Sinkhole at Yangyang Naksan Hotel Construction Site... Blamed on 'Poor Construction' to Prevent Construction Delays

[Image source=Yonhap News]

Groundwater and soil intrusion into the site due to poor construction... Ground subsidence occurred

Severe penalties including 4-month business suspension for the construction company

Strengthening management of soft ground areas such as coastal zones

[Asia Economy Reporter Kim Min-young] The sinkhole (ground subsidence) that occurred near the residential lodging facility construction site at Naksan Beach, Yangyang-gun, Gangwon Province in August was caused by the construction company's hasty and poor-quality work. Due to the coastal characteristics, the loose sandy ground is prone to soil erosion, and the groundwater flow is high due to the sea influence, requiring meticulous construction. However, the ground deteriorated further due to short-term construction aimed at making up for delays, leading to the sinkhole. The Ministry of Land, Infrastructure and Transport plans to allow construction to resume only after all accident risks are eliminated through a thorough investigation by external experts in soil and foundation fields. In addition, the Seoul Metropolitan Government will impose strict measures such as business suspension on the construction company and other firms involved in this project.

On the 3rd, the Central Underground Accident Investigation Committee, chaired by Professor Lee Seung-ho of Sangji University (President of the Korean Society of Civil Engineers), announced the investigation results of the ground subsidence accident in Yangyang-gun that occurred in August.

◇ Construction company recognized poor quality but applied patchwork measures... Surrounding ground worsened = On the morning of August 3rd at around 6:40 AM, a sinkhole measuring 12 meters wide, 8 meters long, and 5 meters deep occurred near the residential lodging facility construction site at Naksan Beach, Ganghyeon-myeon, Yangyang-gun, causing partial collapse of a nearby convenience store building. Although no one was injured, confusion ensued as the convenience store owner and 96 guests staying at nearby lodging facilities were urgently evacuated. There were also multiple reports from the surrounding area that ground subsidence had occurred 25 times from late December last year to mid-February this year, indicating warning signs.

The investigation by the committee revealed that the main cause of the sinkhole was the construction company’s failure to fully consider the site’s special conditions during construction. Due to poor construction by the company, small gaps appeared in the temporary earth retaining wall, through which some groundwater and soil from the surroundings infiltrated, leading to ground subsidence. The temporary earth retaining wall is a provisional structure used to prevent soil from flowing into or collapsing into the excavation site during ground excavation.

The accident site is a coastal area with loose sandy ground prone to soil erosion, and due to the sea influence, groundwater flow is high. Therefore, construction quality and safety management at a higher level than inland areas composed of solid granite and gneiss are essential during underground development.

However, the construction company, despite recognizing the poor construction, only carried out localized reinforcements and applied patchwork measures. Subsequently, to make up for construction delays, they conducted short-term, intensive construction. This further deteriorated the earth retaining wall and surrounding ground. As poor construction accumulated, holes formed in the earth retaining wall, allowing rapid infiltration of groundwater and soil, resulting in large-scale ground subsidence.

The underground safety evaluation company omitted safety reviews of the nearby convenience store building and failed to report design changes and small-scale ground subsidence incidents to the licensing authorities. Most of the site monitoring instruments installed by the construction company (such as inclinometers and groundwater level gauges) were lost or damaged, making timely accident prevention measures difficult.

◇ Construction to resume only after all accident risks are eliminated; 4-month business suspension for construction company as severe penalty = The Ministry of Land, Infrastructure and Transport plans to request the competent authorities to impose penalties according to relevant laws and regulations based on the investigation results, including △ 4-month business suspension for the construction company, △ work suspension of up to 2 years for the supervising engineer, △ 3-month business suspension for the underground safety evaluation company, and △ 3 to 9 penalty points for construction technicians depending on their affiliation.

Considering the possibility of additional risks, the Ministry plans to allow construction to resume only after a thorough investigation by external experts in soil and foundation fields eliminates all accident concerns. Upon resumption, the damaged temporary earth retaining wall will be supported by ensuring sufficient strength of the main structure’s floor slab, with Yangyang-gun responsible for management.

To prevent recurrence of similar accidents, the Ministry will require the licensing authority, Yangyang-gun, to have construction companies of nearby underground development projects carefully review design drawings and underground safety evaluation reports, and to reinforce vulnerabilities in earth retaining walls and waterproofing methods. Furthermore, from this month, joint inspections by the Wonju Regional Land Management Office, Yangyang-gun, and related agencies will be conducted quarterly at all sites including the accident site.

◇ Raising safety management standards for development projects on soft ground such as coastal areas = Separately, safety management for development projects on soft ground such as coastal areas will be strengthened. First, standards for soft ground will be established in legislation, and safety management standards will be raised to require construction companies to use construction methods with high rigidity and waterproofing performance, improving the underground safety system.

Additionally, the development and expanded use of advanced underground safety technologies (such as smart monitoring management and integrated underground space mapping) will be encouraged, and emergency safety order authority will be granted to heads of metropolitan governments.

To strengthen overall underground safety, the expansion of emergency ground surveys by national specialized agencies will be promoted, and through inter-ministerial cooperation, vulnerable and aging underground facilities will be maintained or replaced.

Moreover, when there is a risk of ground subsidence, local governments will conduct a ‘ground subsidence risk assessment’ and be able to charge costs to the parties responsible for causing the risk.

Lee Sang-il, Director of Technical Safety Policy at the Ministry of Land, Infrastructure and Transport, stated, "Based on the cause investigation results identified by the committee, we will demand strict measures from related agencies for any violations, and continuously manage to ensure thorough implementation of the safety measures proposed by the committee at the accident site and adjacent construction sites."

This content was produced with the assistance of AI translation services.