Obsolescence Risk Assessment of Infrastructure Stocks: A Case Study of Japan's Sewer Pipes

Abstract

The aging of urban structures such as buildings and infrastructures has been getting serious in these years. Those material stocks should be appropriately maintained for a long period of time, however, budget constraints and labor shortage due to population decline seem to make the situation more difficult. This study aims to estimate the amount of Japan's sewer pipe stock and compare the obsolescence risk with combinations of soundness of the existing stock and population forecast among prefectures. As results, the amount of sewer pipe stock was estimated to be 115 million t in 2018, and the rates of aged stock requiring urgent maintenance were 29% for concrete pipes and 13% for PVC pipes, respectively. Obsolescence risk was high in Hokkaido, Nara, Yamaguchi, Miyazaki and Kagoshima, indicating that those especially need deliberate countermeasures for a long-term stock management.