Rare Earth Elements: A Review of Production, Processing ...

Rare Earth Elements Review Section 3 – Life-Cycle Stages of Rare Earth Elements Mines
In some cases, reclamation may not be possible to a level that would support past uses, and long-term
monitoring and management may be required.
Mines close for a variety of reasons, including economic factors due to a decline in the market value of
the metal; geological factors such as a decrease in grade or size of the ore body; technical issues
associated with geotechnical conditions, such as mine stability or in-rush of ground water at rates too high
to manage; equipment failure; environmental impacts; and community pressures (Laurence, 2003).
Often, mines will not close but rather become idle, with plans for reopening when the market will support
the venture. Idle mines can continue to cause a variety of health-related hazards and threats to the
environment if not properly managed. While the mine is idle, the waste piles, the tailings ponds that are
associated with the processing plant, and other mine areas must be stabilized and managed, potentially
over many years.
Mines can be adequately managed to avoid log-term problems; however, the pollution and contamination
issues that generally require environmental management over the life of the mine can remain after mine
closure, such as the following:
� Sedimentation of surface waters
� Effluent and drainage (e.g., due to heavy precipitation during the rainy season and snow melt)
from the mine, storage piles, or tailings management areas that can impact downstream drinking
water sources and aquatic habitat
� Acid mine drainage (AMD) and enhanced acid rock drainage (ARD) that also effect aquatic
habitat
� Continued pumping of mine water and contaminant plume migration control pumping that causes
drawdown of nearby aquifers
� Contaminated dusts
� Subsidence or collapse of tunnels and subsurface structures, which also represents a safety hazard
� Hazardous materials remaining on-site (e.g., fuels, lubricants, other chemicals).
These management activities must be planned for long after operations cease and the mine is closed. The
risks associated with these impacts are discussed in Section 6.
3.4 Characteristics of Mining Waste Sources
Mining wastes could be referred to as (managed) materials of concern and, in general, some materials are
not considered wastes until a particular time in their life cycle. However, that is not to imply an absence
of environmental risk from stockpiled or stored materials. Mined materials that are generated may only
occasionally or periodically be managed as wastes. Often, these materials are used for various onsite or
offsite purposes instead of being stored as wastes, although the volume of waste material can often exceed
the demand for reuse alternatives.
EPA evaluates the risks to human health and the environment from reuse of various types of industrial
sector wastes, including mining; however, many of these studies are ongoing, and this report does not
specifically address reuses or reuse issues as they relate to mining wastes from hardrock mining
operations (e.g., REE mines). Reuse of mine wastewater is a common practice. The wastewater is
removed from underground workings or open pits and then re-circulated for onsite use (e.g., processing
areas) or even offsite use if the water is of adequate quality. However, these waters must meet discharge
limits for concentrations of metals or other constituents and also be permitted for discharge to surface
waters. Unless it represents a problematic waste, rock waste materials may be used as aggregate for a
variety of onsite and offsite construction purposes. These might include uses such as base material for
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