Confined Spaces Regulations 1997 requirements for drainage infrastructure
Legal requirements for work in manholes, sewers, chambers, and service ducts under the Confined Spaces Regulations 1997. Covers definition, avoidance duty, safe systems of work, emergency arrangements, atmospheric monitoring, permits, rescue equipment, and competency.
- Primary legislation
- Confined Spaces Regulations 1997 (SI 1997/1713), made under the Health and Safety at Work etc. Act 1974
- Approved Code of Practice
- L101 - Safe work in confined spaces (Third edition, 2014)
- Definition of confined space (Reg 1(2))
- Any place, including a chamber, tank, vat, silo, pit, trench, pipe, sewer, flue, well, or other similar space in which, by virtue of its enclosed nature, there arises a reasonably foreseeable specified risk
- Specified risks
- Serious injury from fire or explosion; loss of consciousness from raised body temperature; loss of consciousness or asphyxiation from gas, fume, vapour, or lack of oxygen; drowning from rise of liquid level; asphyxiation from free-flowing solid
- Drainage confined space examples
- Manholes, inspection chambers, sewers, pumping stations, wet wells, valve chambers, service ducts, culverts, and underground storage tanks
- Duty to avoid entry (Reg 4(1))
- No person at work shall enter a confined space to carry out work unless it is not reasonably practicable to achieve the purpose without entry
- Alternatives to entry
- Remote inspection (CCTV surveys), mechanical cleaning (jetting), automated monitoring equipment, redesign of work method
- Safe system of work (Reg 4(2))
- Where entry is unavoidable, a safe system of work must be established that renders work without risk to health, so far as is reasonably practicable
- Safe system components
- Appointment of supervisor, isolation of services, atmosphere testing, ventilation, suitable equipment, communication procedures, personal protective equipment, and limited working time
- Emergency arrangements (Reg 5)
- Suitable and sufficient arrangements for rescue must be in place BEFORE any person enters a confined space
- Emergency plan contents
- Rescue procedures, rescue equipment provision, trained rescue team availability, raising the alarm, safeguarding rescuers, fire and rescue service liaison, first aid, and hospital proximity
- Atmospheric monitoring - oxygen
- Normal range 20.9%; minimum safe level 19.5%; enriched atmosphere above 23.5% (fire and explosion risk)
- Atmospheric monitoring - hydrogen sulphide (H2S)
- Workplace Exposure Limit 5 ppm (8-hour TWA), 10 ppm (15-minute STEL); deadly above 100 ppm; common in sewers from decomposition
- Atmospheric monitoring - methane (CH4)
- Lower explosive limit (LEL) 5% by volume; gas detection alarm typically set at 10% LEL (0.5% by volume)
- Atmospheric monitoring - carbon dioxide (CO2)
- Workplace Exposure Limit 5,000 ppm (8-hour TWA), 15,000 ppm (15-minute STEL); may accumulate in deep chambers and manholes
- Atmospheric monitoring - carbon monoxide (CO)
- Workplace Exposure Limit 20 ppm (8-hour TWA), 100 ppm (15-minute STEL)
- Monitoring requirement
- Continuous atmospheric monitoring throughout the period of work using a calibrated multi-gas detector
- Pre-entry testing
- Test atmosphere before entry using remote sampling probe; do not rely on sense of smell (H2S deadens olfactory nerve)
- Permit to enter system
- Formal documented permit specifying the confined space, work to be done, hazards identified, precautions required, time limits, and authorised personnel
- Permit authorisation
- Issued by competent person who has assessed the risks and verified precautions are in place
- Permit duration
- Time-limited; must be cancelled and re-issued if conditions change
- Rescue equipment requirements
- Rescue harness and lifeline, mechanical lifting device (tripod and winch), breathing apparatus (self-contained), resuscitation equipment, and communication equipment
- Trained rescue team
- Minimum one trained person must remain outside the confined space at all times; trained in rescue techniques, use of breathing apparatus, and first aid
- Entrant competency
- Adequate training and experience in confined space work, atmospheric monitoring equipment, and emergency procedures
- Attendant (top person) competency
- Trained in communication procedures, monitoring entrant welfare, raising the alarm, and initiating emergency rescue without entering the space
- Rescue team competency
- Trained and practised in rescue from confined spaces, use of breathing apparatus, casualty handling, and first aid
- Common drainage hazards - H2S
- Hydrogen sulphide produced by anaerobic decomposition of organic matter in sewers; heavier than air; accumulates in low points; deadens sense of smell above 100 ppm
- Common drainage hazards - CH4
- Methane from decomposition of organic material and from natural gas leaks; explosive between 5% and 15% by volume in air
- Common drainage hazards - oxygen depletion
- Biological and chemical processes consume oxygen in enclosed sewers and chambers; rust on metal surfaces also depletes oxygen
- Common drainage hazards - drowning
- Sudden rise of water level from upstream discharge, storm water ingress, or tidal influence
- Common drainage hazards - engulfment
- Collapse of trench sides, silt, or debris in deteriorated sewers and chambers
- CDM 2015 Schedule 3 classification
- Work in confined spaces in drainage falls within Schedule 3 particular risks (item 6: underground work, item 1: burial and engulfment, item 2: hazardous substances). Construction phase plan must address these specific risks
- RIDDOR reporting
- Loss of consciousness due to gas or asphyxiation in a confined space is a reportable dangerous occurrence under RIDDOR 2013 (Schedule 2, Part 1, item 14)
- Maximum penalty for breach
- Unlimited fine and/or up to 2 years imprisonment on indictment
- Enforcing authority
- Health and Safety Executive (HSE)