04_CS Barite Hill Gold Mine Site.pdf

Low Cost Treatment of aHighly Contaminated Pit LakeUsing Innovative TechnologyBarite Hill Gold Mine SiteLeo Francendese USEPA OSC, Mike Gobla BOR, Joe Harrington Alexco,Ed Bates EPA/ORDOSC Readiness Presentation 2009

Barite Hill Gold Mine SiteMcCormick, South CarolinaMined from 1991 to 1995Partial PRP Reclamation until 1999Abandoned in 1999Removal Project 2007 to 2008NPL Listed in 2008

ERT LVBio Assessment TeamField Investigation TeamBORSite Inventory TeamEngineering Design TeamDefining the ProblemRemedialProgramORD CinnGeophysics/GeochemGeochem TeamSCDHECWater Quality ProgramHazardous Waste ProgramMining Program

2 miles fromStrom ThurmondLake …drinking waterreservoir andrecreation lakeAMD from theSite hassignificantlyimpactedstream up tothis point ..halfway to theLake

AMD impactdocumentedby ERT

2001 2007Imminent Pit Lakeoverflow threatdocumented byBOR

Emergency Actions Taken

Demolition of theFurnace Building dueto high heavy metalscontent

Disposal of thebuilding and 1 tonof abandoned acidsand bases

Defining the Primary Sourceof the AMD

The “80%of the AMDProblem” at Barite HillThe Site has an est5000 yrs of acidproducing potential.Percent pyrite in theore is one of thehighest in NorthAmerica.60 million gallon10 acre Pit Lakeup to 60 feetdeep.

Probable risk ofcatastrophic releasewithin 3 to 5 years.Over 250,000CYS of pyriticwaste rockrecharging thePit Lake withsulfuric acid.

250,000 CYSof pyriticwaste rockFeS2+ 3.5O2 + H2O FeSO4 + H2SO4

Pit Lakegeneratedepisodic SO2 fogevent requiringLevel B PPE.Springtimerains releasedstored saltsgeneratingnegative pH

Sonar mappingsuperimposed onSite aerial

The Remedy

BOR conducted a Streamlined Remedy Review in under60 days and option 6 was selectedRemedy OptionCost1No action$0. Risk of catastrophic failure would remain.23456Construct spillway andfencingPerpetual water treatmentNeutralize, backfill, andreclaimBlast the pit rim, partiallybackfill, and reclaim as adry basinMinimal waste backfill,lime neutralization, carbonloading$300,000. A 1” rain would cause 500,000 gallons of acid water toflow out of the pit.$5,700,000. Plus $1 million/year for operation. Acid would becontained but an acid lake would still be present at the site.$21,710,000. 1.15 million cubic yards of waste would be hauled into fill the pit. The fill would cover the sulfide bedrock exposures, butsome seepage could remain.$12,390,000. Difficult to implement, a dry basin would remain,some acid seepage likely.$2,600,000. The acid pit lake would be transformed to a clean lakerequiring minimal long term maintenance. Waste fills would begraded and capped. This is the selected remedy.

Pit LakeExpandedWatershedGraded andCapped AreasBOR provided “as built” engineeringsupport resulting in Engineer Certified(Remedial Quality) design/plans.10% project cost.

Subaqueous Capping ofapproximately 50,000 CYSThe rate of pyrite oxidation isreduced by approx 200,000 Xvia subaqueous capping.

Moving the Mountain

Taking Shape

Location ofthe spillwayto beconstructedfor the flowthru Pit LakeDesign

Rough Cuttingthe Pit LakeSpillwayBackside ofthe SpillwayOverflowBOR DesignedOverflow

Carbide Lime used forChemical Neutralization

Contractor Designed andBuilt Aerated Batch System

ChemicalNeutralizationCarbonAmendmentsGradingContinues

Methanol addedas “candy” forthe young SRBs

Combination of Carbon Loading andLime Neutralization compacted theclassic fluffy lime sludge. Expected20 feet reduced to inches6(CH2O) + 2FeOOH + 3SO4 + 6H -> > CO2 + 2FeS + S +10 H2O

Iron MonosulfideSludge

Breaking the Acidic Ferric Cycle• Pyrite exposed to the environment during mining andexcavation reacts with oxygen and water to form sulfuricacid.• This process, known as acid mine drainage, involves theaction of Thiobacillus bacteria, which generate theirenergy by using oxygen to oxidize ferrous iron (Fe2+) toferric iron (Fe3+). The ferric iron in turn reacts withpyrite to produce ferrous iron and sulfuric acid. Theferrous iron is then available for oxidation by thebacteria.• This cycle may continue until the pyrite is exhausted ORthe ferric creation is minimized and/or the treatmentsystem is designed to have the ferric preferentiallyattack the iron monosulfide which does not create acid.

FerricFerrateThe Zonefor Ferrousvs Ferricproduction.FerrousFerric HydroxideFerrousHydroxide

Currentstatus ofPit Lake

What’s s so innovative here ?• Subaqueous capping• Use of carbide lime• Compression and chemical conversion ofclassic lime sludge to 30x denser sulfides• Creation of a flow thru design• Successful attainment of water qualityusing a proprietary blend of carbon to laythe foundation for a self sustaining lake

What’s s so special about thecarbon loading ?• Carbon loading results in rapid formation of iron monosulfide thusavoiding fluffy hydroxide sludges.• Proprietary carbon blends of sugars and alcohols start and contrololmixotrophic bacterial growth.• Organic acids are formed through alcohol intermediates; acidformation is modulated/reduced by alcohol addition; therebyassisting in oxidoreductase expression and hydride export.• Denatured molasses mixture eliminates the rate-restrictingrestricting cysteine;cysteine is a key control on sulfur metabolism and is the only sulfurentry point into protein synthesis; limitation of cysteine encouragesdirect sulfidogenesis over fermentative loss pathways• Solid carriers help to overcome metal toxicity• Control of ferric ion early on (February 2008) was key to avoiding“stall-out” of dissimilatory biological processes; control of ferric wasachieved by sugar dosing levels, wood chips and density of sugarsolutions, which controlled the ultimate settling depth of the sugarss

Finishing up the Cap andFlow Thru Design

Waste rock cap beingbordered with gabionswhile cap with 3 footsaprolite/clay layercontinues to be laid.

Approximately ½ the capwas designed andconstructed with anHDPE linerMSOffice1

Slide 41MSOffice1 , 11/29/2008

All earthen materials used in thecap came from the nearbyborrow pit which was thenincorporated into the watersheddesign. In addition, GeorgiaPacific donated all the mulchnecessary to create SCDHECrecommended topsoil blends.

The cap …2’ of saprolite base1 foot of clay1 foot of topsoil½ HDPE linedGabion toeWatershed OverflowSpillway Overflow

Stoichiometrically, , the Pit Lake hasbeen calculated to currently possessenough acid neutralization potential tohandle 3 25 year drought events.

Life returns to the PitLake and itssurroundings

Conclusions1. The remedy allows permanence for approx 80% less costthan traditional mining remedies.2. Current acid neutralization potential has been establishedto continue performing for decades, , including accountingfor several 25 year type drought events.3. Simultaneous use of carbon loading and limeneutralization can create a compact sludge that is left inplace augmenting the overall performance of the remedy.4. Project completed on budget and on schedule using asbuilt and certified designs satisfying Remedial quality.5. Detailed data reports, workplans and calculations can befound at:http://epaosc.net/baritehillnevadagoldfieldsremoval

EXTRA PANORAMASLIDES