UNDERSTANDING AND CONTROLLING LANDFILL FIRES

Monitoring

Leachate Management:

Application of large quantities of water will invariably produce leachate.  It has been our experience at Delta Shake and Shingle Landfill where leachate management proved to be a significant issue that the concentration of contaminants found prior to the fire remained unchanged. In addition, elevated levels of hydrocarbons and BOD were observed and the leachate became carbon black in colour.

To minimize the environmental impacts of leachate, recirculation of fire fighting water should be considered on projects where large volumes of water are used.  Recirculation requires that leachate be directed into settling ponds, preferably including filtration and that booster pumps be brought on line to augment water supplies from nearby fire hydrants.

Implementation of Fire Breaks:

Soil fire breaks have proved invaluable in controlling the spread of the large landfill fire at Delta Shake and Shingle and on several other fire control projects.  To be effective in preventing uncontrolled spread of the fire underground, the fire breaks must fully encapsulate the waste on all sides, top and bottom.  Placement of intermediate cover on top of each lift is not sufficient.  In fact, by driving hot gases laterally and inducing horizontal convection currents, continuous cover layers may actually promote the spread of deep seated landfill fires.

To minimize the spread of landfill fire and to control oxygen entry, we recommend that waste be placed in soil encapsulated cells with volumes not exceeding 5,000 to 20,000 m³, depending on the size of the landfill operation.

We have not been able to reference any literature that provides firm recommendations on the minimum cover soil thickness required to achieve a functional fire break.  It has been our experience that soil barriers in excess of 1,000 mm thick are generally effective, providing they are free of organic contamination, that fire breaks more than 500 mm thick are usually effective and that fire breaks less than 150 mm thick are totally ineffective.  Until a number of case studies of fire break performance are documented in the literature to guide performance based design, we generally adopt design guidelines calling for 300 mm of inert soil cover to encapsulate individual cells and a minimum 600 mm of soil cover to provide major fire breaks between completed landfill phases.

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