The Range of Environmental Concerns - Mining and the Environment: From Ore to Metal - page 525

FIGURE 13.4
Waste Rock and Tailings, the Two
Main Waste Streams in Mining

Topsoil Management

Topsoil

Overburden

400 tons
Waste Rock

The amount of mine wastes depends
on mineral type, stripping ratio, and
mine size. Higher mineral values allow
mining of ore bodies with lower min-
eral concentration which in turn leads
to higher mine waste generation.

Geological
Envelope

Ore Body

Ore Dressing 100 tons Tailings

Assumption
Stripping Ratio 1:4
Mineral Concentration 1%

1 ton Mine Product

Disposing of such large quantities of mine wastes poses enormous challenges for the
mining industry, with signii cant environmental impacts that are difi cult if not impos-
sible to avoid. Mine waste management is more of a challenge for open-pit than for
underground mining which generally produces relatively little waste. In a sense min-
ing companies are primarily in the waste disposal business, with the i nal metal merely
a byproduct of excavation and processing (Navin 1978). Taking the average multiplier in
copper mining as an example, 1/450th of the entire mass of material managed has to defray
the costs of all the rest that is unwanted earthen materials, tailings, slag, and sulphur. Since
mine waste management is also non-revenue producing, it must be conducted efi ciently.
All mine wastes are of environmental concern. Waste rock storages and tailings
impoundments stand out in this regard, not only because of their size but also because these
are the storages in which toxic contaminants, if present at all, are to be found. Contaminants
associated with these areas include metals, reagents, salts, and acidic solutions that may con-
tinue to degrade groundwater, surface water, and soil long after mine closure.
The issue of whether a particular material is a mine waste often depends on the spe-
cii c circumstances surrounding its generation and management at the time (USEPA
1994), as well as on the jurisdiction of the host country. Mine wastes such as waste rock
and tailings are generally considered to be of no value and are managed as such, typically
in on-site management units. Some of these materials, however, may be useful (either on-
or off-site). Waste rock and tailings, for example, may be used for construction of roads,
embankments, and other engineered i lls. For example, tailings embankments are often
constructed, at least partially, from waste rock. And depending on economic conditions
and technological improvements, today's waste rock may become tomorrow's ore resource.
Research conducted to i nd benei cial uses for tailings, however, has been unproductive
for a variety of reasons, some as in Case 13.4 , quite unexpected. Realistically, there is lit-
tle scope for i nding benei cial uses for most mine wastes, because they do not contain
valuable substances or properties and they are usually (although not always) sited well
away from potential markets.

In a sense mining companies are
primarily in the waste disposal
business, with the fi nal metal
merely a byproduct of excavation
and processing.

Depending on economic
conditions and technological
improvements, today's waste
rock may become tomorrow's
ore resource.