chapter 4: temperature inside the landfill

and
_ _
t − − >
T + Y T t Y
then a significant temperature drop event has occurred.
_
X
(4-4)
Where T t−Y
is the mean of the temperature readings over Y days before time t, T t+
Y is the
temperature averaged over Y days after time t and X is the difference between the two averages.
The values of X and Y are dependent on the sensor location (injection well or monitoring
location). The sensitivity of the results with respect to Y was tested by using different values of
Y varying from 4 to 20 days. The number of events did not vary with the change in the value of
Y. A value of 20 days for injection wells and 15 days for monitoring locations gave the most
reasonable detection of injection events.
The value of X affected the number of identified events significantly. The various values
of X tested were 0.1, 0.2, 0.3 and 0.4 0 C for the monitoring locations and 0.4, 0.5 and 0.6 0 C for
injection wells. Because of temperature sensor sensitivity, the use of a small number for X
overestimated the number of detected injection events while a large number underestimated it.
After numerous trials, 0.5 0 C gave the most reasonable detection of injection events for the
injection wells as confirmed by the injection records. A value of 0.2 0 C for X at the monitoring
locations was used to minimize the excessive number of false readings.
When moisture arrives, the resistance reading of the moisture sensor falls. Therefore to
detect moisture arrival using moisture sensors, the difference in the natural log values of the
mean of resistance values Y days before and after the event was the criterion as log of the
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