Today, as the global population and number of cities continue to rise, another critical issue emerges: the aging of urban areas and their infrastructure systems. Old pipeline networks suffer from significant issues such as fractures, collapses, and blockages. Currently, nearly half of all newly produced pipes are used to replace these deteriorated pipelines.

According to a Canada-based research group (NRC), the cost of replacing water pipelines in North America is estimated at $400 billion. The American Water Works Association (AWWA) projects that over the next 30 years, $250 billion will be required for pipeline rehabilitation. Similarly, a study in Germany found that replacing pipelines installed since the early 20th century would demand €12 billion annually. Despite these findings, water authorities are slow to act, with annual pipeline replacement rates lingering at only 0.5–1%. This raises serious concerns for environmental and public health, emphasizing the need to accelerate new pipeline installations and adopt modern rehabilitation techniques.

In water transmission lines, excavation, covering, bracing, and insulation account for 85–95% of initial investment costs. In comparison, pipe materials, transportation, and installation contribute only 5–15% of total costs. A 10% change in the cost of pipe and fittings has a negligible impact of 1–1.5% on total project expenses. Consequently, operational and long-term performance considerations, as well as minimal maintenance and spare parts requirements, should take precedence over initial material costs.

Regardless of the pipe type, underground pipeline systems are susceptible to various damages caused by external mechanical factors, soil movement, corrosion, and improper pipe connections. Time-dependent characteristics such as resistance to vertical loads, deformation under stress, and the maintenance of fluid purity are equally significant. Over the past decade, nearly all major metropolitan municipalities have implemented substantial infrastructure projects.

Infrastructure Management

a) Life Cycle Analysis

Renewing infrastructure services is an expensive and labor-intensive process. For this reason, infrastructure transmission lines are expected to have long service lives. With repairs, maintenance, and rehabilitation applied to existing lines, the service life of these systems is extended. Life cycle analysis is the most important approach for prioritizing repairs, maintenance, and rehabilitation of lines. The cost of a pipeline to the public is the total cost incurred throughout its service life. This includes repair, maintenance, and rehabilitation costs during the system’s operational period. Accordingly, infrastructure services should be designed to allow easy repair and rehabilitation. Thus, the total cost of infrastructure systems throughout their service life can be minimized. Although the initial installation costs of a pipeline may seem reasonable, frequent costly repairs and the resulting need for advanced materials and equipment can significantly increase the total cost over its lifetime.

The design, installation, and rehabilitation of pipelines and related drainage services are critical engineering fields. As with all engineering sciences, the preparation of projects in this field should depend on the choice of materials and/or systems. During the installation of hydraulic structures, considering multiple criteria simultaneously is essential and necessary for proper design. These criteria include hydrology, hydraulic principles, long service life, material-strength relationships, standards-specifications, planning, management, control, statistical data, and total cost. In prepared projects, initial installation cost is often the primary focus, and the application of advanced, high-strength materials is neglected. The costs arising from repair and rehabilitation efforts due to damages in the system are not considered. As a result, the total cost incurred throughout the service life of the system increases significantly. In life cycle analysis, the initial installation cost is the least significant factor among those contributing to the total cost throughout the system’s lifetime.

b) Social Costs

Social cost can be defined as the side effects of all actions performed to execute a project. Although many items in these actions are calculated as project costs, some unaccounted-for actions also incur costs. All of these costs impact society. Calculating social cost is not easy. For example, transporting materials and equipment used in a project constitutes part of the social cost. The cost to society of a project must also be taken into account, with the aim of minimizing societal impact. Social cost groups are divided into five categories: traffic, environment, commerce, industry, and urban/societal.

Figure: Total Costs Arising in Infrastructure Rehabilitations 

Traffic

When certain sections or the entirety of a road are closed due to excavation, traffic disruptions occur. Alternative routes lead to increased fuel consumption, and accidents may result from roadside construction activities. Roads used as alternatives may not be durable enough for extended use and can suffer damage. Some excavations may lead to fatal accidents, and the associated costs are included in social costs.

Figure: Road Damage and Traffic Disruptions Caused by Infrastructure Line Repairs

Environment

Factors occurring during a project may also harm the environment. These harms include cutting trees or roots, damage caused by machinery, contamination of water during excavation, and fuel leaks from vehicles used in the project.

Commerce and Industry

Interruptions in access to warehouses or factories due to excavations can lead to financial and labor losses. Construction activities during rehabilitation may prevent business access, leading to sales losses in commerce and production losses in industry.

Urban and Societal Impact

When infrastructure becomes unusable, society and public services are adversely affected, resulting in additional public costs. For example, open excavations and damaged road surfaces after project completion necessitate additional public expenditures for repairs.

Figure: Disruption of Daily Activities Due to Ongoing Infrastructure Rehabilitations

Health and Safety

Infrastructure rehabilitation strategies range from regional repairs to lining and replacing old pipes with new ones. Occupational safety is of primary importance in all methods. While some applications require human entry, remote-controlled imaging methods are also used.

When workers are required to work inside pipelines, they face specific risks. Safety procedures must be established and implemented for worker protection. Before work begins, the area to be worked on should be evaluated for potential hazards. Certain chemicals used in wastewater rehabilitation, such as styrene found in resins and coatings, can have adverse effects on human health through skin contact or inhalation. These chemicals can cause severe health problems, including long-term illnesses. To prevent toxic exposure and inhalation in pipeline environments, protective clothing and appropriate ventilation must be ensured.

The Turkish Society for Infrastructure and Trenchless Technologies is committed to advancing construction methods and infrastructure systems. Through national and international collaboration, the association seeks to provide optimal solutions to manufacturers, users, and researchers a like.