Environmental Engineering Reference
In-Depth Information
4.6 Outcomes
The objective of the remediation was to increase the hydraulic gradient in the
areas of high TCE concentration in order to achieve a significant contaminant
transport toward the wells despite the low hydraulic conductivity. By infil-
trating remediated groundwater at the fringe of the plume, the gradient is
further increased. The simulations, however, show that an extensive increase
of the hydraulic gradient is only possible with a larger number of extraction/
injection wells, because even with the maximum pumping/injection rate the
cone of depression/groundwater elevation of each well covers only a very
small zone (see Figure 4.6).
If, on the other hand, the extraction wells are positioned close to each
other, the cones of depression form a connected drawdown which enhances
the remediation significantly. The evenly distributed infiltration wells at the
fringe of the plume have little influence on the hydraulics.
Whether the whole contaminant plume is captured by pumping can be
ascertained from particle tracking calculations. If a TCE molecule at the
500 μg/L fringe of the plume is actually transported toward an extraction
well and if the injection of water at the boundary of the contamination does
0.39 m
1.50 m
0.39 m
2.28 m
Remat-filled extraction well
Limits of influence
FIGURE 4.6
Hydraulic effect of a large diameter extraction well.
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