Environmental Engineering Reference
In-Depth Information
TABLE 19.1
(Continued)
Characteristic
Comparison
Suitability for Encapsulation
of Potential Acid Generating Waste
TDC dumps are unsuitable for encapsulation of sulphidic
materials, because:
There is no control over where the materials will come to rest,
after they are dumped;
Cross Section Through Dump
Compaction of encapsulating layers to achieve the required low
permeability would be difficult if not impossible; and
Cracking would probably destroy any encapsulating layers.
BUC storages are suited for encapsulation. An example
arrangement is shown in the figure to the left.
Outer Limit
of Compaction
Cost of Construction
Initial construction cost for TDC dumps is much lower than
for BUC storages. Even with the cost of regrading, TDC costs are
usually lower. However, costs of remediation, repair and
consequences of accidents could cause TDC costs to exceed
those of BUC storages.
Rehabilitation Considerations
TDC dumps can not be rehabilitated until after dumping and
reshaping have been completed. BUC storages can be
rehabilitated progressively as each layer is completed.
This has major advantages in:
Remove Top Soil
from Bench 2
Foundation
Reducing the work and time required for mine closure; and
Providing erosion protection during waste dump construction.
Place on
Slope of
Bench 1
The sequence involved in bottom-up waste rock dump construction, including topsoil
placement and vegetation establishment is shown on Figure 19.5 .
19.6 LANDFORM DESIGN
Here, discussion of landform design is focused on waste rock storages. However, it should
be born in mind that planning for mine closure needs to encompass the entire project area
of which the waste rock storages represent only one component.
A range of different landforms that may be constructed using waste rock are shown in
Figure 19.6 .
In mountainous terrain, single bench or terrace landforms are common for under-
ground mines producing small quantities of waste, while multiple terraces are common
for more extensive waste rock storages. In flat or gently sloping terrain, the mesa, break-
away (or hog-back) and mound landforms are used. Ideally, the selection of landform is
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