COMBININGINSITUTREATMENTANDACTIVEWATERTREATMENT:

CASESTUDYATSCHWARTZWALDERURANIUMMINE

JIMHARRINGTONALEXCOENVIRONMENTALGROUP171 N COLLEGE, FORT COLLINS CO, 80524 USA JIMHARRINGTON@ALEXCORESOURCE.COM

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!  InSituTreatment:methodsandapplicationsformines

!  SchwartzwalderMinehistoryandwatertreatmentprocessconsiderations

!  InSituPretreatmentatSchwartzwalder!  ActiveWaterTreatmentProcessatSchwartzwalder

!  ReverseOsmosiscombinedwithInSituTreatment

!  Discussion

TalkOverview

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!  Primarywatertreatment!  Toachievealicence/permitdischargestandard

!  Pretreatment!  Toreduceconstituentconcentrations,reducereagentrequirements,orimproveconstituentratios,orreducethenumberofconstituentsrequiringactivetreatment

!  Treatmentwasteproductdisposal!  Toincreasepermanenceofdisposal,reducecostsofdisposal,allowwastetobestabilizedonsite

InSituTreatmentApplicaGons

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!  Openpitlakes!  Pondsettings(tailings,seepagetoes)!  Undergroundmineworkings!  Groundwateraffectedbyminesources(whereverthereisahydraulicdriver)

InSituTreatmentSeJngs

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!  Primarywatertreatment!  SweetwaterMine(Se,U),SilverKingMine(Zn,Cd),Crplumes

!  Pretreatment!  PlatoroMine(As,Zn),15in-heapleachfacilities(CN,Nspecies,metals),SchwartzwalderMine(U,Se,Mo)

!  Treatmentwasteproductdisposal!  PlatoroMine(Fecoagulation(As),limeprecipitation(Zn,Mn,Fe)sludge),SchwartzwalderMine(U,Se,MoinROconcentrates)

InSituTreatmentExamples

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!  Typicallylowercapitalcoststhanactivewatertreatmentbecausemineinfrastructure(pit,u/gworkings)isreusedasthetreatmentvessel

!  Anaerobicconditionscanbecreatedatsource:!  BeneTitofpreventingoxidativeleaching!  Atsiteofinsitutreatment:elevatedFe2+,alkalinity,DOC,sulphide,andsomereductivelydissolvedtracemetals

!  Tracemetalsprecipitatedasmetalsulphides!  Treatsourceratherthanwaittillcontaminantiscollected!  Geochemicalgradients(comparetostirredreactors)

!  Fe2+toFe3+,Mn2+toMn3+/4+,pHandalkalinitygradients(CO2off-gassing)

!  Enhancesengineeredcontrols(covers,waterdiversions,backTill,etc.)!  Enhancesactivetreatmentperformance(ifstillrequired)becausereducedsludgeproduction,betterFe/tracemetalratio

WhyInSituTreatment?

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!  DiscoveredbyjanitorFredSchwartzwalderin1949nearstartofcoldwar;veindeposit

!  Pitchblendmineral(UO2/U3O8)hostedingneiss,schist,quartzite

!  DroveTirstadit1953,produced1955,andby1957waslargestUmineinUS

!  99%ofColoradoUproductioncamefromSchwartzwalderUMine

!  17millionlbs.Uproduced;16millionlbs.Ureserves!  Closeddownin2000!  Dewateringstoppedinearly2000’s

SchwartzwalderMineHistory

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SchwartzwalderMine,Colorado

Schwartzwalder Mine

Denver CO

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SchwartzwalderMine

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HeadlinesYouDon’tWant

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!  Duringoperations,watertreatmentofdewateringwaterwaspartofUrecoveryprocess(IXresin)

!  Uponreceiptofordertostarttreatment,IXwasinstalledforalluvialgroundwater(mixedstream,wasterock,andminewaterinTluence)

!  IXresinfoulingfromCa/Mghardness,highFe/Mnwithalluvialwater

!  IXresinfoulingmuchworsewithminewater(3xhigherhardness)

!  ROwithinsitupre-treatmentwasauthorizedasremedytoprovidehydrauliccontrolofthemine

WaterTreatmentSelecGonProcessatSchwartzwalderMine

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!  Dewaterminetoatleast150’belowStevelevel;dischargeatlessthan30µg/LU(i.e.,99.9%reduction)

!  MaintainhydrauliccontroloverthemineasalluvialTilliscleanedup

!  MaintainhydrauliccontroluntilTinalremedyisimplemented

ReverseOsmosisObjecGves

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!  Surfacewaterdischarge!  LandApplication(e.g.,irrigation,roadde-icing,dustcontrol)

!  Publicworks(sewer,etc.)!  Furtherconcentration(evaporation,dryer/concentrator/Tilter,secondarymembranetreatment,VSEP,etc.)

!  Deepwellinjection

ROConcentrateDisposalOpGons

!  Uranium25.75mg/L!  Molybdenum1.30mg/L!  Selenium0.118mg/L

!  ProvideslowerstartingpointforRO

!  Increasescertaintyachievingdischargecriteria

!  Allowsforon-siteROconcentratemanagement

!  Preventsbuildupofconstituentsofconcerninminepool

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BeforeTreatmentAverage(8samples2011-2013)

BeneAitsSummary:PretreatmentandBrineDisposal

WhyInSituTreatment

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!  Objectives:! ReduceROfeedconcentrationofU,Se,Mo! ROrejectaverages99.4-99.7%ofconstituents!  Initialconcentration:25mg/LU,1.3mg/LMo,0.12mg/LSe

!  Interimgoalsofinsitutreatment:3mg/LU,0.2mg/LMo,0.05mg/LSe

! GoalwasexpressedintermsofdissolvedconstituentssinceanydischargewouldinvolveTilteringprocess

InSituPre-TreatmentofSchwartzwalderMine

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!  Pumpedfrom#2Shaft(~300’bgs)

!  Reinjectin#1shaft(800’deep),#2shaft(1160’)oropenstopebehindbulkhead

InSituLayout

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SchwartzwalderMine

LEVEL 2

LEVEL 3

LEVEL 4

LEVEL 5

LEVEL 6

LEVEL 7

LEVEL 8

LEVEL 9

STEVE LEVEL

CHARLIE LEVEL

UPPER LEVEL

LBJ LEVEL

MINNESOTA LEVEL

CV LEVEL CV GLORY HOLE

RALSTON CREEK

EX

HAU

ST B

OR

E-H

OLE

SECONDARY TREATMENT ZONE

PRIMARY TREATMENT

ZONE(E.G. MINE SHAFT)

PretreatmentTargetLocaGons

!  Uranium25.75mg/L!  Molybdenum1.30mg/L!  Selenium0.118mg/L

!  Uranium3.4mg/L=87%reduction

!  Molybdenum0.081mg/L=94%reduction

!  Selenium<0.018mg/L=>98.5%reduction

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BeforeTreatmentAverage(8samples2011-2013)

AfterTreatmentAverage(8samplesAugust-December2013)

PretreatmentResults:First4Months

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!  5.5daystorm!  14-19inches!  AccesstositewaslostafterSeptember2013untilsummer2015

1:1,000+yearflood

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UraniumPretreatmentResults

0

10

20

30

40

Jan-11 Jan-12 Jan-13 Jan-14 Jan-15 Jan-16 Jan-17

Uranium

(mg/L)

uranium(total) uranium(dissolved)

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MolybdenumPretreatmentResults

0

0.5

1

1.5

2

Jan-11 Jan-12 Jan-13 Jan-14 Jan-15 Jan-16 Jan-17

Molybde

num(m

g/L)

Molybdenum(total) Molybdenum(dissolved)

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ROConcentrateInSituTreatment

Pump set ~300’ below Steve Option to inject 1160’ below Steve (Shaft 2) 800’ below Steve (Shaft 1) or “open hole”

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!  “Permanent”treatmentfacilityconstructed!  Pumpingfrommineandalluvialsumps!  Separatetrainsforminewaterandalluvialwater! Mine:pre-Tilter,RO:permeateconditionedanddischarged,concentrateamendedandreinjected

! Alluvial:chemicalprecipitation(sludgeamendedandinjectedintomine),Tiltration,ROwithpermeatedandconcentratecomingledwithminewaters

!  Insitupre-treatmentcampaignwinter2016-7! Alluviumremoval2017-2018! NegotiatestabledischargescenariowithStateofCO

NextSteps

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QuesGons?