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FEATURED APPLICATION
GoldSim Enhances the Environmental Assessment of the DeBeers
Snap Lake Diamond Mine Project
Kenneth J. DeVos,
Hydrogeochemist - Golder
Associates, Mississauga, Canada
Donald F. Haley and Scott B. Donald, Hydrogeologists - Golder
Associates, Guelph, Canada
Before a new mine can be developed, it is necessary for an
environmental assessment (EA) to be completed and accepted
by the regulatory agencies responsible for project approvals
and licensing. Recently, De Beers Canada Mining Inc. (DeBeers)
has submitted an environmental assessment study for a major
new diamond mine in Canada's Northwest Territories. This study
relied on an integrated GoldSim model to assess the impacts
of mining and site activities on site water quality.
The successful completion of EAs for large scale development
projects requires the involvement of a large number of technical
specialists and the communication of detailed scientific data,
calculations, findings and conclusions to the regulatory agencies.
Geologists, geotechnical engineers, hydrogeologists, hydrologists,
geochemists, biologists, toxicologists, etc., each provide
input based on their respective areas of expertise, and their
inputs must be integrated in order to assess the overall environmental
impact of the proposed development. The integration of the
technical information, and the ability for others (e.g., regulators)
to understand and review the assessment, is an extremely challenging
task. From a technical perspective, over-simplification of
the linkages between the various types of information can
erode the technical quality of the assessment and therefore
the quality of the decisions made on the most suitable manner
in which to develop the project. From a process perspective,
a lack of clarity or transparency in the calculation methodology
will lead to lengthy reviews, increasing the time (and costs)
required for regulatory approvals.
The DeBeers Snap Lake Diamond Mine Project
The Snap Lake Project is a proposed 22.8 Mt diamond mine
located in the Northwest Territories, Canada. The kimberlite
dyke that contains the diamonds extends beneath Snap Lake,
such that lake water will recharge the underground mine workings
during development. This water, along with groundwater and
surface water in the area of the mine, will pick up chemicals
and sediments associated with the blasting and processing
of the host rock formations. Unless carefully managed, this
water has the potential to produce unacceptable water quality
in nearby water bodies. A key component of the EA was therefore
to develop a Site-Wide Water Quality Management Plan such
that the project could be developed in an environmentally
acceptable manner.
The Site-Wide Water Quality Management Model
The development of an effective plan to manage water quality
at the Snap Lake Diamond Mine was enhanced by using GoldSim
to dynamically link the physical and chemical processes associated
with the movement of chemicals and sediments through the mine
system. By dynamically linking all of the mine site components,
the key factors controlling water quality could be readily
identified, and additional resources applied to those particular
aspects. For example, early in the process of developing the
site-wide water quality management model, it was found that
residues from explosives use within the mine and chemical
reaction rates were key controlling factors for downstream
water quality. This allowed for these scientific issues to
be examined more closely and the water management plan adjusted
accordingly.
In addition to the benefits found by dynamically linking
all components of the system in the GoldSim model, the use
of GoldSim allowed the following technical enhancements to
the environmental assessment:
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The GoldSim model simulated, concurrently, the dissolved
phase and particulate movement of 39 different solutes
through the subsurface mine and surface facilities. This
is considerably more than the number of chemicals typically
assessed (in a formal manner) in a simulation model for
site wide water quality.
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GoldSim was able to easily simulate separate solubility
constraints for different regions of the flow system (e.g.,
underground mine; treatment facility; surface water bodies)
without "breaking" the model simulations at
these locations.
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Being located in the Northwest Territories, low temperatures
play a key role in evaluating flow and water quality aspects
of the surface sources of chemical and sediment loadings.
The effects of temperature (e.g., freeze-thaw cycles,
chemical reaction rates) were dynamically included within
the GoldSim simulation model.
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The results of external detailed process models (e.g.,
3D groundwater flow models; geochemical speciation models),
were linked with other site-wide water quality management
components (e.g., the water treatment plant and the sedimentation
pond), so that the total system could be simulated within
a single simulation model - a Total System Model.
Results
Site-wide water quality modeling results from GoldSim indicated
that during operation of the mine, the key factor governing
solute concentrations and mass releases from the site would
be the mine water production. Following closure of the mine,
the discharge from the above ground waste rock and tailings
storage area most influences the discharge chemistry. Other
key factors included explosives use, mine water inflow rates,
waste rock reaction rates, and the effectiveness of the treatment
plant. An understanding of these key controlling factors allowed
the water quality management plan to develop in a manner that
would minimize the environmental impact of the project.
The Regulatory Perspective
Equally important in the EA process is the communication
of the scientific rationale and methodologies used to demonstrate
the environmentally acceptable development of the project.
GoldSim provided significant advantages in this regard compared
to more traditional methods. The GoldSim simulation model
combined all of the technical considerations into a single
(visual) simulation model, and the model was then demonstrated
and physically used in an interactive session with the regulators.
This dramatically improved the transparency of the scientific
approach and calculations used by DeBeers for the EA submission,
removing the "black-box syndrome" typically associated
with these types of analyses. This has proven to be an important
aspect of the GoldSim modelling approach for DeBeers' Snap
Lake Diamond Mine EA as regulatory questions and concerns
in follow-up supplemental work to the original EA have focused
on the interpretation of the input data, rather than on the
assessment methodology or calculations.
In summary, GoldSim was proven to be an effective simulation
environment for developing a comprehensive and technically
sound Site-Wide Water Management Plan for DeBeers' proposed
Snap Lake Diamond Mine, and, in addition, improved the communication
of the EA methodology and results to the regulators responsible
for licensing and application approvals.
Location of Snap Lake Diamond Project
 
Principal components of the GoldSim Water Quality Management
Model include Snap Lake, the Mine, aboveground Waste Rock
and Tailings Storage, Point and non-Point Sources at the Site,
and a Water Treatment Plant
Temperature dependent kinetic dissolution rates for different
rock types were modelled using results of heat flow calculations
through a vertical profile in the tailings pile and geochemical
data.
Time history plots of mass loadings and concentrations
throughout the total system model allow for key controlling
factors to be identified and assessed.
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