Storm tanks and combined sewer overflows collect and hold excess flows during heavy rainfall before returning them to the treatment process. These structures are often deep, open-topped, and subject to sudden filling during storm events. Work on storm tanks and CSOs combines drowning risk, confined space hazards, and biological exposure. This talk covers the specific safety requirements for working on storm infrastructure.
Key Hazards
Drowning from falling into deep storm tanks that fill rapidly during rainfall
Confined space atmosphere in drained tanks with H2S from residual sludge
Sudden tank filling from upstream storm flows trapping workers inside
Biological infection from contact with raw sewage deposits in storm structures
Control Measures
Wear a personal flotation device at all times when working above or adjacent to filled storm tanks.
Monitor weather forecasts continuously and set withdrawal triggers for incoming storm events.
Treat entry into any drained storm tank as a confined space requiring a full permit and rescue plan.
Monitor the atmosphere for H2S and methane before and during all work inside storm structures.
Install edge protection around all open tank edges and access points during construction.
Isolate inlet penstocks and confirm with the control room before anyone enters a drained tank.
Wear full biological hazard PPE and ensure current hepatitis A and tetanus vaccinations.
Brief all operatives on the storm response procedure and the escape route from the tank area.
Install a visual or audible high-level alarm to warn of rising water levels in the storm tank.
Emergency / Rescue
If a storm tank begins filling while workers are inside, evacuate immediately via the designated escape route. Call 999 if anyone is trapped. Throw a lifebuoy if a person enters the water. Do not re-enter to rescue without appropriate water rescue training and equipment.
Remember
Wear a personal flotation device at all times near filled storm tanks and CSO chambers
Monitor weather forecasts and withdraw from storm structures before incoming rainfall arrives
Treat all drained storm tanks as confined spaces with full permit and atmospheric monitoring
Isolate inlet penstocks and confirm with control before anyone enters a drained tank
Know the escape route and respond immediately to high-level alarms in the storm tank area
Applicable Legislation: Confined Spaces Regulations 1997 · COSHH 2002 · CDM 2015 · Work at Height Regulations 2005