Firefighters rescue and transport a buried worker following the collapse of a boiler tower at the Ulsan Thermal Power Plant in Nam District, Ulsan, on Nov. 7. The worker was later pronounced dead at a hospital. [ULSAN FIRE DEPARTMENT]

The recent collapse of a boiler tower at the Ulsan Thermal Power Plant that killed at least three workers has exposed a regulatory blind spot that allowed the aging structure to be classified as an "installation," rather than a building, to bypass the safety checks required for its demolition.

Under Article 2 of the Building Act, any installation with a roof, pillars or walls should be considered a building. For buildings taller than six stories or with a total floor area of more than 1,000 square meters (1,200 square yards), demolition requires approval from the local government. The process includes a review of the building's structural safety and the adequacy of the demolition plan.

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"The boiler tower was not subject to the Act on the Management of Buildings, so no demolition or safety plans were submitted, and no supervision took place before the work," an Ulsan Nam District Office official said.

The official added that the main building in the same power plant complex, classified as a building, "did receive approval last November after a demolition plan was submitted in September."

Nighttime recovery operations are underway at the site of a boiler tower collapse at the Ulsan Thermal Power Plant in Nam District, Ulsan, on the evening of Nov. 6. [YONHAP]

This classification gap has raised concerns among safety experts that the tower may have been dismantled without a proper structural review or adherence to demolition protocols.

"Buildings must go through demolition review to ensure the plan is appropriate and to identify points that need reinforcement, which makes the process safer," said a construction engineer, who requested anonymity.

The engineer added that the Ulsan boiler tower had not gone through any such procedure, suggesting the demolition may have been structurally unsound.

"When dismantling installations, engineers sometimes weaken the structure by cutting certain sections or loosening bolts, a process called 'pre-weakening,'" the engineer added.

Whether that work was carried out appropriately, the industry insider said, should be examined.

Firefighters rescue a buried worker following the collapse of a boiler tower at the Ulsan Thermal Power Plant in Nam District, Ulsan, on Nov. 7. [ULSAN FIRE DEPARTMENT

Even if the engineer's review was correct, mistakes could have occurred if the original design drawings were flawed or if workers weakened the wrong parts.

The boiler tower, built 44 years ago and decommissioned in 2021, was already deteriorating. That decay, combined with possible errors during demolition, may have accelerated the collapse.

Oh Sang-hoon, a professor of architectural engineering at Pusan National University, said that while it was difficult to draw conclusions from video footage alone, "the entire structure collapsed within about nine seconds, a pattern that typically occurs when a critical load-bearing point is cut or damaged."

"Structural damage during the demolition process could have triggered the failure," Oh added.

Police said the contractor, HJ Shipbuilding & Construction, told investigators that it had prepared a demolition plan and reviewed safety measures. "We have yet to verify [the related] documents, but we will review them through further investigation," police said.

Nighttime recovery operations are underway at the site of a boiler tower collapse at the Ulsan Thermal Power Plant in Nam District, Ulsan, on the evening of Nov. 6. [YONHAP]

Experts also pointed to possible shortcomings in on-site safety protocols.

Lee Sang-dae, director of a local disaster safety research institute, said after reviewing the footage of the boiler tower collapsing that the accident could have been prevented or its impact reduced if safety measures had been in place.

"Collapse risks are a foreseeable part of demolition work, and to prepare for them, crews typically hold what's called a 'toolbox meeting' before starting," Lee said.

A toolbox meeting is a pre-work safety briefing in which team members review the day's tasks and share job-specific precautions.

Lee said such a meeting should have identified the need for safety devices -- such as wires to anchor unstable structures or props to support sections at risk of collapse -- before demolition began.

"Even if the tower's center of gravity shifted, proper safety devices discussed in a toolbox meeting could have minimized casualties," Lee said.

The police, the National Office of Investigation and the Ministry of Employment and Labor have launched a joint probe into the collapse.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.

BY KIM YOUN-HO,MOON HEE-CHUL,KIM MIN-JU [[email protected]]

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