Municipalities face to challenges related to urban infrastructure, mainly related to aging infrastructure. The metropolitan area of Seoul, Korea, reported that more than half of the entire sewer systems are over 30 years old. The deteriorated sewer systems caused serious safety disaster such as sink hole and other social problems. Furthermore, these phenomena continue to accelerate because the sewer systems are seriously affected by variability of rainfall which results from the climate change and human migration from the social change. Therefore, it is necessary to do proactive rehabilitation instead of overdue maintenance considering the social and environmental change. This research presents the conceptual framework for deciding the priority for investment in the borough of Seoul which is based on the extensive evaluation for identifying the sewer pipelines which need rehabilitation work. To address the comprehensive evaluation of priority for investment, Genetic Algorithm (GA), is adopted to find optimal budget allocation for each borough which is derived from considering the technical, economic, environmental, and social aspects. The result can be used as reference to budget allocation to improve the sustainability of the sewer systems.