Groundwater Contamination at the Carp Rd. Landfill Site

A more consistent explanation for this data is that leachate from the older closed sections of the
site and possibly the active fill zone has crossed the boundary of the landfill property. This leads
to elevated levels on contaminants in the purge wells and down -gradient wells from the southern
edge of the old fill zone (~200 m north of Highway 417) to the northern edge of the active zone
(~800 north of Highway 417).
Sodium Concentration (mg / litre)
350
300
250
200
150
100
50
0
Up-gradient Wells
Purge Wells
0 200 400 600 800 1000
Distance from Highway 417 (m)
Down-gradient Wells
Figure 3 - Average sodium concentration (2000-2004) along lines perpendicular to Highway 417
and parallel to Carp Road. The concentrations at the purge well line and a transect ~100 m downgradient
from the purge wells are high relative to the up-gradient transect. The curve is a guide
for the eye.
The data for many of the other leachate indicators show similar trends. The consistency of the
patterns allows estimated contamination contours to be drawn. These are shown in Figure 4
where the figure of merit is the percentage of RUG exceedances measured between 2000 and
2004. This is not the only set of contours that can be drawn through the data but these do take
into consideration the previously established groundwater flow direction from west to east. More
data would be required to map out the distribution more precisely.
The pattern is consistent with a landfill leachate source. It is similar to the leachate plume
mapped out in the late eighties (c.f. Figure 1). It seems to have expanded to the north, as one
might expect with new landfill activity to the north of the original landfill zone (now closed).
There is little that can be said whether there have been the changes in the severity of the
contamination, since there is no quantitative data presented in this report from the off-site downgradient
wells prior to the year 2000. Over the following four years, however, the leachate
indicators in each well vary significantly. There is no consistent downwards trend to support the
conclusion of the author of the WESA report that the purge well system has been effective. That
conclusion was based on improvements in the surface water quality. On the contrary, many of the
indicators in the groundwater increase over this time frame.
Sept 28, 2006 - Groundwater Contamination at the Carp Rd. Landfill Site
Report prepared on behalf of The Coalition of Citizen’s Groups Opposing the Expansion of the Carp Rd. Landfill
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