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Landfill fires – controlling the risk

HSE has become aware of a limited number of recent incidents of fires and releases of flammable gases at landfill sites around the UK. With the recent introduction of the Dangerous Substances Explosive Atmospheres Regulations (DSEAR) 2002, the transition period up to 2006 for full implementation of these regulations on existing installations, provides a good opportunity for industry and the regulators together to refocus efforts on process safety risk controls.

At a strategic level the hierarchy of safeguards that are required to either eliminate, control or mitigate safety risks are set out within the recently published HSE Approved Codes of Practice and Guidance on DSEAR 2002. HSE in conjunction with EA are supporting industry representatives in drawing up more detailed sector specific guidance on how effective safeguards can be applied on site.

In practice there are 6 key areas where the hierarchy or risk control applies and that HSE would wish to see addressed with respect to fires and explosions.

  1. Avoidance or minimizing the uncontrolled release of gases, for example regular inspection for gas leakage from vulnerable areas such as, temporary pipes, gas and condensate extraction equipment, knock-out pots, etc. These inspection programs need to be supported with appropriate maintenance systems to ensure defects reported are rapidly repaired.
  2. Controlling the release of gas at source by appropriate consideration being given to gas well location and other control systems. For example, gas extraction wells potentially interfacing with other control equipment such as, leachate side wall risers, leachate shafts, or leachate recirculation systems that may in extreme cases result in air ingress and fire.
  3. Prevention of the formation of flammable or explosive atmospheres: By minimizing oxygen ingress into the waste through for example cap defects, extraction pipes and equipment etc. Within extensive and dynamic structures such as gas fields, extraction needs a high level of control and monitoring. Action limits for oxygen and methane should be established as part of the process safety control system. In some circumstances this might require alarmed continual monitoring of elements of the gas field.
  4. Ensuring any release of a dangerous substance, which may give rise to risk, is suitably collected, is safely contained, removed to a safe place, or otherwise rendered safe. As one example; gas transmission pipework should be laid to predetermined falls to avoid condensate blockages, and unplanned gas releases, or damage to equipment. Where pipes are subject to excessive movement or modification falls or effective drainage should be regularly checked and dead-legs avoided.
  5. Within the context of the above DSEAR requirements and the Confined Spaces Regulations 1998 review of the standards of design and construction of head works; to avoid access to confined spaces, for gas monitoring, control manifolds, valve operations, etc, is needed in some instances. Consideration of flooding risks at submerged valves and sample points should also be included.
  6. 6. As part of the DSEAR requirements all sites, and processes within the landfill sector will need to be classified into hazardous zones as defined within Regulation 7. Whilst this has long been established within the oil and other extractive industries this is a new area for the waste industry sector and specific guidance on how to apply the zoning criteria to this industry is now desirable and underway.. The zone assessment exercise will need to be applied to the whole site but in reality hazardous zones will be restricted to specific locations such as inside well head works, leachate wells, around tank vents, some transmission and utilization equipment, etc. Once defined appropriate categories of equipment may only be used within the defined zones.

HSE is supportive of the industry in taking a proactive stance on the generation of guidance for this sector, and is confident that by adopting a firm but positive approach to regulation, in cooperation with representative bodies, good safety standards for this revised guidance can be established and then maintained.

Area classification for Landfill Gas Extraction, Utilisation and Combustion - Industry Code of Practice. November 2005

HSE believes that the contents of this new code of practice demonstrates good practice in the landfill industry and recommends its use. It was prepared by the Environmental Services Association (ESA) in consultation with HSE, and endorsed by the Waste Industry Safety and Health (WISH) forum which represents the interests of the industry.