Ulsan power plant collapse that killed 7 was caused by over-cut columns, Korean investigators say

The finding comes from a commission that spent 11 months on the case, from Nov. 18, 2025, to Oct. 17, 2026, the Ministry of Land, Infrastructure and Transport said Friday, according to the Seoul Economic Daily. The Unit 5 tower, finished in July 1980, came down on Nov. 6 during pre-weakening, the stage when parts of columns and beams are cut so a structure falls the planned way. Nine workers were buried. Seven died.

The cutting limits rested on bad numbers. The column plates thin out toward the top, but the demolition subcontractor never got the as-built drawings and measured one column at ground level, JKN reported. It applied that 24 mm reading to every floor. At 26.2 to 27.2 meters, where the failure began, the plate was 15 mm. The review also put the tower at 3,005.8 tons against an actual 3,525.8, about 520 tons light, and left no margin for local buckling or for damage from age and cutting. It showed loads at 95% of design strength. The commission's recalculation put them at 120% at the collapse point. The subcontractor told the panel it did not measure higher up because the climb was dangerous. Investigators found no evidence that crews cut more than the plan specified.

Oversight failed as well, the commission said. The prime contractor, HJ Shipbuilding & Construction, leaned on the specialist firm's judgment and did not confirm that the shop drawings matched the site. The owner, Korea East-West Power, supervised the job itself without a separate construction manager.

The panel recommended stronger site surveys before demolition, technical standards for demolition work, closer control of high-risk jobs and more duties for owners. It will file its final report in November. The ministry intends to make independent structural experts verify high-risk demolitions, JKN reported, and will pass the findings to agencies handling penalties and legal investigations.