GENERAL52763

• Permit No: M1977342
• IBM Index Class Name: General Documents
• Doc Name: ENVIRONMENTAL SUCCESS STORY CASE HISTORY
• Media Type: D
• Archive: No

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III ~I~{II!sll~~{~I~~ ~ M Enaronmen BSuce s Taolry gse~td
Situation
The Twin Creeks Mine produces gold using the milling and dump-leach methods to process gold-bearing ore.
Gold Fields Mining Company, which was acquired recently by Santa Fe Pacific Gold Corporation, wanted co develop
amine tailings facility that minimized any potential threat to surrounding surface water, grotndwater, au and wildlife.
Background
The Twin Creeks Mine began operation in 1987. The mine is located at the foot of the Osgood Mountains,
35 miles northeast of Winnemucca, Nevada.
During processing, a dilute sodium cyanide solution is mixed with ground ore to remove the gold. Next, the
solution is treated to separate the gold and then the ground ore is drained into a tailings pond.
When the mine engineers designed the tailings disposal pond, they wanted to stabilize the pond so that the tailings,
after they dried, would not present a dust problem. They also wanted to minimize the pond size. By keeping the pond
as small as ppossible, they would be able to reduce the threat to surface water or groundwater. Just as importantly, wildlife
would not be as attracted to the pond, thereby reducing any potential threat.
ActionlSolution
The company's experiments resulted in the design and installation of a subaerial de osition tailings facility.
A typical tailings and resembles a soup bowl where all of the railings settle to the ottom. hen the water evaporates,
the remaining flu tailings are blown everywhere, creating a dust problem. At this facility, thc~ pond is comprised of a
sloped expanse of and, creating abeach-like delta. This sloped design serves two purposes: the surface area of the pond
is minimized; and the delta, which is composed of many layers, acts as a filtering system for high-density tailings.
The delta also contains a compacted layer of silt under the strata that provides a high le~~el of containment.
Finally, as a safeguard, an artificial impermeable liner has been placed underneath the pond.
Result
The sloped design has proven successful in helping the company meet several environmental goals. First, the
surface area of the pond is smaller, therebyposing less of a threat to wildlife. Second, the process isself-rejuvenating:
each successive layer provides yet another filtering strata. Third, because the pond has less surface area, less water is
lost to evaporation. Finally, underdrains, which were engineered into the facility and evaporation combined to create
a hard, crusty, stable tailings facility that eliminates dust, groundwater and surface problems. T}re sturdy tailings also
aze easier to reclaim once mining operations have ceased.
The mine's tailings facility provides an example of successfully combining environmental knowledge with
better design. Santa Fe Pacific Gold Corporation has been successful in modernizing its practice:: by investing and
testing new designs that are beneficial For the environment and For mining.
For additional information, contact:
Jim Arnold
Mine Operations Manager
Twin Creeks Mine
PO Box 69
Golconda, NV 89414
[phone]
[phone] (fax)