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                                                        VANCOUVER LANDFILL DEMOLITION FIRE 

Why The Fire Started

Spontaneous combustion is the outbreak of fire without application of heat from an external source. Spontaneous combustion may occur through the storage of organic materials such as woodwaste, coal, tire chips, compost or hay.

In organic materials, spontaneous combustion occurs when heat initially produced through biological degradation is not allowed to dissipate thus raising the temperature of the material. Biological degradation will generally cause temperatures to increase to approximately 70 °C. At temperatures much higher than 70 °C microorganisms die. Temperatures beyond 70 °C are associated with chemical oxidation of organic materials in the presence of oxygen. For wood, exothermic oxidation of wood commences around 200 °C and combustion with open flame commences aroud 300 °C (National Fire Protection Association, 1976).  Following is a practical reference summary for evaluating landfill fire temperatures based on our experience on six major landfill fire projects. 

<60° C             Anaerobic Decomposition
<75
° C             Aerobic Decomposition
80
°C               Microbes Die-off
93
°C               Pyrolysis Starts
149
°C             Exothermic Oxidation of Wood Starts
315
° C             Wood Ignites Spontaneously (Combustion)
 

For spontaneous combustion to occur, conditions must be ideal. The following conditions may lead to spontaneous combustion: 

-    a pile of sufficient size to retain heat (the Ontario Fire Marshal’s office recommends that woodchip piles be stored in piles less than 4 metres high, 8 metres wide and overall volume of 1,000 cubic metres to avoid spontaneous combustion (Government of Ontario, 1998))

-     moisture content around 25% on a wet basis (House, 1998) (dryer conditions prevent biological activity, wetter conditions reduce porosity and prevent temperatures increasing beyond biological levels)

-     supply of oxygen (many spontaneous combustion fires occur near the windward edge of a pile of material during windy conditions)

-     sufficient insulating capabilities to retain heat in the pile (Swedish researchers found that uncovered loosely packed piles of demolition material piled up to 5 metres high did not spontaneously combust whereas compacted piles regularly spontaneously ignited (Hogland et. al., 1996))

-     prolonged storage of organic materials (the Ontario Fire Marshal’s office recommends storage of wood chips for less than 3 months (Government of Ontario, 1998).

1 .  Partially Capped Bank on Edge of  Demolition Cell


In the case of the Vancouver Landfill fire, the fire occurred behind an approximately three metre high bank of demolition material adjacent to an internal site access road. The road was located on top of the first layer of demolition material, and the bank represented the edge of the second layer of demolition material.  The bank had been partially covered with soil, but sufficient void space was present to allow wind to blow into the bank. The bank was located on the windward side of the demolition lift. Material in the area of the fire had been in place approximately six months.


   

Papers   IntroductionBackgroundWhy The Fire StartedFighting The FireMonitoring ProgramConclusions and Lessons Learned   next page Fighting The Fire