Botkin Environmental Science Earth as Living Planet 8th txtbk

526 CHAPTER 23 Materials Management
23.5 Impacts
of Mineral Development
The impact of mineral exploitation depends on ore quality,
mining procedures, local hydrologic conditions, climate,
rock types, size of operation, topography, and many
more interrelated factors. In addition, our use of mineral
resources has a significant social impact.
Environmental Impacts
Exploration for mineral deposits generally has a minimal
impact on the environment if care is taken in sensitive
areas, such as arid lands, marshes, and areas underlain
by permafrost. Mineral mining and processing, however,
generally have a considerable impact on land, water, air,
and living things. Furthermore, as it becomes necessary
to use ores of lower and lower grades, the environmental
effects tend to worsen. One example is the asbestos fibers
in the drinking water of Duluth, Minnesota, from the disposal
of waste from mining low-grade iron ore.
A major practical issue is whether open-pit or underground
mines should be developed in an area. As you saw
in our earlier discussion of coal mining in Chapter 15,
there are important differences between the two kinds of
mining. 2 The trend in recent years has been away from
subsurface mining and toward large, open-pit mines, such
as the Bingham Canyon copper mine in Utah (Figure
23.5). The Bingham Canyon mine is one of the world’s
largest man-made excavations, covering nearly 8 km 2
(3 mi 2 ) to a maximum depth of nearly 800 m (2,600 ft).
Surface mines and quarries today cover less than 0.5%
of the total area of the United States, but even though their
impacts are local, numerous local occurrences will eventually
constitute a larger problem. Environmental degradation
tends to extend beyond the immediate vicinity of a
mine. Large mining operations remove material in some
areas and dump waste in others, changing topography. At
the very least, severe aesthetic degradation is the result. In
addition, dust may affect the air quality, even though care
is taken to reduce it by sprinkling water on roads and on
other sites that generate dust.
A potential problem with mineral resource development
is the possible release of harmful trace elements into
the environment. Water resources are particularly vulnerable
even if drainage is controlled and sediment pollution
is reduced (see Chapter 15 for more about this, including
a discussion of acid mine drainage). The white streaks in
Figure 23.6 are mineral deposits apparently leached from
tailings from a zinc mine in Colorado. Similar-looking
deposits may cover rocks in rivers for many kilometers
downstream from some mining areas.
FIGURE 23.5 Aerial photograph of Bingham Canyon Copper Pit,
Utah. It is one of the largest artificial excavations in the world.
FIGURE 23.6 Tailings from a lead, zinc, and silver mine in
Colorado. White streaks on the slope are mineral deposits
apparently leached from the tailings.