Seoul launches inspection to search for underground cavities

The Seoul Metropolitan Government on Monday launched a five-day inspection to look for large underground cavities that could potentially pose hazards to drivers and pedestrians, part of a response to concerns following a series of fatal accidents this year.

The inspection will cover the vicinities of Jongno 3-ga Station, Yeouido Station and Seoul National University of Education Station - all crowded subway stations with multiple lines that have a number of underground facilities, including deteriorating water pipes.

However, the Seoul city government said the assessment will not cover the Jamsil area, where a number of potholes and large underground cavities were discovered over the past few months, because it had already completed an evaluation of the neighborhood, particularly the construction sites for Subway Line No. 9.

Seoul is collaborating with Geo Search, Japan’s biggest geological prospecting company, on the assessment. The company has agreed to provide a vehicle-mounted ground-penetrating radar (GPR) and an endoscope, which will offer a more detailed look at suspect areas.

The city government said that the Tokyo-based Geo Search owns 100 vehicle-mounted GPRs and 40 endoscopes and has so far found about 26,000 underground cavities over the past 25 years, during which it has inspected an area of about 125,238 kilometers (77,819 miles).

The GPR that will be used this time covers 2.4 square meters (25.8 square feet) at once and is loaded onto a vehicle for easy mobility. The tool provides visual data of a scanned area, while the endoscope will be used to take a look at ground believed to contain air pockets.

The local government also owns a GPR, but it must be moved manually and is not as effective as a vehicle-mounted apparatus.

“We have had difficulty searching for underground cavities with our equipment, and I expect that this inspection, using high-end equipment, will be a great help to us,” said Lee Taek-geun, head of the Road Management Division in the Seoul Metropolitan Government. “We will do our best to take preventive measures to create a safe environment for our citizens.”

The controversy over underground cavities intensified in the summer when several large underground cavities were discovered under the Seokchon Underpass, one of which was 80 meters (262 feet) long.

A probe by the city government determined that the underground construction for the extension of Subway Line No. 9 underneath was to blame.

BY KIM BONG-MOON [bongmoon@joongang.co.kr]