OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

These effects are usually ameliorated by a variety of control measures, including: landscaping and revegetation;
constructed, realigned and protected drainage systems; regular use of dust suppression measures;
spoil capping with waste rock and stockpiled soil; collection and treatment of contaminated drainage water prior
to discharge.
Oxidation of exposed and stockpiled ores (both sub-economic and economic) and waste rock leads to increased
acid rock drainage as sulphide minerals are transformed. The resulting seepage has low pH values, as well as
high concentrations of dissolved metals and total dissolved salts. This leads to extensive adverse effects of
aquatic ecosystems and decreases the fitness of local water resources for use by other users.
2.3.3 Removal and storage of ores and waste material
The removal and storage (stockpiling) of ores prior to milling and extraction is usually the most intensive activity
on any mine operation. The process involves large-scale exposure of ore bodies, followed by blasting, loading
and transportation of various ore grades to the stockpile sites where the ores are separated on the basis of their
ore grade (see Table 2.2). Waste material, including waste rock and soil overburden, are separated and
stockpiled for possible later use during mine rehabilitation after closure. These activities are characterized by
large-scale disturbance due to noise, vibration and wind-blown dusts. Rainfall is contaminated by eroded and
oxidized materials, leading to varying degrees of sedimentation and pollution in local watercourses.
Remediation techniques are very difficult to apply to ore stockpiles since these are “live” and undergo changes
on a daily basis. Waste rock dumps can be rehabilitated as soon as they reach their planned extent.
2.3.4 Blasting, milling and grinding activities
The routine operational phases account for most of the environmental impacts associated with mining (see
Table 2.2) and are considered to have the greatest potential to drive environmental change. The extent to
which mining operational activities act as drivers of environmental change depends in part on the type, scale,
duration and magnitude of the activities, and the sensitivity of the receiving environment. General overviews of
the main types of impacts associated with the operational phases of mining are described briefly below.
2.3.4.1 Environmental changes associated with surface and underground mining methods
Surface mining methods, including strip mining, open pit mining, dredge, placer and hydraulic mining, may drive
environmental change of the affected land surface in the following ways (Brink et al., 1990):
• Changes in topography and surface drainage with the potential for increased soil erosion, long-term
compaction, subsidence and reduced agricultural capacity;
• Disturbance and disruption of the natural groundwater regime with the potential for both ground and surface
water pollution; and
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