Workshop #3: Preparing for unexpected outcomes at mine sites and means to control contamination

Workshop #3: Preparing for unexpected outcomes at mine sites and means to

control contamination

Barbara A. ButlerMarch 5, 2013

Mine Drainage Control and Mine Drainage Control and Treatment OptionsTreatment Options

Region 10 Webinar Workshops – Hardrock Region 10 Webinar Workshops – Hardrock mine geochemistry and hydrologymine geochemistry and hydrology

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DisclaimerDisclaimer

Mention of trade names or products does not constitute the U.S. EPA’s

endorsement. The information presented is the sole

responsibility of the author and does not necessarily represent the

views of the U.S. EPA

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OverviewOverview DefinitionsDefinitions How does mine-drainage form?How does mine-drainage form? Mitigation measuresMitigation measures

Design and operationDesign and operation What happens when drainage enters What happens when drainage enters a stream?a stream? Precipitation and sorption reactionsPrecipitation and sorption reactions

Remedial optionsRemedial options Active treatmentActive treatment Passive (semi-passive) treatmentPassive (semi-passive) treatment

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DefinitionsDefinitions

MitigationMitigation All steps taken to prevent (avoid), All steps taken to prevent (avoid), reduce (minimize), treat, and reduce (minimize), treat, and compensate for any potential adverse compensate for any potential adverse impacts (risk) on the environment impacts (risk) on the environment from a given activity (hazard)from a given activity (hazard)

Proper planning, design, construction, Proper planning, design, construction, operation, management, and closure of operation, management, and closure of waste and water containment and treatment waste and water containment and treatment facilities, monitoring and maintenance facilities, monitoring and maintenance over all mine-life phases, including after over all mine-life phases, including after mine closure. mine closure.

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ReclamationReclamation Refers to restoringRefers to restoring11 a disturbed a disturbed area to an acceptable form and area to an acceptable form and planned use, following active planned use, following active miningmining

Includes actions taken to Includes actions taken to mitigate against future risksmitigate against future risks

11Rarely is a site able to be restored to what it was prior to mining, which is the strictest definition of restoration.

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RemediationRemediation Refers to correcting an issue Refers to correcting an issue that has become evident, such as that has become evident, such as cleaning up a spill or an cleaning up a spill or an abandoned mine siteabandoned mine site

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Best Management Practice Best Management Practice (BMP)(BMP) With respect to the CWA, this With respect to the CWA, this term generally applies to term generally applies to specific measures for managing specific measures for managing non-point source runoff from non-point source runoff from storm water (40 CFR Part storm water (40 CFR Part 130.2(m)). 130.2(m)).

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Design and operationDesign and operation What happens when drainage enters a What happens when drainage enters a stream?stream? Precipitation and sorption reactionsPrecipitation and sorption reactions


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How Does Mine-Drainage Form?How Does Mine-Drainage Form?

Mining ProcessMining Process Exposes pyrite and other Exposes pyrite and other minerals to the atmosphereminerals to the atmosphere

Grinding processesGrinding processes Larger surface areas for exposure Larger surface areas for exposure (weather more quickly)(weather more quickly)

http://en.wikipedia.org/wiki/File:Pyrite_3.jpg

Pyrite

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http://en.wikipedia.org/wiki/File:Pyrite_3.jpg

Pyrite

HSOFeOHOFeS 225.3 24

2222

322

2 5.025.0 FeOHHOFe Bacteria

HSOFeOHFeSFe 16215814 24

222

3

Initiator Reaction

Propagation Cycle

Pyrite

106 x faster

1010


Acidic, neutral or alkalineAcidic, neutral or alkaline11?? Acid-producing reactionsAcid-producing reactions

Pyritic minerals; oxyhydroxide Pyritic minerals; oxyhydroxide formationformation

Acid-consuming reactionsAcid-consuming reactions Carbonate minerals (produce Carbonate minerals (produce alkalinity)alkalinity)

E.g., limestone and dolomiteE.g., limestone and dolomite Aluminosilicate (clay minerals)Aluminosilicate (clay minerals)

E.g., muscovite, kaoliniteE.g., muscovite, kaolinite Formation from non-pyritic mineralsFormation from non-pyritic minerals

11Mining-influenced waters (MIW) coined by Dr. Ron Schmiermund in 1997 to encompass all types1111




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Mitigation MeasuresMitigation Measures Waste rock pilesWaste rock piles

Tailings storage facilitiesTailings storage facilities

Measures presented are not inclusive of all options available.

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Mitigation MeasuresMitigation Measures Waste Rock Piles Waste Rock Piles

Minimize leaching of acidity Minimize leaching of acidity and ionsand ions

Minimize exposure of water Minimize exposure of water bodies to seepage/drainagebodies to seepage/drainage

Minimize acid generationMinimize acid generation

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Minimize leaching of acidity Minimize leaching of acidity and ionsand ions Encapsulation with impermeable Encapsulation with impermeable layerlayer

Minimize infiltration, seepage, and Minimize infiltration, seepage, and oxygen transferoxygen transfer

CompactionCompaction Minimizes voidsMinimizes voids

Progressive reclamationProgressive reclamation

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Minimize exposure of water Minimize exposure of water bodies to seepage/drainagebodies to seepage/drainage Locating piles within cone of Locating piles within cone of depressiondepression

Drainage flows to pit and is pumped Drainage flows to pit and is pumped out with groundwater (GW)out with groundwater (GW)

Under-drains, diversions, GW Under-drains, diversions, GW monitoring wells, liners (clay monitoring wells, liners (clay and/or geosynthetic), and/or geosynthetic),

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Minimize acid generationMinimize acid generation Segregation of potentially acid-Segregation of potentially acid-generating (PAG) rock with non-acid-generating (PAG) rock with non-acid-generating (NAG) rockgenerating (NAG) rock

Mining of sub-economic ore (PAG) as Mining of sub-economic ore (PAG) as blending material, or at end of blending material, or at end of operationsoperations

Layering of PAG rock NAG rockLayering of PAG rock NAG rock Blending with acid-consuming materialsBlending with acid-consuming materials BactericideBactericide Isolation (encapsulation)Isolation (encapsulation)

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Mitigation MeasuresMitigation Measures Tailings Storage Facilities Tailings Storage Facilities

Wet storageWet storage Most commonMost common

Mining uses a lot of water and Mining uses a lot of water and facility provides dual purpose as facility provides dual purpose as storagestorage

Seismic and flood considerationsSeismic and flood considerations Dry storageDry storage

Filtered tailings removes maximum Filtered tailings removes maximum amount of wateramount of water

Not appropriate for PAGNot appropriate for PAG

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Isolation of PAG materialIsolation of PAG material Selective processing methodsSelective processing methods Sub-aqueous disposal to minimize Sub-aqueous disposal to minimize oxidationoxidation

EncapsulationEncapsulation

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Minimize exposure of water Minimize exposure of water bodies to seepage/drainagebodies to seepage/drainage Liners, under-drains, decant Liners, under-drains, decant systemssystems

Diversions for clean waterDiversions for clean water Seepage collection systemsSeepage collection systems Monitoring wells downstreamMonitoring wells downstream Caps on beaches, drawdown water, Caps on beaches, drawdown water, erosion control – closure erosion control – closure

2020




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What happens when the What happens when the drainage enters a stream?drainage enters a stream?

DissM.PartM

Water Column

Sediment

DissM.PartMPrecipitation / Sorption

Dissolution / De-sorption

Exchange Scouring

Settling

Flow

‘‘M’ = metal; ‘Diss’ = dissolved; M’ = metal; ‘Diss’ = dissolved; ‘Part’ = particulate‘Part’ = particulate 2222

What happens when the What happens when the drainage enters a stream?drainage enters a stream?

DissM.PartM

Water Column

Sediment

DissM.PartMPrecipitation / Sorption

Dissolution / De-sorption

Exchange Scouring

Settling

Flow

‘‘M’ = metal; ‘Diss’ = dissolved; M’ = metal; ‘Diss’ = dissolved; ‘Part’ = particulate‘Part’ = particulate 2323

What happens when the What happens when the drainage enters a stream?drainage enters a stream? Iron (HFO)Iron (HFO)

Rapid formation in water Rapid formation in water column at pH > ~ 3.5column at pH > ~ 3.5

Oxidation of ferrous Oxidation of ferrous iron precedes iron precedes precipitationprecipitation

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What happens when the What happens when the drainage enters a stream?drainage enters a stream? Aluminum (ALO)Aluminum (ALO)

Rapid formation in water Rapid formation in water column at pH > ~ 5column at pH > ~ 5

No oxidation necessaryNo oxidation necessary

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What happens when the What happens when the drainage enters a stream?drainage enters a stream? Manganese (HMO)Manganese (HMO)

Requires oxidationRequires oxidationRequires a surfaceRequires a surfaceFormation at pH > ~ 9Formation at pH > ~ 9

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Formation may be Formation may be facilitated by facilitated by periphytonperiphyton

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Formation may be Formation may be facilitated by facilitated by periphytonperiphytonAlgal photosynthesisAlgal photosynthesis

2612623 6666 OOHOHCOHHCO h

)(222 sMnOOMn phhigh

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Remedial OptionsRemedial Options

Isolation, removal, Isolation, removal, treatment of sourcetreatment of source Physical removalPhysical removal Grouting reactive rock surfacesGrouting reactive rock surfaces Redirection of water flowRedirection of water flow Adding neutralizing agents Adding neutralizing agents

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Remedial OptionsRemedial Options

Water treatmentWater treatment Removal of acidityRemoval of acidity Removal of metalsRemoval of metals Removal of salts (Na, Mg, Ca, K)Removal of salts (Na, Mg, Ca, K) Removal of sulfateRemoval of sulfate Ultimately – removal of toxicityUltimately – removal of toxicity

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Remedial OptionsRemedial OptionsWater TreatmentWater Treatment

ActiveActive

PassivePassive

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ActiveActive Ongoing humanly operatedOngoing humanly operated Frequent maintenance and Frequent maintenance and monitoringmonitoring

Generally requires external Generally requires external energy sourceenergy source

Generally type chosen for Generally type chosen for active miningactive mining

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Passive (semi-passive)Passive (semi-passive) Constant human intervention Constant human intervention not requirednot required

Natural processesNatural processes Natural materialsNatural materials Regeneration of materialsRegeneration of materials Gravity feed versus pumpingGravity feed versus pumping

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Remedial OptionsRemedial OptionsActive TreatmentActive Treatment

Chemical ReactionChemical Reaction OxidationOxidation

Aeration to increase oxygen content Aeration to increase oxygen content or use of oxidizersor use of oxidizers

Neutralization, precipitation, Neutralization, precipitation, and sorptionand sorption

Hydroxide, Ca(OH)Hydroxide, Ca(OH)22, CaO, NaOH; MgO, , CaO, NaOH; MgO, Carbonate, CaCOCarbonate, CaCO33, Na, Na22COCO33

Fly ash; slag; kiln dustFly ash; slag; kiln dust Coagulation, flocculationCoagulation, flocculation

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Remedial OptionsRemedial OptionsActive TreatmentActive Treatment

PhysicalPhysical MembraneMembrane Reverse osmosisReverse osmosis Micro, ultra, or nano-filtrationMicro, ultra, or nano-filtration Ion exchangeIon exchange

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Remedial OptionsRemedial Options Passive/Semi-passive Treatment Passive/Semi-passive Treatment

OxidationOxidation AerationAeration

Neutralization and Neutralization and precipitationprecipitation

Ion exchange Ion exchange Sorption (organic and Sorption (organic and inorganic)inorganic)

Plant uptakePlant uptake3737


Aerobic wetlandAerobic wetland Anoxic limestone drain (ALD)Anoxic limestone drain (ALD) Anaerobic wetlandAnaerobic wetland

Sulfate-reducing bioreactor Sulfate-reducing bioreactor (SRBR)(SRBR)

Biochemical reactor (BCR)Biochemical reactor (BCR) Permeable reactive barrier Permeable reactive barrier (PRB)(PRB)

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Aerobic wetlandAerobic wetland Best for net alkaline drainageBest for net alkaline drainage Precipitation and sorptionPrecipitation and sorption Shallow – aerationShallow – aeration Plants – uptakePlants – uptake

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Anoxic limestone drain Anoxic limestone drain (ALD)(ALD) Best for net acidic, low FeBest for net acidic, low Fe3+3+, , low Allow Al3+3+, and low dissolved , and low dissolved oxygenoxygen

Neutralize acidityNeutralize acidity Effluent to aerobic pondEffluent to aerobic pond

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Reducing alkalinity Reducing alkalinity producing system (RAPS)producing system (RAPS) Similar to ALD, but reduces the Similar to ALD, but reduces the water then adds alkalinitywater then adds alkalinity

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Anaerobic wetland (BCR)Anaerobic wetland (BCR) Best for net acidic, low FeBest for net acidic, low Fe3+3+, , low Allow Al3+3+, high metals, high metals

Reduction of redox active Reduction of redox active elementselements

Microbial reduction of sulfate Microbial reduction of sulfate to sulfideto sulfide

Metal sulfide precipitationMetal sulfide precipitation Sorption of metalsSorption of metals

Organic / inorganicOrganic / inorganic

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Anaerobic wetland (BCR)Anaerobic wetland (BCR) Natural materialsNatural materials

Hay, straw, wood chips, manure, Hay, straw, wood chips, manure, crushed limestonecrushed limestone

Layer of waterLayer of water Generally vertical flowGenerally vertical flow Effluent to aerobic pond or weir Effluent to aerobic pond or weir

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Permeable Reactive Barrier Permeable Reactive Barrier (PRB)(PRB) Similar to BCR, but treat Similar to BCR, but treat groundwatergroundwater

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Remedial OptionsRemedial OptionsWhat to Choose?What to Choose?

Choice depends onChoice depends on Amounts - money, time, land, Amounts - money, time, land, metals, acid, flowmetals, acid, flow

Site accessSite access Active or abandoned mineActive or abandoned mine Specific contaminantsSpecific contaminants

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Passive Treatment Case StudyPassive Treatment Case Study(Standard Mine, Colorado)(Standard Mine, Colorado)

Operation began in the 1930’sOperation began in the 1930’s Ag, Au, Pb, ZnAg, Au, Pb, Zn Abandoned in 1966Abandoned in 1966 Adit drains into Elk CreekAdit drains into Elk Creek

Devoid of aquatic lifeDevoid of aquatic life Cd, Cu, Fe, Pb, Mn, and Zn exceed WQSCd, Cu, Fe, Pb, Mn, and Zn exceed WQS

Elk Creek feeds into Coal Elk Creek feeds into Coal CreekCreek Source of DW for Crested ButteSource of DW for Crested Butte

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Photo by Scott Jacobs - NRMRL

Standard MineStandard MineCrested Butte – remote locationCrested Butte – remote location

Constructed in 2007Constructed in 2007

11,000 ft11,000 ft

1.2 gpm1.2 gpm

Cd, Cu, Fe, Pb, Mn, ZnCd, Cu, Fe, Pb, Mn, Zn

No electricityNo electricity4747

Aerobic Polishing Cell(s) [2008]Aerobic Polishing Cell(s) [2008]

Remove biological oxygen demandRemove biological oxygen demand

Increase dissolved oxygenIncrease dissolved oxygen

Degas sulfide and ammoniaDegas sulfide and ammonia

Reduce total suspended solidsReduce total suspended solids

Oxidize and precipitate any FeOxidize and precipitate any Fe

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Year-round treatmentYear-round treatment Automated samplingAutomated sampling

pH, temperature, ORPpH, temperature, ORP Satellite reportingSatellite reporting Protection from weatherProtection from weather

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http://dept.ca.uky.edu/asmr/W/Full%20Papers%202008/0892-Reisman-OH.pdf

33-58 feet annual snowfall 5050


MethodsMethods Whole effluent toxicity tests Whole effluent toxicity tests (WET)(WET)

Ceriodaphnia dubia Ceriodaphnia dubia (water flea)(water flea) Pimephales promelas Pimephales promelas (fathead (fathead minnow)minnow)

Acute 48-hr LCAcute 48-hr LC5050 Percentage of waterPercentage of water

Control survival > 90%Control survival > 90%

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Analyte SiteBCR APC

Al N/A N/AAs N/A N/ACd 100 +/- 2 100 +/- 2Cu 94 +/- 9 94 +/- 9Fe -266 +/- 518 100 +/- 10Ni N/A N/APb 94 +/- 16 91 +/- 17Zn 100 +/- 3 100 +/-3SO4 39 +/- 4 72+/- 5


% Removal% Removal

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Standard Mine Acute Toxicity

0

20

40

60

80

100

INF-A INF-B

BCR-EFF-A

BCR-EFF-B

APC-EFF-A

APC-EFF-B

Sample ID

LC50

(%, v

/v)

† † † †#

1% 1% 2% 2%

Gray = water fleaGray = water fleaBlack = fathead Black = fathead

minnowminnow

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0

20

40

60

80

100

INF-A INF-B

BCR-EFF-A

BCR-EFF-B

APC-EFF-A

APC-EFF-B

Sample ID

LC50

(%, v

/v)

† † † †#

35% mortality 35% mortality

Gray = water fleaGray = water fleaBlack = fathead Black = fathead

minnowminnow

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0

20

40

60

80

100

INF-A INF-B

BCR-EFF-A

BCR-EFF-B

APC-EFF-A

APC-EFF-B

Sample ID

LC50

(%, v

/v)

† † † †#

Not different Not different from controlfrom controlGray = water fleaGray = water flea

Black = fathead Black = fathead minnowminnow

5555


0

20

40

60

80

100

INF-A INF-B

BCR-EFF-A

BCR-EFF-B

APC-EFF-A

APC-EFF-B

Sample ID

LC50

(%, v

/v)

† † † †#

Effluent Effluent samples samples

more toxic more toxic to fathead to fathead minnow than minnow than

to the to the water fleawater flea

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Effect of Aeration

0

20

40

60

80

100

SM-A SM-B SM-A aerated SM-B aerated

Sample ID

Per

cent

Sur

viva

l (10

0%

sam

ple)

<20%<20%

100%100%

5757

Dissolved Gaseous Species Standard Mine

0

0.5

1

1.5

2

2.5

2 4 6 8 10 12pH

Sulfi

de (m

g/l)

0

0.01

0.02

0.03

0.04

0.05

Am

mon

ia (m

g/l)

H2S (aq)

NH3 (aq) (10C)

NH3 (aq) (20C)

2 ug/l H2 ug/l H22SS

.2 to 5 mg/l .2 to 5 mg/l NHNH33

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Concluding remarksConcluding remarks Results strongly suggest Results strongly suggest toxicity from dissolved hydrogen toxicity from dissolved hydrogen sulfide gassulfide gas

Other BCRs may have different Other BCRs may have different toxicants, depending on:toxicants, depending on:

Contaminants present and efficiency Contaminants present and efficiency of removalof removal

Concentrations of dissolved gasesConcentrations of dissolved gases pH of effluentpH of effluent

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Thank you!Thank you!

Study at Standard Mine and 3 other sites:Study at Standard Mine and 3 other sites:

Butler, BA, Smith, ME, Reisman, DJ, Lazorchak, JM. 2011. Butler, BA, Smith, ME, Reisman, DJ, Lazorchak, JM. 2011. Metal removal efficiency and ecotoxicological assessment Metal removal efficiency and ecotoxicological assessment of field-scale passive treatment biochemical reactors. of field-scale passive treatment biochemical reactors. Environmental Toxicology & Chemistry. 30(2):385-392.Environmental Toxicology & Chemistry. 30(2):385-392.

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Workshop #3: Preparing for unexpected outcomes at mine sites and means to control contamination