EXTINGUISHING THE DELTA SHAKE AND SHINGLE LANDFILL FIRE 

The Monitoring Program.
Geotechnical, temperature and gas composition monitoring was conducted throughout the course of the firefight and landfill restoration to ensure that the fire fighting activities would not lead to a slope failure and that the fire was not spreading into the main fill zone.

To determine whether earth moving activities, particularly relocation of the cold waste to the top of the landfill and construction of storage areas adjacent to the sewer and water mains, were having a destabilizing influence on the stability of the utility corridors, a comprehensive network of geotechnical instrumentation was installed and monitored daily. Nine inclinometers capable of recording as little as 2.0 mm of deflection provided the primary warning mechanism against excessive movement. Also, total station survey benchmarks were established along the crest and mid-slope on the north and south landfill sides and along the sewer main/water main right-of-way. Piezometers that measured water levels in the fill zone were also installed to provide early warning of pore pressure build up within the refuse that could potentially trigger a slope failure.

The geotechnical monitoring program confirmed that height restrictions on storage piles and setbacks from utility corridors were effective. Movements in all sensitive areas proved to be less than 4 cm.

As the fire spread throughout the horseshoe the fire fighting team became concerned that the fire may have spread into the main fill zone, especially when the fire was noted on the backside of the landfill (later determined to have been a separate incident of spontaneous combustion). To establish how far the fire had penetrated, Thermistor strings were installed in five boreholes around the horseshoe. Thermistors are essentially strain gauges that stretch and contract in response to temperature changes, much like mercury in a thermometer. The wire deformations affect the electrical conductivity and this is measured at surface. In each borehole temperature measurements were obtained by lowering three thermistors into the cased boreholes at 4.5, 9 and 14 m below surface.

Also the hand held infra-red heat sensors shown in Photo10 were used to monitor temperatures from surface vents and test pits. From experience gained at Delta Shake and Shingle and other landfill fire projects, temperatures above 75% C. provide cause for alarm, and temperatures above 93 degrees C. provide a very strong indication that there is a landfill fire. The following table provides a practical reference guide to evaluating a practical reference guide to evaluating field temperature measurements.

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

Gas composition monitoring was used to provide additional data on the location and intensity of the fire. Landfill areas that were on fire were associated with carbon monoxide concentrations above 1,000 ppm, oxygen levels between 15% and 20% and little, if any, methane. On the other hand, areas of the landfill that ere not on fire exhibited elevated methane concentrations (20 to 45% methane), no oxygen and little if any carbon monoxide(<100ppm).

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