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Case No.60

Overcome by anoxia while working in a shaft to confirm the nature of the soil

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[Description of the Accident]

A worker who went down the shaft to check the nature of the soil at a sewerage pipe construction site and another worker who went down to rescue him were both overcome by anoxia.

As it had been raining all morning on the day of the accident, the site supervisor decided not to carry out excavation work and instead gave instructions to subcontracting workers to carry out repair work on the paved sections surrounding the cover plates of the shaft. As the ground near the shaft was very hard, the site supervisor planned to make arrangements with the order-placer to shift to a different type of excavation machine. Before the representative from the order-placer arrived, however, the site supervisor decided to carry out some investigation on the soil conditions, and he and the subcontractor's technical chief section decided to go down into the shaft.

The chief climbed down a ladder into the shaft, followed by the site supervisor. As soon as they stepped off the ladder at the bottom, they collapsed one upon the other. Watching this from the top of the shaft, the subcontractor's work chief tied a rope around his waist and went down into the shaft to try to rescue the two. However, he was overcome as well, and was pulled up to the ground level by other people tugging on the rope.

While the two workers who first went down into the shaft were rescued by ambulance team, one died the next day and the other died on the third day after the accident.

[Causes supposed]

1.    Although the site was obviously a hazardous workplace of anoxia, the oxygen density was not measured.

2.    An operations chief was not assigned.

3.    Ventilation was not properly carried out, and equipment such as a self-contained respirator was not used.

4.    Special education concerning oxygen deficiency was not carried out.

[Type of business] Water supply and sewerage construction
[Caused by] Abnormal environment, etc.
[Type of accident] Oxygen deficiency
[Number of victims] Two fatalities and one injury causing an absence from work