MOM takes enforcement action after fatal Choa Chu Kang Waterworks workplace incident

Stargroup, its authorised manager, and PUB face enforcement action following investigations into safety lapses during tank cleaning operations that exposed workers to toxic hydrogen sulphide gas.

The Ministry of Manpower (MOM) is taking enforcement action against several parties allegedly responsible for safety lapses following a workplace incident at PUB’s Choa Chu Kang Waterworks on 23 May 2024.

The incident involved tank cleaning operations carried out by contractor Stargroup Est Pte Ltd (Stargroup), where three workers collapsed after entering an enclosed passage beneath a water treatment tank. Two workers later passed away, while the third worker was discharged after receiving medical treatment.

Details of the incident

At the time of the incident, PUB was the occupier of Choa Chu Kang Waterworks, while Stargroup was engaged to carry out tank cleaning operations.

As part of the cleaning works, Stargroup had taken over a water treatment process tank, with a team of four workers from Stargroup and its subcontractor carrying out the work.

Three workers subsequently entered an enclosed passage beneath the tank to close hand valves that had been opened earlier to drain water from the tank.

The workers collapsed after entering the enclosed area and were conveyed to Ng Teng Fong General Hospital. Of the three, two passed away on 24 and 28 May 2024 respectively, while the third worker was discharged after receiving medical treatment.

Workers exposed to toxic hydrogen sulphide gas

MOM’s investigations found that the workers had been exposed to hydrogen sulphide gasposed to hydrogen sulphide gas, a toxic gas that is typically emitted when sludge is drained from water treatment tanks.

Hydrogen sulphide gas is colourless and can be lethal even at low concentrations.

During the incident, sensors installed at the location recorded hydrogen sulphide levels that exceeded safe thresholds, and the alarm had been triggered.

Following the incident, MOM issued a stop-work order to PUB to cease cleaning works on pre-treatment water tanks and entry into confined spaces adjacent to these tanks. The stop-work order was lifted on 6 August 2024 after PUB satisfied the stipulated conditions.

Stargroup and authorised manager face charges

Following MOM’s investigations, charges were brought against the parties on 16 July 2026.

Stargroup, as the employer and principal of persons at work, was charged with one count under Regulation 4(2) read with Regulation 8(1) of the Workplace Safety and Health (Risk Management) Regulations.

The charge relates to an alleged failure to implement reasonably practicable measures to minimise the risk to any person who may be affected by its undertaking at the workplace.

Lim Beng Hock, authorised manager for confined space entry permits of Stargroup, was charged with 12 counts under Regulation 13(3) read with Regulation 13(1) and Regulation 24(1) of the Workplace Safety and Health (Confined Spaces) Regulations.

The charges relate to an alleged failure to exercise due diligence when carrying out his duties as authorised manager in relation to the issuance of confined space entry permits.

MOM also took further enforcement action under the Workplace Safety and Health Act (WSHA) and its subsidiary legislation.

A stern warning was issued to a PUB officer for allegedly failing to cooperate with his employer to the extent required to enable compliance with the WSHA on the night before the incident.

MOM also offered a composition fine to PUB for allegedly allowing its employees to enter confined spaces for short periods without adequate ventilation on previous occasions.

Employers reminded of confined space safety duties

Under the WSHA, stakeholders are required to take reasonably practicable measures to ensure the safety and health of persons who may be affected by work activities.

Employers carrying out work in confined spaces are legally required to conduct a risk assessment before works commence, test the atmosphere within the confined space, provide workers with appropriate respiratory protective equipment, and ensure a trained standby person is stationed outside the confined space at all times.

Workers are also responsible for complying with confined space safety requirements, including using the required protective equipment and following safe work procedures.

MOM reminded employers that the WSH Council’s publication on confined space-related incidents, published in September, serves as a guide for industry stakeholders and aims to reinforce awareness of good practices for protecting workers from confined space hazards.

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Lead image / PUB website