on a literature review that explores decision theories, project definitions, and project models, and compares the typical characteristics of pipe renewal projects with those of other infrastructure projects. The research highlights that structured and standardized decision-making processes are essential to ensure appropriate asset management of the pipe network and sufficient pipe renewal. The main outcome of this research is a tailored project model that supports better front-end decision-making in pipe renewal projects through improved information flow.

1. Introduction

Clean, fresh, and sufficient potable water is so important that the UN has included it on the list of sustainable development goals (goal 6). Access to clean, hygienic, and safe water is a growing concern in most countries and an important factor in improving public health. In many countries, there is a backlog of municipal pipe network renewal projects and a vast need for investments to replace pipes and raise the general condition of the pipe network to an acceptable standard [1,2,3,4,5,6,7,8]. In Canada, USD 61 billion is needed to replace the water, wastewater, and stormwater pipe network [9], which translates to USD 1649 per capita [10]. In the USA, USD 271 billion in investments is needed over 25 years for wastewater and stormwater infrastructure [9]; this translates to USD 813 per capita [11]. Saad, Mansour and Osman [12] found that the backlog in infrastructure investments, when including other technical infrastructure, is USD 3.6 trillion in North America. The situation in Europe is similar. For example, in Sweden, the investment required for pipe renewal and replacement is estimated at USD 1.55 billion per year for 20 years [13], reaching USD 31 billion in total. This equates to USD 2927 per capita [14]. The national association Norwegian Water estimates that USD 41 billion is needed to raise the quality of the public waterworks services to an acceptable level by the year 2045, of which USD 22.5 billion should be dedicated to pipe network renewal [15], equating to USD 4040 per capita [16].

Pipe renewal is defined as the replacement of deteriorated pipes through open trench methods and the rehabilitation of pipes through refurbishment using various trenchless technologies [17,18]. Furthermore, renewal of services may include the installation of a new section in the network to meet updated needs. Choosing the most appropriate technology requires alternatives to be screened [19]. In Norway, when comparing actual efforts at renewing the pipe network [20,21,22] to those recommended for the municipal pipe network [23,24], there is a large infrastructure investment gap. Bridging this infrastructure investment gap requires increased spending on infrastructure-related projects. For instance, to facilitate pipe renewal, one must increase the use of resources, both economic and human, or use currently available resources more effectively. Developing new and effective methods for the planning and execution of pipe network renewal projects is necessary to help close the infrastructure gap.

Establishing new approaches to concept development, better front-end decisions, and improved project execution is essential for reducing the backlog in pipe renewal through choosing the optimal technology. The use of decision-making models/frameworks, along with principles, processes, and structures developed to facilitate the decision-making process, is a way to increase efficiency in front-end planning and project execution [25,26]. Different public enterprises and government agencies in Norway have developed different decision-making frameworks to govern their investment projects [27]. Similarly, some larger municipalities have developed decision-making models to govern their investment projects effectively. Some studies have identified decision-support tools for pipe renewal and risk mitigation methods [4,18,28]. However, few studies discuss how these tools—particularly decision-making models and decision support systems (DSS)—contribute to pipe renewal project performance when a front-end decision-making model in municipalities is used. Hazır [29] proposes that managers might not be aware that relevant decision support systems (DSS) can be applied in practice or might perceive them as too sophisticated to use. Therefore, this paper aims to establish a reference decision-making model for pipe renewal projects, situated within a project framework and supported by decision-support tools, including decision support systems (DSS) and decision models. This is achieved by addressing the following research question:

“How can decision-making in pipe renewal projects be improved by using a project model linking planning goals from the front-end to project execution and on to operation and asset management?”

This paper begins with a brief introduction that summarizes the theory related to decision-making and project stage–gate models. The main part consists of a summary of the systematic literature review conducted, along with a discussion and suggestions on how a project model will be best utilized in pipe network renewal and installation projects. Finally, we conclude on the research question and outline the future work required.

2. Theoretical Background

2.1. General Decision-Making (Decision Theory)

Decision-making is an important process in project governance and management. Many studies have addressed decision-making processes and decision-making theories [30,31]. For example, Elliot [32] discusses decision theory as the interdisciplinary study of choice. A decision is defined as a choice between mutually exclusive options for solving a problem, a selection of options, and a ranking of alternatives. Different research groups have divided decision theories into two branches: normative and descriptive [33,34,35]. Normative decision theory refers to how a representative should make a decision when faced with a problem [32,35]. The representative analyzes their own goal and the consequences of various decisions and determines the optimal one based on this [36]. On the other hand, descriptive decision theory refers to how decisions are made based on analyzing the past actions of people and involved parties [30]. Rationality, a key feature of decision-making, is characterized by making a sound decision involving a multi-stage selection process, thus enabling the decision-maker to make the best selection among various alternatives.

Decision-making is an important skill that is necessary for any organization managing public investment projects. Skaar, Stevik and Johansen [37] found that there was a lack of resources in Norwegian municipalities, which impacted the time spent on each project and the ability to coordinate with other actors. They suggested the use of decision-support tools to free up resources, increase the time spent on renewal projects, and reduce the backlog in pipe renewal. Furthermore, they found indications in their study that decision-support tools such as PARMS-Planning/Priority [38,39], TAG-R [40] and CARE-W [41,42] are not widely used in Norway, and this represents an opportunity to streamline project implementation and increase the pipe renewal rate to a sustainable level.

Hazır [29] states that academic studies mainly investigate closed systems, often assuming that the information is known in advance, and therefore only work in less complex situations. Furthermore, Hazır [29] claims that managers face multi-dimensional, dynamic, and open systems and require solutions and predictions for more complex and non-deterministic problems. A standardized framework provides a good basis for comparison and learning across sectors in infrastructure projects [43].

Moutchnik [44] states that standardized quality management helps organizations develop feedback loops for continuous improvement of the overall management system. Häußler and Borrmann [45] used a standardized evaluation for quality assurance in infrastructure projects, analyzing individual quality criteria. They found that the quality of a model can vary considerably depending on the selected quality parameter.

Most of the pipe system, possibly close to 99%, is already in place, meaning that maintaining the functionality of this asset is an important issue. Asset management is defined as a “coordinated activity of an organization to realize values from an asset” [46]. The value of a pipe network is its ability to supply a reliable and safe service to the public [47]. This is a long-term engagement, and its objectives may be categorized as strategic, tactical, or operational [46], each with different time frames: 10–20 years (strategic), 1–5 years (tactical), and 1 year (operational) [24,48,49].

NS-ISO 55000:2014 describes an asset management system as a “set of interrelated elements to establish asset management policy, asset management objectives and the processes to achieve those objectives” [46]. Moreover, the asset portfolio comprises assets within the scope of the asset management system. In this research, the asset portfolio consists of pipe renewal projects.

2.2. Project Models

Decision-making is the process of choosing between alternative courses of action to fulfill one or more goals [50]. Turban, Aronson and Llang [50] state that planning involves a series of decisions. Harmonization of the decision process requires various analyses and the formulation of concrete goals and strategies, the identification of needs, and an evaluation of economic uncertainty [51]. Samset and Volden [52] note that the benefit of adding information is at its highest in the earliest stage of a project, while the costs of making amendments show the opposite trend. Furthermore, they argue that major issues must be addressed as early as possible, such as agreeing on the most effective or appropriate solution to a problem and the choice of concept.

Olsson, Nyström and Pyddoke [53] present the use of stage–gate models as an established best practice in project management. They further define a stage–gate project model as a standardized classification of project phases with specified decision points and supporting documentation. Their study indicates that formal reviews in the form of decision gates contribute to providing realistic cost estimates and support the development of better project concepts [53]. There are several approaches to stage–gate models in infrastructure projects and other large investment projects, which they are primarily used for, as they take into consideration both the front-end and the implementation phases of the project.

In 2000, the Norwegian Ministry of Finance introduced a quality-at-entry regime (project governance model) to mitigate cost overruns in large public projects [54]. The regime is based on a model that emphasizes front-end decision-making and includes two decision gates for quality assessment, named QA1 and QA2, each with defined actions and assessment criteria. Volden and Samset [55] define the phases of a project as front-end, implementation, and operation. This three-phase structure is a simplified framework derived from a comparative evaluation of project governance models in six countries: Denmark, Sweden, the Netherlands, Canada, the United Kingdom, and Norway. These countries typically use more detailed phase structures, such as “Idea/conceptual phase”, “Pre-study”, “Pre-project”, “Detailed engineering”, “Construction”, and “Commissioning and operation” [55]. Most of these systems include more than two decision gates and quality assurance points [56].

Complementing these governance-oriented models, the association Norsk Eiendom [57] developed a project implementation model with defined steps, or phases, for building construction projects. This model is a project delivery model (PDM) [58] and consists of eight steps: “Strategic definition”, “Program and conceptual development”, “Processing of chosen concept”, “Detailed engineering”, “Production and deliveries”, “Hand-over and commissioning”, “Use and asset management”, and “Decommissioning”. The aim is to coordinate actors in building, construction, and civil projects and to serve as a framework for the implementation of building projects [57].

To further illustrate the structure and roles associated with project governance, the division between the corporation (permanent organization) and the project (temporary organization) is shown in Figure 1. Furthermore, the figure illustrates a project delivery model with stages of development outlined from the very beginning (starting with the idea that a change or new asset is needed) to the phasing out of an asset (demolition or sale), as described by Klakegg [58]. The project organization may be given a wide and independent mandate, or a narrow mandate that is tightly interwoven with and dependent on daily business. Roles and responsibilities are defined and described in the corporative system to ensure that the resource control and decision-making process is effective.

When applied to public infrastructure, like a municipal pipe network, the asset will be renewed or replaced rather than phased out or decommissioned. Leitão et al. [49] describe this characteristic as a time-moving window: we receive infrastructure from others; then, we use it and manage its value; and lastly, we pass it on to the next generation. Therefore, such infrastructure often has an indefinite lifespan, as it is constantly maintained, renewed, or upgraded rather than fully decommissioned. The different levels of renewal planning, asset management, and project execution, when an asset is renewed or upgraded and typically managed as a project, are commonly classified as strategic, tactical, or operational [24]. The strategic level in asset management takes into consideration the long-term goals of pipe renewal, while tactical asset management focuses on a bottom-up approach and the short-term effects of coordinating infrastructure upgrading or rehabilitation [59]. Vladeanu and Matthews [28] describe a decision-making model for pipe renewal at the operational level, with phases that they have named data input, data analysis, decision-making constraints, optimization process, and optimal decision.

3. Methods

In this study, mixed methods were utilized. Observations from conversations with sector professionals, a paper from Skaar, Stevik and Johansen [37], and professional experience led to an assumption that decision-making models or other decision-support tools would be a factor in improving pipe renewal projects. The research process was inspired by Stingl and Geraldi [60] and Azarian et al. [61] and used the following steps.

• A methodology to answer the research question was chosen. As a data source for the research, a literature review was considered appropriate.
• Planning stage, in which how the methodology would be executed was discussed.
• Execution stage, as presented in Figure 2.
  • The research need was defined by a gap between the stated pipe renewal need and actual pipe renewal efforts.
  • Problem definition was initiated based on professional observations and common statements in the water sector, followed by scoping and mapping to obtain an overview of relevant literature to further develop the research design. Inputs gained in parallel research aided in refining the problem definition and establishing a precise research question.
    • The parallel research consisted of the following:
      • Conversations with sector professionals to gain context understanding. This formed the direction of the first set of preliminary interviews.
      • Preliminary interviews were conducted to identify the root cause of the backlog in pipe renewal. First, these were conducted assuming a technical cause. In the second round, they were conducted with an understanding that the problem is more complex than technical challenges.
      • The first preliminary interviews sparked a search for literature related to operational decision-making for choosing technology. Later, the second set of preliminary interviews directed the search towards strategic and tactical decision-making in an organizational setting. This formed the basis of this article.
      • In parallel to the literature search, a survey was conducted in 70 municipalities throughout Norway. The aim was to uncover the use of decision support systems and the knowledge of international decision-making models. This formed the assumption of a gap in decision-making for pipe renewal.
      • Finally, the above steps led to a series of semi-structured interviews with Norwegian municipalities with the aim of uncovering the following:
        • Normal practice for project execution regarding project models, decision-support tools, and use of trenchless technology (16 interviews).
        • Decision-making processes in planning and projects leading up to technology choices (16 interviews).
        • Stakeholder’s impact on pipe renewal projects (13 interviews).
        • Project models and processes for pipe renewal (16 interviews).
    • Results from the parallel research concluded on the need for a stand-ardized project process to mitigate limited human resources and varied competence in decision-making, impacting the ability to optimize pipe renewal projects [37]. The ambition to address this need formed the fi-nal problem definition.
  • Development of a research design and a research question to bridge the gap identified in the problem definition.
  • Keyword search for decision-making models for pipe renewal and decision support systems.
  • Refinement of search covering decision-making models, in general, and DSS related to trenchless technology.
    • Screening of abstracts.
    • Thoroughly reading remaining abstracts.
  • Snowball sampling from papers to elaborate on chosen topics.
  • Data analysis and presentation of findings.
    • General decision theory regarding project models.
    • Decision models and DSS for trenchless technologies.
    • Existing decision models and DSS for trenchless technologies relative to a generalized project process.
  • Discussion of the results in order of generalized project processes, leading up to a tailored project model for pipe infrastructures.

The research design is illustrated as a flow chart in Figure 3, which highlights the different steps and results that will be presented in the Results Section and later discussed.

The research process started with an initial problem statement that was discussed with the industry and potential users of new methods for front-end planning and execution of pipe renewal projects. The focus of the literature review was, at first, research papers and grey literature relating to front-end governance of projects, in general, and front-end governance and execution of pipe renewal projects in particular.

Main search engines used were Google Scholar and Oria, supported by Web of Science. Search words and phrases were “project models” and “decision-making models”, including “project models pipe renewal”, “project model nodig”, “decision-making models nodig”, “decision-making models trenchless technology”, and “decision-making pipe renewal”. Furthermore, a snowballing effect from references in papers resulted in articles for “pipe renewal planning” and “infrastructure asset management”. The literature review focused on collecting, summarizing, and evaluating relevant literature. It started as a mapping review to map out and categorize existing literature to commission further reviews and studies, according to Grant and Booth [62]. In total, 284 articles were screened, some with overlapping keywords, and 55 articles were used.

Parallel research was used to calibrate the problem definition and provide more granularity to the literature search. This initiated the need for a more substantial literature review and systematization of decision-support tools and models for pipe renewal. The new search was conducted in Google Scholar, Web of Science, and Oria, using the words and phrases “decision-making models”, “decision support systems”, “Decision-making models trenchless technology”, and “Decision-making models pipe renewal”. This review branched into two directions, covering general decision theory and project implementation, as well as decision support systems for trenchless technology.

4. Results

4.1. Generalized Project Definitions and Models

The research explores project definitions and project models in the context of asset management, aiming to uncover suitable approaches for the water sector. The water sector’s projects, particularly those related to maintaining and developing the public pipe network, have characteristics that differ from traditional construction and large-scale infrastructure projects.

4.2. Asset Management and Long-Term Planning

Figure 3 summarizes the general definitions of asset management planning stages as outlined in the International Standard Organisation (ISO) [46,63] and compares them with the defined infrastructure asset management (IAM) planning scheme used in the water sector. ISO 55000:2014 [46] describes a strategic planning level containing a strategic asset management plan (SAMP) for setting an organization’s asset management objectives. The standard divides these objectives into strategic, tactical, and operational objectives. The SAMP is intended to be used as a guide for an asset management plan at the tactical level, which, in turn, defines specific activities to be undertaken on assets with measurable objectives. These objectives help align operational plans with broader organizational and unit-level business plans. ISO 55000:2024 [63] contains definitions of SAMP and AMP, as well as three stages of objectives. However, it does not explicitly mention operational plans, timeframes, or decision-making steps.

Figure 3. Summary of general definitions of asset management planning stages compared to defined levels of infrastructure asset management (IAM) planning used in the water sector [24,28,46,48,49,63,64].

Figure 3. Summary of general definitions of asset management planning stages compared to defined levels of infrastructure asset management (IAM) planning used in the water sector [24,28,46,48,49,63,64].

To address this gap, researchers in the water sector have proposed a more granular structure by linking planning levels to typical time horizons. Cardoso et al. [48] and Bruaset [24] describe the strategic level as spanning 10–20 years, typically involving master plans that set overarching aims and goals for the asset system. The tactical planning level, spanning 1–5 years, focuses on prioritizing renewal actions within the pipe network. Lastly, the operation level has a shorter perspective of 1–2 years [8,24,48,64]. And it is at this level that we expect to find most pipe renewal projects with corresponding detailed objectives.

4.3. Reviewed Project Definitions

To explore the relationship between general project concepts and asset management in a large system, for example, municipal pipe networks, this study compares some commonly used project definitions, as summarized in Figure 4.

The first model represents governmental project implementation as described by Volden and Samset [55]. It begins with a front-end phase after the allocations of a project mandate, correlating to a strategic planning level, outlined in Figure 4. This is followed by the implementation phase aligned with tactical planning and, finally, an operational phase, where the project results are delivered and utilized. Kalsaas et al. [65] describe how the Norwegian state project model is applied to large-scale public investment projects such as fighter jet acquisitions, railway corridors, airport development, and similar initiatives.

Kalsaas et al. [65] defines a model with a front-end phase followed by a conceptual development phase. The model uses a general implementation phase comprising all engineering steps and deliveries before the final phase: operations. Williams et al. [66] define the front end as a bridging phase between the permanent organization and the temporary organization. This phase includes project initiation and corresponds to a strategic planning level, where key decisions and approval are made to enable the implementation phase. The third project definition introduces a post-project phase, tailored more to infrastructure projects in an asset management context [67]. However, it is more suited for large infrastructure projects, such as highway construction projects, and less applicable to smaller infrastructure projects. The project definition from the Royal Institute of British Architects (RIBA) [68] is more refined and caters to construction projects aimed at completing building projects. This definition encompasses pre-design, design, construction, and a handover phase, aligning with the implementation phases described in the other models. Additionally, it adopts a life cycle perspective for a project, namely, a phase for the building in use and the end of its life. Among the models reviewed, this definition most closely resembles a typical pipe renewal project.

The project model definition presented in Figure 4 is a synthesis of a model designed for projects with a clearly defined start and end, typically spanning a few years. In this context, the permanent organization approves the initialization of a project and receives the infrastructure after construction [66].

Figure 5 illustrates the strategic master plan, which serves as the basis for concurrent renewal and action plans for the zones of the pipe network, presented vertically. According to Bruaset [24], these strategic plans are typically revised every 10 to 20 years, with overlapping renewal plans at the tactical level, typically updated every 1–5 years. Conceptual development and refinement of objectives occur at this tactical level [65]. This places the strategic and tactical planning levels in the front-end phase of the pipe renewal project. Operations in the pipe network, such as data collection and distribution, support future planning [69]. Therefore, the operations will coincide with a new planning phase and, therefore, be part of the front end for future pipe installation or renewal projects. Figure 5 reflects this by merging operations with the front-end phase of subsequent projects.

Furthermore, in Figure 5, the continuous lifespan of the pipe infrastructure project is illustrated horizontally. The illustration begins with the installation of pipe sections in various zones of the entire pipe network. This is followed by a combined operations and front-end phase, which represents maintenance, data collection, and planning for the renewal of sections in each zone. Figure 5 also depicts parallel pipe installation or renewal projects, each with distinct scenarios.

For example,

• Projects 1 and 2 represent the renewal of two and three sections in two different zones.
• Project 3 represents a change in demand, such as urban transformation from industrial to residential use, requiring new installations.
• Project 4 is initiated by external stakeholders, such as road authority, resulting in joint infrastructure development.

These examples demonstrate how water organizations typically manage multiple concurrent projects across different zones. Each project enters a new operations and front-end phase, contributing to an ongoing asset management cycle.

Figure 5 thus illustrates how continuous planning, implementation, and data collection extend the functional lifespan of the pipe network beyond the technical lifespan of individual segments.

4.4. Step Models

To support more detailed project definitions, a compilation of relevant project step models is compared to a proposed project model in Figure 6.

This figure illustrates how the phases and milestones from the Norwegian quality assessment (QA) schemes, with the steps from the ISO standard 55000 and the RIBA Plan of Work model, align with the proposed project model for pipe renewal.

The renewal plans developed by the permanent organization provide the input to the project, including defined goals and stated needs. These objectives form the basis of the project’s mandate and represent the main output from the project’s front-end phase of pipe renewal projects. In these projects, the conceptual phase and development are often shared across multiple projects, as illustrated in Figure 5, which aligns with the pre-project phases in conventional step models. The first phase in the proposed project model involves a feasibility study and an alternative analysis to identify solutions that fulfill the stated needs and goals of the initiative. As shown in Figure 6, the pipe renewal model features a phase-shifted project start compared with the current project step models. This shift reflects how conceptual planning is handled earlier within the permanent organization, before project implementation begins. The distinction is also emphasized in Figure 6, which shows that implementation in pipe renewal projects is initiated later than comparable sectors’ models.

4.5. Proposed Project Model for Pipe Renewal

Pipe renewal projects realize the prioritization and plans made in asset management, some in the form of realization plans [70]. The analysis of the projects’ place in asset management planning [58,66] for goal realization presented in Figure 3, the project definitions in Figure 4 [65,66,67,68,71], the characteristics of pipe renewal processes in Figure 5, and the project step models presented in Figure 6 [55,57,68] collectively point to the need for a project model tailored to pipe infrastructure projects. A model addressing this need is presented in Figure 7, which outlines the steps relative to a general project definition and the granularity of the pipe network, represented by system, zone, and section.

4.5.1. Project Implementation: Pipe Renewal or Installation

Phase 1 in the proposed project model (Figure 7) is a feasibility study that ranks alternative renewal approaches, typically consisting of one technology or a combination of technologies. Other project step models integrate the conceptual phase and strategic definition in the first step, followed by a pre-study or conceptual development in the second [55,57,68].

In the first phase, the needs of other organizations, agencies, and stakeholders are addressed in more detail, and initial assessments of other buried infrastructure, traffic, and soil conditions are made. The main task is to evaluate and rank alternative technologies using Multi-Criteria Decision Analysis (MCDA), identifying the most suitable approach for renewing the specific segment. Furthermore, this is where risk management, according to Vladeanu and Matthews [28] and Brillinger et al. [72], is performed. This makes phase 1 well-suited for using decision support systems (DSSs) in MCDA.

It is important to ensure that the overall needs of asset management are carried forward to the subsequent phases.

The output is one or two preferred approaches and a specific aim for detailed engineering and installation, anchored in the strategic plan’s main objectives.

Phase 2 involves detailed engineering based on the recommended technology or combination of technologies from phase 1. Further investigations into other infrastructure, soil conditions, and stakeholder coordination are conducted and incorporated into design decisions. If phase 1 is executed well, less additional information will be needed during this phase. Phase 2 concludes with tender documents or similar materials for contractor planning.

Phase 3 is the installation phase, during which the project owner typically follows up on production and deliveries. Potential design revisions may occur, usually based on findings during installation or excavations of open trenches. This phase realizes the project’s mandate and fulfils needs according to strategic and tactical plans. Thorough follow-up is essential to ensure that the installation meets the project’s aims.

Phase 4 is where the installed or renewed pipe section is tested before operation. This is the phase that includes the handover of documentation from the project organization to the main water and wastewater organization, typically in the form of a database or a GIS-based map. It represents the transition from the temporary to the permanent organization [66], as illustrated in Figure 4. Complete documentation for operations and maintenance should be registered and approved, marking the conclusion of project deliveries within the organization and the end of the project.

4.5.2. Operational Phases

Phase 5 involves the operation and maintenance of the pipe network managed by the water and wastewater organization as part of asset management [46,63]. In this phase, the permanent organization gathers data for future renewal. Thus, it is depicted as both the operational phase for the previous installation and the front-end for future renewal projects, as shown in Figure 5.

Phase 6 involves renewal planning or decommissioning of the same pipes installed or renewed previously. This is a part of decision-making in long-term planning [73] and, therefore, represents the front-end of the next renewal cycle.

A population will always need a water supply and wastewater disposal system. Therefore, the public need for a pipe network extends beyond the technical lifespan of the individual pipes [74]. The pipe life cycle is illustrated as a continuous timeline, not a circular pattern. These phases will be repeated until the section related to the pipe renewal project is decommissioned and its function is replaced by another part of the system.

5. Discussion

5.1. Asset Management and IAM-Planning

Asset management is defined as an organization’s coordinated activity to realize value from assets. These activities include both planning and implementation [63], aligning with the definitions of long-term planning in infrastructure asset management (IAM) [48,49]. The International Standard Organization (ISO) outlines asset management in three stages in ISO 55000:2014, with corresponding objectives that place the asset portfolio within operational objectives [46]. The updated ISO 55000:2024 no longer uses the term “operational objectives” [63] but introduces the strategic asset management plan (SAMP) as a framework for establishing the organization’s overarching objectives. The SAMP includes a more focused asset management plan (AMP), which may also function as a subsidiary of the SAMP. This structure corresponds to the strategic and tactical planning levels in IAM, linking the three levels of objectives from the ISO standard to the three levels of IAM planning described by Cardoso et al. [48], Leitão et al. [49], and Bruaset [24]. These correlations are summarized in Figure 3. From this alignment, we can derive the timeframe for the SAMP and AMP in IAM and place the implementation of IAM plans at the operational level. For pipe networks, this implementation is primarily carried out through pipe renewal projects.

5.2. Project Definitions

5.2.1. General Project Definitions

The reviewed literature on asset management does not mention project mandates or implementation, focusing instead on operational objectives and prioritization of actions on the pipe network [24,48,75,76]. In some cases, choosing the correct technology is discussed in early project phases, for example, the introduction of trenchless technologies (no-dig) as a strategy in the conceptual project phase [8].

In Figure 4, a pipe renewal project is shown to have a mandate to meet a defined need through the acquisition or construction of an asset, followed by a handover of the installed or renewed infrastructure. Asset management by water and sewer organizations essentially involves delivering safe drinking water and wastewater removal. A key part of this service is the maintenance and operation of a public pipe network. Typically, pipe network renewal involves ongoing replacements of parts of segments over decades, or even centuries. This may include installing new segments to meet emerging needs or renewing an aging segment with poor reliability due to leaks or breaks. In a sense, the management and operation of a pipe network can be viewed as a large-scale program consisting of continuously ongoing, parallel projects. This is illustrated in Figure 5, where n + 1 pipe installation and renewal projects are shown parallel to each other. These correspond to a master plan for water and wastewater infrastructure, along with renewal and action plans for several zones of the pipe network.

5.2.2. Pipe Renewal Projects

Figure 5 shows the project definition and steps relative to the pipe network as a complete system, as pipe network zones, and as single pipe sections.

In the project definition presented in Figure 5, asset management is represented by master plans and the associated renewal and action plans that lead up to the first phase of the project. In Figure 7, these steps constitute the front end of the renewal project. Currently, there is no universal definition of the front-end phase [66]. Berg et al. [77] argue that the front end is inherently tied to the nature of a project, defining it as the permanent organization, while the project itself is defined as a temporary organization. This view is supported by Samset and Volden [52], who place the front-end under project governance, while project implementation comes under project management. The front end of projects is where concepts are identified and the decision to proceed with project implementation is made. Therefore, strategic and tactical plans align with the front end of pipe renewal projects.

Master plans are strategic documents, covering periods spanning 10–20 years [24,48], for networks ideally lasting for centuries. In Figure 5, this is illustrated by consecutive master plans—past, current, and future. This research focuses on the pipe network and discusses master plans as strategic plans for water and wastewater systems. However, the full system also includes pumping stations, water and wastewater treatment plants, and other infrastructure [69]. As shown in Figure 3, it is at the strategic planning level that the conceptual approach to services is taken [55], and the overarching objectives for the system are established. Figure 5 illustrates how the current master plan forms the basis for action plans, which, in turn, provide the basis for pipe renewal projects.

Figure 6 compares existing step models with a project model for pipe infrastructure installation. The existing phase and step models comprise a general governmental project model, a step model for building and construction projects, and a plan of work model for building projects. The proposed model differs from RIBA, QA1/QA2, and ISO-based systems because it is designed for pipe renewal projects that are part of an ongoing infrastructure system, rather than stand-alone projects. It embeds the project within the permanent organization, integrates asset management planning with project phases, and improves information flow for better front-end decisions—elements not addressed by the existing models.

As noted in the Results Section, the Norwegian Governmental project model, as described by Volden and Samset [55], is structured for large-scale public investments, which limits its applicability to smaller, decentralized infrastructure projects like pipe renewal. Pipe renewal projects tend to differ in investment size and time perspective, and they are often implemented in parallel within the managing organization.

Although the governmental model [55] includes steps similar to more focused models [57,68], its granularity and scope differ significantly from the needs of the water sector. These steps have also been compared to the levels of project definition in Figure 4, revealing a key difference in how the front-end definitions of a project are understood. In the proposed project model, the conceptual definition and development are placed within the planning stages of the permanent organization, whereas Volden and Samset [55] place these activities within the project organization.

In water and sewer organizations, data and information are used to decide on and prioritize necessary pipe renewal projects in a vast pipe network [39,64,76,78,79,80,81]. Therefore, concept evaluation and assessment should occur within the permanent organization, and the front end of pipe renewal projects should start in the planning phases [48,49] of the permanent organization [66], as shown in Figure 4.

The Next Step project model is based on an analysis of 10-phase models [57], with a granularity well-suited for building projects. It begins with a strategic definition phase corresponding to the water sector’s action or renewal plans. The subsequent phases are program development and conceptual development, pre-project development, preparation for production and delivery, production and deliveries, handover or commissioning, use, and, finally, decommissioning.

This model is similar to that proposed by Volden and Samset [55]. The phases following strategic definition may serve as a basis for pipe renewal projects with some alterations, including the decommissioning phase. In pipe renewal, a section is typically replaced to maintain the larger network. Decommissioning, in this context, refers to end-of-life status for the section rather than the entire system. Hence, this phase must be tailored to reflect the characteristics of pipe renewal.

The RIBA Plan of Work project model is derived from a review of nine-step models [68]. It begins with “0 Strategic definition”, correlating to the strategic level of asset management. This is followed by “1 Preparation and Briefing”, which overlaps with tactical and operational planning and the front-end phase in project definitions. Later phases are in the operational segment of asset management and correlate to project implementation. These phases are “2 Concept Design”, “3 Spatial Coordination”, “4 Technical Design”, “5 Manufacturing and Construction”, “6 Handover”, and, lastly, “7 Use”. The last phase is considered part of the post-project phase [67].

The RIBA model is similar to the Next Step model, covering phases from conceptual assessment to handover and decommissioning [57,68]. However, these models do not fully accommodate the nature of pipe installation and renewal projects, which involve many external stakeholders [37,82,83] and often include several parallel projects within managing organizations, as shown in Figure 5.

5.3. Project Model for Pipe Renewal

In the proposed model, infrastructure asset management provides the strategic and tactical plans that form the basis for project mandates. Front-end planning translates these plans into specific project objectives and guides the conceptual development phase, where alternative solutions are evaluated to conform to the system’s needs. Conceptual development is thus embedded within the front-end planning and serves as the bridge between long-term asset strategies and project execution. This layered interaction ensured that each project aligns with broader infrastructure goals while responding to local needs.

Front-End of Pipe Renewal Projects

Samset [54] divides a project into a strategic part, which addresses societal factors, and a tactical part, which focuses on project-specific factors. Williams et al. [66] emphasize that the front-end is inherently tied to the definition of a project, placing it in the permanent organization, while the project itself is defined as a temporary organization. This view is supported by Samset and Volden [52], who placed the front end of a project in project governance and project implementation in project management.

Samset and Volden [52] define the front end as essential for strategic project success, noting that the alignment of objectives is achieved through clearly defined goals. These goals relate to the output of project results, the effect of their outcome, and the long-term benefits arising after project completion. However, currently, there is no universally accepted definition of the front-end phase [66,77].

One view is that the front-end of projects is where concepts are identified and the decision to proceed with project implementation is made. Samset and Volden [52] further suggest that the recommended concept should align with the organization’s strategic objectives. These characteristics correspond with the strategic and tactical planning levels in the water and wastewater sector [48,49,75]. Therefore, the front end of the pipe renewal project is composed of strategic and tactical aims and objectives taken from the overarching organizational plans, such as asset management plans and long-term infrastructure strategies [24,49,63,73,75,84]. Furthermore, the utility of adding information is the highest early on in the project, when the opportunity space for solving the problem is greatest, and the cost of changes is the lowest [52]. Thus, the front end of the project model should be a conceptual phase where alternative renewal solutions aligned with asset management goals are identified, analyzed, and, where possible, ranked.

The first phase involves identifying typical needs and general aims, as outlined in strategic and tactical plans [46,63]. This includes the prioritization of segments and condition assessment using asset management planning tools [38,39,41,85]. In pipe renewal, a conceptual approach involves developing alternative solutions, such as renewing existing pipes with similar capacity (e.g., CIPP and sliplining); upgrading the capacity based on updated needs (e.g., pipe bursts); replacing existing pipes with new pipes (e.g., open trenches); or addressing the need with a new corridor (e.g., HDD, pipe ramming, open trench, etc.) [19]. Other typical tasks in this phase include stakeholder analysis [86] and need analysis [52,66,67,87], which help to determine whether the pipe should be renewed or replaced, or if a new segment is needed to meet the objectives of the overarching plans.

Additional assessments may include stormwater management strategies in pipe renewal [8], coordination with other infrastructure needs [88], or evaluating whether a segment can be decommissioned and its function can be fulfilled by another section in the system. Risk management may be performed at a strategic level [24], facilitating more detailed risk management later on in the project [28,72]. Underground infrastructure projects (e.g., pipe installation) impact a wide range of stakeholders. Johansen, Eik-Andresen and Ekambaram [82] argue that risk management of stakeholders may identify opportunities in a project by achieving a better objective. An example of this is improved inter-disciplinary project coordination between road authorities and utility companies, resulting in better scheduling, a shortened construction period, lower costs, and less impact on stakeholders and the surrounding environment.

The output from this phase provides the next phase with a specific renewal approach and narrows the project’s aim. This typically involves ranking different trenchless technologies, open trench pipe installation, a combination of both open trench and trenchless technologies, or a combination of different trenchless technologies. Therefore, the front-end phase is important to give the project a wide range of opportunities and a good foundation to fulfill the overall goals of asset management plans. Moreover, a concise perspective of the concept will provide better cost estimates.

Organizations in many sectors use structured processes to support decision-making, aiming to make decisions more transparent and rational [31]. A standardized framework for project execution and implementation provides a good basis for comparison and learning across sectors [55], and also supports quality assurance management and improves the overall management system [44], optimizing learning and improvements for future projects.

This is why individual organizations in the private and public sectors develop their own project models, and why industries develop common models for implementation or as a reference for best practice [57,58,68]. Among these, stage–gate models are considered best practice in project management, offering structured decision points and enabling more realistic cost estimates [53].

In the water sector, there is a need to improve the management and governance of current and future water systems and corresponding services [89]. This need can, in part, be addressed by adopting a standardized approach to project governance. The proposed project implementation model responds to this need by integrating asset management steps with characteristic project step models [57,68].

Typical project models start with the project idea (cradle) and end with decommissioning (grave), which is executed by the temporary project organization [58]. However, in public infrastructure projects, such as pipe renewal, projects are initiated based on needs identified in asset management plans rather than originating from conceptual ideas. The project’s aims are therefore rooted in long-term planning and strategic priorities.

Following the execution of renewal or replacement, the operations phase encompassing future maintenance is normally transferred from the temporary project organization to the permanent organization responsible for asset management. Moreover, the traditional decommissioning phase is often replaced with a renewal phase administered at both tactical and strategic levels [24,48,49,75]. This diverges from the step models used in other sectors [57,68] but aligns with the project phases that come under the project delivery model presented by Klakegg [58], particularly in terms of how the project phases relate to the overarching organization.

This reflects the typical nature of pipe renewal projects, where the renewed pipe segments are parts of a larger system, and the segments may be replaced or upgraded independently, repeatedly, and in parallel over decades. The overarching elements of the project implementation model represent the asset management levels within water and wastewater organizations, similar to the corporate level, as illustrated by Klakegg [58].

Renewal projects form part of the asset portfolio, which is central to asset management [46]. This level corresponds to the project level in the framework proposed by Klakegg [58] and aligns with the operational level in infrastructure asset management [24,48,49]. It also reflects the business operations of the managing organization [58].

According to Standard Norge [46], asset management is a “coordinated activity of an organization to realize values from an asset”. In infrastructure asset management, the core values for the pipe network, besides the value of the pipes themselves, concern the delivery of a reliable and safe service for the public [47].

This study found that a structured and standardized model contributes to better decision-making early on and reduces costs later on in projects. Moreover, a tailored project model facilitates better decision-making in municipalities and utilities across all levels of asset management. This is relevant for aiding decision-makers in front-end planning by providing better objectives and mandates to project managers.

Future research should investigate a more detailed decision-making process for pipe renewal and interdisciplinary infrastructure projects, such as city street construction combined with subsurface infrastructure and projects involving multiple utilities. Other relevant topics include an exploration of decision support systems, such as Multi-Criteria Decision Analysis for technology choices, and their application in a project context. Furthermore, the transition between front-end decision-making and project implementation for pipe networks needs further exploration to aid project managers in fulfilling objectives set by project owners.

6. Conclusions

We conclude that there is a gap in project models addressing typical project processes for pipe renewal. To ensure the achievement of planning goals, a tailored project model is needed that links front-end decision-making with project execution and operations, contributing to reducing costs and addressing the renewal backlog through efficient technology choices.