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Busan City Sasang~Hadang Line Sinkhole Accident: Revealing the True Face of Poor Construction through Audit Results
The Busan Urban Railway Sasang~Hadang Line is a large-scale infrastructure project underway to resolve traffic issues in the western region of Busan.
However, on September 21, 2024, at 8:50 AM, a major sinkhole accident occurred at the starting point of section 2, causing great anxiety among citizens. This accident is known to have arisen from the combination of heavy rain measuring 379mm, poor construction management of the cofferdam works, and problems with the junction of the drainage system. Since then, several smaller sinkholes have appeared throughout the Busan area.
This incident was not a problem that could simply be attributed to a natural disaster. The Busan City Audit Committee conducted a special audit from October 21 to November 15, 2024, and announced the results on April 22, 2025. The investigation revealed serious structural defects and negligence in management in several aspects of the construction.
Poor Construction and Management Revealed by Audit Results
The Audit Committee recently reported 10 administrative measures and 33 personal measures based on the results of the audit, along with a demand for a reduction in design costs by 1.159 billion won.
In particular, the location of the accident appears to be the result of multiple issues accumulating over time.
Firstly, the quality of the cofferdam works was lacking, resulting in the outflow of cofferdam materials, loss of soil retaining plates, failure to install thumb piles, and poor securing of wooden soil retaining plates, causing groundwater and outflow water to wash away the soil, further exacerbating the ground collapse.
Secondly, the construction of the drainage junction was inappropriate. Damage to the U-shaped ditch and the occurrence of outflow water, along with poor handling of the connection points with corrugated steel pipes, accelerated ground weakening.
Thirdly, safety management was also neglected. The construction project management engineer, while also handling material inspection and process management, allowed actual safety work to be sidelined.
Lastly, the construction project management team directed the contractor, who was unqualified for the cofferdam testing, to perform work based on an inappropriate quality test report without verifying it, causing significant disruptions to the construction from issues like groundwater and soil outflow during excavation. These problems require improvements in the future.
Measures and Tasks to Prevent Recurrence
Busan City has identified overall problems in the construction from the recent audit and has prepared improvement plans for the construction and management systems.
The Audit Committee has called for improvements in the following areas: First, there is a need for improvements in design and construction methods. Approximately 893 million won could have been reduced from the duplicated calculation of plain concrete, asphalt sheet waterproofing, and partition wall construction.
Secondly, issues of inadequacy in managing environmental impact assessments have been pointed out. Warnings were issued for the sloppy conduct of services that randomly changed soil investigation points or reused photos.
Thirdly, problems with unit price designs were also revealed. An electrical and mechanical construction project worth about 1 billion won was designed with a unit price, and it was confirmed that improper payments were made for unexecuted items.
Lastly, it was indicated that management of project delays was lacking. There was no analysis of causes for sections where the construction schedule was delayed by more than 5%, nor were recovery measures prepared.
If such problems persist, public trust in Busan's urban railway projects will inevitably decline. To ensure citizen safety and prevent budget waste, rigorous quality management and transparent administrative procedures are essential.
Large SOC Projects Must Adhere to Fundamentals
The accidents and audit results from the Sasang~Hadang Line construction project illustrate a comprehensive management failure that transcends mere technical errors. The construction of public infrastructure demands a high level of responsibility, where even a moment of negligence is not acceptable.
Busan City must establish a thorough recurrence prevention system through this audit and needs to implement strict standards and monitoring systems to prevent similar incidents in future urban railway construction processes.
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