DAM/General/TBT-DAM-017

Valve Tower and Shaft Work

Dams, Reservoirs & Flood Defence › General › Valve Tower and Shaft Work

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Valve towers are vertical structures within reservoirs that house control valves, penstocks, and pipework.
Access is typically via internal ladders or spiral staircases descending below the water surface level.
Valve tower interiors are classified as confined spaces due to restricted entry, poor ventilation, and water proximity.
Drowning risk exists from rising water levels, valve failures, and the proximity of open water within the tower.
The atmosphere inside valve towers can become oxygen-depleted or contain hydrogen sulphide from stagnant water.
Working inside valve towers combines confined space, working at height, and water safety hazards simultaneously.
Access may be by boat or causeway from the reservoir embankment, adding further marine-related risks.
The Confined Spaces Regulations 1997 require a formal risk assessment, permit, and rescue plan.
Mechanical equipment inside the tower including valves, actuators, and sluice gates can cause crush injuries.
Many valve towers are Victorian-era structures with corroded metalwork, narrow access, and limited lighting.

Prevent drowning	Valve towers sit within or above deep reservoir water — a fall from the structure into water is likely fatal.
Confined space risks	Poor ventilation, toxic gases, and restricted access make valve tower interiors dangerous confined spaces.
Combined hazards	The overlap of confined space, height, water, and mechanical risks demands comprehensive planning and controls.

Don't

Treat every valve tower entry as a confined space requiring a permit and rescue plan
Test the atmosphere for oxygen, H2S, and flammable gases before entering the tower
Wear a PFD when accessing the tower by boat or walking on causeways over water
Use fall arrest equipment when descending ladders or working at height inside the tower
Ensure a rescue team is on standby with appropriate equipment throughout the work
Confirm all valves and mechanical equipment are isolated before working on them
Maintain continuous communication between the entrant and the top man at all times
Check structural integrity of ladders, platforms, and handrails before loading them
Carry adequate portable lighting as many valve towers have no permanent electrical supply
Monitor water levels continuously and establish a clear evacuation trigger and procedure

DON'T enter a valve tower without a confined space permit and approved rescue plan
DON'T assume the atmosphere is safe — test before every entry and monitor throughout
DON'T access the tower by boat without a PFD and trained boat operator present
DON'T work on valves or penstocks without confirming mechanical and hydraulic isolation
DON'T rely on old fixed ladders and steelwork without inspecting their structural condition
DON'T enter alone — a standby person with rescue equipment must be present at all times
DON'T ignore rising water levels inside the tower — evacuate immediately if levels change
DON'T use petrol or diesel-powered equipment inside the tower due to fume accumulation
DON'T leave access hatches open and unguarded when the tower is not being worked in
DON'T block the escape route with tools, equipment, or materials inside the tower

See also: Dam and Reservoir Safety Awareness | Confined Space Entry Procedures

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