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SME Annual Meeting

March 1-3, 1999, Denver, Colorado

Preprint 99-47

THE STATE OF MINE CLOSURE: CONCEPTS,

COMMITMENTS, AND COOPERATION

T. Mudder

TIMES Ltd.

Bozeman, MT

K. Harvey

Bozeman, MT

ABSTRACT

The objectives for closure of a hard rock mineinclude minimizing long term environmental liability,attaining regulatory compliance, and maintaininggeotechnical stability, while closing as cost-effectivelyas possible. Proper planning for closure shouldcome during the feasibility study, design andpermitting phases, and during operations as updates.The lack of a proper or updated closure plan canresult in severe environmental and economicconsequences. Effective mine closure is the result of

a combination of innovative concepts, long-termcommitments, and multi-party cooperation. Thepurpose of this paper is to discuss concepts,commitments, and cooperation as they relate to aneffective closure plan.

INTRODUCTION

The objectives for closure of a typical hard rockmine include minimizing long term environmentalliability, attaining regulatory compliance, andmaintaining geotechnical stability, while closing as

quickly and cost effectively as possible in a mannerthat returns the land to a safe and stableconfiguration for post-mining uses. Some of the keyfeatures that must be considered duringdecommissioning and closure of a mine couldinclude any underground workings, a tailingsimpoundment, an open pit, surface waste rock piles,and spent leach pads.

The environmental concerns surrounding each ofthese features have changed dramatically over theyears with varying economic consequences to mineclosure. Of particular interest is the heap leachoperation and the related features of an open pit,waste rock piles, and the spent leach pads. Theopen pit has become a center of controversy due toits physical aspects and the potential for becoming atemporary or permanent water impoundment. Theresultant quality of the pit lake and its subsequentclassification becomes important as to "waters of thestate. The primary concern with waste rock piles is

the potential for oxidation of reduced sulfides and therelease of acid and metals contained in the drainage.Lastly, there is the spent leach pad and its draindownsolution which contains cyanide, metals, and otherinorganic constituents. Although the fear of cyanideprompted the initial regulations related to rinsing ofspent leach pads, it is the potential release of metalsand other inorganic constituents that have becomethe major regulatory focus over the years. Theenvironmental issues related to closure ofunderground workings, tailings impoundments, andconventional milling operations present similarchallenges but appear to be less of an issue to the

public and the regulatory agencies.

Proper planning for closure should come during thefeasibility study, design and permitting phases of amine, and during operations as upgrades. Thisapproach has become the standard or is a requiredpractice today. The lack of a proper or updatedclosure plan for a mine can result in severeenvironmental and economic consequences.

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Inadequate closure activities, water management,and waste rock disposal plans have promptedunexpected and, in some instances, unwarrantedsecondary environmental impact statements orassessments.

In other cases, the lack of proper planning forclosure has resulted in major changes to the required

reclamation bonding for a mine. More emphasis isbeing placed upon the initial and ongoing bonding ofmining operations due to concerns arising from thefinancial status of a company and the potential forlong term environmental damage from acid minedrainage. The examples of improper managementand the related consequences are well documentedand are too numerous.

Beyond the direct economic aspects of inadequateclosure plans and bonding, are the indirect impactsbeing felt by the mining industry. For example, theState of Wisconsin recently passed legislation that

stopped further hard rock mining until an examplecould be identified that had operated for ten yearsand had been closed for ten years without anyenvironmental impacts to ground or surface waters.In the State of Montana various referenda have beenput forth over the last two years, with the most recentone calling for a ban on further open pit mines thatuse cyanide. A few years ago there was areferendum in South Dakota calling for completebackfill of open pits to original contours. These typesof legislation are not generally prompted by concernsover improper mine permitting or operation; they arethe direct result of issues related to improper mineclosure and abandonment.

Proper mine closure is the result of a combinationof innovative concepts, long term commitments, andmulti-party cooperation. Public education, in additionto participation, is a major factor because in theabsence of knowledge, fear resides. The purpose ofthis paper is to discuss concepts, commitments, andcooperation which can be blended into an effectiveand implementable closure plan.

CONCEPTS

There are many different words used to describeclosure including decommissioning, reclamation,rehabilitation, and post-closure. In this paper,decommissioning is referred to as the transitionalperiod between cessation of operations and finalclosure. Reclamation refers to the physical aspectsof earth moving, regrading, and revegetation.Rehabilitation is another word for closure usedprimarily in countries other than the United States, for

example Australia. Closure is a term reserved for thepoint in time at which revegetation has beencompleted, excess solutions have been eliminated tothe extent practical, the maximum degree of passivemanagement has been implemented, and a finalsurface and/or ground water monitoring program hasbeen initiated. The ability to "walk away" from a minesite at closure is dependent upon the degree of

passive management that can be implemented, ascompared with long term operation of a mechanicalwater treatment plant. Post-closure, a term oftenused improperly, is the point in time beyond which nofurther monitoring or passive management is neededor required. The same basic concepts and termsapply to the different types of mining operations atany location.

The inability to "walk away" from a mine site atclosure has related primarily to the two issues ofwater management and waste rock disposal. Theenvironmental and economic aspects of water

management and waste rock disposal duringdecommissioning and following closure of a hardrock mine have not always received the level ofattention warranted during project development andoperation. Historically, the focus of decommissioningand closure has been on physical reclamation andrevegetation. In coal mining, these issues are of lessconcern than for hard rock mines, due to the practiceof continuous reclamation. Both open pit andunderground hard rock mines have incurredunexpected and increased levels of expenditures andenvironmental liability at the end of active operations,at a time when revenues can be declining. Thesingle most important issue which directly affects allother aspects of closure is water management.Often a mining operation, and in particular an openpit heap leach facility, can operate with a "zero" waterbalance due to evaporative losses and the wetting ofore. As a result, there is initially no need for adischarge permit and a major regulatory issue iscircumvented. But as decommissioning and closureapproach, the site water balance remains as before,but the entire water management system is replacedby the need to eliminate large stored inventories. Acommon misconception regarding the mine site waterbalance stems from the belief that watermanagement is automatically successful if annual

evaporation exceeds precipitation.

In wetter climates, the management and eliminationof the relatively large solution inventories present anumber of challenges due to the continuedaccumulation of runoff within underground workings,open pits, and tailings impoundments; infiltrationthrough surface waste rock; and long-term draindownfrom spent leach pads. Although the historical

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approaches of continuous fresh water rinsing orrecycle of treated water through a spent leach padadequately addressed the standards associated withWAD cyanide or pH, they did not always satisfy theregulatory requirements for metals or other inorganicconstituents. Each open pit heap leach miningoperation presents a unique set of circumstances forconsideration during decommissioning and closure.

Based upon a thorough understanding of the quantityand quality of remaining solutions and application ofproven water management and treatment concepts,a suitable closure scenario can be designed andimplemented. The water management andtreatment concepts range from enhancedevaporation, to land application, to passive andmechanical treatment. An excellent handbook forminesite water management has been recentlypublished in Australia (Minerals Council of Australia,1997). Of equal importance and concern is the waterbalance situation created at temporarily shutdownmines.

In addition to solution and water management,long-term commitments are needed with respect toreducing infiltration through surface waste rock piles,spent heap leach pads, and tailings impoundmentsthrough design and construction of appropriatesynthetic or natural barriers and revegetative covers.Depending upon the site water balance and themanagement of sulfide containing waste rock duringoperations, unnecessary and expensive long-termcommitments to water treatment may occur duringdecommissioning and following closure.

The direct impacts of treating acid mine drainageand indirect negative publicity associated with it aresubstantial. In a recent report prepared by the Officeof the Supervising Scientist and the Australian Centrefor Minesite Rehabilitation Research, an in-depthevaluation of the anticipated cost of treating acid minedrainage was presented. The total economic liabilitycould reach $A80,000,000 per year with an overallliability to the industry nationwide of about$A1,000,000,000 over the next fifteen years (Harries,1997). The economic estimate to deal with acid minedrainage for the Canadian mining industry has beenplaced at $C2,000,000,000-$C5,000,000,000(Feasby and Jones, 1994; MEND, 1995; and MEND,

1996). Although comparable values are not availablefor the United States, the Bureau of Mines estimatedthat several thousand miles of surface waters hadbeen impacted by acid mine drainage, the treatmentof which was costing the mining industry over$US1,000,000 per day nationwide (Kleinmann, 1991).This cost of treatment translates into$US365,000,000 per year, or nearly

$US4,000,000,000 over the last decade of thiscentury.

From a short term perspective, the prediction andevaluation of pit lake chemistry and the associatedrisks has resulted in substantial and unexpectedexpenditures ranging from several hundreds ofthousands of dollars to over a million dollars. The

concern over pit lake chemistry stems from the needto define its ultimate beneficial use andcorresponding standards. In many instances theregulatory requirements are not well defined.

The traditional approach to closure of spent heapleach pads has been to rinse continuously with freshwater. Unfortunately, this approach has workedacceptably for run-of-mine (ROM) materials, but notso well for agglomerated pads. The cost of pumpingand recirculation of solution onto the pad hasbecome excessive as many more pore volumes ofrinsing are required than anticipated to achieve

standards for constituents other than WAD cyanideand pH.

Another approach involves the recirculation oftreated solution to minimize pumping costs, but it hasbecome apparent that WAD cyanide and pH are notthe only constituents of concern, and that metalsstandards are difficult to achieve with recirculation oftreated solution alone. In order to reduce the solutioninventory for closure, enhanced evaporation hasbeen a favored approach coupled with landapplication and passive in-situ treatment.

A variety of technical concepts are available to aidin the efficient and cost-effective closure of a heapleach facility. A summary of the basic closureapproach for heap leach facilities is presented in aliterature publication (Mudder and Miller, 1998). Themajor point to be noted relates to the unique andvarying situations that exist at different miningoperations and the fact that environmental concernschange with time. As a result, closure concepts mustbe modified periodically to reflect technologicaladvancements, to account for current regulatoryrequirements, and to allow development of the mostcost-effective closure plan.

COMMITMENT

Although consideration of closure in associationwith mine design and permitting is often requiredtoday, there are some existing operations that do noteven have a conceptual closure plan, let alone a planthat can be reviewed and updated on a periodicbasis. Without a closure plan, a new environmental

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COOPERATION

Above all, there must be both internal and externalcooperation and understanding between participatingstakeholders in the closure process. Consistentcooperation, coordination, and communication resultsin good corporations. There must be internalunderstanding of concerns and cooperation between

the daily operational staff and the corporatepersonnel. There also must be coordination andcooperation among the mining, metallurgical, healthand safety, and environmental staff within theindividual operation. When there is a lack ofcommunication between management and theworkers, then the sag mill is replaced by the rumormill, with a reduction in productivity.

As decommissioning and closure of a mineapproaches after years of operation, the emotionalaspects become as important as both the economicand environmental issues. Through a combination of

cooperation, communication, and coordination, atransitional team should be assembled toaccommodate all aspects of decommissioning andclosure. Being humans, we tend to be morecomfortable with stability and routine; we havedifficulty during transitional periods.

From an external viewpoint, there must becooperation among the mining operation, thecommunity, and the regulatory agencies. Permitting,operations, and closure often becomes time-consuming due to mistrust, inflexibility,misinterpretation, and a lack of closure concepts andgoals. The regulatory process has not kept pace withthe changing times. When cooperation fails, litigationcan prevail. Prolonged legal confrontations are notproductive and do not serve the purpose of protectingthe environment. Although lawsuits may benefitcertain personal agendas, they usually do not resolvethe long-term issues, and the environment and mosteveryone else involved suffers as a result. There is atendency in the mining industry to not upgrade ormodernize a closure plan, since the need for asimple technical revision has often resulted in a fullscale environmental impact assessment orstatement. Such a situation recently occurred at amining operation regarding its management plan for

sulfide waste rock. In addition, there is the impact ofother regulatory requirements (for example, fromBiological Opinions which are prepared regardingendangered species at minesites).

Over the next decade, scores of mining operationsthroughout North America and the world will beginthe decommissioning and closure processes. It isimportant for politicians and the regulatory agencies

to consider the consequences of rigid andprescriptive regulations. A cornerstone of ourmodern society has been accepting and reducingrisks through innovation and imagination.

There is frustration within many different groups ofstakeholders and stockholders regarding the miningindustry as a whole. A conflict has arisen between

the need for the industry and the desire for itsproducts. Each year there is a growing demand forthe products of mining, with more reliance on foreignsuppliers of those products as the industry in theUnited States declines. There is an economic,environmental, and emotional price to pay forincreasing our reliance on foreign metals andminerals.

The consulting industry must do a better job ofresponding to the future needs of the industry throughdevelopment and implementation of innovativeapproaches. There is no single approach that can

resolve all of the closure issues. Consulting must gobeyond simply responding to the Request forProposal (RFP) and the mining industry must gobeyond thinking of closure as merely engineering andearth-moving. There are many interrelated issuesthat must be integrated into a comprehensive closureplan.

It is recommended that about three years beforedecommissioning begins, a closure strategy team,comprised of both internal and external personnel, beformed. The closure strategy team should then meeton an annual basis to identify issues early in theprocess with sufficient time for resolution to avoidcrisis management. Initially, a closure audit shouldbe conducted to determine the status and success ofthe ongoing operational environmental managementsystems. About a year before the decommissioningprocess begins, a final or revised closure plan shouldbe submitted to all involved entities.

These time frames are variable due to theregulatory requirements that exist from state to state.

An educational program should be initiated for thepublic and the mine personnel as the transition periodapproaches. From a cooperation, coordination, andcommunication standpoint, there is a need for the

global mining community to share ideas and closureplans. In this era of electronic and instantaneouscommunications, there is no excuse for the lack ofinformation exchange. In addition, there is a need fora major mining closure conference to discuss currentthinking and present the state-of-the-art information.

The success and future of mining will not be tied tothe promises made during permitting or to the actual

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environmental, health, and safety record compiledduring operations; it will, however, be tied to thecondition of the mining site after closure.

REFERENCES

Bogovich, W., 1992. "Twelve Years of Abandoned

Mineland Reclamation Activities by the U.S. Dept. ofAgriculture and Soil Conservation Service inSouthwest Pennsylvania, Land Reclamation:

Advances in Research and Technology, AmericanSociety of Agricultural Engineers Publication 14-92.

Coeur The Precious Metal Company, 1998.Golden Cross REHAB. News, Edition 1, Waihi, NewZealand, April.

Feasby D. and Jones, R., 1994. Report of Resultsof a Workshop on Mine Reclamation, CanadianCentre for Mineral and Energy Technology, Ottawa,

Ontario, March 10-11.

Harries, J., 1997. Acid Mine Drainage in Australia:Its Extent and Potential Future Liability, SupervisingScientist Report 125, Office of the SupervisingScientist, Environment Australia, and AustralianCentre for Minesite Rehabilitation Research(ACMRR), Canberra, Australia.

Homestake Mining Company, 1996. Environment,Health, and Safety Report, San Francisco,California.

Kleinmann, R., 1991. "Acid Mine Drainage: AnOverview, Proceedings of a Specialty ConferenceSponsored by the Energy Division of the AmericanSociety of Civil Engineers, American Society of CivilEngineers, Pittsburgh, Pennsylvania, March 10-13.

MEND, 1995. Economic Evaluation of Acid MineDrainage Technologies, MEND Report 5.8.1, EnergyMines and Resources Canada, Ottawa, Ontario,Canada, January.

MEND, 1996. "What is MEND? Mine EnvironmentNeutral Drainage, Natural Resources Canada,www.nrcan.gc/mets/mend, September 6.

Minerals Council of Australia, 1997. Minesite WaterManagement Handbook, ISBN 0909276730, 125 pp.

Mudder, T. and Miller, S., 1998. "ClosureAlternatives for Heap-Leach Facilities, MiningEnvironmental Management, Volume 6, Number 1,January.