WWT/Infrastructure/TBT-WWT-014

Clean Water Reservoir Safety

Water & Wastewater Treatment › Infrastructure › Clean Water Reservoir Safety

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Location		Date

Clean water reservoirs store treated drinking water and are typically covered or underground structures.
Entry into service reservoirs is a confined space operation requiring permits, monitoring, and rescue plans.
The interior is dark, wet, and slippery with deep standing water that creates a constant drowning hazard.
Chlorine residuals in the water and atmosphere can irritate eyes, skin, and the respiratory system.
Access is usually through small hatches, making entry and especially rescue extremely difficult.
Contamination of the drinking water supply during construction or maintenance must be prevented absolutely.
Tools, materials, and chemicals used inside must be approved to avoid contaminating potable water.
Structural columns and limited headroom create restricted movement and head injury risks inside the reservoir.
Communication from inside covered reservoirs can be difficult due to concrete construction blocking signals.
All work must comply with the water company's hygiene protocols and WRAS-approved material requirements.

Drowning risk	Deep standing water inside reservoirs with limited escape routes creates a serious and constant drowning hazard.
Water quality	Contamination of the public drinking water supply during works can cause widespread illness in the community.
Confined space	Covered reservoirs are confined spaces with restricted access, limited ventilation, and rescue difficulties.

Don't

Obtain a confined space entry permit and follow the safe system of work
Monitor the atmosphere for chlorine levels and oxygen before and during entry
Wear a personal flotation device when water depth exceeds 300mm inside
Use only WRAS-approved materials and tools that will not contaminate the water
Follow the water company hygiene protocol including boot dipping and hand washing
Ensure a rescue plan is in place and the rescue team is briefed and equipped
Provide temporary lighting inside the reservoir that is suitable for wet environments
Maintain communication with the surface team using wired or radio systems
Brief all workers on the drowning hazard, chlorine exposure risk, and escape routes
Drain or lower water levels where practicable before personnel enter the reservoir

DON'T enter a service reservoir without a confined space entry permit
DON'T use non-approved materials or chemicals that could contaminate drinking water
DON'T enter deep water areas without a personal flotation device and rescue cover
DON'T ignore chlorine irritation to eyes or throat — exit and reassess exposure
DON'T bring food, drink, or tobacco products into the reservoir area
DON'T work alone inside the reservoir at any time during the operation
DON'T skip the hygiene decontamination procedure when exiting the reservoir
DON'T allow untreated surface water or debris to enter the clean water storage
DON'T store unnecessary equipment inside the reservoir where it could fall into water
DON'T assume shallow water is safe — hidden drops and submerged obstacles are common

See also: Confined Space Entry Procedures | Chlorination and Flushing Procedures

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