Mining Hydrogeology

Hydrogeologic studies are an integral part of the modern mining industry, where investigations are required for mine permitting, planning, and financing. The studies provide the necessary information to assess baseline conditions, potential impacts due to mining, and the effects of surface and ground water to the mining process.

Mine dewatering and water control can be a major cost for a mining operation, and a potential threat to personnel and equipment, as well as a limitation on operational flexibility. Our team of scientists has extensive experience throughout the world in mine dewatering, control investigations, and systems design. Detailed analyses of existing wells, or exploration boreholes, local and regional geologic data, and mine water inflows are used to design investigative programs. This helps to minimize costs while still providing a sufficient level of confidence in the quality of information for mine planning, development, and regulatory requirements. Eon designs and installs dewatering systems using state-of-the art field testing, analytical methodology, and modeling techniques to assess potential water inflows and optimize design criteria.

Eonís team can draw on experience from work on over ninety mining or milling permits in eighteen states. The permit activities have included, ground water and well analysis and modeling, surface water flow rates and peak flows, average annual runoff, and ground water recharge as well as the relationship of the ground and surface water regimes to water related ecological systems and water rights evaluations. In addition, the water resources related portions of nineteen Environmental Impact Statements (EISs) or Environmental Assessments (EAs) have been completed for projects in the continental United States, Alaska, the Czech Republic, and Kazakhstan. Eon professionals have also contributed to the completion of Clean Water Act permit applications, including various Sections of 404 Permits and wetlands issues.

Typical Mining Hydrogeology Projects:

Name of Project: "Crown Jewel EIS"
Client: U. S. Forest Service, Washington State Department of Ecology, and Battle Mountain Gold Company

Project work involved the complete analysis and description of the ground and surface water regimes for the Environmental Impact Statement for the proposed project. The area investigated is located on over 4,000 acres of a geologically complex mountaintop with varied surface water relationships encompassing five separate catchments. An extensive review of existing ground water data was conducted and additional packer testing recommended. Surface water hydrographs were constructed based on flow measurements, and analyzed in conjunction with well hydrographs to relate the surface and ground water regimes. A finite element model of the pre-project and post-project ground water conditions was completed. The model calculated the ground water inflow to the mine during and after the completion of mining and assessed the potential mining impacts on ground water. Filling of the open pit after mining was modeled, and the post-project water table and streamflow changes and the potential ground and surface water related wetland hydrologic regime analyzed.


Name of the Project: "Alumbrera Project"
Client: Minera Alumbrera Limited, Argentina

The Alumbrera Project is a world class copper and gold mine located in northwestern Argentina. The project is a joint venture between several international mining companies and is scheduled to begin production in 1997. The project is located in an arid region of Argentina where water resources are limited and are closely regulated by local government agencies. Project work involved complete hydrologic consulting services for the pre-feasibility, feasibility, and developmental phases of the project. Hydrogeologic investigations were completed for the mine site, waste disposal, tailings, water supply, and project facilities areas.

Work included the design and implementation of hydrologic characterization studies involving the development and installation of a baseline data monitoring system, water supply evaluation, and potential impacts of mining operations on local water resources.

Several ground water flow models were developed, based on baseline data, to assess potential impacts of mine development on local water resources. The modeling studies involved potential seepage from the open pit mine, waste rock disposal facility, and tailing impoundment areas.

A preliminary study was completed for the project to determine the potential ground water inflow into the mine and the filling of the mine after operations. Potential water quality of the pit water after filling was also analyzed. This study used available pit wall rock geochemistry, chemical equilibrium modeling, and an "in house" computer model developed to estimate pit water inflow and pit filling after mining.