Mine Rehabilitation Handbook - Mining and Blasting

• Drainage control structures will be required wherever water
concentrates (refer section 5.3.2). Revegetation is likely to be the
best long-term method for stabilising the surface of the dump but
without some form of temporary erosion control and drainage
structures, the dump will be inherently unstable.
• In arid and semi arid areas a number of techniques have been
developed to provide increased protection against erosion, to
increase the capture and infiltration of rainfall and to create protected
micro-climates. These methods include “dimpling” (refer 5.3.1),
“moonscaping”, basin listing (using reciprocating tines) and the use
of rock cladding to provide a protective armour.
• “Moonscaping”, illustrated in figure 6.2, provides an alternative way
to stabilise steeper slopes and improve conditions for revegetation.
Figure 6.2
• For “moonscaping” to be effective, it is essential that each run of
craters and mounds is interlocking to avoid channeling runoff. On
long slopes, a contour bank or bench may be required.
• Rock cladding can frequently be obtained from selected “slabby” or
“blocky” overburden material 150mm or greater in diameter. The
resistance of selected materials to weathering must be confirmed in
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advance. Rock-cladding is used as a very coarse mulch to provide
an erosion resistant surface similar to scree slopes commonly found
in arid areas.
• Care is required to ensure material selected for rock cladding does
not produce an acid environment after weathering and is suitable
colour to blend with the existing environment.
• The coarse irregular surface created by rock cladding provides
protected crevices that act as traps for wind-blown dust and seed.
Hydroseeding and similar techniques can be used to encourage the
more rapid establishment of vegetation (refer section 5.5).
6.2 Tailings Storage areas
Tailings vary greatly in their physical, mineralogical and chemical
properties but are usually difficult to stabilise and vegetate.
Tailings storage structures fall into three main categories: dumps,
impoundment dams and storage in existing mine pits. Specialised
geotechnical and engineering assistance should always be sought when
planning the design and siting of tailings areas. Tailing storage areas
should be:
• non-polluting while they are operating and after de-commissioning
(dust, surface water or groundwater pollution);
• structurally stable (including under earthquake loading);
• resistant to erosion;
• visually compatible with the surrounding landscape; and
• have adequate capacity to cope with the output of tailings.
The siting, design and operation of the storage area will affect how
quickly, after de-commissioning, equipment can be used to assist in the
rehabilitation process.
In most circumstances, it is important to avoid designing and operating
a tailings impoundment as a water storage facility. Tailings should be
discharged so as to maximise density within the storage area. By doing
so, the storage area will accommodate a greater volume of tailings, the
hydraulic pressure on the floor of the storage area will be reduced and
rehabilitation will be more readily achieved.
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