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Workshops >> Mine Closure Workshop
7:30 – 8:30: Registration 8:30 – 9:00: Welcome and Review of Mine Closure Workshop
9:00 – 9:30: Session 1 – Corporate Strategies
10:30 – 11:00: Refreshment Break 11:30 – 12:00: Session 2 – Mine Closure Planning
12:00 – 1:30: Lunch 1:30 – 5:00: Session 3 – Evaporation/ Evapotranspiration Cells
3:00 – 3:30: Refreshment Break
5:00 – 5:30: Discussion 5:30 – 7:00: Reception Thursday, July 26 8:15 – 10:15: Session 4 – Updates: New Approaches and Technologies
10:15 – 10:30: Refreshment Break 10:30 – 2:30: Session 5 – Case Studies
12:00 – 12:30: Sandwiches for lunch – working lunch
2:00 – 2:30: Discussion and Closure LIFE CYCLE Approach to Mine Closure Dan Ramey, Resource Management, Freeport McMoran, Copper and Gold, Inc., Tucson, Arizona Abstract: Freeport McMoRan Copper and Gold (FMI) recognizes that minimizing current and future environmental and closure liabilities by active, focused mine life cycle planning and implementation is a key to assuring continued fiscal success. FMI has assembled an Integrated Life-cycle Team to assist operating branches with life cycle planning. The integrated team coordinates life cycle planning and implementation efforts with the branches to help assure the sound management of life cycle obligations. The integrated
team has been specifically charged with the responsibility to “Manage/influence
all facilities to reduce potential future liabilities” relating to mine
closure and environmental remediation. The most cost-effective method to
reduce future liabilities at an operating branch is to identify current or
potential liabilities, to evaluate options to reduce these liabilities by
integrating liability management with ongoing operations and considering
liability management in developing alternative operating plans. The
integrated team has developed the Life Cycle Process to assist branches in
their integration of liability management with ongoing operations.
Rio Tinto and Kennecott Minerals Approaches to Mine Closure Fred Fox, Kennecott Minerals, Salt Lake City, Utah Abstract: Kennecott Minerals Company has received national attention in the United States for going beyond minimum reclamation requirements in reclaiming and closing the Flambeau Copper Mine located in the state of Wisconsin, the Ridgeway Gold Mine located in the state of South Carolina, the Nevada Copper Smelter and Tailings Facilities located in the state of Nevada and is currently in the process of closing the Kennecott Rawhide Mine also located in the state of Nevada. The degree, effort and innovation in the reclamation and closure planning for each facility can result in financial rewards for the company as well as enhanced reputation that is so desperately needed in the mining industry today. This presentation will discuss the need to incorporate sustainable development objectives as part of post closure planning and the fact that there is probably very few, if any, walk away closure scenarios in the real world today. Key lessons learned include developing partnerships with stakeholders to assist in fulfilling your "vision" of reclamation and closure. The use of Community Advisory Groups at each operating and reclaimed site has helped Kennecott frame issues and gain community buy-in of post mine landuses. Each mine site and community can vary greatly, requiring tailor-made reclamation and closure plans to address local conditions. Incorporating sustainable development into mine development, from exploration to closure, will help ensure a successful project creating value for your company stakeholders. The need to be
proactive from the start of exploration, going beyond minimum reclamation
requirements and addressing technical challenges through creative development
and innovation has allowed Kennecott to address those critical of our industry
by having examples of achievements in reclamation and mine closure that create
value for the company.
Barrick Goldstrike Mine Closure Planning Darek Huebner, Barrick Goldstrike, Elko, NV Abstract: currently not
available
From Start to Finish – Planning for Closure at Rosemont Copper Jamie Sturgess, Augusta Resource Corporation Daniel Roth, M3 Corporation David Krizek, Tetra Tech, Tucson, Arizona Abstract: From start to finish – the Rosemont Copper Project (Rosemont Copper) is being built for closure. The Rosemont site is located in southeastern Arizona and is owned by Augusta Resource Corporation (Augusta). Augusta purchased the property in 2005 and has since completed a Mine Plan of Operations and Feasibility Report. At $1.50 per pound copper, the estimated project life is 19 years. In addition to employing concurrent reclamation practices, construction of the tailings and waste rock storage facilities will be designed and built to facilitate closure. To date, significant planning has gone into the staging of facility construction as well as into the facility design itself. In addition to limiting facility placement to a single drainage, visual impacts of the site, both during operations and at closure, were also considered in the feasibility level design. As much as practicable, perimeter berms are staged around the facility footprint to minimize the visual impact of both construction and operation from State Highway 83. To visually blend the facilities in with the adjacent native terrain, the perimeter berms will be graded as natural landforms. Operationally, dry-stack tailings will be used at the site. This has a profound impact on water usage issues as well as on aquifer protection, a paramount concern in the desert southwest. Tailings are placed “dry” behind a thick waste rock shell. Placing the tailings in this manner eliminates the possibility of off-site migration of contaminated stormwater as well as minimizes any potential for downward migration of interstitial tailings water as in conventional tailings disposal systems. A fully-lined heap leach operation is also envisioned for Rosemont. At closure, the leach stacks and ponds will be encapsulated by up to 50’ of waste rock. In terms of
using technology, creativity in staging construction, as well as a commitment
to concurrent reclamation, Rosemont Copper is poised to be a model copper
mining and processing facility, adding value to the Arizona economy for years
to come.
Closure Planning Concepts Dave Bentel, SRK, Reno, Nevada Abstract:
A Review of the State of Practice in Nevada Kurt Kolbe, NDEP-BMRR, Carson, City, Nevada Abstract: It is common for permanently closed heap leach pads, tailings impoundments, and occasionally waste rock dumps, to discharge a continuous, relatively poor quality, low flow solution. Specific site conditions may preclude a discharge of this solution, more specifically the pollutants mobilized by the solution, into the environment. The requirement to actively manage this solution (pollutants), into the long-term, is not a desirable permanent closure scenario. As such, the Nevada Division of Environmental Protection believes that the first and foremost goal of all permanent closure plans, applied to each individual mine facility 'source', should be a passive, long-term configuration resulting in a 'zero discharge of pollutants' into the environment.
There are two distinct 'paths', each with a variety of options, currently available with respect to attaining a passive, long-term component configuration providing for a 'zero discharge of pollutants'. One path 'treats' or attacks the pollutants (i.e., cyanide elimination via hydrogen peroxide), effectively reducing or completely eliminating this threat to the environment. The second 'path' acts to reduce or eliminate the 'mobilizing' agent that provides the pollutants 'vehicle' into the environment - generally meteoric water introduced, via infiltration, into the component (source). Options here can be further delineated as either 'front end' or 'back end'. A 'front end' approach may include a component 'barrier', seeking either to reduce meteoric water infiltration (i.e. reshaping, simple cover, revegetation) or completely eliminating infiltration (i.e. engineered/capillary break or synthetic material covers). One 'back end' approach into reducing solution volume requires the conversion of existing process ponds into either Evaporation (E) or EvapoTranspiration (ET) cells. This discussion will focus on this approach.
In actual
practice, combining site specific options provided from both 'paths' is
common. However, the NDEP believes strongly that a 'front end' approach
(passive component configuration precluding most if not all meteoric water
infiltration), whether used in combination with other options or not, is the
best method for attaining the passive configuration providing for the desired
'zero discharge of pollutants' into the long-term.
History of Evapotranspiration Basins in Reclamation at the Aurora Partnership Mine, Mineral County, Nevada Keith Whaley, Humboldt-Toiyabe National Forest, Bridgeport, California Abstract: In late 1999,
the Aurora Partnership abandoned the Aurora Mine heap leach facility, located
in the Aurora Mining District on National Forest System lands. Due to the
abandonment, the USDA Forest Service redeemed the reclamation bond and
commenced reclamation activities. Among these activities were questions about
handling effluent discharge from the heap into three processing ponds, two of
which were partly filled with water. With discharge running 20-30 GPM, the
Forest Service, in partnership with the Nevada Division of Environmental
Protection, elected to convert the three process ponds into evapotranspiration
(ET) basins and also construct a leach field as a backup for overflow. With
engineering provided by SRK, the work was contracted to N.A. Degerstrom, Inc.,
who constructed the basins in late 2000, completing final reclamation work in
late 2001. The ET basins now have seven years of successful history.
Quarterly effluent samples have been taken for analysis through 2005 when the
Forest Service elected to acquire samples semi-annually. Basin fluid levels
have also been monitored regularly. The history to date has given insight
into basin construction, water quality, lessons learned and provides
recommendations for future ET basin utilization in reclamation.
Case Studies – NDEP - BMRR *Getchell, Rick Frechette, Knight Piesold, Elko, Nevada *Big Springs, Jonathan Gorman, AgloGold Ashanti *Golden Butte, Kurt Kolbe, NDEP-BMRR, Carson, City, Nevada Abstract:
The Final Solution for the Final Solution: Treatment of Residual Pond Solution and Residual Draindown in a Copper Heap Leach Pad - Equatorial Mine, Tonopah, Nevada Tim Dyhr, The Mines Group, Tucson, Arizona and Reno, Nevada Jeremy Dowling, Water Management Consultants, Tucson Arizona Abstract: In 2004, Equatorial Tonopah had completed the majority of closure and reclamation at this copper mine and heap leach facility. Two remaining actions remained: (1) Eliminate 5 million gallons (19 million liters) of residual pond solution with very high concentrations of leached metals and dissolved solids (330,000 ppm) ; and (2) Design and construct a system to manage long term residual draindown from the heap. A lime treatment method was selected amongst several alternatives to treat and stabilize residual pond solution. The primary objective was to produce a solid paste precipitate that could be placed on lined containment and covered with growth medium. This design alternative reduced the area of disposal from up to 50 hectares to less than 5 hectares. This consequently reduced significant costs of placement of final cover. Residual pond solutions and lime were very reactive, producing an exothermic hydration reaction that reached boiling in less than a minute and solidification in several minutes if mixed in the right proportions. A portable treatment plant was constructed for the project to mix lime with the residual pond solution. After mixing the partially reacted slurry was pumped into containment cells on the heap, where the hydration-precipitation reactions completed.
Paste precipitates were tested for in-place density to insure that they would have sufficient compressive strength to support a final cover. Paste precipitates were tested after treatment with the Meteoric Water Mobility Procedure (MWMP) that showed that potential leachates were significantly better than pond solution or existing residual draindown. Upon completion of treatment operations, the paste precipitate backfill cells were covered with two (2) feet of growth medium. The entire 5,000,000 gallons of residual pond solution were successfully treated and stabilized within lined containment.
The second
aspect of the project was to reconfigure former process ponds to manage
long-term residual draindown from the heap. The design included placement of
agglomerated fill and piping systems to deliver draindown to reconfigured
ponds, and attenuate up to ~ 25 million gallons (~100,000,000 liters) of long
term residual draindown. The system has been successfully treating draindown
since then.
A Survey of Current Trends in Heap Leach Facility Closure in Nevada and Tips for Future Successes Rick Frechette, Knight Piesold, Elko, Nevad Abstract:
Results from a
survey of the projects completed in the past few years in Nevada are
summarized and the industry and regulatory perspectives on trends for the near
future are briefly discussed. Heap leach facility closure elements that are
addressed include (1) the stabilization and rehabilitation of the spent ore
pile; and (2) dealing with both the short term and long term drainage from the
leached ore (i.e. draindown). Recently, industry and regulatory attention has
focused on methods for draindown disposal more so than for spent ore pile
rehabilitation. Concluding thoughts are provided on measures to be taken
during initial permit-level design, operation and closure implementation to
better facilitate successful closure and attendant performance monitoring.
The ADTI-MMS Pit Lake Workbook: Progress and Preliminary Conclusions Devin Castendyck, Earth Sciences Department, State University of New York, Oneonta, New York Ted Eary, MWH Americas, Fort Collins, Colorado Abstract: The Acid Drainage Technology Initiative, Metal Mining Sector (ADTI-MMS, http://www.unr.edu/mines/adti/) is sponsoring a series of workbooks that will in total comprise the “Handbook of Technologies for Management of Metal Mine and Metallurgical Process Drainage.” The Pit Lake Workbook will comprise one chapter of this handbook. A proposal has been made to the Society for Mining, Metallurgy, and Exploration (SME) to publish the workbooks over the next few years as they are completed. Pit lakes form after mine closure and reflect permanent modifications to hydrologic systems resulting from mining. Given the current high price of precious metals, the global abundance of pit lakes will increase in coming decades. With sufficient planning, pit lakes with good water quality have the potential to be useful surface water resources. At the opposite end of the spectrum, pit lakes with poor water quality pose potential risks to ecosystems. In consideration of these alternatives, the goals of sustainable development associated with hardrock mines require evaluations of pit lake water quality and the long-term mitigation efforts, if any, needed to insure that pit lakes become water resources rather than environmental problems.
The purpose of the Pit Lake Workbook is to provide a thorough description of the current understanding of pit lakes and best-practice management approaches for predicting, influencing, and remediating pit lake water quality. This information is applicable to permitting studies for new hardrock, open pit mines, developing closure strategies for existing open pit mines, and designing monitoring programs.
The development of the Pit Lake Workbook has been an international volunteer
effort and draft papers have been provided by 31 authors and co-authors.
These drafts are currently undergoing review. The breakdown of the chapter
structure of the workbook is: Introduction (2 papers), Characteristics and
Classifications (4 papers), Conceptual Models (1 paper), Sampling and
Monitoring of Existing Lakes (1 paper), Predictive Modeling of Future Pit
Lakes (10 papers), Remediation (5 papers), Post-mining Uses and Considerations
(3 papers), Conclusions (1 paper), and a Bibliography. The structure and
content of the Pit Lake Workbook will be described as well as general
conclusions about current
understanding of pit lake science.
Update on the INAP GARD Guide Terrence Chatwin, INAP, Salt Lake City, Utah, Keith Ferguson, Sustainability Engineering, North Vancouver, BC Abstract: The objective of the INAP GARD Guide (Global Acid Rock Drainage Guide) is to produce the broadest and most up-to-date reference for the mining industry, regulators, NGO’s and the public on the subject of acid-rock drainage (ARD). The Guide will address the production of contaminants from sulfide mineral oxidation that can result in ARD, neutral mine drainage (NMD) and saline mine drainage (SD). Research into ARD formation and methods to minimize its impact has been conducted for over 50 years. Much progress has been made in the last 20 years through a number of research consortiums. As such, there is a considerable body of scientific and engineering guidance available on ARD already through INAP, MEND, BCARD, ADTI, ACMER, WRC, PADRE and other programs. The research however is in disparate references, not easily accessible and tends to be issue, commodity or geographical centric. INAP desires to consolidate the information and produce a guide that would be up-to-date and global in scope.
The GARD Guide
is bringing together best technical and management practices with the
objective of creating a body of work with high industry and external
stakeholder credibility. The Guide will cover all phases of a mining
operation from initial discovery through to final closure
(“cradle-to-cradle”). Thus, it will assist industry in providing high levels
of environmental protection, assist governments in the assessment and
regulation of facilities under their jurisdiction and enable the public to
have a higher degree of confidence in and understanding of acid prevention
proposals and practices.
Permanganate Passivation: Scale Up and Surface Characterization Rick Glover, Graduate Student, Environmental Science and Health, University of Nevada, Reno Abstract: Permanganate passivation of sulfide containing materials is a source control technology for the prevention of acid rock drainage (ARD). The method was originally patented by DuPont in 1996 and donated to the University of Nevada, Reno in 1999. Further tests by UNR on acid generating rock have shown that the process can be performed on a laboratory, pit wall, pilot waste rock piles, and humidity cell scale. In these experiments permanganate passivation was effective at lowering metals release, lowering sulfate production, and maintaining pH under oxidizing conditions. Rock containing pyrite (FeS2) is reacted for three hours at pH > 12 with MnO4-, and MgO creating a passivated layer containing Mn, Mg, Fe, and O. Recent experiments scaled up the process to 250 kg samples in barrels using both freshly mined and previously oxidized rock of the same origins. Specifically chemical consumption (permanganate, magnesium oxide, calcium oxide, and sodium hydroxide), ideal reaction conditions, effectiveness of the process on weathered rock, and best application methods were examined. To assess effectiveness of passivation a 4.5% hydrogen peroxide test was performed over treated rock and the pH of the solution was monitored for 24 hours.
We found a direct relationship between material surface area and chemical
consumption. Weathered rock required a greater volume of base to adjust pH
and had greater permanganate consumption compared to fresh rock of the same
origin. Successful passivation of weathered rock was difficult to confirm, a
long term test will show if passivation is viable. Successful passivation was
achieved with fresh rock in beaker, column, and barrel scales. The barrels
with passivated and control samples will be monitored on a regular basis over
a period of five years to evaluate the efficacy of permanganate passivation.
Geographic Information Systems, Landscape Ecology, and Geomorphometry: What are they and how can they Assist with Mine Reclamation? Tom Dilts, Graduate Student, Department of Geography, University of Nevada, Reno Abstract: Geographical
information systems (GIS) have been implemented and used widely by many
organizations that manage natural resources. Tasks can range from simple map
making to enterprise-wide database management to conducting spatial analysis
and modeling for the purpose of decision making. Increasingly, scientific
disciplines have become focused on incorporating spatial data into statistical
analyses. Subdisciplines of geography, biology, and geology have emerged that
are strongly oriented towards quantitative analysis of spatial data. These
fields include geographic information science, landscape ecology, and
geomorphometry. Although each is unique in its origins and goals, all of
these academic disciplines share the common objective of improving upon
techniques used to analyze spatial data. Furthermore, these academic
disciplines have the potential to aid organizations that have implemented a
GIS by providing a strong theoretical grounding and by fostering improvements
in techniques and tools. This talk presents an overview of some of the tools
used for analyzing spatial data and of some of the relevant academic
disciplines with an emphasis on how they can be applied to assist with mine
closure and reclamation.
Large Column Tests on Heap Leach Materials: Monitoring, Measurement and Modeling Vivek Galla, Graduate Student, Department of Mining Engineering, University of Nevada, Reno Abstract: Two Large
columns (4 feet diameter by 6 feet tall) were used for unsaturated flow tests
on run-of-mine and crushed rock taken from two different heap leach
facilities. The columns were instrumented to measure moisture content, matric
suction and discharge as a result of different flow rates. The measurements
recorded from the columns were compared with the numerical modeling results
using SVFlux and Hydrus-2D. Unsaturated hydraulic parameters obtained from
laboratory tests and estimated from Soil Vision were used in the modeling. Large amounts of data were collected during the almost one year of laboratory
testing. Final modeling and interpretation of results are still underway.
A New Twist on Acid Mine Drainage Treatment: The Rotating Cylinder Treatment System Tim Tsukamoto, Ionic Water Technologies, Reno, Nevada Abstract: The oxidation of
dissolved ferrous iron and manganese is a common component of most
neutralization processes for metals removal because the oxidized forms of
these metals precipitate more readily and at a lower pH than the reduced
forms. The Rotating Cylinder Treatment System™ (RCTS™) “patent # 7011745”
utilizes rotating perforated cylinders to transfer oxygen and agitate the
water that is contained in a shallow trough. When compared with conventional
systems the RCTS™ requires less power and less space and is more effective at
mixing which results in lower chemical costs and sludge production. In
addition, the oxidation reaction times are shortened and treatment can be
achieved at a lower pH. These systems have been utilized on multiple sites to
treat water containing ferrous iron at concentrations greater than 7,000 mg/L
and are effective at removing manganese from ~20 mg/L to less than 0.02 mg/L
at pH 9.5 with ~75 seconds of residence time. The current systems have a
hydraulic capacity of over 500 gpm and can be transported behind a standard
pickup truck providing a mobile system for emergency applications as well as
permanent treatment systems.
Development of Modern SRBrs for Treatment of Mine Waters Eric Blumenstein, Jim Gusek, Golder Associates, Lakewood, Colorado Tom Wildeman, Colorado School of Mines, Golden, Colorado David Reisman, EPA, Cincinnati, Ohio Abstract: Since the introduction of Sulfate-Reducing Bioreactors (SRBRs) in 1988, considerable progress has been made on the engineering and macroscopic biogeochemistry of these systems. Among the important achievements are:
To make these
treatment systems more space-efficient and reliable, studies emphasizing the
molecular, biochemical nature of SRBRs were needed. A number of these studies
have been undertaken and preliminary results have yielded a better inherent
understanding of the complex nature of what was previously believed to be a
simple bioreactor. Issues still to be developed include the dependable
control of hydraulic conductivity, accurate determination of the longevity of
the substrate, and dependable methods to handle waters with high mineral
acidity.
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The Use of Hydro-Jex Technology in Closure of Heap Leach Facilities Thom Seals, Newmont Mining Corporation, Elko, Nevada Abstract: Hydro-Jex
technology has been used on various Nevada heap leach operations for 3 years.
It has become an important tool for characterizing the chemistry of the
interior of mature heap while identifying the location of un-leached and
under-leached inventory. In addition, the technology flushes and leaches
these zones in 3-D for enhanced metal recovery that has shown very promising
economics. Plus the technology allows introduction of pumpable reagents to
target zones to affect internal heap chemistry for closure. The Hydro-Jex
technology is presented for industrial adoption as a standard operational
technique on mature heaps to prepare
for closure.
New Laboratory Methods to Determine Hydraulic Properties of Mine Waste Materials Aaron Graham, Mike Milczarek, Sheng Peng, Tzung-Mow Yao, Robert Rice, Dale Hammermeister, Geosystems, Inc., Tucson, Arizona Abstract: Mine waste rock and heap leach material can contain substantial amounts of gravel and larger-size particles. If there are significant percentages (i.e. > 30%) of these large particles, contact between the particles will create macro-pore (preferential) flow and discontinuity of pore size distributions. The effect of gravelly material on unsaturated flow characteristics is significant: heap leaching relies extensively on macropore flow to ensure rapid solution transport and element recovery; capillary breaks rely on discontinuity of pore sizes to retain moisture in overlying finer grained material. Nonetheless, currently accepted moisture retention characteristic laboratory procedures to determine unsaturated flow characteristics were not designed to quantify macro-pore flow, and the theoretical assumptions for estimating unsaturated hydraulic conductivity are frequently invalid. There are three obstacles to determining the hydraulic properties of gravelly soils in the laboratory; 1) increasing amounts of gravel particles increase the sample size needed for representativeness; 2) large pores may only fill at near-saturation (wet-end) where accurate measurements are difficult; 3) the unsaturated hydraulic conductivity may become extremely low at moderate tensions making measurements impossibly slow at the dry end.
To overcome these obstacles we have developed different methods to measure the
range of unsaturated hydraulic properties for gravelly materials. Large core
diameter cells are used to accommodate large gravel sizes and are further
instrumented with water content and tension sensors to measure these
properties in-situ. Direct unsaturated conductivity is measured at various
steady state irrigation rates to determine the wet end hydraulic properties,
whereas air drying is used to accelerate the dry end measurements. The
addition of “wet” and “dry” end methods to supplement normal moisture
retention characteristic tests to provide a more robust approach towards
determining the true hydraulic properties of mine waste and heap leach
material. Finally, refinements in modeling approaches are needed to better
simulate unsaturated flow characteristics in these material types.
Do you Really Know the Gravity of your Decant? Chris Hatton, URS Corporation, Denver, Colorado Abstract: Gravity decants
are historically the standard and most popular method for removing supernatant
from hydraulic filled tailing dams. These structures have been constructed of
a myriad of materials and combination of materials and in an array of
configurations. The fundamental process consists of decanting water from the
pond surface and conveying the flow through a pipe located in the foundation
and passing under the embankment. This presentation will review the historic
design, construction materials used, operational controls and risks, common
modifications modifications, and, most importantly, changes that occur with
time. The presentation will discuss blockage, chemical deterioration and will
conclude with a discussion of decant closure techniques and methodologies. Case studies of several decant investigations and closures will be reviewed
and recommendations for operation of active gravity decant structures will be
discussed.
Cyanide Heap Biological Detoxification - Phase II Diane Jordan, MSE Technology Applications, Butte, Montana Diana Bless, EPA, Cincinnati Jim Whitlock, Spearfish, South Dakota Abstract: Many active mine sites, mines in the closure stage and some abandoned mines are and have utilized cyanidation to remove and recover precious metals. Discharges from these sites normally contain significant amounts of metal cyanide complexes and concentrations of thiocyanate, soluble heavy metals and ammonia, nitrate and sulfate. Chemical, physical and biological processes have been developed to attempt to clean up seeps and discharges. Strong oxidants such as hydrogen peroxide, chlorine dioxide, Caros Acid, ozone and sulfur dioxide have shown effectiveness in some applications. Biological processes, alkaline chlorination, reverse osmosis and ion exchange have been effective in removing thiocyanate, cyanides and heavy metals.
Typically, biological processes incur lower capital costs at substantially lower operational costs while producing a treated effluent that is compatible with receiving waters and the environment.
Environmental health pressures are being brought to bear on the mining companies worldwide. Viable treatment technologies must therefore, be highly efficient in terms of cost and reduction of contaminants to very low concentrations while producing an environmentally benign effluent.
In a previous demonstration through the Mine Waste Technology Program (MWTP), Cyanide Heap Biological Detoxification, four biological technologies were evaluated in large-scale column testing as to their effectiveness in reducing cyanide and heavy metals to at or below regulatory limits within an acceptable timeframe and with low operational costs. Phase II of this demonstration (the technology which showed significant reduction of cyanide and heavy metals within 120 days) was emplaced in the fall of 2004 at a cyanide heap leach pad located at the Cortez Mine in Crescent Valley, Nevada. The progress of the heap detoxification was monitored through November of 2005.
The results of
this demonstration will be presented and discussed.
Designing With Geosynthetic Clay Liners in Mine Closures and Tailings Impoundments Chris Athanassopoulos, Colloid Environmental Technologies Company, Arlington Heights, Illinois Abstract: Geosynthetic clay liners (GCLs) are sodium bentonite-based hydraulic barriers commonly used as alternatives to compacted clay liners in waste disposal and pond applications. The low hydraulic conductivity of GCLs also makes them viable alternatives for mining applications, including mine closures, tailings impoundments, heap leach pads, and process solution ponds. The presentation will focus on design considerations specific to mining applications, including:
A case study
involving the use of GCLs in a recent tailings impoundment project will also
be presented. |
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University
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