Blind Spots Remain in Underground Excavation... Underground Safety Act Enforcement Must Be Strengthened [New Traffic Refugee Report] 17

70% of Excavation Projects Are 10 to 20 Meters Deep
No Post-Construction Investigation for Small-Scale Underground Safety Assessments
Verification Needed to Ensure Proper Implementation After Construction

The perception of sinkholes as a disaster among citizens dates back 11 years to the construction site of the Jamsil 2nd Lotte Tower. At that time, the extension work for Subway Line 9 was identified as the cause of the sinkhole, which led to the enactment of the Special Act on Underground Safety Management.

On March 24, a large sinkhole spanning four lanes occurred at an intersection near Daemyeong Elementary School in Gangdong-gu, Seoul. On the 25th, the area around the accident site was cordoned off. One passenger car and one motorcycle fell into the sinkhole, and one occupant of the passenger car was transported to a nearby hospital. Currently, one motorcycle driver is buried under the sinkhole. The depth is estimated to be 30 meters. 2025. 03. 25 Photo by Dongju Yoon

The Underground Safety Act stipulates that for development projects involving excavation deeper than 20 meters, an underground safety assessment must be conducted before the project begins, and an underground safety investigation must be carried out after construction starts. For excavation work deeper than 10 meters but less than 20 meters, a 'small-scale underground safety assessment' is required. Once this small-scale assessment is completed before construction, there is no separate investigation procedure after construction begins. Therefore, there are concerns that, rather than simply strengthening the current Underground Safety Act, its enforceability should be enhanced to reduce ground subsidence accidents.

About 70% of excavation projects undergo a small-scale underground safety assessment, but there is no verification process to check whether the assessment is properly implemented after construction begins, which is also a problem. For the underground safety assessment, which is currently conducted once a month, there are calls to introduce a system where investigations are carried out weekly and measurement reports are submitted monthly.

An expert in civil engineering and safety stated, "The underground safety assessment is ultimately conducted before construction, but the investigation during actual excavation is the most important. Even if the design is perfect, it may not match the real conditions. It is necessary to closely observe the state of the construction site, including the geology and groundwater."

This year, as a series of large-scale ground subsidence accidents occurred in areas such as Myeongil-dong in Gangdong-gu and the Gwangmyeong Shinansan Line construction site, the government has also focused on improving the underground safety management system. In the past five years, there have been a total of 867 ground subsidence accidents, and among the 57 major incidents, 21 cases (37%) were caused by poor excavation-related construction. Previously, ground investigations were conducted only at the request of local governments, but now the Ministry of Land, Infrastructure and Transport has decided to carry them out ex officio. High-risk areas, such as those with a history of ground subsidence, regions with significant groundwater outflow, and sections adjacent to subway stations, will be investigated first. In May, the Ministry amended the Underground Safety Act to grant itself the authority to directly conduct on-site investigations.

The government is also considering a plan to divide underground safety assessments by section or extension for large-scale excavation sites. In order to ensure appropriate compensation for post-construction underground safety investigations, the criteria for calculating required personnel will also be adjusted. In the second half of the year, the Underground Safety Act will be amended to introduce a new penalty clause, imposing a fine of up to 10 million won on companies that conduct inadequate underground safety investigations after excavation work begins.