The Importance of Groundwater in the Mining Life Cycle
by: Christoph Wels, Ph.D., M.Sc.
Baseline Characterization
The early phases of project development, characterized by exploration and feasibiity studies, present an opportunity to study the hydrogeological conditions encountered at the proposed mine site under natural (or pre-mining) conditions. This information is critical for an assessment of (i) available groundwater resources for mill and drinking water supply, (ii) potential dewatering rates into the open pit and/or underground workings, and (iii) pre-mining groundwater levels and water quality. The last aspect is critically important for future environmental assessments as it provides a benchmark against which to assess the environmental impact of the mining project on groundwater during operation and to judge any control and/or remediation efforts, which might be implemented during operations, at closure and/or post-closure.
The requirements for the scope of a baseline characterization study depend on the regulatory framework, the scope of the proposed mining project and the local hydrogeological conditions. A baseline characterization study typically includes the following activities:
Geological & Structural Mapping;
Drilling and Monitoring Well Installation;
Groundwater level and Streamflow Monitoring;
Water Quality Monitoring (groundwater, springs & streams);
Climate Monitoring (precip, evaporation, temp etc.);
Hydraulic Testing (pump/slug tests, packer tests); and
Preliminary Flow Analysis.
In most projects, significant savings can be realized if the baseline characterization study is coordinated with the exploration drilling program. For example, exploration holes can often be completed as water level and/or water quality monitoring wells for only a small additional cost. Similar synergies exist between the hydrogeological baseline characterization study and the data requirements for an environmental assessment (e.g. drill cuttings may be essayed for ABA to determine ARD potential in the local rock). As a result the initial characterization studies during exploration and feasibility assessments should be planned by an interdisciplinary team familiar with mine exploration, mine engineering, and environmental issues related to surface water and groundwater.
The extent of interpretation of the field data and flow analyses again depend on local regulatory requirements and the mining project. However, it is customary to obtain at least preliminary estimates of aquifer properties (permeability, storativity, potential yield) and potential groundwater inflows to the open pit and/or underground mine. The hydraulic properties of the aquifer are often estimated from the hydraulic testing results using Aquifer Testing Software (see Software Tools). Preliminary estimates of groundwater flow and potential inflow into a mine can be obtained by using analytical solutions (see Flow Analysis Tools).
Please contact Christoph Wels if you would like to feature an interesting example of a baseline characterization study for a mining project on this website.
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