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RGC: Project Experience
Grey Eagle Mine
California, USA
- Client:
- Noranda Mines
- Years of Service:
- 1984 to 1988
- Project Description:
- At the Grey Eagle Mine in northern California, gold was
mined from an open pit, milled and leached in a conventional
cyanide leach circuit, and tailings were disposed of in a
small (15 acre) but high (420 ft toe to crest) tailings
impoundment, constructed from the mine waste rock. Cyanide and
metals contaminated seepage was experience from the tailings
impoundment prior to mine closure. Dr. Robertson was the
Project Principal for SRK for the investigation into the cause
of the seepage and the evaluation and design of remediation measures.
- Services Provided:
- Geotechnical and geochemical investigations, drilling and testing
were performed to define the contaminant source terms and plume
pathway. Of particular interest was the need to determine the long
term consolidation and settlement characteristics of
the tailings in order to model the long term expulsion of
contaminated tailings pore water. Specialized laboratory testing
was performed to enable the consolidation settlement to be determined
using non-linear finite strain consolidation theory. Both
self weight consolidation and consolidation under cover loads
were estimated together with the long term contaminated water
expulsion to both the foundation and surface discharge pathways.
Remediation measures implemented include the design and placement
of a multiple layered cover over extremely soft tailings. Methods of
advancing this cover over the very soft tailings were developed,
tested and finally implemented.
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