Environmental Engineering Reference
In-Depth Information
(a)
Valley impoundment for containment of slurry tailings
Plan view
A
Cross Section A-A
Slurry tailings
Slope between hills
A
Constructed embankment
Hill
(b)
Containment pond with constructed embankments
Slurry tailings
Constructed
embankment
FIGURE 5.8
Illustration of valley impoundment for containment of slurry tailings (a) and constructed pond (b).
There are at least three basic types of slurry tailings impoundment facilities: (1) aban-
doned, used-up, fully exploited mine pits, (2) dammed-up valleys, as illustrated in
Figure 5.8, and (3) constructed ponds with containment embankments (Figure 5.8). The
choice of containment facility depends on many factors, not the least of which is site condi-
tions and company mining strategy. These are not within the scope of this topic and will
not be addressed.
There are two distinct categories of slurry tailings contained in the containment facili-
ties or structures:
1. Containment structures that contain sedimented solids and particulates dis-
charged from mineral extraction processes. These structures will show a
“solids-sedimented” layer overlain by water as illustrated by the containment
pond shown in the top diagram in Figure 5.9. For such kinds of sediment slurries,
treatment of the supernatant (liquid) may or may not be necessary—depending on
the chemistry and/or toxicity of the supernatant. In some mining processes, such
as aggregate harvesting from transported surface soils, since water is the only
agent used in the beneiciation process, the supernatant obtained is considered to
be nontoxic. As an example, tin mining of placer deposits using the gravel pump
and dredging method will leave behind slime ponds with well-developed sedi-
ments and clear supernatants.
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