Erosion - Mining and the Environment: From Ore to Metal - page 792

FIGURE 20.11
Techniques for Energy Dissipation Vary

They range from a relatively simple
protective rip rap lining of the stream-
channel close to the outlet to per-
manent structures comprising heavy
gabions (baskets of rocks), stones or
concrete structures along an entire
stream section.

20.2 WIND EROSION

Wind erosion is the detachment, transportation and re-deposition of soil particles by wind.
The risk of wind erosion is increased by loss of vegetative cover, a loose, dry and smooth
soil surface, large barren areas, equipment movement and strong winds.
In farming, the most familiar result of wind erosion is the loss of topsoil and nutrients,
which reduces the soil's ability to support crop production. Wind removes the smaller dry
silt and clay particles and dry organic matter from the soil surface, while coarser materi-
als are left behind. The continued loss of i ne particles reduces soil quality. In mining, the
most familiar result of wind erosion is the receipt of complaints from community mem-
bers living near the mining operation. For them, air borne dust is not merely a visual nui-
sance; long-term exposure to mine dust may impact health.
Clearly, dust is more an issue for mining projects in arid and seasonally dry areas.
Particularly in the early stages of a project when weaker, weathered materials are being
mined, large quantities of dust can be produced by blasting as well as by loading and
trucking of ore and overburden. Dust due to blasting may be quite dense ( Figure 20.12 ),
but particles are relatively coarse. The dust cloud is generally short-lived and most parti-
cles settle relatively close to the source. On the other hand, dust due to loading and haul-
age operations, while not so dense, is generally i ner. Dust clouds produced by trafi c can
persist all day and may drift over long distances ( Figure 20.12 ) .
Wind erosion is more likely to occur during dry weather periods with or followed by
high winds. Given the i ne-grained nature of deposited materials, tailings impoundments
can be a major source of wind blown dust. Dust may not be generated from tailings areas
until after i nal completion of the tailings disposal operations, when the tailings material
dries out. Only then may elevated levels of metals in wind blown particles (such as cad-
mium or arsenic) start triggering health concerns. As discussed elsewhere, mine wastes at
metal mines commonly contain metals that may be released as fugitive dust, contaminat-
ing areas downwind, as particles settle out of suspension in the air.

In mining, the most familiar result
of wind erosion is the receipt
of complaints from community
members living near the mining
operation.

Dust clouds produced by traffi c
can persist all day and may drift
over long distances.