Workshops >> Heap Leach Closure Workshop

AGENDA

Tuesday, March 25, 2003

• 8:30 - 9:00 Welcome Dirk van Zyl | Presentation |

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Numerical Simulation of Solute Transport in a Spent Heap Leach Pad
Dr. George Danko
Professor, Mining Engineering Department, University of Nevada Reno
Tel (775) 784-4284
danko@mines.unr.edu

Abstract:

A mathematical model based on a Set of Partial Differential Equations (SPDE) is used for the simulation of a conservative solute transport in a spent heap leach pad. The model is solved using the MULTIFLUX code, a software developed at the University of Nevada. MULTIFLUX is configured for the solution of an SPDE for the prediction of the time- and spatial-dependent concentration variation in a heterogeneous formation. Four equations in the SPDE are found sufficient for adequate modeling solute transport in a rock formation typical to heap leach pads. The numerical model results are validated against experimental results obtained in a large-scale in situ field test. After calibration of the hydrotransport properties and coefficients of the SPDE model from the field experiments, it is used to predict temporal and spatial concentration variations for an assumed conservative solute in four different, characteristic regimes of a heterogeneous leach pad. These regimes are the mobile (1) and stagnant (2) phases, and two new domains representing preferential flows (3), and the lysimeter samplers (4) used for calibrating and validating the numerical model. The results indicate that the concentration differences between the regimes rapidly diminish with time. The variation of concentration with time is described with an attenuation function and/or coefficient both of which can conveniently be used for the prediction of rinsing time necessary to achieve a given target concentration.

Construction and Performance of Heap Closure-A Case Study of the Reclamation of the Getchell Gold Mine Heap Leach Facility

Rick Frechette, MFG Inc., Fort Collins, CO
Tel: (970) 206-4237

Abstract:

The Getchell Gold Mine has a long history of operation, including the heap leaching of gold from the mid-1980's to the late 1990's. The leaching complex includes a collection of leach pads, an offloaded spent ore pile, five lined ponds and a small carbon column recovery plant. The leach pads exist in two clusters, the first of which was operated originally as an on-off pad (the 85-86 pads). The larger cluster was constructed as a dedicated heap leach pad (the 86, 87, 92, 94 pads). The pond facilities were likewise expanded over the years. The site-specific drivers for closure, in addition to the regulatory codes, were Sb, As, Se and SO4 levels present in the interstitial fluids. Reclamation of the facilities involved installation of a vegetative water balance cover (VWBC) as a "store and deplete" system. In addition, three of the ponds were converted to evapotranspiration cells with contingency storage compartments. A leach field was also permitted, but its construction deferred, as a further contingency measure. The plan was developed in 2000 and implemented in the winter of 2001/02. This presentation provides a case study brief of the design, construction and subsequently monitored performance of the final closure measures.

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Innovative Closure Approaches at the Hollister Mine
John Mudge, Newmont Mining Co., Reno, NV
Tel (775) 784-8181
Jmud5884@nevada.newmont.com

Abstract:

Approximately 6 years ago, Newmont Mining Corporation (Newmont) initiated reclamation/closure at its' Hollister operation in Nevada. Reclamation/closure challenges existed at three primary areas within the operation. One the open pits had a small, low pH lake. The primary waste rock dump had a collection system for seepage of low pH solution. The heap leach had a typical inventory of process solution. In each of these three areas water quality and water quantity challenges existed. Reclamation/closure techniques were employed that utilized run-on controls, re-sloping, capping/topsoil placement, pit backfilling and vegetation for water quantity control. Water quality controls included installation of passive, anaerobic systems. These mechanisms have effectively limited water volumes that require treatment and effectively treated the water to meet standards.

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Lessons Learned from the Closure of the Yankee Heap Leach Pad,

Bald Mountain Mine, Nevada
Jeff Parshley, SRK Consulting, Reno, NV Tel: (775) 828-6800 jparshley@srk.com
Randy Buffington, Bald Mountain Mine, Eklo, NV Randy_Buffington@placerdome.com
Maritz Rykaart, SRK Consulting, Vancouver, B.C., Canada

Abstract:

Closure work on the Yankee heap leach pad began in late 2000, and the closure plan was approved by the NDEP and BLM by early 2001. By mid-2001, the solution inventory had been largely eliminated through land application, the leach pad had been regraded and covered, and draindown flows had reached the predicted late draindown rate of 2 gpm. By the spring of 2002 monitoring data showed that the draindown was not nearly as progressed as had been predicted, with flow rates ranging from 5-15 gpm. A detailed review of the original analysis revealed that application of several standard analytical and calculation methods led to an underestimate of the total draindown volume and the time required to achieve draindown. Further examination revealed that nature of the flaws in the original analysis also have potentially profound implications for rinsing, long-term geochemical predictions and bonding.

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Treatment For Immobilizing Metals in Leachate From Heaps and Tailings - Optimized Disposal Process
Joe Harrington, Arcadis, Denver, CO
Tel

Abstract:

ARCADIS has developed, and applied at over 130 sites, IRZ(TM) technology to treat plumes containing metals, CVOCs and other contaminants. The Green World Science(R) process (now owned by ARCADIS) was developed in parallel to prevent the formation of a plume from these types of contaminants in leachate during land application or infiltration from leaking systems. It has successfully been applied to leachate in Nevada and elsewhere to close heap leach systems and further has demonstrated no degradation impacts to waters of the State. The process is implemented by the application of microbial nutrients to the leachate source (such as a tailings pond, or heap leach pad), or the leachate stream after it drains from, or is dewatered from, the source materials. These microbial nutrients are added in sufficient concentration to efffectuate microbial sulfide formation, metal sulfide precipitation and further encapsulation by protective compounds that prevent remobilization. By avoiding above-ground active treatment, ARCADIS technologies can substantially reduce the costs of closure, preventing and treating the risks to water quality. ARCADIS has used these innovative technologies at over 50 sites as part of a guaranteed closure for a fixed price with no change orders that works in concert with alternative financial assurance mechanisms, thereby lowering the total cost of closure compared to the required surety bonds and the associated implementation costs.

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Defining the Purpose of Water Quality Assessment As Part of a Cyanide Heap Leach Closure Project
Rob Bowell, SRK Consulting, Reno, NV
US Tel (775) 828-6800
rbowell@srk.co.uk/srk003@aol.com

Abstract:

A significant part of any closure evaluation for a cyanide heap leach is the assessment of water quality. This covers not just the quality of spent process solution during the drain down period but also long-term seepage and possibly runoff associated with the final rehabilitated heap. For most cyanide heap leach circuits in Nevada and indeed the southwest United States, the most persistent chemical parameters of concern with respect to water quality are arsenic, antimony, nitrate, cyanide, selenium, sulfate, chloride, mercury, highly alkaline pH and saline water quality. A number of passive and active schemes have been proposed to address the need to meet regulated water standards. However, very often the imposed standards do not take into account local geological variations that give rise to variable local groundwater quality. Under Nevada regulations, the over-ridding concern is to demonstrate that any water leaving the pad or ponds at any time (operations) as well as closure must not "degrade waters of the state" that in most cases is shallow alluvium groundwater. A survey of Environmental Impact Statements for northern Nevada revealed that considerable variation existed in what would be described as "background" or "baseline" water quality for groundwater that is not in contact with mineralised rocks. Thus the setting of an arbitrary lower or more rigid standard to that of the "background" would appear to be unreasonable. This presentation reviews data acquired from more than thirty heap leach closure projects in Nevada and the southwest United States and examines how the predicted chemistry for draindown and long term runoff influenced the use of passive and active management mitigation methods to ensure that "waters of the state" were not degraded. The presentation also contrasts these predictions with potential ranges of "background" water and soil quality and examines the need for better site assessment as part of closure studies for cyanide heap leach operations.

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A Review of the Passive Treatment of Arsenic
Thomas R. Wildeman, Colorado School of Mines, Boulder, CO Tel:
Alvaro Pinto, Knight Piesold & Co., Denver, Co. Tel:
James J. Gusek, Golder Associates, Lakewood, CO. Tel:

Abstract:

Over the past decade, a number of our passive treatment projects on mine drainage have included arsenic. In some cases, As was a secondary objective; in others, a primary objective. Laboratory and pilot-scale studies at a mine site in Nevada on an acid mine water and a neutral tailings pond water showed As can be released as well as removed. In the acid water, precipitation of Fe(OH)3 at pH ~3 decreased As from 12 to 3 mg/L. Subsequent treatment in a sulfate reducing system decreased As to ~ 0.4 mg/L. Under sulfate reducing conditions using the tailings water, As increased from 0.09 to 0.2 mg/L. Treatment under aerobic conditions reduced the As in the tailings water to below 0.05 mg/L. Based on these studies, subsequent laboratory and bench-scale studies in Montana and Brazil used zero valent iron in anaerobic systems. The results have been quite encouraging. In aerobic systems, we consider that the presence of As(III) in the water can make treatment problematic. It should be the case that As(III) does not adsorb onto Fe(OH)3 as readily as As(V). Consequently, we have been concentrating on maximizing the photochemical oxidation of As(III) to As(V).

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Solution Chemistry of Heap Leach Solutions from Carlin Trend Ores
Thom Seal, Newmont Mining Co., Reno, NV
Tel (775) 778-4776/4964
Tseal@nevada.newmont.com

Abstract:

A presentation will be made of the concentration of various cations and anions, tracked monthly for the last few years, in the pregnant solution flowing from heap leach operations north of Carlin Nevada. Solution drain down curves for a couple of isolated heap leach cells will also be presented.

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Decommissioning, Closure and Rehabilitation of the Heap Leach System at the Girilambone Copper Mine, Central New South Wales, Australia
Paul L. Brown and Andrew M. Garvie, Sulfide Solutions, Australian Nuclear Science and Technology Organisation, Menai, NSW, Australia Tel:
Phillip Davidson, Barry Deans and Brian Pocock, Straits Resources Limited, West Perth, WA, Australia Tel:

Abstract:

The Girilambone Copper Company (GCC), a subsidiary of Straits Resources Limited, has used heap leach and solvent extraction technologies at its Girilambone Copper Mine to recover LME grade copper from either oxide or sulfidic ores involved crushing the ore, stacking it into heaps via conveyor or stacking system, irrigating the heaps with raffinate delivered by drippers, blowing air into some heaps and collecting the leachate via a geomembrane (HDPE plastic) underlying the heap that directs the leachate to solution drains and ultimately to a pregnant liquor solution pond from where it is pumped to a solvent extraction plant. The mine has now reached the final phase of production and is nearing final shut-down and mine closure. As the recovery rate of copper from some leach heaps decreased towards that, which was deemed to be uneconomical, GCC initiated a project aimed at addressing potential environmental risks associated with effluent released from the heaps after closure. Two specially designed test heaps were made available to Sulfide Solutions to undertake a detailed monitoring program aimed at estimating the future chemical loads and the concentrations of contaminants in effluent from the copper exhausted heaps. The data from the test heaps was supplemented by additional laboratory, geotechnical and modelling data. A process for closing the leach heaps proposed by GCC included the rinsing of the heaps with water. The objective was to wash oxidation and secondary reaction products that were stored during raffinate application, from the heaps whilst the water supply facilities remained at the mine site. The present paper describes the field, laboratory and modelling work undertaken by Sulfide Solutions and provides an overview of the understanding gained of the processes occurring within the heaps, and the implications that have arisen from the work in relation to the future monitoring, management and decommissioning of the heaps. A key component, at closure of the mine, is the management of acid leachates that will potentially exit the rehabilitated heap leach complex. A closed system for solution management and final landform development is also discussed in relation to cover modelling and final collection points for potential solution discharge, developed in conjunction with government regulators in New South Wales.

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Equatorial Tonopah, Inc. (ETI) owns and, until recently, operated the Tonopah Copper Mine. The facility is a large copper heap leach operation that was expected to produce at least 54 million pounds of copper per year for more than ten years. Due to poor metallurgical performance and other adverse factors, mining operations were suspended on March 7, 2001. Subsequently, the leaching operations were ceased and the premature closure of the process components took place on July 26, 2001. In 2003, ETI became the world's first to close and reclaim a copper heap leach facility.

• Estimation of quantity of flow (predictive modelling). Actual vs theoretical.
• Quality of flow. Present actual no need to predict. Discuss futility of rinsing which was not done.
• Cover design (factors considered : ore mineralogy, meteorology, evaporation, precipitation, delta temperature.)
• Cover construction. Present actual with photos. Completed February 6, 2003.
• Fluid Management System at cessation of copper production.
• Post Closure Fluid Management System. Present design and timing of construction.
• Groundwater protection. Discuss regional geology/hydrology. Cross-sectional drawings to illustrate.
• Economics. Savings realized by fluid management plan. Two releases from Interim Fluid Management Bond used to finance capping the leach pad. Termination of solution application to pad saved $$$ spent on electrical pumps. Allowed additional time to dry the heap surface to form a crust and allow heavy equipment to efficiently cap the heap without getting stuck.

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Treatment of Sulphate in Mine Effluent
J. Jay McNee, Lorax, B.C.Canada
Tel

Abstract:

In the treatment of Acid Rock Drainage (ARD), little attention has focused on the mitigation of dissolved sulphate; this may be attributed to its lower environmental risks and regulatory standards when compared to those for acidity and dissolved metals. However, regulatory agencies are becoming increasingly concerned over elevated sulphate concentrations in effluents owing largely to its impact to the salinity of receiving waters. The primary objective of this review was to present a cross-section of the current state of the art treatment processes to reduce sulphate (with or without dissolved metals) in mine effluents. After a review of the available information, several treatment processes were selected and organized into 4 categories:

1. chemical treatment with mineral precipitation (lime or limestone addition, addition of barium salts, the SAVMIN process and the cost-effective sulphate removal (CESR) process);
2. membranes (Reverse Osmosis (RO), the SPARRO process and Electrical Dialysis Reversal (EDR);
3. ion-exchange (the GYP-CIX process and Metal Precipitation and Ion-Exchange (modified GYP-CIX)) and,
4. biological sulphate removal(bioreactors, constructed wetlands, alkalinity producing systems, and permeable reactive barriers).

The review compares and contrasts the various approaches to sulphate removal based on cost and effectiveness of treatment and applicability to mine-site effluents.

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Evaluation of the Long-Term Performance of Dry Cover Systems - A Summary of the INAP Project on Dry Cover System Longevity
Mike O'Kane, D, Christensen, G. Meiers and B. Ayres, O'Kane Consultants, Saskatoon, SK, Canada Tel: (306) 955-0702 mokane@okc-sk.com
S.L. Barbour and R. Shurniak, Department of Civil and Geological Engineering, Univeristy of Saskatchewan, SK, Canada

Abstract:

Dry cover systems have been used at a number of sites around the world as a prevention and control technique for the management and decommissioning of waste rock, tailings, and spent heap leach material. The objectives of dry cover systems are to minimize the influx of water and provide an oxygen diffusion barrier to minimize the ingress of oxygen. Apart from these functions, dry covers are expected to be physically stable and resistant to erosion over the long term, and provide support for vegetation. The long-term performance of dry covers was examined in a research study funded by the International Network for Acid Prevention (INAP). The study was separated into two phases. Work during Phase 1 identified and defined the processes affecting long-term performance of dry cover systems, and examined "typical" numerical models utilized for predicting long-term cover performance. Identification and research of the physical, chemical, and biological processes that could potentially alter long-term cover performance showed that changes in cover performance could be related to changes in the saturated hydraulic conductivity, soil-water characteristic curve, and oxygen diffusion characteristics of the cover material, as well as changes in the physical integrity of the cover system. Phase 2 of the research study involved the selection of five mine sites with a minimum of three years of field monitoring data for analysis of cover performance. These sites included: Syncrude Canada Ltd., Equity Silver Mine (Placer Dome), Mt. Whaleback Operations (BHPBilliton), Kimberley Operations (TeckCominco), and a rehabilitated coal spoil in Montana (blind study). Three of the mine sites (Syncrude, Equity, and Mt. Whaleback) were analyzed with the numerical model deemed most appropriate during Phase 1 of the project. In addition, field saturated hydraulic conductivity tests were completed at three mine sites (Kimberley, Equity, and coal spoil) to investigate the change in field hydraulic conductivity of the cover system materials. This paper will summarize the results of each phase of the project. Recommended improvements to existing numerical models are also summarized. Field observations and/or measurements, as well as historic cover system performance monitoring data, provided the necessary information to develop hypotheses as to the likely site-specific processes that led to a change in key performance indicators. The research project highlighted the need to install (and maintain in good working order) a dry cover system performance monitoring system. It is only through in situ cover performance monitoring that the mining industry will continue to improve the ability to understand the processes influencing cover system longevity, and to improve on the ability to predict long-term cover system performance.

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Performance Monitoring of Mono-Layer Evapotranspirative Covers in Response to High Precipitation and Extended Drought Periods
Mike Milczarek, J. Vinson, M. Yao, GeoSystems Analysis, Inc., Tuscon, AZ
Tel:(520) 628-9330 mike@gsanalysis.com
J.Word, Phelps Dodge Mining Company, Copper Queen Branch, Bisbee, AZ
B.Musser, Phelps Dodge Morenci, Inc., Morenci, AZ
R.Mohr, Phelps Dodge Corporation, Phoenix, AZ

Abstract:

Properly designed evapotranspirative (ET) cover systems can greatly reduce the amount of infiltration and groundwater recharge (deep percolation) into potential acid generating mine waste. In arid and semi-arid environments, infrequent precipitation, low measurable subsurface fluxes, spatial variability within mine waste and cover material, and evapotranspiration from below the cover system create challenges to monitoring moisture flux in these systems. To monitor the performance of different ET cover systems in response to precipitation patterns, four different test plots consisting of two different ET cover depths and good vs. poor vegetation have been instrumented with heat dissipation sensors nests at a copper mine in southeastern Arizona. The sensors measure the soil water pressure potential and allow hydraulic gradients (direction of water movement) to be determined within and below the cover systems. Three replicate sensor nests were installed in each test plot to depths of 180 cm to account for variability in materials and test plot treatments. Data collection occurs twice daily and is ongoing.
Weather during the 26-month monitoring period was characterized by 2 months of higher than normal precipitation followed by 9 months of normal precipitation and then 15 months of abnormally dry conditions. Monitoring data indicate that deep percolation occurs in response to periods of extended precipitation, however, subsequent drying was observed to depths of six feet below the surface in all test plots. Using conservative assumptions regarding tailing hydraulic properties, one-dimensional flux predictions based on the monitoring data indicate very low (< 1.6 mm/year) deep percolation rates, even in response to large precipitation events.

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Rum Jungle Waste Rock Cover
Paul L Brown, Sulfide Solutions, Australian Nuclear Science and Technology Organisation, Menai, NSW, Australia
Tel

Abstract:

The design, construction and monitoring of the Rum Jungle covers have been well documented since their placement 18 years ago in Northern Territory, Australia. In the past few years, lysimeter measurements have indicated that water infiltration has increased significantly. Rum Jungle offers a special opportunity to understand the medium-term behaviour of covers and provide important lessons for their design, use and long-term risk. Between February and December 2002, a project was funded by INAP to determine the reasons for deterioration of the cover. ANSTO and CSIRO carried out the work, managed by ACMER. Five criteria were assessed: design, construction, cover materials, physicochemical characteristics and biological characteristics. Findings from the first site visit at the end of the rainy season indicated that construction of the covers, drains and erosion prevention features were generally in accordance with design specifications. No major changes to the mineralogy of the cover materials was found, but physical and geotechnical testing indicate that the cover materials do not meet the original specifications. The permeability in some places has increased by several orders of magnitude, which might explain the greater infiltration into the dump. The increased permeability appears to be mostly due to biological processes - galleries formed by termites and ants, and root growth from pasture grasses and volunteer trees. The OpCom approved an extension of the study to the end of the dry season in October 2002. The dry season site visit allowed for the examination of changes to the biophysical characteristics resulting from high temperatures and dessication. Permeability, oxygen flux, moisture content, chemical profile, dessication cracks, changes to blocky structure and biological activity were observed.

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Predictions of Long-Term Flow from Vegetative Covers, Why Are We SO Far Off?
Walter L Niccoli, Fred Marinelli, and Barry Carlson, Telesto Solutions, Inc., Fort Collins, Co Todd Welty, Florida Canyon Minind, Imlay, NV
Tel (775) 538-7324
twelty@apollogold.com

Abstract:

Consultants and mining personnel have used sophisticated unsaturated flow models to evaluate the performance of heap leach covers. Most of these models have the ability to simulate soil hydraulic responses, plant growth, atmospheric/soil interactions, rainfall-runoff, and multiple boundary conditions. Engineers have used these tools in heap cover designs to minimize net infiltration into the underlying heap materials, often predicting that zero net infiltration will result. Kampf, e.t. al. (2002) reviewed available long-term drainage rate data from 37 closed or nearly closed heaps throughout Nevada. They found that for sites with less than 7.9 inches of annual rainfall, the net infiltration (recharge) through heap covers ranged from 4% to 7% of annual rainfall. Recharge through the heap cover ultimately controls the long-term steady-state drainage at the heap base. Additionally, practical experience and anecdotal information from mining personnel confirm that steady-state drainage rates from most closed heap leach pads are not zero. This presentation explores some potential reasons why cover design infiltration analyses typically under predict what it observed in the field. A set of data, typically available at the time of cover design, is presented along with the results of an unsaturated model based on these data. Sensitivity of model components is explored and the resulting influence on model predictions discussed. Also discussed are hydraulic and plant transpiration mechanisms that cannot be readily simulated in current unsaturated flow models. Recommendations are provided to guide future investigations and research efforts.

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Concurrent Heap Closure at the Rochester Mine
Jerald N. Hepworth, Rochester Group, Lovelock, NV
Tel (775) 273-7995, ext. 245
jhepworth@couer.com

Abstract:

In 1999, Rochester made the commitment to decommission the Stage I heap leach facility located in the center of existing operations. Stage I heap contains approximately 25 million tons of crushed (~1/4?) material, occupies about 80 acres and is 250 feet thick at its deepest cross section. Concurrent closure of the Stage I heap leach facility at Rochester represents a proactive, state-of-the-art effort. The main project goal has been to ?prove the technology?, or demonstrate that a relatively large precious metal heap leach facility can be successfully closed.
With at least six years remaining in the mining/processing life at Rochester, sufficient information should be analyzed to fulfill this goal well before final facility closure. As a result, Rochester should realize significant direct cost savings, while reducing bond requirements to the lowest possible level.
The following activities have been completed:

• Evaluated and selected the most appropriate chemical treatment closure technology.
• Completed two (2) applications (1999 & 2000) of Green World Science (GWS) treatment technology.
• Re-evaluated the cover design to best fit site materials, with subsequent modeling, earthwork evaluation, recontouring, soil amendment application, growth media placement and seeding.
• Established ongoing monitoring of pore space water quality, in-heap solution water quality and down gradient monitor well water quality.
• Demonstrated, by strategic analysis and monitoring, the effectiveness of the chemical treatment.
• Selected, installed and are currently monitoring the moisture sensor array to validate cover effectiveness.
• Evaluated, scoped and developed a preliminary design for the drain down treatment facility.
• Completed a study to identify bacterial processes within the heap to further validate chemical treatment effectiveness.
• Developed a draft Final Closure Plan for Stage I facility and submitted to the regulatory agencies.
The following activities are planned, but have yet to be accomplished:
• Re-calibration of the cover model using actual moisture sensor array data.
• Finalize drain down treatment facility, with subsequent installation, operation and monitoring.
• Reduce the regulatory bond currently held by the regulatory agencies, specifically for successful chemical stabilization.
• Validate the effectiveness of revegetation as related to cover design.
• Continue to monitor all data and modify, where possible, closure plans and cost estimate.

To date, the closure strategy for the Stage I heap leach facility has been successful. Technical studies and ongoing monitoring is in place to validate, or facilitate modification, of future activities. This effort will serve as a template for future mine closure, which should result in knowing "what to do, when to do it and how much it should cost".

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Hydrologic, Erosional and Revegetation Performance Evaluation
of the Cover System on the AA Heap Leach Pad at Barrick's Goldstrike Mine
Ken Myers The MINES Group, Inc., Reno,NV Tel : (775) 833-3383 KMyers4978@aol.com
Ron Espell Barrick Goldstrike Mines Inc., Reno,NV Tel: (775) 778-8191respell@bgmi.com
Johnny Zhan Barrick Management Corporation, Salt Lake City, UT
Tel: (801) 741-4679 jzhan@barrick.com

Abstract:

In order to eliminate/minimize infiltration of meteoric water into the reclaimed leach pad, a cover with capillary barrier effects (CCBE) was constructed on the AA Leach Pad at Barrick's Goldstrike Mine near Carlin, Nevada. A comprehensive drainage network was established on the surface of the cover to enhance surface water runoff and sediment control.
On June 1, 2002, the newly completed cover experienced an extreme event with total rainfall of 1.6 inches during a 20-minute period. A detailed analysis was performed following the storm to assess the damage on the reclaimed pad that included rilling and gullying on the surface, and limited gullying within the drainage channels. Field measured discharge rates and soil losses due to the storm were compared with values obtained from software predictions. A survey of the vegetation was performed to establish the relationship between plant density and observed erosion. Lessons learned from the storm event were summarized and used to guide the repair work. The hydrologic performance of the cover system was also evaluated using data collected from Time Domain Reflectometers (TDR) and Heat Dissipation Sensors (HDS). The collected hydrologic data indicated that cover system maintained its overall integrity during the storm event described. In addition, measured draindown from the reclaimed pad was compared to predicted draindown from numerical simulations.

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