Schlumberger Water Services has designed, permitted and implemented mine closure systems for surface and underground mines. These systems take advantage of site hydrologic regimes to reduce or eliminate mine water discharges and long-term treatment requirements. Our closure systems include the innovative use of evaporative covers, passive treatment systems, adjustments to the site water balance and natural attenuation to reach closure goals in a cost-effective manner. Schlumberger Water Services designed and implemented one of the first major pit lake closure projects in Nevada, which has now become a guideline for such projects. We have a track record of designing and implementing closure systems that are cost effective, meet regulatory approval and, most of all, work. We have also helped mining companies develop closure criteria and monitoring programs that will demonstrate successful closure to the regulatory agencies, allow for timely release of bonding, and minimize any long-term liabilities at the site. Services provided for mine closure include:
- Site water balance modeling to optimize closure design
- Cap and cover systems using both natural and synthetic materials to minimize infiltration
- Evaporative cover systems in arid environments
- Management of sulfide waste by submergence and use of organic layers
- Numerical modeling of unsaturated flow, saturated flow, and geochemical reactions to demonstrate performance during closure and post-closure
- Detailed engineering design and costing
- Development of closure and bond release criteria
- Regulatory presentations and permits
- Risk assessments
- Closure monitoring programs
Project Examples:
| Title: |
Golden Cross
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| Location: |
New Zealand
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| Client: |
Coeur d’Alene Mines |
| Description: |
Schlumberger Water Services developed closure options for the open pit and underground workings, based on an assessment of costs, impacts on the local river system, and the requirements for long-term treatment of discharge from the closed mine. A conceptual hydrogeologic model for the site was
developed and used in conjunction with rock geochemistry data
to predict the long term chemistry of water discharged from the site under a number of closure scenarios. The study indicated that sealing and backfilling of the open pit would be required in order to minimize flow through the underground workings, which could not be isolated from the environment.
A flexible closure plan for the mine was prepared and successfully executed
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| Title: |
Sleeper
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| Location: |
Nevada, USA
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| Client: |
Amax Gold
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| Description: |
Schlumberger Water Services prepared a heap leach closure plan to address the stabilization of the five leach pads and associated solution control facilities. Of particular concern was the potential for acid rock drainage. Schlumberger Water Services performed the following services:
- Compilation and evaluation of existing geochemical data for the leach pad solids and rinse waters
- Estimation of daily precipitation, evaporation, and temperatures for the site
- Completion of a water balance on the leach pads for the short-term dewatering and the long-term draindown period of 100 years
- Estimation of the time needed to evaporate draindown solution in existing solution ponds
- Prediction of the final discharge water chemistry
- Preliminary design of infiltration cells for long-term seepage
- Evaluation of potential impacts to groundwater from closure.
The plan showed that the long-term draindown rate from the pads is insignificant and that the preferred method of closure can be accomplished with no significant water quality or other environmental impacts. |
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| Title: |
Haile gold mine closure
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| Location: |
South Carolina, USA
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| Client: |
Kinross Gold Corp |
| Description: |
Schlumberger Water Services assisted with the design, permitting and closure construction for this historic open pit gold mine. The mine is located in a humid climate and contains extensive sulfide materials that could contribute to ARD if not properly managed. We designed closure systems for several open pits, waste rock dumps and historic tailings facilities that effectively minimize potential ARD through the application of physical and geochemical controls. A major objective for the closure system is to minimize active water treatment and discharge permits. Passive methods are being implemented which are expected to eliminate or reduce active treatment requirements and permits. |
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