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A
series of heap leach pad closure workshops were presented in 2001 by the Mining
Life-Cycle Center, Mackay School of Mines, University of Nevada, Reno. The
series was presented in four parts, each covering a different aspect of heap
leach pad closure to better understand heap dynamics or point out areas of data
deficiencies. Field and laboratory data from several mine sites in Nevada was
presented for each workshop by the host of the workshop series, Dirk van Zyl,
University of Nevada Reno.
The first workshop
was presented in Reno, NV at the
Holiday Inn on January 26, 2001. The topic was "Estimation of Leachate
Quantity". Seven presentations were given describing hydrogeologic,
hydrologic and geochemical processes; comparisons of draindown from several
mine sites; laboratory testing; and modeled versus observed draindown rates.
The invited speakers were: Dr. Scott Tyler, University of Nevada Reno; Jeff
Parshley, SRK Consulting; Gene McClelland, McClelland Laboratories; Tom Myers,
Great Basin Mine Watch; Michael Henderson, SRK Consulting; and Chuck Zimmerman,
Brown and Caldwell.
The second workshop
took place at the Winnemucca
Convention Center on February 16, 2001. This topic covered the "Estimation
of Leachate Quality". Seven papers were presented covering geochemical
processes; modeling of transport and quality; chemical data from leachate;
long-term chemical predictions of draindown chemistry; and factors affecting
leachate water quality changes. The invited speakers were: Dr. Ulrich Mayer,
University of British Columbia; D. L. Becker, Desert Research Institute; Terry
Albert, Kappes, Cassidy and Associates; John Bennett, Brown and Caldwell; and
Dr. William Schafer, Schafer Limited, LLC. Randy Buffington from Placer Dome
was not able to present his paper, in his place was a presentation by Jeff
Parshley, SRK Consulting.
The third workshop
was held at the Elko Convention
Center on April 6, 2001. Nine presentations were given on the topic of
"Cover Design". Papers were presented on design considerations and
criteria; instrumentation to monitor the cover effectiveness; designs at
several mine sites; and monitoring of the covers. The invited speakers were:
Dr. Ward Wilson, University of British Columbia; Johnny Zahn, Barrick Goldstrike; Peter
Kowalewski, SRK Consulting; Jonathan Gorman, Anglogold
Corporation; Mike Milczarek, GeoSystems Analysis, Inc.; Bill Albright, Desert
Research Institute; and Christy Granquist, Couer Rochester Mine.
The final workshop
returned to Winnemucca’s Convention
Center on May 11, 2001. This topic covered "Leachate Management and
Mitigation". Four presentations were given on the optimization of heap
leach pad closure; abandoned sites and their closure; and mitigation methods
with a comparison among mine sites. A discussion followed the presentations
with respect to the following ideas:
- to develop a sense of where closures stand with the science
and modeling involved, and with respect to predicting closure performance and
mitigation
- concerns of the quantity versus the quality of leachate for
infiltration into the subsurface
- the reliability and applicability of risk assessment as a
tool for evaluating mitigation proposals; and
- if infiltration of leachate into the subsurface represents a
measure of good environmental stewardship.
The invited speakers were: George Fenemore for Andy
Davis, Geomega; Mary Beth Marks, U. S. Forest Service; and Bill Upton for Randy
Buffington, Placer Dome.
Click here for details of workshops
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