PUBLISHED ONJuly 16, 2026 4:20 AMUPDATEDJuly 16, 2026 10:09 AMBYSean LerA cleaning contractor and a manager responsible for issuing confined space entry permits were on Thursday (July 16) charged over alleged workplace safety offences after two workers died while carrying out tank cleaning works at Choa Chu Kang Waterworks in May 2024.
The Ministry of Manpower (MOM) said in a news release on Thursday that cleaning and maintenance contractor, Stargroup, was engaged by the national water agency to carry out tank cleaning operations at the plant.
On May 23, 2024, a team of four workers from Stargroup and its subcontractor carried out cleaning works at a water treatment process tank.
Three of them later collapsed after entering an enclosed passage beneath the tank to close hand valves that had been opened earlier to drain water from the tank.
They were taken to Ng Teng Fong General Hospital where two workers later died on May 24 and 28, with the third worker discharged after receiving medical treatment.
MOM said its investigations revealed that the workers had been exposed to hydrogen sulphide gas, a toxic gas that is typically emitted when sludge is drained from water treatment tanks.
According to the UK government's health and security agency, hydrogen sulphide is a gas that is rapidly absorbed by the lungs into the bloodstream. It is colourless and can be lethal even at low concentrations.
MOM's investigations also found that sensors installed at the location had recorded hydrogen sulphide levels that exceeded safe thresholds and the alarm had been triggered.
With the conclusion of its investigations, MOM on Thursday charged Stargroup for failing to implement reasonably practical measures to minimise the risk to any person who may be affected by its undertaking at the workplace.
Lim Beng Hock, the authorised manager for confined space entry permits of Stargroup, was also charged for failing to exercise all due diligence when performing his function as authorised manager in relation to the issuance of confined space entry permits.
The ministry also took enforcement actions against a PUB officer by issuing him with a stern warning for failing to cooperate with his employer to enable his employer to comply with the Workplace Safety and Health Act on the night before the event.
PUB was also offered composition for allowing its employees to enter the confined spaces for short periods without adequate ventilation on previous occasions.
In a statement issued to the media on the same day, PUB said it blacklisted Stargroup for 18 months, from August 2024, after the incident.
This means that the contractor was barred from tendering for any PUB projects during that period.
"PUB has also enhanced our contractor management processes, in confirming, through first instance checks, that the measures implemented on the ground are in accordance with contractors' stated risk assessments, safe work procedures and emergency response plans."
In relation to the composition offered by MOM, PUB said it has since put in place permanent ventilation for confined space work and requires all confined spaces at its plants to provide adequate ventilation, even for short periods of work.
On the stern warning issued to its staff, PUB said it is reviewing the matter and will take appropriate follow-up actions.
The national water agency also assured members of the public that safety remains its top priority.
"We are committed to upholding the highest safety standards for our staff and contractors," it said.
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