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Department of Justice

Old town gas pipes

WorkSafe have investigated incidents where civil workers have been exposed to harmful gases and Volatile Organic Compounds (VOCs) whilst excavating beneath traffic easements in Hobart and Moonah. The sources of the contaminants are mostly related to the old town gas (coal gas) pipes that were made redundant in Hobart in 1978 and decommissioned in Launceston in 1995.

Contributing factors

  • The fracturing or removal of the redundant town gas pipes
  • The decomposition of the redundant town gas distribution pipes
  • The atmospheric, oxygen inhibiting contents within the town gas pipes
  • Ignorance of unusual odours and soil discoloration whilst excavating
  • Contaminated soils leeching VOCs from town gas pipes and their bedding material
  • Enclosed Excavation (Thrust Boring, Soil Displacement Drilling and Horizontal Directional Drilling)
  • The absence of VOC monitors at excavation sites
  • Inadequate Risk Assessments or Job Safety and Environment Analysis
  • Gas/cyanide/VOC entrapment within excavator cabin

Action required

  • Hazard identification and risk management actions must be taken before starting any excavation work. Any significant hazards remaining after applying mitigation measures should be subjected to a comprehensive qualitative risk assessment to ensure any residual risk is ALARP (As Low as Reasonably Practicable)
  • Ensure you and all your work crews have the skills, training and knowledge appropriate for the hazards/dangers involved when excavating near abandoned town gas pipes
  • Monitoring equipment suitable for the detection of VOC’s should be in place adjacent to all excavations and within excavator cabins when excavation work is undertaken within the zones defined on page 3 of this Alert
  • Core sampling for the presence of VOCs, prior to excavation, will assist in mitigating the risk associated with release and exposure
  • If unusual ‘tar/bituminous like’ odours are noticed whilst excavating, work must cease immediately and all operatives are to relocate to a safe distance away from the excavation (upwind)
  • Your Supervisor is to be contacted who will need to advise WorkSafe, Emergency Services and the presiding Council of the incidents occurrence
  • An adequate exclusion zone is to be put in place with signage and barriers erected, preventing unprotected operatives or members of the public from entering the excluded area
  • Traffic management personnel (if present) to either divert traffic away from the excavation or advise drivers to keep windows up and air conditioning systems (fans) off within their vehicles as they pass the exclusion zone
  • Any evacuations of persons from houses deemed necessary by emergency services must be undertaken by Tasmania Police
  • Do not under any circumstances encroach back into the exclusion zone without full Self Contained Breathing Apparatus (SCBA) or until VOC monitoring equipment has been utilised and levels in and around the excavation have been sampled and recorded as non-dangerous

Personal protective equipment

The following should be worn within a live exclusion zone.

  • Chemical goggles
  • Gloves (Viton/nitrile/PVC)
  • Protective footwear
  • Disposable Coveralls (ensure hair and body is completely covered)
  • Full SCBA if cyanide alarms are high or half-face respirator, (VOC cartridge for chemical exposure) if cyanide is not present.

Further information

  • Town gas pipes if broken can contain cyanide and other harmful gases, which when released can starve the brain of oxygen leading to long term or permanent illness/injury such as memory loss, impaired spatial ability and nerve damage
  • The bedding or soil surrounding town gas pipes can be contaminated with Type 1 carcinogenic VOC’s
  • Town gas pipes have been found to contain large amounts of foul smelling, contaminated water
  • Town gas service pipes (house pipes) can also contain the same harmful contaminants
  • If a black ‘coal like’ soil is uncovered whilst excavating, use appropriate PPE and a VOC analyser prior to proceeding
  • Check with your local council to see if plans are available for town gas pipes in your area
  • VOC or cyanide releases from town gas mains or their adjacent soil in excess of 50ppm are reportable incidents and WorkSafe must be notified

Cities and suburbs reticulated with old town gas mains

Hobart

  • Central Business District (CBD)
  • Battery Point
  • Dynnyrne
  • Glebe
  • Lenah Valley
  • Mount Stuart
  • New Town
  • North Hobart
  • Ridgeway
  • Sandy Bay including Lower Sandy Bay
  • South Hobart Cascades
  • West Hobart

Glenorchy

  • Berriedale
  • Chigwell
  • Claremont
  • Derwent Park
  • Glenorchy including Elwick
  • Goodwood
  • Lutana
  • Montrose
  • Moonah
  • Rosetta
  • West Moonah

Launceston

  • Central Business District (CBD)
  • East Launceston
  • Invermay
  • Mowbray
  • Newstead
  • Punchbowl
  • South Launceston
  • Trevallyn
  • Waverley
  • West Launceston

Gas pipe photo gallery