TUN/General/TBT-TUN-004

Shaft Sinking Safety

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Shaft Sinking Safety

Toolbox Talk Record

Ref: TBT-TUN-004  |  Issue: 1  |  Date: March 2026
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What?

  • Shaft sinking involves excavating vertical openings from surface to depth for tunnels or services.
  • Shafts can range from small access chambers to large structures over 20 metres deep.
  • The main hazards include collapse, falling objects, flooding, hazardous gases, and restricted access.
  • Ground conditions must be fully investigated before sinking begins to prevent fatal surprises.
  • Shafts become confined spaces once they exceed 1.5 metres deep and must be treated as such.
  • Support systems such as caissons, secant piles, or sheet piles prevent collapse during sinking.
  • The Confined Spaces Regulations 1997 and CDM 2015 both apply to shaft construction work.
  • Continuous gas monitoring is essential — methane, CO2, and H2S can accumulate at depth.
  • Safe access and egress must be maintained at all times via fixed ladders or personnel hoists.
  • All materials and equipment must be lowered by crane or winch — never thrown down a shaft.

Why?

Prevent fatalitiesShaft collapses, falls, and gas exposure have caused deaths in UK construction.
Confined space riskDeep shafts create toxic or oxygen-depleted atmospheres that kill in minutes.
Legal complianceConfined Spaces Regulations and CDM impose strict duties on planning and control.
Falling object dangerObjects dropped into open shafts are a constant hazard to workers below.
Do Don't
  • Complete a full ground investigation before starting shaft sinking work.
  • Treat every shaft over 1.5 metres deep as a confined space entry.
  • Install continuous gas monitoring with audible alarms at working depth.
  • Maintain safe access with fixed ladders or a personnel hoist at all times.
  • Use a crane or winch to lower all tools and materials into the shaft.
  • Install edge protection and toe boards around the full shaft perimeter.
  • Brief all operatives on the emergency rescue plan before entry.
  • Monitor ground and support conditions throughout the sinking operation.
  • Ensure a top man is stationed at the shaft opening at all times.
  • Keep a shaft entry log recording all personnel entering and leaving.
  • DON'T enter a shaft without confirmed atmospheric monitoring results.
  • DON'T throw or drop any items into the shaft — use controlled lowering.
  • DON'T work in a shaft without a rescue plan and trained rescue team.
  • DON'T remove or alter shaft support without engineering approval.
  • DON'T allow unauthorised persons near the shaft opening.
  • DON'T ignore water ingress — report and manage dewatering immediately.
  • DON'T work below without overhead protection from falling objects.
  • DON'T assume ground conditions are uniform — they change with depth.
  • DON'T leave a shaft unattended without barriers and warning signage.
  • DON'T bypass the permit to enter system for any reason.

See also: Tunnelling Safety Awareness | Confined Space Entry Procedures
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