Risk of Ground Subsidence... Now Inspections Will Be Done with "Underwater Drones" Instead of Excavation

Aging Water Pipes Inspected Without Excavation
Comprehensive Survey Unlike Endoscopic Methods
Checks Not Only Corrosion but Also Sediment and Joints
Expansion Considered After Pilot Projects in Hoehyeon-dong and Other Areas

The Seoul Metropolitan Government is introducing "underwater drone CCTV" to manage aging water supply pipes, which are the main cause of ground subsidence accidents. It is expected that the current inconveniences-such as deploying large-scale equipment and personnel, digging up the ground, and restricting roads when inspecting or repairing vulnerable sections-will be significantly reduced.

According to the maintenance industry on August 19, the Seoul Metropolitan Government and the Central Waterworks Office have recently begun establishing a system to utilize advanced underwater drone CCTV for precise diagnosis of water supply pipes.

The scene of a large sinkhole that occurred on the road near Daemyeong Elementary School in Gangdong-gu last March. A motorcyclist fell into the large sinkhole, which is approximately 20 meters in diameter and 18 meters deep. Photo by Yonhap News

Aging water supply pipes are identified as a primary cause of ground subsidence. A typical case involves unused and abandoned pipes being left unattended, leading to internal corrosion and collapse, which in turn causes the surrounding soil to cave in. Even if the pipes do not corrode, aging can result in leaks, washing away the surrounding soil and causing the ground to collapse.

The problem is that prevention is not easy. Although the Seoul Metropolitan Government inspects aging water supply pipes, it has not been able to avoid large-scale excavation using equipment and personnel. Even when excavation is carried out, the inspection range is limited, and traffic control is required, leading to continued complaints from citizens.

The increase in aging pipes is also steep. As of last year, the total length of water supply facilities in Seoul was 13,288 kilometers, of which 9,460 kilometers-or 70%-are pipes that have been in place for more than 20 years. An official from the Seoul Metropolitan Government added, "When including not only excavation but also road repaving and reinstallation of buried objects, the restoration costs are increasing every year."

In response, the Central Waterworks Office has decided to deploy "underwater drones" equipped with advanced CCTV technology for pipe inspections. Unlike endoscopic inspections, which target short sections, underwater drones can operate underwater and inspect 100% of the internal conditions of the pipes, including corrosion, sediment, and joints. Most importantly, the operating cost is low. The inspection coverage per underwater drone is wide, making the cost-effectiveness only 3,200 won per meter. Since there is no need for excavation or restoration work, the inspection period is also expected to be significantly reduced.

The Seoul Metropolitan Government plans to launch a pilot project at two to three locations in the city. In Hoehyeon Intersection, Hoehyeon-dong, Jung-gu, underwater drones will be used to examine the status and aging of abandoned pipes. In the areas of Namyeong-dong and Ichon-dong, transmission and distribution pipes that have been in use for over 20 years without any cleaning history will be inspected. Depending on the diagnostic results, dismantling work may follow in addition to maintenance.

The related data is highly likely to be linked to the ongoing sewer pipe inspection project and the construction of a ground characteristics analysis map being promoted by the Seoul Metropolitan Government. If the scope of underwater drone inspections is expanded as part of efforts to prevent ground subsidence or water quality accidents, the speed of related projects is expected to increase further.

Currently, the Seoul Metropolitan Government has begun a phased, comprehensive inspection of sewer pipes over 30 years old to prevent large-scale ground subsidence accidents. This is the first stage of a long-term plan to manage all aging sewer pipes over 30 years old (6,029 kilometers). The city has decided to prioritize inspection of 1,848 kilometers of old circular sewer pipes within "priority maintenance zones (D and E grades)," which have the highest likelihood of ground subsidence.

Following the accident in Myeongil-dong, Gangdong-gu in March, the city also began developing a "ground characteristics analysis map" as part of its "underground space management innovation plan." The city is expanding analysis factors such as groundwater, ground subsidence, and cavity occurrence, and incorporating predictive models based on time history. Recently, a system has been established to immediately dispatch experts to the site when signs of ground subsidence are detected. The city will also operate a separate advisory panel in cooperation with organizations such as the Korean Society of Civil Engineers, the Korean Geotechnical Society, and the Korean Tunneling and Underground Space Association. The panel plans to prioritize reviews of the following: areas with a surface area of at least 0.8 square meters or a depth of at least 0.8 meters; areas where ground subsidence has resulted in casualties; and areas where ground subsidence has repeatedly occurred near excavation sites, adjacent roads, or the same location.

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