Citizens Anxious Over Series of Sinkhole Accidents
6,028 km of Seoul’s Sewage Pipelines Over 30 Years Old
Enormous Replacement Costs
"Underground Facilities Managed Separately by Ministries and Agencies
Need for Comprehensive Understanding of Entire Underground Space"
"My child also passes by this way every day..."
On the afternoon of the 17th, Mr. Lee (45), a resident of Sinnae-dong, Jungnang-gu, Seoul, sighed as he looked at the sinkhole site. Recently, a sinkhole measuring 40 cm in width and length and about 1 meter deep occurred at the crosswalk near Jungnang-gu Office intersection. Although officials from Jungnang-gu Office discovered it during a patrol and filled it with soil and asphalt, the nearby residents' anxiety has not subsided. Mr. Lee said, "Sinkholes, which I only saw on the news every day, have appeared in our neighborhood, so it's scary," adding, "I repeatedly tell my child to be careful on the way to and from school."
Last September, a large sinkhole measuring approximately 10 meters wide, 5 meters long, and 8 meters deep occurred on a road in Sasang-gu, Busan, with two trucks trapped inside. Photo by Yonhap News
Sinkholes, which occur frequently across the country, are threatening daily life. According to the Ministry of Land, Infrastructure and Transport, there were 2,085 sinkholes nationwide over the past 10 years from 2014 to 2023. By region, Gyeonggi had the highest number with 429 cases, followed by Gangwon with 270, Seoul with 216, Gwangju with 182, Chungbuk with 171, Busan with 157, and Daejeon with 130.
A representative case was a large sinkhole with a diameter and depth of 20 meters each that occurred on the 24th of last month in Gangdong-gu, Seoul, resulting in the death of a motorcycle rider. Earlier this month, on the 13th, a sinkhole measuring 40 cm in diameter and 1.3 meters deep occurred near Exit 2 of Aeogae Station in Mapo-gu, Seoul. Although temporary repairs were completed about eight hours after the report, nearby residents were left shaken. Sinkholes also occurred in Bupyeong-gu, Incheon, and Dong-gu, Gwangju, with depths of 10 cm and 1.7 meters respectively, as well as on a roadway near the dawn market in Gamjeon-dong, Sasang-gu, Busan.
Sinkhole site on the road near Jungnang-gu Office intersection in Sinnae-dong, Jungnang-gu, Seoul. Photo by Byeon Seon-jin
The primary cause of sinkhole accidents is attributed to aging water and sewage pipes. According to the Ministry of Environment, as of December 2023, the total length of buried water pipes and sewage pipes nationwide is 246,126 km and 172,495 km, respectively. Among these, water pipes and sewage pipes installed before 2003 account for 93,969 km (38.2%) and 18,144 km (10.5%), respectively. Generally, water and sewage pipes are considered aged if they have been installed for more than 20 years. Professor Bae Woong-gyu of Chung-Ang University's Department of Urban Engineering explained, "Aging water and sewage pipes prone to leakage gradually wash away underground soil, creating empty spaces, which causes the surface to collapse and increases the likelihood of sinkholes."
The problem lies in the enormous replacement costs. Although Seoul City spends 200 billion KRW annually to maintain 100 km of aging sewage pipelines, considering that there are 6,028 km of sewage pipelines over 30 years old (according to Seoul City statistics), the maintenance speed is far too slow. The older the water and sewage pipes, the more difficult the repairs. The Korean Spatial Information Society pointed out in its 2010 report titled "Research on Improvement of Underground Water Facility Survey" that the average error in underground water facility location (the average distance difference between actual and map locations) reaches 79 cm (based on Seoul City data).
Each local government is struggling to devise measures to prevent sinkhole recurrence. Seoul and Busan cities have planned to actively conduct GPR (Ground Penetrating Radar) surveys. However, since GPR can only survey up to a depth of 2 meters underground, questions remain about its effectiveness. There are opinions that 3D GPR, which collects data in width, length, and depth directions simultaneously, should be introduced, but again, insufficient budgets are an issue.
Experts point out that to fundamentally prevent sinkhole accidents, a control tower related to underground safety must operate organically. Moon Hyun-chul, vice president of the Korean Disaster Science Society, said, "Various facilities such as water and sewage pipes, communication lines, and subways are intertwined underground roads, but each is managed separately by different ministries and agencies," adding, "The government should prepare measures to comprehensively understand and respond to the entire underground space."
Professor Bae Woong-gyu also added, "Individual local governments' response capabilities will have limitations in dealing with sinkholes," emphasizing, "Active budget support at the government level is also necessary."
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