Workers who died after inhaling toxic gas did not wear respirators or follow safety protocol, inspector testifies

They had to enter the enclosed passage beneath the tank to drain the water in it before they could clean it, said Mr Hafidz.

Mr Izzat and another worker went through the gate to open all three hand valves while Mr Sivaraman stood outside nearby, in line with the buddy system required by safety protocol. None of them were wearing respirators and the valves were opened within five minutes without incident, the inspector said.

Mr Sivaraman conducted a gas check before the two workers entered the passage, using a personal gas detector that did not sound an alarm, the inspector said.

Mr Hafidz testified that with all three valves open, the wastewater was likely to have been flowing out “quite rapidly”, which could have accelerated the release of hydrogen sulphide.

After opening the valves, the workers returned to cleaning the tank above the passage. At about 10am, a worker from another PUB contractor told Mr Sivaraman that the wastewater was flowing rapidly into the next tank and that he had detected a strong rotten smell, the court heard.

Mr Sivaraman instructed an employee to bring someone, go back to the passage and close the valves, the inspector testified.

He also confirmed that nothing had been established about any instructions given by Mr Sivaraman about equipment.

The third worker and Mr Izzat both entered the enclosed passage without respirators. Mr Izzat was wearing a personal gas detector, the inspector said.

The alarm on his personal gas detector, as well as the ones mounted around the passage, were sounding, he added.

This indicated a hazardous environment, but they went into the passage nonetheless, Mr Hafidz said.

When questioned by State Coroner Adam Nakhoda, the inspector confirmed that the workers should not have both entered the passage – one of them should have remained outside.

Citing the third worker’s account of the incident, Mr Hafidz said the worker and Mr Izzat entered the passage and collapsed.

Mr Hafidz said investigators could not establish what happened between 10.30am and about 11am, when the three men were discovered.

He testified that Mr Sivaraman likely entered the passage later to check on the workers or attempt a rescue, before being overcome by the gas.

The three men were found unconscious in the passage. After they were rescued, they were taken to hospital, where Mr Sivaraman and Mr Izzat died.

After the incident, PUB blacklisted Stargroup, barring it from tendering for any of its projects for 18 months from August 2024. 

MOM also issued PUB a stop-work order covering cleaning work on pre-treatment water tanks and entry into confined spaces adjacent to the tanks. The order was lifted on Aug 6, 2024, after PUB satisfied the stipulated conditions.