Aging sewer lines have been cited as a major cause of ground subsidence. Water leaking through cracks can erode soil beneath roads, leading to sinkholes. (Image courtesy of Yonhap)
SEOUL, April 16, (Korea Bizwire) — Nearly one-third of Seoul’s underground sewer lines have surpassed 50 years of age, with some districts relying on antiquated infrastructure for more than half of their networks, raising concerns over public safety and the growing risk of sinkholes.
According to data disclosed by Rep. Jin Sun-mi of the Democratic Party and submitted by the Seoul Metropolitan Government, as of December 2023, 3,300 kilometers — or 30.4 percent — of the capital’s 10,866-kilometer sewer system are more than 50 years old. Over 55 percent of the system is older than 30 years, the general threshold for infrastructure considered at risk of failure.
The most aging networks are concentrated in central and older districts. Jongno District topped the list, with 53.5 percent of its sewers exceeding 50 years, followed by Yongsan (48.5%), Seongbuk (47.7%), and Yeongdeungpo (45.7%). More than 66 percent of sewer pipes in Jongno and Dobong districts have been in use for over three decades.
Aging sewer lines have been cited as a major cause of ground subsidence. Water leaking through cracks can erode soil beneath roads, leading to sinkholes. Government data show that of 867 sinkholes reported nationwide between 2020 and 2024, nearly half — 394 cases — were attributed to sewer line failures.
To prevent further incidents, the city employs ground-penetrating radar (GPR) to detect underground voids and conducts repair work. However, GPR is limited to depths of only two meters, leaving deeper vulnerabilities undetected.
Despite Seoul’s current annual budget of 200 billion won (approximately $147 million) to refurbish 100 kilometers of sewer lines each year, officials acknowledge that it falls short of what is required to keep up with aging infrastructure. City officials estimate that 150 kilometers need to be repaired annually to stabilize risk levels.
To accelerate replacement, the city is considering tapping into its disaster management fund in addition to its dedicated sewer maintenance budget. It is also in talks with the national government to secure additional funding.
“We cannot leave the safety of roads that citizens use daily to chance,” Rep. Jin said, calling for increased transparency and urgent joint action between local and central authorities to modernize the capital’s underground infrastructure.
M. H. Lee (mhlee@koreabizwire.com)
