OKAYAMA – Divers from Kajima Corp. on Thursday began examining a seabed indentation that may be linked to the accident that flooded an underwater tunnel at an oil refinery in Okayama Prefecture, leaving five workers missing.
According to Kajima, the dip, about 20 meters in diameter, had extended 4 to 5 meters below the general seabed level. It was right above the tunnel the workers were building, 11 meters under the seabed.
The Health, Labor and Welfare Ministry said the same day that Kajima did not conduct a geological survey before starting to build the tunnel. Instead of conducting a new survey, Kajima submitted data from soil research undertaken 10 years earlier for a separate tunnel construction project in the nearby area.
The ministry said it will examine whether Kajima’s use of old data violated the Industrial Safety and Health Act, which makes it mandatory to conduct geological surveys prior to tunnel construction projects.
The debris and murky seawater that flooded the shaft has so far hindered the search for the missing, but Kajima purified some of the seawater Thursday using water processing devices.
The company said the seabed dip’s role in the accident remains unknown. The coast guard has also checked the dip but said it could not confirm whether the dip was responsible for the accident.
The tunnel was being dug for a pipeline that would link two plants at the refinery operated by JX Nippon Oil & Energy Corp., and has a 34-meter deep shaft measuring 11 meters in diameter. Kajima has been working on the tunnel since 2010 and it was slated for completion in 2013.
The five subcontracted workers were operating machinery Tuesday when seawater flooded into the tunnel.