EXTINGUISHING THE DELTA SHAKE AND SHINGLE LANDFILL FIRE
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
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.
<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).
Cost of Extinguishment