Environmental Aspects of Phosphate and Potash Mining

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ClosureThe Environmental Approach of the Phosphate Rock and Potash Mining Industry363.7 Mine ClosureMine closure activities occur on cessation of miningand beneficiation activities, following the exhaustionof the ore reserve. The aim focus of mine closure is toleave the mine site in a stable and safe condition. Thisinvolves: Finalizing rehabilitation that commenced earlierin the mine life; Rehabilitation and other activities such as sealingshafts and removing plant and equipment thatcould not be removed until after mining and beneficiationwere completed; Monitoring the keep of rehabilitation and closureactivities in the long term; Rehabilitation is generally conducted progressivelythroughout the mine life, as discussed in detailin the next section; Social impacts on the workforce and on the community,associated with the closure of anoperation, may be complex. They are importantbut fall outside the scope of the present publication.Figure 3.7.1Potential environmental effects : closureMonitoringRemoval of equipmentand plant, shaft sealing,stabilisation, monitoringOngoing monitoring and management is importantto satisfy local communities, government agenciesand other stakeholders, that the agreed post-miningland use has been established. Once verified, the sitemay be returned to the pool of available land.Financial SuretyReturn of site to poolof available landLong term stabilitySafetyFuture land useAir emissionsHazardous waste disposalGovernments increasingly move towards securingadequate financial provisions to deal with closure liabilitiesassociated with mining operations.Environmental financial sureties are one of the mechanismsthat governments have adopted to ensure thatcompanies meet closure liabilities.Various forms of financial surety instruments havebeen applied in different jurisdictions. Instrumentsthat leave the funds available for use by the companymay include: Self-funding through financial reserves; Balance sheet tests; Asset pledges to government in the event ofdefault; Parent company guarantees.More commonly, governments require that producersset aside financial resources. These instruments mayinclude: Cash deposits with government institutions;Trust funds;Financial institution guarantees such as performancebonds and letters of credit.Mine Closure Case StudyIn view of the large reserves and extended life of mostphosphate rock and potash mining operations, thereare few experiences of mine closure in the fertilizerraw material mining industry to learn from and provideguidance.The MDPA potash operation in France has beendeveloping and implementing plans as it approachesclosure.3.8 RehabilitationRehabilitation activities generally involve the designand creation of stable and safe landforms, followed bythe establishment of self-sustaining ecosystems toreplace those disturbed during the mining process.The effectiveness of rehabilitation is enhanced by integrationwith the mine plan and conducting itprogressively throughout the life of the mine. Theobjectives of rehabilitation can range through a spectrumof: Complete restoration of the areas original naturalvalues; Reclamation to re-establish the pre-mining landuse; Development of a completely new land use for thearea, such as lakes, forestry or agriculture; Leaving land of marginal value in a safe and stablecondition.In some countries, the post-mining land use is determinedthrough discussion and consultation withstakeholders, such as state and local government agen-
Environmental Aspects of Phosphate and Potash MiningEnvironmental Financial Sureties: South African and Australian CasesIn South Africa, financial provisions for closure havebeen required since 1994. Four types of financial suretyare currently permitted: A dedicated trust fund; A cash deposit to an account with the Department ofMinerals and Energy; A guarantee from a financial institution; Other arrangements approved by the DirectorGeneral of the Department of Minerals and Energy.Trust funds are the most common instrument adoptedby larger companies, both because of the greater inhousefinancial management resources, and the taxadvantages offered. Contributions are spread evenlyover the life of mine with the financial liability assessedon an annual basis. Allowances are made for new disturbanceand rehabilitation activities conducted duringthe period.The financial provision system is currently beingreviewed through ongoing discussion between governmentand industry. Several additional financialsurety methods are being proposed, such as parentcompany guarantees and the use of insurance policies.A means of recognizing and providing credit for previousgood performance is also proposed.The Phalaborwa operation of Foskor Limited has establisheda trust fund to satisfy the environmental financialprovision requirements. The fund is registered with thegovernment, but operated by the company.Contributions to the fund are determined by the quantityof production and made on a monthly basis, withregular audits conducted by financial advisers. Whenthe company wishes to use some of the funds for thepurpose of rehabilitation, a proposal must be submittedfor government approval.In Australia, WMC Resources Ltd. owns and operates thePhosphate Hill phosphate rock operation in the State ofQueensland.The state government requires the lodgingof financial assurances to guarantee conduct of therehabilitation plan as outlined in the EnvironmentalManagement Overview Strategy (EMOS), prepared inaccordance with regulatory requirements. The amountis based on the maximum cost of rehabilitating the netdisturbance of the lease during the life of the currentplan of operations, reduced by a discount for past goodenvironmental performance. This discount can varyfrom 15 to 75%, creating an incentive for good performanceby companies demonstrating their environmentalcredentials through past behavior.Closure of the Mines de Potasse d'Alsace (MDPA) OperationsFigure 3.7.1Waste piles dissolution schematic. MDPA, France.Depollution wellRainAccelerated dissolving processSprinklers or monitorsGroundwaterPercolationRun-offTowardsRhineTrenchcollectLateralresurgencesTowardsRhineImpervious basementDepollution wellMines de Potasse d'Alsace (MDPA) currently operatesthe Amelie underground potash mine and processingplant and the Marie-Louise underground mine nearMulhouse in northeast France.Mining of the potash orebodies in the region began in1910. The workforce peaked in 1965 at around 14,000and dropped to 1,300 by mid 2000. The number ofoperating mines and plants has fallen similarly, and atpresent two mines and one plant are in operation. Theore deposit is approaching exhaustion, with completionof mining anticipated by 2003. Planning andpreparation for this eventuality began a number ofyears back.The long potash mining history of the region has left alegacy of challenges. Closure planning and preparationhas focused on:Water production wellImpervious basementDepollution well Rehabilitation of the surface waste piles (referred toas terrils); Remediation of the salt-contaminated surfaceaquifer; Removal of decommissioned plant, equipment andmaterials; Creation of alternative employment for the workforceand community.The major environmental issue revolves around thewaste piles dumped adjacent to the beneficiationplants prior to 1934. These were placed without linersor other containment features. Subsequent dissolutionof the salt by rain has contaminated theunderlying aquifer giving rise to plumes of salt contaminationdown flow from the piles. Rehabilitationactivities have focused on both removing the source
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Page 4 and 5: AcknowledgementsA number of people
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Page 8 and 9: Introduction2During recent decades,
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