Approaches to Waste Rock Disposal - Mining and the Environment: From Ore to Metal - page 775

TABLE 19.2
Land Capability in Relation to Slope

Slope Suitable Land Uses

Up to 6º All including residential*, industrial, intensive agriculture, sporting

7º to 9º As above except that more site preparation may be required

9º to 13º Horticulture, grazing, forestry, vehicular access possible

14º to 17º Horticulture, grazing, forestry, off-road vehicular access diffi cult

18º to 24º Horticulture, grazing, forestry, vehicular access requires roads

25º to 32º Grazing, natural vegetation, forestry, roads can be established

More than 32º Marginal for grazing except for goats. Natural vegetation, forestry. Generally too steep for road

access. Not recommended for Waste Rock Storage slopes

* Assumes that ongoing consolidation/settlement is not a problem

19.7 SHORT-TERM AND LONG-TERM EROSION CONTROL

The potential for soil erosion depends on soil properties, slope angle and slope length,
among other factors (see also Chapter Twenty). Slope angle and slope length are deter-
mined in the design of the overall landform, but further erosion protection may be pro-
vided by various measures designed to protect against raindrop impact or to interrupt
surface flow. Protection from raindrop impact may be provided using gravel or vegetative
mulch, or by spreading a degradable fabric such as jute netting. Examples of treatments to
interrupt surface flow include (1) hay bales; (2) micro-terraces; (3) furrows created by deep
ripping; (4) low fences such as the bamboo fences supported by stakes; (5) living hedges,
such as formed by planting strips of Vetiver Grass (see Chapter Twenty-One on Mine
Closure); and (6) stone walls or catch dams.
These erosion control treatments should be oriented along the contours of the waste stor-
age. Clearly, some of these measures, such as furrows or hay bales, provide only temporary
erosion protection while others such as living hedges and stone walls provide long-term pro-
tection. The choice will depend on local availability of suitable materials, labour costs and
the time required to establish a cover of vegetation sufficient for longer term erosion control.
The distance between treatments to interrupt surface flow will depend mainly on the
slope angle. Table 19.3 provides a guide for the spacing of treatments, for different slopes.
The spacing may be increased if the surface soil is very gravelly or stony.
As previously mentioned, long-term erosion control is best achieved by the establishment
of appropriate sustainable vegetation. This is discussed in detail in Chapter Twenty-One
under the topic of Rehabilitation.

Long-term erosion control
is best achieved by the
establishment of appropriate
vegetation.

19.8 MONITORING

Monitoring of waste rock storages involves inspections to identify any problems so that
appropriate precautions, repairs or maintenance can be undertaken. For large top-down