Mining Practices with Objective of Sustainability

Author: Partha Das Sharma (B.Tech – Hons., in Mining Engineering) 1 Website: http://miningandblasting.wordpress.com/

SUSTAINABLE DEVELOPMENT Aims at meeting the needs of present generation without adversely affecting its availability for future Rate of depletion of non-renewable resources should be judicious Minimum adverse impact to the environment Maintaining equilibrium in eco-system.

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SALIENT FEATURES OF MINING PROSPECTING & EXPLORATION MINE DEVELOPMENT WASTE DISPOSAL DRAINAGE TRANSPORT END USE OF MINERAL PRODUCED BENIFICIATION PRACTICE SITE SRVICES ENVIRONMENTAL MANAGEMENT POST MINING LAND USE 3

PROSPECTING & EXPLORATION

It is the most important exercise, to be carried out very faithfully because entire fate of future lies upon this

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PROSPECTING vs. EXPLORATION

Prospecting is premining stage operation mainly confines to establishing sufficient evidence of mineral occurrence in respect of shape, size, quantity, quality & economics

Exploration is a dynamic process & continues during subsistence of mining period. It is expected it should lead ahead of mining operation for consistent updating the mineral reserve 5

It also should include Identification of various litho-units occurring in & around the proposed mining site Establishing sufficient evidence of mineral occurrence in respect of shape, size, quantity, quality & economics Correct assessment of geo-technical properties of rock mass including their toxic values.

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CONCEPTUAL MINING PLAN Long-term Perspective view of mining Time frame for assessing the true potentiality of area Visualization and determination of ultimate pit limit Waste disposal management Post-mining land use Ensuing mining operation are part of it.

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MINE DEVELOPMENT Selection of method of mining Opencast Underground Mixed

Mode of Mining Mechanized Semi-mechanized Manual Conventional Non-conventional

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OPEN CAST MINING Precise assessment of optimum stripping ratio for amenability by open pit mining Determination of ultimate pit limit precisely in advance Separate removal of top soil, mine-waste Advance removal of waste to avoid any possibility of interruption in work or ore dilution/contamination 9

OPEN CAST MINING continued‌.

Proper laying of mine faces for winning of different grades simultaneously to ensure judicious blending of ROM Aiming to mine up to optimum depth Minimum mineral loss / dilution Safe, secure & energy saving haul road

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UNDERGROUND MINES

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Selection & location proper mode of entry & exit i.e.

Vertical shaft Inclined Shaft Decline/Ramp Auxiliary/staple/ventilation shaft System of winding & access 11

UNDERGROUND MINES

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continued

Selection of proper method of work in relation toOptimum recovery Geotechnical properties of ore & wall rocks Adequate size of openings, blocks, pillars etc & long-term sustainability Complete width of ore body is to be worked Ensure least surface damage 12

MINERAL CONSERVATION Waste should not be allowed to mixed with non-saleable fraction.

Ground selected for waste disposal is to be proven for mineral occurrence and should be away from ultimate pit limit.

Separate stacking of sub-grade mineral Judicious blending by different combination In case of underground mine, subgrade mineral is to be brought to the surface.

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BENIFICIATION OPERATION

All attempts are to be made for upgradation of low-grade mineral to make it saleable fraction.

Beneficiation Investigation are to be carried out Regular analysis of ‘feed’, ‘product’ & ‘tailings’ 14

PLANT & MACHINARY

Selection of matching machinery to the mine design parameters & local conditions.

Optimum utilization Time & motion study Least waiting/idle time 15

PLANT & MACHINARY continue..

Energy saving & conformity to emission standards Attenuation of noise at the source itself Dust suppression at the source of generation Planned preventive maintenance Minimum re-handling 16

BLASTING Proper Blast design Optimum utilization of blast energy Desired fragmentation Neither under break nor over break Least ground vibration Least air blast Least fly rock Least nuisance attracting public annoyance Regular scientific investigation 17

SOLID WASTES GENERATED

MINE WASTES Large in quantity Mostly inert Large in size- Solids Represents in-situ

MILL/PLANT WASTE Less in quantity Can be toxic Fine particles-Slurry Altered Product

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ENVIRONMENTAL PROBLEMS

Leaching & wash off - heavy metals & toxic elements -acid mine drainage Dust pollution with toxic metals Phyto-accumulation of heavy metals Effect on vegetation & aquatic eco-system, Entry into food chain Effect on landscape 19

WASTE DUMP DESIGN Height, area & shape with regard to the area available, topography & vegetation.

Avoid Proliferation of dumps.

Surfaces should be stable & resist long term erosion.

Peripheral dumping, with simultaneous afforestation.

Toxic waste dumps to be contoured and/or sealed to minimize water penetration.

Potentially acid forming material to be sealed by inactive waste that has a buffering capacity.

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WASTE DUMP DESIGN Construction of drainage to handle heavy rainfalls.

Topsoil scraped out from dumpsite in advance, to be preserved, spread over surface & revegetated.

Provision of garland drains surrounding the dumps Provision of Retaining walls/Toe walls.

Completed overall out-slopes do not exceed 20 degree Provision of benches/berms.

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DUMP INSTABILITIES (Long-term instability) REASON Due to saturation with water & reduction in strength of material due to water action.

SOLUTION Growth of permanent vegetation over dump surface & establishment of proper drainage.

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DUMP INSTABILITIES (short-term instability) REASON Poor material strength, improper heights & slope angles.

Long unbroken slopes produce rill & gully erosion

SOLUTION Benches, of heights not more than 10 to 15 m, with min. berm width of 4 m.

Berm to have gentle slope, say 0.5%, towards high-wall side, with toe wall along periphery of dump.

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Estimated relationship between the angle of dump slope and soil erosion & efficiency of revegetation

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VARIOUS TYPE OF DUMPS

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Management of Waste Dumps (Physical Stability)

ISSUES Steep slopes Unstable surfaces Erosion Drainage Dust Generation Hazardous waste Control 26

Management of Waste Dumps (Physical Stability) Control Methods Site selection Peripheral dumping, Retaining walls/Toe walls Internal drains & garland drain Gentle slopes & heights Berms, with rock-lined drains Cover & secure containment of hazardous waste, Cap with soil Settling ponds Vegetation along slopes Green barriers 27

Management of Waste Dumps (Chemical Stability)

Issues Metal leaching Seepage Acid drainage Contaminants Effects on surface and groundwater Dump design 28

Management of Waste Dumps (Chemical Stability) Control Methods Analyze the samples Isolation of reactive material No deterioration in groundwater Cap/enclose toxic material with inert & impervious material Control surface drainage & runoff Collect and treat effluent Cap with topsoil & vegetate Effective water management Monitor 29

Management of Waste Dumps (Land-use)

Issues Productivity Visual impacts Restore to original or accepted alternative use Establish land drainage

Control Methods Marketing/reuse of waste Back-filling Avoid dump proliferation Design for minimum area Re-contour Establish vegetation Landscaping

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Management of Waste Dumps (Biological Stability) Issues Re-vegetation Bio-diversity Survival of vegetation Phyto-accumulation of toxic & heavy metals Entry of toxic & heavy metals into food chain Development of selfsustaining plant community Forestry

Control Methods Soil Fertilization/stabilization Planting leguminous plants Draught resistant species Selection of Phyto-resistant species Successful re-vegetation with indigenous plants Protection for animal grazing Monitoring for soil quality Congenial environment for wildlife, with fodder & water 31

TOP-SOIL MANAGEMENT Recovery is essential for rehabilitation work. Sooner it is reused the better the results will be.

Soil Stacks: Low heights, Should not get washed off Leguminous plants are to be cultivated In areas of poor soils, nutrient levels is low Fertilizer application is soil cheaper than soil stabilizers Single application will suffice in all areas except those prone to high soil leaching - eg over tailings 32

TAILING IMPOUNDMENT

Design requirements of dam & impoundment: Impoundment to be competent to support Not to be located in recharge zone, establishing hydraulic with aquifer Relatively impervious, otherwise an impervious layer/dyke to be provided at bottom Foundation soil of the dam and the dam it self be competent to support & relatively impervious, otherwise internal drainage to be provided in side the dam Dam should have stable slopes- downstream slopes 1:3 33

Design requirements of dam & impoundment Adequate drainage features to be provided As much as water must be re-cycled Conduits from decant towers passing below the dam be avoided A floating or moveable pump hose located on the shore is better for water reclamation At each stage, dam raising should be fast to stay ahead of the rising tailings in the pond.

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Management of Tailing Impoundment (Physical Stability)

Issues Dam wall stability & foundation Dust generation Erosion & Sediment deposit Dam drainage & Seepage Control on Phreatic line Overtopping of dam Earthquakes Access and security

Control Methods Site capacity & impervious Dam erected by competent rock Spillway/Adequate freeboard –1m Decant towers or floating pump Diversion of runoff to out side Stage-wise raising to be fast Tailing disposal Downstream Construction Final re-profile, Instrumentation Cap with soil & vegetate Plug intakes & decants

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Management of Tailing Impoundment (Chemical Stability)

Issues Changes in tailings geochemistry Metal leaching Acid drainage Mill reagents Dam structure Groundwater- seepage effect past the dam & from impoundment base Surface water management

Control Methods Leaching tests Non-reactive material in dam wall Impervious layers- seepage Establish drainage within dam Control reactions Divert run-off Collect and treat effluent Acceptable water quality in downstream Monitor

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Management of Tailing Impoundment (Land- use)

Control Methods

Issues n n n

Productivity Visual impacts Restore to accepted alternative use

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n n

n

Re-contour to mach surrounding landscape Provide soil capping Provide sedimentation tank Establish vegetation 38

Management of Tailing Impoundment (Biological Stability)

Issues

Re-vegetation Bio-diversity Survival of vegetation growth Phyto-accumulation of toxic & heavy metals Entry of toxic & heavy metals into food chain

Control Methods Soil stabilization Planting leguminous plants Indigenous species Draught resistant species Selection of species resistant to phyto-accumulation & concentration of toxic elements Protection of re-vegetated area against animal grazing Monitoring for soil quality & for phyto-accumulation 39

WATER QUALITY Quantitative & Qualitative studies, for Surface & Ground Water characteristics Available Site Water Sources Catchments area Water Management & upstream pollution sources Maximum & Lean Rainfall Runoff rate at Peak Rainfall Potable Water Supply Sources, Quality & Quantity Domestic & Process Waste Water discharge Discharge points, Quality & Quantity 40

WATER BALANCE AT SITE Lean season water availability Source tapped with competing users (River, Lake, Ground, Public supply) Changes observed in quality & quantity of ground water Present recharging & extraction details Quantum of surface waste water to be released with treatment details Quantum of quality of water in receiving body, before & after disposal of waste /effluent Quantum of waste/effluent water released on land & type of land

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Water balance diagram Schematic diagram linking up flow of water to & from the facilities, Showing water supply source (s), Water discharge points), Evaporation areas & potential seepage points, with step wise indication of flow rates, in cum/day & quality, into & out of facility 42

Management of Water Quality (Physical Stability) Control Methods

Issues Erosion, wash-off & sediment deposit Blockage in natural flow Sewage & effluent treatment plants & sludge Discharge of drainage Structural Safety & flood capacity Intrusion of sea water Water balance, recharge

Remove/restore unwanted structures, Fill in ditches Plug intakes & decants Upgrade flood design Reinstall pre-mining drainage Dispose plants & plant sludge Install check dams/settling pond Develop re-charge wells/holes Re-vegetate Install pre-mining water balance for mine area 43

Management of Water Quality (Chemical Stability) Control Methods

Issues Contamination of surface and /or groundwater Acid drainage Leaching of toxic metals

Prevent/remove contamination of surface &groundwater with: -Acid drainage -Leaching of toxic metals Install new settling ponds Erect stopping or flood the pit Drainage - treat & discharge Install barriers/grout curtains Establish phyto-accumulant vegetation Monitor

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Management of Water Quality

(Land-use) Control Methods

Issues Interruption of water supply in catchment area Productivity of land drainage Sediment deposition (Nalla sediments) Return to appropriate land use

Avoid interruption of water supply Establish erosion-resistant drainage Restore drainage patterns or establish effective alternatives Install retaining walls Stabilize and maintain dam or breach Establish vegetation Establish effective rehabilitation 45

Management of Air Quality

(Physical & Chemical Stability & Land-use)

Issues Wind Erosion Effect on vegetation Pollution of air with toxic substance Contamination of surface Productivity of land

Control Methods Cap toxic & hazardous waste Remove or prevent contamination Land fill & capping Establish vegetation Develop thick green barriers Monitor Establish erosion-resistant Structures Return to appropriate land use or establish alternatives 46

Monitoring of Water & Air Quality To demonstrate remedial/ restoration work is successful.

To meet closure objectives & performance criteria.

To compare results with earlier monitoring data.

Monitoring for dry season, as per IBM/MoEF norms.

Climactic data also to be coupled 47

RECLAMATION & REHABILITATION

Creation of adequate green belt in and around mining lease area It gives a green curtain is to be set against all scars i.e. excavation, dumps etc and improves aesthetic sense of the area It effectively arrests all the dust generated from mines It effectively attenuate unpleasant noise Lessens the adverse effect of green house gas emission

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RECLAMATION & REHABILITATION continued‌.

Incase of availability of mine waste, voids are to be filled back & efforts are to be made to bring them near original shape Incase of partial availability of waste, possibility of part reclamation is to be thought. Remaining voids can be converted as water reservoir 49

RECLAMATION & REHABILITATION continued‌. n

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Possibility of filling by fly ash or other waste material available nearby is also to be thought but a prior study thereof is also to be undertaken for any apprehended adverse impact on water regime In case of shallow excavations, quarry floor plantation is to be undertaken along with adequate drainage arrangement 50

RECLAMATION & REHABILITATION continued‌.

Incase of arid regions, converting the pits as water reservoir is best post mining land use. But its slope should be adequate & should also act as shield against drowning.

Incase of hilly terrain dense plantation is to be undertaken on finalized bench.

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Conclusion: Mankind should learn the correct way of enjoying the natural wealth from the Honeybee as they continue to collect Honey from the flowers without causing any detrimental impact or deformation to the nature’s beautiful gifts.

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