Environmental Engineering Reference
In-Depth Information
Mine closure is not always permanent. Some circumstances lead to temporary mine clo-
sure. Metal prices may drop to a level that makes it attractive to temporarily stop mining
earlier than originally planned. A future increase in metal prices may lead to the re-opening of
the mine. Some mines such as the Climax Molybdenum Mine, near Leadville in Colorado,
USA, have closed and re-opened several times over a period of decades. Advances in min-
ing and mineral processing technologies may also make it i nancially attractive to re-open
past mining areas. On the other hand, temporary or permanent mine closure may result
from unsafe conditions, a major mine accident and/or public opposition. The tailings
spill in 1989 at the Marcopper Mine in the Philippines led to mine closure. Civil unrest in
Bougainville involving opposition to mining, resulted in the closure of all mining activities
at the Bougainville Copper mine in 1989, and it is unlikely that the mine will re-open in
the near future, if ever. A detailed examination of the environmental issues related to mine
closure follows in Chapter Twenty One.
Mine closure is not always
permanent.
CASE 4.7
Remediation at Mines de Potasse d'Alsace, France
DEPOLLUTION WELL
ACCELERATED DISSOLVING PROCESS
Mines de Potasse d'Alsace (MDPA) operates the Amelie
underground potash mine and processing plant and the
Marie-Louise underground mine near Mulhouse in north-
east France. Mining of potash ore bodies in the region
began in 1910. The workforce peaked in 1965 at around
14,000 and declined to 1,300 by mid-2000. The number
of operating mines and plants has similarly reduced. The
ore deposit is approaching exhaustion, and planning and
preparation for this eventuality began a number of years
ago. The long potash mining history of the region has
left a legacy of challenges. Closure planning and prepara-
tion has focused on: (1) rehabilitation of the surface
waste piles (referred to as terrils); (2) remediation of the
salt-contaminated surface aquifer; (3) removal of decommis-
sioned plant, equipment and materials; and (4) creation of
alternative employment for the workforce and community.
The major environmental issue revolves around the
waste piles dumped adjacent to the benefi ciation plants
prior to 1934. These were placed without liners or other
containment features. Subsequent dissolution of the salt by
rain has contaminated the underlying aquifer giving rise
to plumes of salt contamination down-fl ow from the piles.
Rehabilitation activities have focused on both removing the
source of the pollution (the waste piles) as well as reduc-
ing the level of salt contamination in the groundwater.
Seventeen salt piles covering an area of 220 hectares
are to be rehabilitated. Two methods are currently used to
rehabilitate them. One involves reshaping the piles, capping
them with plastic, clay or bituminous liners to isolate the
Rain
Sprinklers or Monitors
Towards
Rhine
Towards
Rhine
Runoff
Lateral
Resurgences
Percolation
Ground
Water
Trench
Collect
Impervious Basement
Impervious Basement
Depollution
Well
Water
Production Well
Depollution
Well
waste from the rain, then covering with a growing medium
and revegetation with grasses. The other method involves
accelerating the dissolution of the salt component of the
pile using fresh water. The resulting brines are discharged
in a controlled manner to the adjacent Rhine River, while
the insoluble clay residue piles are reshaped and reveg-
etated. Both these methods are intended to prevent any
further contamination of the groundwater. The existing salt
contaminated groundwater is contained and remediated by
a pumping programme. A series of wells have been drilled
down-fl ow from each of the piles. Pumping from these
wells both restricts further contamination of the aquifer
by salt, while providing the processing operations with a
source of industrial water.
The former mine land is being converted mainly to
industrial use following removal of unwanted plant,
equipment and infrastructure. Incentives have been pro-
vided for the creation of new businesses with an emphasis
on small and medium size enterprises. A number of the old
mine buildings are being refurbished to provide space to
house some of these new enterprises. Training is provided
to interested employees to allow them to develop their
own businesses or prepare for work in a new industry.
In addition, a hazardous waste management company
has begun operation, using underground openings created
by mining rock salt for long-term storage of hazardous
waste. Communication with employees and the community
on the closure plans and activities has been important in
alleviating concerns. An interesting method that has been
used to assist this process is the publishing of a comic
book story on the MDPA operation. The story conveys
information about the forthcoming closure in a manner
and style that is easily understood by all.
Source:
UNEP and IFA (2001)
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