# Assessment Framework for the Maintainability of Sewer Pipeline Systems
## 7 Conclusions  
This study assessed 15 sewer pipeline defects and the maintainability of the system in Saudi Arabia. These defects were identified based on the literature and refined by experts through interviews. The experts selected for this study maintain qualification criteria that enabled them to critique and evaluate each defect's probability and impact. The impact involves four parameters: maintenance costs, social inconvenience, environmental risks, and the difficulty of detection, as reported in Table 6. A total of 15 defects were identified, in addition to their possible causes and recommended solutions. Experts then evaluated them to arrive at their RI values, signaling the criticality of each. At the design stage, the designers can use the output of this research to optimize their selections. The sewer system is a vital system in infrastructure facilities. Eliminating unfavorable design decisions and increasing awareness of recurring issues triggered by design or implementation errors can help achieve greater maintainability. This study focused on sewer pipelines and their outputs. It is important to highlight that this study reported minimal variations in RII and RI values, indicating that the identified defects are of almost equivalent importance. As for the study's findings, they can be applied in Saudi Arabia and other countries with similar infrastructure characteristics since sewage line systems, specifications, and standards differ from one country to another. Specifically, the findings of this study have implications for design teams and planners in Saudi Arabia because they provide valuable insights into sewer system design, especially in the form of improved maintainability, which leads to reduced maintenance costs, better system performance, and improved service quality. Thus, making the right decisions in the early stages of design and implementation can mitigate the negative effects of customer complaints and obstructed traffic, reducing environmental pollution and associated costs. However, some limitations exist. Firstly, sewer pipeline maintainability studies are scarce, providing little comparable benchmarking data. The authors collected data from various research articles, case studies, and reports; nevertheless, the experts' interviews helped shape a considerable part of the understanding of sewer pipeline defects and maintenance. On the other hand, the authors endeaved to maintain an analysis of the input and the evaluations provided by the experts that was as balanced as possible. Secondly, the study took place in specific locations since the participating experts were distributed just in two cities, Riyadh and Jizan, which do not necessarily coincide with other geographical locations. Engineering, construction, and maintenance practices may vary geographically, so it is logical to assume a variability factor when applying the results of this study to multiple separate locations. In summary, this study rigorously examined the maintainability of sewer pipeline systems in Saudi Arabia, assessing 15 defects identified via expert evaluations. The impact parameters, encompassing maintenance costs, social inconvenience, environmental risks, and the difficulty of detection, were analyzed (as depicted in Table 6). The findings reveal a critical insight into the significance of these defects, with minimal variations in risk index (RI) values, underscoring their equivalent importance. This insight can serve as a valuable tool for designers and planners not only in Saudi Arabia but also in countries sharing similar infrastructure characteristics. By incorporating these findings into the early stages of sewer system design, decision makers can significantly enhance maintainability, leading to reduced maintenance costs, better system performance, and improved service quality. These benefits translate into mitigating negative customer complaints, alleviating traffic disruptions, and reducing environmental pollution, thus minimizing associated costs.