Evaluation of ARD from Britannia Mine and the Option for Long Term
EVALUATION OF ARD FROM BRITANNIA MINE AND THE OPTIONS FOR LONG TERM REMEDIATION OF THE IMPACT ON HOWE SOUND
BCAMD 3.31
This project was prepared for Ministry of Energy, Mines and Petroleum Resources B.C. Acid Mine Drainage Task Force By Stephen, Robertson and Kirsten (B.C.) Inc.
November 1991 EVALUATION OF ARD FROM BRITANNIAMINE AND THE OPTIONS FOR LONG TERM REMEDIATION OF THE IMPACT ON HOWE SOUND
Prepared for:
Ministry of Energy, Mines and Petroleum Resources B.C. Acid Mine Drainage Task Force Room 105 - 525 Superior Street Victoria, B.C. WV lx4
.
Preparedby: In associationwithz
Stephen,Robertson and Kirsten (B.C.) Inc. Gormley ProcessEngineering 580 Homby Street #6l2 - l200 West Pender Street Vancouver, B.C. Vancouver, B.C. V6C 3B6 V6E 2S9
November 1991
This project was funded by the Province of British Columbia Sustainable Environment Fund. EVALUATION OF ACID MINE DRAINAGE (AMD) FROM BRJTANNIA MJ.NE AND THE OPTIONS FOR LONGTERM REMEDIATION OF THE IMPACT ON HOWE SOUND
Prepared by
ReclamationSection ResourceManagement Branch Ministry of Energy, Mines and Petroleum Resources
The Britannia Mine is located at Britannia Beach, on the east shore of Howe Sound, approximately48 km north of Vancouver. Operated from 1905to 1963 by the Britannia Mining and Smelting Company Ltd., and from 1963 to 1974 by Anaconda Mining Company, in its prime the mine was one of the biggest copper producers in the British Empire. The mill/mine complex fmally shut down in 1974, and nowadaysis used as a museum. The area containing the mine workings and the mill is currently owned by Copper BeachEstates.
The major environmental concem at Britannia Mine is with acid mine drainage, and associatedhigh copperand zinc levels emanatingfrom old adits and waste dumpsl. While dissolvedcopper concentrationsare an order of magnitudeless than they were during mine operation, they still have an impact on the invertebrate and fish in Howe Sound. This study was carried out to assistthe present owner in dealingwith this problem. Funding was granted by the SustainableEnvironment Fund (SEF), with managementprovided by the British Columbia Acid Mine Task Force. The objectivesof the study were to review ail available information, critique the present systemof control, and to recommend posstble long-term solutionsto reduce or eliminate acid mine drainage.
Mining at Britannia was carried out in seven ore bodies, all located east of Britannia Beach, in the ridge between Britannia and Furry Creeks. Over the seventy years of operation, 80 km of underground workings - the sourceof 95% of the or6 - and five open
1 Waste Dump: Barren or submarginalrock or ore which has been mined but is not of suffrcient value to warrant treatment, and is therefore removed ahead of the milling process. pits were created. Accessto the underground workings was primarily provided through portals at 200, 1550, and 2100 ft above sea level. Surface pit excavationocctirred 5 km inland, largely between 3000 and 4500 ft above sea level. In addition to portals and oben pits, surface disturbance associatedwith mining included three small waste dumps, the road network, a series of dams on Britannia Creek, and subsidenceassociated with the underground workings.
Ore generated by mining was processedin milling facilities at Britannia Beach. During operation, approximately45 million tonnes of ore were processed,predominantly copper, but lesser amounts of silver, zinc, and gold were also recovered. Tailingss,the main waste product from the mih, were either dischargedinto ‘Howe Sound or used underground as backfilk Concems regarding the fate of the tailings were addressedin a recent study of Howe Sound, paid for in part by the Ministry in conjunction with the British Columbia Acid Mine Drainage Task Force.
Acid generation results from the oxidation of sulphide minerals contained in rock exposed to air and water. Water draining through areas of sulphide oxidation cari transport the reaction products. While this phenomenon is often referred to as acid mine drainage, it is not confined to lands disturbed by mining; for example,natural Springsare often acidic in the vicinity of outcrops of sulphide-bearingrock.
The principal ingredients in the AMD processare reactive sulphide mine&, oxygen and water. The oxidation reactions are-often acceleratedby microbiological activity. Not all mining operations that expose sulphide-bearingrock result in acid mine drainage. For example,AMD will not occur if the sulphide minerais are non-reactiveor if the rock is not leached. If alkaline material is availablein the rock waste, pH changesmay be buffered by neutralizing reactions as the drainagepasses through the waste.
The main impact of acid mine drainage is caused by the dissolution of heavy metals. ‘Qpically, mined rock contains abnormally high concentrations of a number of heavy metals that will be releasedby weathering reactions occurring concurrently with sulphur oxidation. In the usual pH range of soils and water, heavy metals releasedby weathering normally precipitate in immobile compounds. However, under highly acidic conditions, the heavymetals dissolveand are entrained in runoff and seepage,and cari causea detrimental impact on water quality in the receiving environment.
2 Or-e: A mineral, or mineral aggregate,containing precious or useful metals or metalloids, and which occurs in such quant@, grade, and chemical combination as to make extraction commerciallyprofitable. 3 Tailings: The portion of the ore which after grinding and washing is regarded as too poor to be treated further; used especiallyof the debris from stamp mills or other ore-dressingmachinery, as distinguishedfrom material (concentrates)that is to be smelted. The geological strata of the ore bodies mined at Britannia consist of massive sulphides, widely disseminated or concentrated in stringers and along bedding planes. Prior to mining, sulphide oxidation will have been limited to a thin surface layer, a few small outcrops, and areas of landslide debris. Exposure, cracking and communition of the sulphide bedrock in the underground workings, pits, and rock dumps have significantly increased the amount of sulphide oxidation, which in tum increasesthe rates of acid generation and metal dissolution. The open pits and gloryholescollect drainage, tünnelling rainwater through the extensiveunderground workings, flushing out the oxidation products.
Under the precepts of sustainabledevelopment, mining is regarded as a temporary land use. This objective is enforced by current mine reclamation legislation requiring that land and water resourcesbe reclaimed to a level of productivity not less than that which existed previously, and that water released from a minesite meet long-term water quality standards.
Acid mine drainage is a major impediment to successfulreclamation for mining operations throughout the world. In British Columbia, AMD presently occursat six operating mines. Four other metal mines and two coal mines are consideredpotentially acid generating, as are severalproposed mines. Under the British Columbia,Mine Development Assessment Process,ail mines with a potential to generate acid mine drainage must develop plans to prevent it.
TO enable the British Columbia mining industty to comply with the present comprehensive reclamation requirements, the Ministry of Energy, Mines and Petroleum Resources is participating in a program of researchaimed at developingcost-effective solutions to major environmentalproblems. A major part of this program focuseson acid mine drainage. As part of this, the Ministry coordinates and provides funding for the British Columbia Acid Mine Drainage Task Force, and strongly participates in activities of the national acid mine drainage program (Mine Environmental Neutral Drainage Program - MEND). In 1992, the proposed researchprogram for the British Columbia Acid Mine Drainage Task Force is $1.5 million, with funding shared by industry and the Provincial and Federal Govemments.
The problems of acid mine drainage will not easily be solved. However, work carried out during the last five years has done much to enhanceour knowledgeand ability to predict, prevent, control, and monitor AMD. The cooperativeefforts betweenour Ministry and the British Columbia mining industry are widely regardedwith envy by the rest of Canada,and we are recognizedby many as world leaders in acid mine drainage technology. As a result, the British Columbia consulting industry is currently selling its services abroad, an important @n-off of the ongoing researchactivity.
At present, six of the mine sites abandoned prior to the enactment of reclamation legislation are acid generating. Fortunately, many of these older sites are small underground operations and the impact is manageable. The administration and control of acid mine drainage tiom historic mine sites is shared between Environment Canada and two British Columbia Ministries: Environment, Lands and Parks and Energy, Mines and Petroleum Resources.
Our Ministry has assumed responsibility for reclamation of several closed mine sites, including the Mount Washington Mine on Vancouver Island. Work carried out at Mount Washington since 1988 has included the testing of various caver types and spoil configurations, and developing monitoring technology. Results to date have included the development of a cost effective asphalt emulsion/geotextile caver designed to seal the surface, thereby redueing the removal of oxidation products. The program of AMD researchat Britannia Beachis being done in concert with that at Mount Washington.
While the Britannia Mine closed prior to the creation of AMD guidelines, it still had to obtain a waste disposalpermit under the Pollution Control Act. This permit ordered that:
s all mine drainagewater be directed to the 200 ft portai, s mine drainage collected at the 200 ft portal be analyzed monthly for copper and three times per year for other elements; s when dissolvedcopper levels in mine drainage exceed 15 mg/l, water be treated in copper recovery (cementation) plant; and mine drainage collected at the 200 ft portal be discharged to Howe Sound via submergedoutf’.
Recent investigations suggestthat contaminated mine water from the 2100 ft level is by- passingthe treatment area, and draining through Jane Creek and then Britannia Creek, directly into Howe Sound. TO prevent this, the property owner is required to develop an abatement plan, including a cost estimatesand a scheduleof implementation. This study, carried out by Steffen, Robertson and Kirsten (Bic.) Inc. (SRK) in association with Gormley ProcessEngineering (GPE), was undertaken to ensurethere are no other sources of Britannia AMD, and to suggestalternative mitigative measuresto prevent any impact. Its detailed objectiveswere as follows:
1. TO conduct a literature review of all information already available on mining, acid generation and drainagecontamination.
2. TO identify the major sourcesof contaminatedloading.
3. TO critically review the present systemof diverting mine water, and to report on the effectivenessof the present treatment facility.
4. TO review the present Ministry of Environment, lands and Parks permit conditions. 5. TO research and report on the current technologies and estimated costs for the removal of copper from water.
6. TO recommend mitigation measuresto reduce Ah4D and remove copper loading and present a timetable with estimatedcosts.
The managementstrategy to control acid generation and the works to treat mine drainage should be based on these results. A museum already existson the site, thereby providing an opportunity for any works constructed to serve an educational function, in addition to the researchand treatment purposes. 166004 - Britiinnia Mi Site Page i
REPORT 166004
EVALUATION OF ARD FROM BRITANNIA MINE AND THE OPTIONS FOR LONG TERM REMEDIATION OF THE IMPACT ON HOWE SOUND
CONTENTS
ExEcuTlvE suMMARY ...... B...e......
1.0 INTRODUCTlON ...... l-l 1.1 Background ...... i...... l-l 1.2 Tems of Reference ...... 1-s 1.3 Approach ...... l-5
2.0 PRE-MINING ENVIRONMENT ...... 2-l 2.1 Surface Topography ...... 2-1 2.2 clinlate ...... 2-1 2.3 Site Hydmlogy and Hydmgeology ...... 2-1 2.3.1 Mine Site Catchments ...... 2-1 2.3.2 Available Data ...... 2-2 2.3.3 Natural Hydmlogy ...... *...... - 2-6 2.3.4 Site Hydmgeology ...... 2-10 2.4 Geochemistry ...... 2-10 2.5 Water Quality ...... 2-11
3.0 METE DEVELOPMENI’ ...... - ...... 3-l 3.1 Mining operations ...... 3-l . 3.2 Geochemistry ...... 3-3 3.3 Water Quality ...... 3-3 3.4 Watq Treatment ...... 3-6 3.5 Existing Envimnmental “Regulation” ...... 3-9
4.0 EUSTJNGEWIRONMENT ...... 4-1 4.1 General ...... 4-1 4.2 Mine Development ...... 4-l 4.2.1 pits ...... 4-l 4.2.2 Underground ...... 4-4
Stefk Robemon md Kirstea 166004 - Brhannia Mine Siti Page ii
4.2.3 Waste Dumps ...... 4-6 4.2.4 Tailings ...... 4-7 4.2.5 Roads ...... 4-7 4.2.6 Landslides ...... 4-7 4.3 Hydrology and Hydrogeology ...... 4-9 4.3.1 Catchment Developments ...... 4-9 4.3.2 Available Data ...... 4-12 4.3.3 Pnzsentday Hydrology ...... 4-13 4.4 Water Qualily ...... 4-15 4.4.1 sampling Pmgram ...... 4-15 4.4.2 Geochemistry ...... 4-19 4.4.3 Flow Reghne ...... 4-23 4.4.4 Water Chemistry ...... 4-26 4.45 Contaminant Loadings ...... 4-30
5.0 ENWRONMENl’AL CONSIDERATIONS ...... 5-l 5.1 Physical,‘Geotechnical ...... 5-l 5.2 Drainage Water ...... 5-l 5.2.1 Sourcesof Water Entry ...... 5-l 5.2.2 Souxtxs of Loading ...... 5-2
6.0 REMEDIATION OPTIONS ...... 6-1 6.1 Water Management - Diversion ...... 6-4 6.1.1 Pits ...... 6-4 6.1.2 -Underground Workings ...... 6-4 6.1.3 Waste Duaqs ...... 6-8 6.1.4 Tailings ...... 6-9 6.1.5 Roads ...... 6-9
6.2 Drainage Collection Systems ...... 6-9 6.2.1 Plts ...... 6-9 6.2.2 Underground Mine ...... 6-10 6.2.3 Waste Dumps ...... 6-10 6.2.4 Tailings ...... 6-11 6.2.5 Roads ...... i ...... 6-11 6.3 Treahnent ...... 6-11 6.3.1 General ...... 6-11 6.3.2 Flows ...... 6-11 6.3.3 Raw Water Characteristics ...... 6-12
Steffen Robemon and Kirsten 166004 - Bxitamia Mine Site Page iii
6.3.4 PrucessTeshvork Description ...... 6-12 6.3.4.1 Lime Neutraiixation ...... 6-15 6.3.4.2 Imn/AIum Coagulation ...... 6-15 6.3.4.3 Soda Ash ...... 6-19 6.3.4.4 Additional Lime and Soda Ash Pmcess Evaluation Results ...... 6-22 6.3.4.5 Sulphide Pmcipitation ...... 6-22 6.3.4.6 Sea Water Dilution ...... 6-24 6.3.4.7 Ion Exchange ...... 6-26 6.3.4.8 Carbon Adsorption ...... 6-32 6.3.4.9 Reverse Osmosis ...... 6-32 6.4 Contaminant Disposal and Sludge Stability ...... 6-32 6.4.1 Metal Recovery ...... 6-33 6.4.2 Remaining Contaminants’ ...... 6-33 6.4.3 Potential for Enhamement and Copper Recovery ...... 6-34 6.4.3.1 Copper Cementation ...... 6-34 6.4.3.2 Other Copper Recovery Appmaches ...... 6-35 6.4.3.3 lZahancedMetal Pmduction Rates ...... 642 6.5 Proposed Treatment Plant Design ...... 647 6.51 Reagent IvExing and Storage ...... 649 6.5.1.1 Lime Slaking ...... 6-49 6.5.1.2 Flocculants ...... 649 6.5.1.3 Soda Ash ...... 6-50 6.5.2 Oxidation and Pmcipitation Reactors and Agitators ...... 6-50 6.5.3 Clarifier Selection and Sizing ...... 6-51 6.5.4 Instrumentation ...... 6-53 6.5.4.1 Reagent dosing system and contml ...... 6-53 6.5.4.2 Turbidity measurement ...... 6-54
6.55 Analytical support ...... l 6-54 6.6 Capital and Operating Cost Estimates ...... 6-55 6.6.1 Flow and Loading ...... 6-55 6.6.1.1 OeotechnicaliHydrological Analysis ...... 6-55 6.6.1.2 Historical Data ...... 6-55 6.6.2 Design Basis ...... 6-56 6.6.3 Equipment List ...... 6-56 6.6.4 Factomd Capital Cost Estimate ...... 6-58 6.6.5 Operating Cost Estimate ...... 6-60 6.6.5.1 Lie Treatment System ...... 6-60
Steffem Robertson and Kirsten 166004 - Britaxmia Mine Site PageW 6.6.5.2 Lime and SodaAsh TmatmentSystem ...... 6-60 6.6.6 Impact of Acidity Load Reductionon Operatig Costs ...... 6-62 6.7 Discussion ...... 6-62 6.8 Permit Conditionsami Monitotig ...... 6-65 6.8.1 DischargeStandards ...... 6-65 6.8.2 SurveillanceMonitotkg Requirements ...... 6-67 6.8.3 Descriptionof AvailableMonitotig Equipment ...... 6-68
7.0 CONCLUSIONSAND RECOMMENDATIONS ...... 7-1 7.1 Conclusions ...... 7-1 7.2 RecommendedApproach to Future Work ...... 7-3
8.0 REFERENCE3...... 8-1
LISTOFFIGURES
Figure 1.1 LocationPlan ...... l-2 Figure 1.2 Site Plan ...... 1-3 [email protected] Locationof RegionalWSC StreamflowGa@ng Stations ...... 2-3 Figure 2.2 Pre-Minillg watemmes ...... 2-4 Figure 2.3 RegionalRelationship Behveen Mean Annual Runoff and CatchmentMedian .- Elevation ...... ~...... 2-7 Figure 2.4 Mean Monthly Distribution of Runoff at RegionalWSC StreamfIowGauging stations h..~ ...... 2-9 Figure4.1 BritanniaMine - Surficial Mine Workings ...... 4-2 Figure4.2 ...... 4-S UndergroundMine Workings . Figure4.3 Cunent Topographyand Drahuxge...... 4-10 Figure 4.4 EnclosedCatchment Amas of JaneBasin ...... 4-11 Figure 4.5 Mean Monthly Runoff and Mine DrainageDisttibution ...... 4-14 Figure 4.6a Water Quality Samptig Stations- September ...... 4-17 Figure 4.6b Water Quality SamplingStations - lkcember ...... 4-18 Fgure 4.7 Compatisonof Sulphateand Acidity ...... i ...... 4-31 Figure4.8 Comparisonof Copperami Zinc Concentrations...... 4-31 Figure 6.1 Locationsof proposedDiversion Ditches ...... 6-5 Figure 6.2 Britannia Mines PxoposedBulkhead Locations ...... 6-7 Figure 6.3 Neutralizationof 2200 Portal Drainage ...... 6-17
Steffen Robeatsonad Kirsten 166004 - Britannia Mine Si Pagev Figure 6.4 NewraIizarionof 4100Portai Drainage ...... 6-17 Figure 6.5 Neutralizationof 2200Poxtai Drainage ...... 6-18 Figure 6.6 Neutralizationof 4100Portai Drainage ...... 6-18 Rgure 6.7 Neutralizationvia SeawaterDilution ...... 6-30 Figure 6.8 Neuuaiizationvia SeawaterDilution ...... 6-30 Figure 6.9 Cido; Ëx&, TestResults ...... 6-31 Figure 6.10 CationExchangeTestResults...... i...... 6-31 Figure 6.11 Trend in CopperTenor ...... 6-39 Figure 6.12 Trend in AverageHouriy Flowrate ...... 6-39 Figure 6.13 ConeiationBetween Copper Tenor and AverageAnnuai Homiy Fiowrate .... 6-40 Figure 6.14 TreatmentProcess Flow Diagram ...... 6-48 Figure 6.15 SettlingTest Resuhs ...... 6-52 Figure 6.16 Evaluationof OperatingCost A~ual OperatingCost vs Load Reduction..... 6-63 Figure 6.17 Evaluationof Acidity Load ReductionOperating Cost vs Load Reduction.... 6-63
LIST OF TABLES
Table 2.1 Detailsof RegionalWSC Streamflow Ga@ng Stations...... 2-5 Table 2.2 PhysiographicCharactetistics of Mine Site Catchments...... 2-6 Table 2.3 EstimatedNaturai Mean Axmual and Montiy Streamflowsfor Mine Site ..... 2-7 Table 3.1 Summaryof Flows,Copper Concentrations, and CopperL&ading from the 4100 PortaI, 1983-1989...... 3-7 Table 3.2 Summaryof AssayInformation on 4100 and 2200 PortalSlows...... 3-8 Table 4.1 Monthly Precipitationat SquamishAirport (mm) ...... 4-16 Table 4.2 Water Quality Data,September 1990 ...... 4-27 Table 4.3 Water Quaiity Data,December 1990 ...... 4-27 Table 4.4 Portal Drainage...... e-27 Tabie 4.5 Comparisonof BritanniaCreek and Major Discharges1972,1976,1980,1983/84, 1990 ...... 4-29 Table 4.6 CalculatedLoadings, September 1990 ...... 4-32 Table 4.7 CakulatedLoadings, December 1990 ...... 4-32 Table 4.8 bhhted Loadingsto HoweSound ...... 4-32 Table 6.1 ProposedRemediarion Options for BritanniaMine 6-2 Table 6.2 Raw Water Characteristics. Physicai Test, Anions andNutri&...... 6-13 Table 6.3 Raw WaterCharacteristics-Metals...... ,:...... 6-14 Table 6.4 Lime PrecipitationTest Results ...... 6-16
Steffen Robemon and Kirsten 166004 - Britamia Mine Site Page vi Table 6.5 SodaAsh NeutralixationTests ...... 6-20 Table 6.6 Lime Precipitationand SodaAsh Addition Tests ...... 6-21 Table 6.7 Lime and SodaAsh TreatmentProcess Simulation Test Results ...... 6-23 Table 6.8 SulphidePrecipitation Tests ...... 6-25 Table 6.9 SeawaterDilution Test Results ...... 6-27 Table 6.10 Ion ExchangeTest Results- 2200 Portal Drainage ...... 6-28 Table 6.11 Ion ExchangeTest Results- 4100 Portai Drainage ...... 6-29 Table 6.12 Sumniaryof Flows,Copper Concentrations and Copper Production from the 4100 Porta&1983- 1989 ...... 6-36 Table 6.13 Summaryof AssayInformation on 4100 and 2200 PortaiFlows ...... 6-37 Table 6.14 Major EquipmentList - BritanniaWater Tmatment Plant ...... 6-57 Table 6.15 FactoredCapital Cost Esthnatefor BtitanniaTreatment Plant ...... 6-59 Table 6.16 OperatingCost Estimate...... 6-61 Table 6.17 Effluent Water Quality Regulationsand Objectives...... 6-65
LIST OF APPENDICES
AppendixA DetailedResults of Site Investigation AppendixB PmlhnmaryBulkheadDesignEstimate AppendixC Resultsof Testing
LIST OF PHOTOS
Photograph4.1 PanoramaLooking Southtowards Fairview, and East Bluff Pits Photograph4.2 Pond at 4200 Level abovetmatment plant Photograph4.3 Seepin East Bluff Pit Photograph4.4 JaneCmek at 1050Level Photograph4.5 JaneCreek at 2150 Level Photograph4.6 Drainagefrom 2200 Poxtal Photograph4.7 Confluenceof JaneCreek ami 2200 Portai Drainage Photograph4.8 BritanniaCreek, Sampling Station B3 Photograph4.9 Tunnel Dam Above StationB2 and J3
Stefkn Robertsonand Khten 166004 - Brida Mine Site Page vii
REPORT 166004
EVALUATION OF ARD FROM BRITANNIA MINE AND THE OPTIONS FOR LONG TERM REMEDIATION OF THE IMPACT ON HOWE SOUND
EXECUTIVE SUMMARY
The deconnnissionedBxitannia Mine is locatedat BritanniaBeach approxhnately 48 km north of the City of Vancouver,on the eastshore of Howe Sound. The undergroundand open pit mine was operatedby the BritanniaMining and SmeltingCompany Ltd. from 1905to 1963at which time it was purchasedand operatedby AnacondaMining Companyuntil shutdownin 1974. The areais currentlyowned by Copper BeachEstates. Duting operation,appmtiately 45 million tonnes of are were processedfor recoveryof copperand lesseramounts of silver, zhx ami gold. Tailings wexedeposited directly hrto Howe Sound throughtwo intertidal outfalls locatednear the mouth of Britannia Creek.
Acid rock drainagecontaining elevated acidity and metal levels has issuedfrom the Britannia Site since the operationalperiod, discharginginto Britannia Creek and Howe Sound. During mine operation, drainagewaters from the 2200 and 4100 levels were directedthrough two copperpxecipitation plants contai&g scrapiron, beforedischarging into BritanniaCreek. Jn 1972,in an attemptto improvedrainage qualily from the site, acidic mine water was diverted within the mine workings to the 4100 level for txeatmentin a coppercementation plant ptior to discharge. Shxe 1978,mine water has beencollected, tmted and dischargedat depth to Howe Sound. Subsequentinvestigations however have mdicatedthat CO- wateris againdraining from the 2200’ level directly into JaneCreek and then into Britannia Creekand ultimately into Howe Sound.
Steffen,Robertson and Kirsten (B.C.) Inc. (SRK) in associationwith GonnelyProcess Engineexing’(GPE) wexeretained by the Ministry of Energy,Mines and PetroleumResources to conductthe initial phaseof this study. ‘I?risphase comprised a mview of the availableinformation, assessment of acid genemtionand contamhrantdrainage ftom the site basedon this data,identification of the major sourcesof contaminant loading, and a critical review of the presentsystem of control, and to identify recommendationsfor possiblelong term solutionsto reduceor elMnate acid drainage. This study is a prelhninaryreview to identify the major connibuting factors to conmminationfrom acidic drainage to Britannia Creek and identify options for remediation. Fuxtherdetailed investigationhave been recommendedwhere the availableinformation is insufficient to deîlne or evaluatean option with confidence.
Steffen Robextsonand Kinten REPORT 166004
EVALUATION OF ARD FROM BRITANNLi MINE AND THE OPTIONS FOR LONG TERM REMEDIATION OF THE IMPACT ON HOWE SOUND
1.0 INTRODUCTION
1.1 Background
The decommissionedBritannia Mine is locatedat Britannia Beachapproximately 48 km north of the City of Vancouver,on the eastshore of Howe Sound,as shown in Figure 1.1. The undergroundand open pit mine was operatedby the BritanniaM.i&g and SmeltingCompany Ltd. from 1905to 1963at which time it was purchasedand operatedby AnacondaMining Companyuntil shutdown in 1974. The area is wrrently owned by CopperBeach Estates. A generalsite location plan is presentedin Figure 1.2.
Dtuing operation,approximately 45 million tonnesof ore wem pxocessedfor recoveryof copperand lesser amountsof silver, zinc andgold. Tailings weredeposited directly into Howe Soundthrough two intertidal outfalls locatednear the mouth of Britannia Creek.
Mhhg at BritanniaMountah~ has disturbed the surfaceand the precipitationfalling on this areafmds its way into the mine ratherthan draininginto the valley bixtoms. In passhrgthrough the mine, it contacts sulphidesurfaces where bacterial and chemical action have solubilizedmetals ami generatedacid. Acidic drainagecontainhIg elevated dissolved metal values,particularly copper.has been issuing l?om the mine site shxx 1905 and discharghrginto Howe Sour~d. .
Dudg mine operation,drainage waters from the 2200 and 4100 levels were directedthrough two copper precipitationplants comai.ning scrap iron, beforedischarging into BritanniaCreek. In 1972,in an attempt ti improvedrainage quality &om the site, acidicmine water was divertedwithin the mine workingsto the 4100 level for treatmentin a coppercementation plant prior to discharge..Shxe 1978,mine water has beencollected, treated and dischargedat depthto Howe Sound. Subsequentinvestigations however have hxiicatedthat contaminatedwater is againdrahring from the 2200’ level directly into JaneCreek and then into Britannia Creek ami ultimately hno Howe Sound.
StefTen Robertson and Kirstem 0 t l , 5, 10 km
MINISTRY OF ENERGY MINES AND PETROLEUM RESOURCES DATEJAN. 1991 ‘*OJ* N‘- 66004 APPROVEO LOCATION PLAN
STEFFEN ROBERTSON 8 KIRSTEN , Consul t ing E ng ineers . 1
1
ru
483.000 E 408.000 E 493,000 E c-c------d
. ‘V 1
LEGEND - Stream, definite .-. Stream. indefinite - Gravel Roads - Paved Roads --- Study Area m Open Pit and Main Woste Dump Area 0 Townsits
mie Ministry of Energy , Mines ond Petroleum Resources lb-ch. 1991 0 mm 2wo 3030 u100 YIOO W” BRITANNIA MINE F SITE LOCATION PLAN 1.2.. STEFFEN ROBERTSON & KIRSTEN, Consultlng Enginears 166004 - Brikmk Mine Site Page l-4
Althoughcopper concentrations in the drainageare about 10 percent of the dischargeconcentrations durhrg operation,this drainagestill posesa seriousthmat to invertebrateand fish populationsin Howe Sound. Investigationsby EnvironmentCanada, Envimnmental Protection Service and the provincial Waste ManagementBranch have shownthat the drainagefrom the mine workingsand the water of Britannia Cxeekare toxic to aquaticlife. The adverseimpact on the marine envhonmenthas been noted up to 18 lan from the mine site, with elevatedmetal levels, particularly copper and zinc, detectedin molluscan bivalves,such as musselsand oystem@rrhqton and Ferguson,1987), in Howe Sound,
The Ministry of Environment,Waste Management Bmnch, pmvided the following discussionsubmitted by Bmnt More, Biologist,(B.C.M.O.E., Environmental Protection Group), of the envhonmentalimpacts on Howe Soundfrom the drainageat the BritanniaSite.
On February19,1991, the undersigned(Bmnt Moore] was askedby the IndustrialSection to provide a brief summaryof identified environmentalimpacts at the BritanniaMines AMD site.
Fmm 1983 to 1986,the EnviromnentalSection studied the impactof the site’s acid mine drainageon receivingwater organisms. It was found that thedischargeflowing out of the 2200Portal into Britannia Cmek- by way of JaneCmek- was of gmatestconcern. This concemwas largely due to the layeringof the creek’scontaminated fmsh waterdischarge over the densermarine water in Howe Sound. Therefore, the effluent wasnot as madily dispersedthmughout the water cohmm,and was allowedto remainin the more biologically productivesurface waters in the Sound. Of lesser,but still significant,importance is the contaminationof the JaneCmek headwaters by leachatefrom wasterock piled in the JaneBasin area.
Even if the cmek contaminationconcems noted above are effectively addmssed,if appeamthat the submerged4100 levd outfall to Howe Soundcould still significantlyimpact on Howe Sound. A survey conductedby the EnvimmnentalSection in 1990has shownthat the nearcopper complexing capacity of the marh~ receivingwaters is exceededeven more significantlynear the depth of the diffuser than at surface,iear the cmekplume.
TOeUmina& signiflcant contamination of the receivingenvimmnent, both the 2200Poxtal and wasterock dischargesto the BritanniaCreek system would haveto be divertedto the 4100discharge system, and the colIectedeffluent would have to be effectively treatedto levels noted in the relevantPollution Control Objectives. A significant data base has now been gathemdto support these conclusions.[End of s-VI.
The pmsentMinistry of Environment(MOE) pollution abatementorder limits dissolvedcopper levels at Britanniato 15 mg/L. A systemis in placeto direct drainagefiom the site thmugh a deepoutfall mto
Steffen Robertsonand Kirsten 166004 - Britannia Mine Site Page l-5
Howe Sound. When the copperlevel is less than 15 mg& the seepageis routeddirectly to Howe Sound througha deepwater outfall Whenthe copperlevel is above15 mg&, seepageis routedthrough a scrap iron cementationprocess. The cementationprocess does not temoveany appteciableamount of acidity and cannotreduce copper concentrations to levels achievedwith conventionaltmatment systems based on neutmlixationand precipitation of copperhydroxide. The dischargefiom the cementationplant is directed to the deepoutfall.
13 Terms of Reference
The site was identified as an atea of study by the B.C. Acid Mine DrainageTask Force. The overall objectiveof this studyis to evaluatethe currentextent of acid mine drainagefrom the BritanniaMine site and developa long tenn remediationplan to mitigate the impactof drainageftom the mine site on Howe sound.
Steffen,Robertson and Kitsten (B.C.) Inc. (SRK) in associationwith GonnelyProcess Engineering (GPE) were mained by thé Ministry of Energy,Mines and PettoleumResources, Dr. JohnErtington, P. Eng. to conduct the initial phaseof this study. This phasecomprised a mview of the available information, assessmentof acid generationand contaminantdrainage fromthe site basedon this data, identificationof the major sourcesof comaminamloading, a critical review of the posent system of control, and identification of possiblelong term solutions to mduce or eliminate acid drainage. This study is a pMminary review to identify the major contributing factors to contaminationfiom acidic drainage to BritanniaCreek and Howe Soundand to identify options for remediation.It was found during the study howeverthat the availableinformation about the physical and geotechnicalstability of the site, ami the natureof the undergroundworkings is limite& It was thereforedecided johrtly by SRK and the Review Committee reptesentingthe B.C. AMD Task Force, to focus efforts on defining further detailed investigationswhere the available information is insufficient to defïne or evahmte an ‘option with confidence. The focus of the study was on the Britannia Creek drainage. The adjacentFurry Creek catchmenthas not been identified as an the acid drahrageproblem, and was beyond the scopeof this investigation.Whete available, information on Furry Cmekhas been provided for a morecomplete picture of the Britannia site.
13 Approach
With the above objectivesin mmd, the approachto this investigationhas been to develop an overall undersmndingof the site from availableinformation and limited site investigations,to identify the major sourcesof environmentalimpact and develop potential strategiesfor remediation,and define futther investigations.
Steffen Robesson and Kirsten 166004 - Brida Mine Site Page 1-6
A numberof key issuesmust be addressedto effectively evaluatethe problemand potentialremediation options: . Sourcesof metal loads and drainagelocations . Drainagecollection to a centraltteannent facility . Water treatment
Thesewere addressedin the following tasks:
Task 1: compilationand mview of data; Task 2: identificationof the sourcesof loading and drainagedischarge locations; Task 3: evaluationof the site hydrology and hydrogeology,and identification of the sourcesof water entry; Task 4: identificationof drainagecollection systems; Task 5: evaluationof treatmentoptions Task 6: review of order and monitor-mgmquirements Task 7: identificationof long term remediationoptions. and identificationof further studies.
The premining conditions were briefly assessedto understandthe nature and potential extent of the environmentalimpacts of acid generation,and provide a xeferencefor site remediationobjectives. Mine developmentand water quality records during operation and since closum were mviewed and the environmentalimpacts defmed. Threesite visits by SRK and/orGPE personnel were conductedto assess the crurent site conditions and environmentalimpacts of these developmentswith mferenceto acid drainage.Potential remediation options were then developed on a preliminarybasis and evaluated in terms of cost and benefit to identify prefenredoptions. A stagedapproach to mmediationis mcommendedto allow rapid hnplementationof initial and possibly short term measums,with an evaluation of the effeçtivenessof eachstage, and allow fmther investigationas requhed. .
Steffen Robertsonand Kirsten 166004 - Britannia Mine Site Page 2-l
2.0 PRE-MINING ENVIRONMENT
2.1 Surface Topography
The BritanniaMine is locatedin the Howe Sound,Coastal Region of B.C. The terrain is mountainous with elevationsranging from sealevel to 4,500 ft. Explorationactivity wasKXIX&A as early as 1888and mine operationsbegan in 1905(Ramsey, 1967). Recordsand maps reflecting this earlyperiod in the mine life are consequentlylimited. All of the availablemaps, data and site information are presentedand referencedto the Imperial systemand are thus presented,as su&, in this report.
22 Clhnate
A climatestation was operatedat the townshipof BritanniaBeach during the period 1913to 1974. This stationwas locatedat elevation49 m and recordeddaily temperature,minfall and snowfall. No officiai climatestations wexe opaated at higher elevatiouswithin the study area.
The total aunualprecipitation at the BritanniaBeach station averages 2164 mm, accordingto the 1951-80 climatencmnals published by the AtmosphericFmironment service. About 96% of this amountfalls as rain andthe xemainderas snow. The monthsof gxwtestpxecipitation axe October to March. On average, the driestmonth is July. The averagenumber of daysin the year with measumblepnzcipitation is 174.
The axa of surfacemining is situatedat high elevationand the=foR experiencessignificantly higher precipitationthen m-d at the coastalclimate station. Within the generaIxegion, the averageammal pxecipitationgradient is about200 to 300 mm per 100m of ascent.The proportionof precipitationthat falls as,.mowalso incxeases with elevatioa
The 1951-80nom& for BritaxmiaBeach show a meanannual t&peratuxe of 9.8OC.July is the waxmest month, with a meaudaily temperatmeof 18.2OC.ami Januaryis the coldestmonth, witb a me& daily tenqwatureof 2.0°C. The extrememaximum and minimum temperatmes on recordare 39.4and -21.7OC, reqectively.
23 Site Hydrology and Hydrogeology
23.1 Mine Site Catchments
The mine developmentis situatedin the drainagebasins of Britannia Creek and Furry Creek. These streamsdrain comparablecatchment areas (i.e., 29 and 54 km’, respectively)ami bath flow westwardto
Steffen Robemon and Kimen 166004 - Britannia Mine Site Page 2-2 dischargeinto Howe Sound. Figure 2.1 showsthe location of the mine developmentin relationto the coasthneand the major streamsin the tegion.
Within the drainagebasin of BritanniaCreek, the mining activity was primarily confïnedto two south bank tributariesknown as Janeand Mineral Creeks. The catchmentsof both tributariesserved as access pointsto the undergroundworkings. In addition,the JaneCmek catchment contained most of the surface mixhg that occurreddurhrg the life of the BritanniaMine.
The amadisturbed by mining within the Furry Creekcatchment is drainedby a numberof small, steep- gradientstreams, one of which hasbeen namedEmpress Creek. Thesestmams sham a commondrainage divide with JaneCmek Figure 2.2 showsthe catchmentareas, and locationsof the watetqursesof the Britanniaarea prior to mine development.
2.3.2 Available Data
No long-termrecords of streamfloware availablefor Brinumiaand Furry Creeks.However, the southem toast of British Columbiaamund Vancouver is well setvedby a nxsonablydense network of streamflow gaugingstations. A total of sixteenof thesemgional stations, all operatedby the WaterSurvey of Canada (WSC),were used to assistin chamcterizationof the pre-mininghydrology. The positionsof the selected WSC stations,in relation to the mine site, are plotted on Figure 2.1 togetherwith outlines of their catchmentboundaries. Reference to this @tue showsthat the assembledstations command catchments having a wide rangeof physiographicchamcteristics.
Table 2.1 is a list of the selectedstmamflow stations showing the period of recordand the meanannual runoff (MAR). The MAR is expmssedas a unit runoff (i.e., ratio of measumdflow rate to contributing catchmentaxa) in ouierto facilitatecomparisonbetween catchments. Au of the selectedstations measure unregulatedflows, or slowsthat havebeen minimally influencedby man’s activities.
The hydrologyof the mine site streamswas estimated using a techniqueknown asregional analysii. This techniquemakes use of generalrelationships between stmamflow and the characteristicsof the catchment that generatedthe sneamfiow.In orderto developthese general relationships, it wasnecessary to measure vaious characteristicsof the catchmentsfrom topographiemaps. Two suitableami easily determined chamcteristicsare drainagea&a and median elevation. Tables 2.1 and 2.2 provide these measumd characteristicsfor the catchmentsof the regional WSC stationsand of the ungaugedproject streams, respectively.
Steffen Robertsonand Kirsten OGMHOl4 - 1.D. NO. FOR WSC STREAMUW - CATCHMENT WUNDARY GAUG ING STATION MINISTRY OF ENERCY MINES AN0 PETROLEUM RESOURCES OAn JAN. 1991 . na 66004 APCaovm LOCATIONS OF REGIONAL WSC . STREAMFLOW GAUGING STATIONS ma 2.1 STEFFEN ROBERTSON a KIRSTEN, Consulting Enginccn . . 1
‘.
LEGEND - Streom, definite ‘-. Stream, indetinite - Grave1 Roods - Paved Roads - Trails --- Catchment Basin Outline m Townsite - Minesite
Ministry of Energy, Minas and Petroleum Resources %rch. 1991 BRITANNIA MINE .26004 PRE-MINING WATERCOURSES STEFFEN ROBERTSON k KIRSTEN, Consultlng Engmeers TABLE 2.1 DETAILS OF REGIONAL WSC STREAMFLOW GAUGING STATIONS
PERIOD MEAN CATCHMENT l=-STREAMFI OW GAUGING STATION OF ANNUAL CATCHMENT MEDIAN RECORD RUNOFF AREA ELEVATION ID No. Name (mm) ounz) (m) t- 1108MHO14 Alouette River at outlet of Alouette Lake 1916 - 1925 3522 203 690 k------II08GAOO8 Brandt Crack near Vancouver (upper station) 1913 - 1921 3798 3.37 1050 Capilano River above intake 1914 - 1988 3670 172 870 l Coquitlam River above Coquitlam Lake 1 1982 - 1988 3693 54.7 l 1090
08GAOO5 Indian River near Vancouver (Upper station) ~ 1912 - 1921 4100 90 950
08ME108 Jacobs Cteek above Jacobs Lake ~ 1965 - 1980 2492 12.2 530
08MEO76 Kanaka Cteek near Webster Cornets ~ 1960 - 1988 1860 47.7 280
08GA054 Ma&quant River above Mashiter Cteek 1966 - 1986 2410 334 1140
08GA057 Mashiter Creek near Squamish 1966 - 1981 2110 38.9 1160
08GA065 Noons Creek at Meridian Substation Road 1976 - 1988 3004 2.59 760
08MHOO6 , North Alouette River at 232nd Sttmt 1960 - 1988 2437 37.3 500
Norton Creek near Vancouver 1912 - 1921 3576 2.36 830
Pitt River near Alvin 1952 - 1965 3301 515 1450
i Seymour Rivet above intake 1914 - 1926 3770 153 860
Stawamus River below Ray Creek 1972 - 1988 2850 40.4 1090
Young Creek near Vancouver 1912 - 1921 3360 6.22 1010 166004- Britaha Mine Si? Page2-6 TABLE 2.2 PHYSIOGRAPHX CHARACI’ERISTICS OF MINE SITE CATCHMENTS
CATCHMENT cA&y cATCHMENT MINE LOCATION AREA MEDIAN - ELEVATION ELJZVATION =(F oanz) Cm) (fil BxitanniaCmek at mouth . 29 1150 3770 530
Empress Creek at mouth 0.41 1210 3970 330 Funy Creek at mouth 54 1070 3510 790 JaneCmek at mouth 1.7 1.210 3970 330. Mineral Cxeekat mouth 2.9 1040 3410 890
* As describedin Section3.1.
2.33 Natural Hydrology
Median elevationgeneraily accourus for a large ptoportion of the variationin MAR betweencatchments. This is iUustmtedin Rgure 2.3 basedon the data fiom the assembledWSC stations. The datafollow the expectedtrend of increasingMAR with incxeasingcatchment median elevation. A secondtrend is also evidentin which unit runoff decreasesas one movesinland.
Basedon the relationshipindicated in Rgure 2.3, estimateswere madeof MAR at variouskey points on the mine site drainages(see Table 2.3). Becauseof the scatterof data usedto developthe relationship, .. a high and low estimatewere provided at each key point that was believedto bound the actual MAR The mine site stteamsexperience mlatively wet conditionswith estimatesof MAR rangingfiom 3000 to 4500 mm. .
The seasonainmoff distributionsfor the mine site streamswere approximatedusing nonnalized average monthly hydrographsfiom the regional WSC stations. Figure 2.4 graphically presents the monthly distributions,expressed as percentagesof MAR, for the four highestelevation WSC stations. As with MAR, catchmentmedian elevation is a good predictorof the seasonalrunoff distributionexperienced at a given location At medianelevations of about 1090m, the normalizeddistributions for the Coquitbun and StawamusRivers match reasonablyclosely and exbibit a bimodal shapewith peaksin May and November. The former peak is due primarily to snowmeltwhile the latter is causedby fall rains. The Mamquam and pitt Rivexshave higher median elevations(i.e., 1140 and 1450 m, respectively)and accordinglyhave distributionswith later snowmeltpeaks and dhuinishedfall peaks.
: Steffen &bertson and Kirstem Figure 2.3 Regional Relationship Between Mean Armual Runoff and Catchment Median Elevation
8 -3 h B B é U . A w
Interpi :ted ri ge foi MAR If min site s
0.4 0.6 1 1.2 . CATCHMENT MEDIAN ELEVATION Cm> TABLE23 EJIZMATEDNATURALMEANANNUALAND MONTHLYSTREAMFLOWSFORMJ.NESlT=
ONTHLYSTREAMFLOW Mean Monthly Distribution of Runoff at Regional WSC Streamflow Gauging Stat.ions
Mean Monthly Discharge (% of MAR) I I 155
I I I I l I I I l I I JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Month
- Coqui tlam + Stawamus * Mamquam + Pitt
Figure 2.4 166004 - Britzmia Mine Site Page 2-10 Basedon similaritiesin medianelevation, the mine site streamswere assumedto have the sameaverage monthly distribution as observedat StawamusRiver. With this distribution,the natural fIows, or flows that existedptior to mine development,wem estimatedat key pointswithin the BritanniaCreek and Ftury Creekcatchments (see Table 2.3). For masonsdiscussed above, Upper and lower estimateswem provided for eachmonth. Theseestimates provide a bound on the long-termaverage stmamflow but not on the naturalvariation of streamflowsfrom year to year (i.e., the Upperand lower estimatesshould not be used as indicationsof dry and wet years).
2.3.4 Site Hydrogeology
Thereis no dataon the hydrogeologyof the pre-miningenvironment. It is probablethat the original water table was a subduedimage of topography. AIong Mineral Ridge and in the area of Jane Basin the groundwatertable wasptobably in the onler of 75 m below the groundsurface (James, 1929). Recharge of the gmundwatersystem would have occurredalong this ridge. The major flow pathswould havebeen from the ridge areatowards the north and south,to Britannia and Furry creeks,respectively. Them may have been a small componentof flow parallel to h4ineral Ridge through the fracture systemof the Britanniashear zone. ‘Ihe potosity of the rocks in Mineral Ridge ate ptobablyin the otder of 1% or less, therefore,groundwater flow and storageis not considereda major componentof the system.
2.4 Geochemistry
The geologyand geochemistryof the ore and wasterock providesan indication of the sourcesand the potentialfor acid generationand metal leaching, potential impacts on waterquality, and the futme pattern for acid generation. The geologyof the areahas been descriid in detail by James,1929; GSB, 1990; McCullough, 1968.
The principle economicmineralization in the ama is associatedwith quartz mineralization,and consists of pyrite andchalcopyrite,.with important concent&.ions of sphaleritein cettainareas of the deposits(Jane and No.8). The seven orebodiesare located witi a shearedband of appamntly steeply dipping metamorphosedsedimatary andvolcanic rocks of varying competencythat form a roof pendanthvo miles wide andseven miles long, sunoundedby granitic rocksof the toast rangeintrusive complex . . . Fractming occurredin the mer teck units permhtingare solutionsto penetmteuntil conditionswen favourablefor ore deposition. Thesefavourable conditions varied in the different sectionsof the mine and resultedin different types of orebodies”(‘I’he Anaconda Company (Canada) Ltd., 1965).
Genemlly the economicmineralization was containedin massivesulphide ombodies,as stringer type deposits,and as disseminatedsulphide and concentrationsalong beddingplanes. The MINFILE report describedthe sulphideombodies at Britannia as ” ...highly heterogeneousmixtures of sulphides,remnant
Steffen Robertsonand Kirsten 166004 - Britannia Mine Site Page 2-11 alteredhost rocks, and discreteveins. The main’mineralogyof orebodiesis simple and fairly constant. Pyrite is by far the most abundantminer& with less chalcopyriteami sphaleriteand minor erratically distributedgalena, tennanite, tetrahedrite and pyrrhotite. The main nonmetallicminerals include quartz and muscovite(chlorhe), anhydriteand siderite.”
Zinc mineralizationtended to occur in the Uppercentral parts of massiveorebodies, as in the Fairview Zinc vein. The main massiveombodies with rich chalcopyriteores were the Bluff, EastBluff, No. 5, No. 8, and040. Severalof the ombodiesshowed variations in sulphidedistribution; No.8 massivegraded fiom zinc to copperalthough the NO.~.and 8A containedhigher zinc than 8B. In the Bluff deposit,sphalerite was found to be abundantonly abovethe 18001eveL
25 Water Quality
The pre-miningsurface water quality from the Brltannia site hasnot beenestablished from the available data. There are indicationshowever that metal leachingand iron stainingwas natumlly occuning from the site as early as the late 1800’s(B.C. Dept. of E.M.P.R. 1890- 1900). This would suggestthat the sulphidemineralization is naturallymactive, and oxidation and acid generation could resultin somedegree of naturalelevation of metal and sulphateconcentrations in surfacewaters prior to-mining development,
The presenceof gypsumand anhydrite throughout the orebodlescould tend to contributeelevated sulphate concentrationsto natural waters. Sulphidemineralization varled over the propetty ftom copper rich thtough copper and zinc to zinc rich. Copper mineralizationdominated, however, and thus elevated copper,iton, and sulphateconcentrations and loadings could be expectedin the long tenn, with lesserzinc basedon relative abuudance.Zinc is, however,soluble over a gmaterpH range than copper,and this elevatedzinc might have been apparentin drainagefrom amasnot undergoingrapid sulphideoxidation ami metal leaching.
It would be expectedthat natural drainage waters fiom the ama could contain elevated sulphate concentrations.Exposed mineralization from outcropsand local disturbancesami naturalerosion appears to be readily oxldiid contributingdissolved and total metalsto the naturaldrainage. Biological dataare not availableand it is not apparentto what degreethe naturalwater quality affectedutihzation of Britannia Cm&. It is beyondthe scopeof this report to determinethe extentof Bsh utilization in BrhanniaCreek prior to mining.
Steffen Robemon and Kirsten 166004- Bhnnia MineSite Page3-l
3.0 MINE DEVELOPMENT
3.1 Mining Operations
Explorationin the Britannia area was f%st recordedin the late 1800sand the Britannia depositswere discoveredin 1888. Themwas essentially no development.,however, untill900 whenappmximately 67 III of undergroundheadings wexe advanced in the Janedeposit, near the 1000 level. Productionfrom the mine beganin 1905. Up to 1911,a total of 203,000tonnes of ore was mined, of which 69,000tonnes was milled. Dming theseearly yearsthere was someopen pit mining althoughthe main sourceof ote was the undergroundproduction. After 1911,ail ore productionwas fmm the undergroundmine, andthe productionrate jumped to over loO,CNIOtonnes per year and roseto nearly 2,000,ooOtonnes per year by 1931. In 1921,however there was no are milIed as the mill was destroyedby fire. Duxingthe depression years to 1935 productiondropped by approximately50 percent after which it jumped back to nearly 2,000,000tonnes per year. Productionagain fti.by 50 percentduring the war’years. After the war, Britannia Mine steadily ptoduced in the onier of 700,000 tonnes per year until the late 1950swhen productionbegan to falL In the 1960s.production was about730,ooO topes per yearwith coppergrades rangingfrom 1.1 to 1.4 pexcentami with zinc gradesof about 1.0 percent Ote productionwas boosted after 1966when open pit mining commencedin JaneBasin. This contmueduntill974 when the mine was shut down pennanently. Gver the mine life a total of 47.9 x ld tonnesof ore was mined,of which 47.4 X lob tonnes WaS milled.
AU ore wastranspoxted to the milling facilities at BtitanniaBeach Ote was transportedfîom the various are zonesto the concentratorusing overheadtramway, inclined railway, and an electrictram litre. The Btitannia mill producedcopper, zinc, and pytite Concentra&s.Gold and silver were recoveredprimarily in the copperand pyrite concentmtes.Jn the Latteryears, tailings Weredischarged directly into Howe Soundptimatily thtough two intertidal outfalls locatednear the mouth of Brima Cmek.
Sevenorebodies wexe mined through open pit, undergroundand gloryholedevelopments. Appxoximately 80 km of undergroundworidngs ami four open pits were excavatedto extractthe ote. The accessto the undergroundworkings from the Btitannia Cmek basin is provided primarily through portals at the 2200 level, 2750 level ami 4100 IeveL (Mean SeaLevel correspondsto appxoximatelythe 4300 level for each 100 foot gain in elevation,100 feet shouldbe sitbtractedfrom 4300 feet.) The refetencelevels for the undergmundworkings at the Britannia Mine wete measuredfmm a datum near the maximum elevationsof the property and, therefore,the 2200 level is at a higher elevationthan the 4100 level.
During the operationalphase, flows in the BritanniaCreek catchment were tegulatedfor the purposesof power genemtion. A total of 9 storageor diversiondams were constructedwithin the drainagebasin of this stream,most of which suppliedthe mquirementsof two power plants. A single diversiondam was
SteffenRobertson and Kirsten 166004 - Briwmia MineSite Page 3-2 also constructedon Furry Creek. Operationof the hydroelectricdevelopment was discontinuedin tbe sameyear as the permanentclosure of the Britannia Mine. At pmsent,only thme of the oxiginaldams remain,namely, Tunnel, Utopia and Park Lane. The latter two damsare locatedin the headwatersof Britanuia Creek. Due to a potential for faihue of tbe damsand subsequentflooding downstream,the Water ManagementBranch recently (May, 1989) blasteddrain holes in Utopia and Park Lane dams. Tunnel dam is locatedapproximately midway along the length of BxitanniaCreek and now servesas the water supply for the high-pressuresystem for Britannia Beachtownship. The reseivoirfor this dam is almostfull of debris,much of which was derivedfiom breachingthe Park Lane dam.
At closum of the mine, a number of stepswere undertakento limit the impact of contaminatedmine drainageon the surfacewater resourcesof the area. Diversiondams were constructedto force the mine waterto drain intemally thmughthe undergmundworkings down to the lowest haulagetunnel, known as the 4100 level. The most importantdiversion dam was constmctedin 1974in the 2200 level tunnelnear the portal. A submergedoutfall wasconstructed at the shorelineof Howe Soundfor the disposalof mine water into the oceanat depth
The dam had beeninstalled in an effort to retain 2200 level mine water in the mine, and direct the flow down thmughthe workingsto report with the effluent from the 4100 portai. Jn 1983drainage was noted again from the 2200 level. Jn 1985, Klohn Leonoff Ltd. was mtainedby Copper Beach Estatesto detenninethe integrity of the dam and to provide mcommendationson imp&ng the intemal drainage. The report pxeparedby Klohn Leonoff (1985)was essentiallya site visit reportwhich concludedthat the accessibleamas of the 2200 tunnel were generallystable. Klohn Leonoff indicatedthat they had been unable to inspectthe dam in detail becauseit was covemd by fonnwork. There did not seemto be sufficient flow capacity within the mine to handle all the drainage,and thus, the dam leaked and overflowed,nxulting in continueddischarge at the 2200 level. A rock sloughon the 2200 level nearthe No. 3 shaft also limited the potential flow downwardsby this means,and pipes that had been installed within the sloughwere inadequatefor the fiow. Tiiber and debris were also p&ent which limited the flows. In additionto a cleanupof the sloughami debris,Klohn Leonoff recommendedthat diversionsor contml stmcturesshould be considemdto help limit runoff enteringthe mine. .
In summary,since the mine shut down, most of the surfacewater entersthe mine workings thmugh the openpits aud gloryholesabove the 1050IeveL Dminageis muted throughthe workings to dischargeat approximatelythe 4100 portai, but actually exits undergroundat the 4150 level. At the presenttime, particularlyduring periodsof high water flow, drainagealso issuesfrom the 2200 level and discharges into Jane Creek which empties into Britannia Cmek. If flow rates are excessivelyhigh, or copper concentrationis less than 15 mg/L, the drainageis routed through a 100 fwt deep outfall into Howe Sourd. lf copperconcentrations in the drainageexceed 15 mg/L, ah drainagefrom the 4150 discharge
Steffen Robertson and Kirsten 166004 - Britannia Mie Site Page 3-3 caribe routedthrough the cementationtmatment plant, prior to dischargeto Howe Soundthrough the deep outfall.
3.2 Geochemistry
Predictionof acid generationpotential was not conductedfor the Britannia site either before mining or during operation. A recentsurvey, by the B.C. Acid Mine DrainageTask Forceof mines,in the province includedthe Britannia Beachoperation. No data were providedin responseto the questionnaireon the quantitiesor acid generationcharacteristics of the waste. A test programwas conductedby Environment Canadain 1983and 1984(Ferguson, 1985) to investigatestatic and kinetic predictiontest techniquesand includeda wasterock samplefrom Britannia. It was noted,however, that this samplewas not necessarily repmsentativeof all of the wasterock from the site.
Acid base accounting on the sample indicated a neutralization potential of +29 tonnes CaCO, equivalent/lOOOtonnes of materialat 16.2percent sulphur content, yielding a net neutralizationpotential of 477 tonnesCaCO, equivalent/lOOO tonnes of material. Khretictesting, usmg humidity cells,confhmed that the material was acid producing, generatinga pH in the drainagewater of 4.8 after 1 week of operationand pH 3.0 after 10 weeksof operation Approxlmately300 mg of sulphatewete producedafter 10 weeks,tiom a 200 g sampleof wastematerial(l.5 mg/g). Acidity and dissolvediron production indicated that the sample neutralization capacity was exceededduring the test, Dissolved metal conèentrationsin the leachateaveraged 5.41 mg/L CU,2.34 mg/L Zn, 22.5 mg/L Al and 26.5 mg/L Fe (equivalentto milligramsof dissolvedmetal per gram of wastemater-i@.
33 Water Quality
The waterquality of drainagefrom the mine workingswas a concemfor most of the mine life. Dissolved copperwas noted in mine watersin the-1920s (IIooper, 1970). Generallyelevated copper was detected with increasedproduction from a mining area. Waterquallty datawere compiled for the pexiodfrom 1923 to 1965 (Hooper, 1970) ami cormlatedwith production from the Fairview zone. The data’showed maximumcopper concentrations of appmximately1300 mg/L copper(up to 1934)decmasing to about700 mg/L in 1938. Productionfmm the Fairview pit had decreasedto less than 100,000tons per yearjust prior to this period (1934-1936).Another peak in copperconcentration was evident in 1944,subsequently followed by decreasingconcentrations down to less.than 400 mg+&in 1965. Mining fiom the Fairview areareached a maximumof 1.1 million tons per year fiom 1937 to 1940. Thus copperconcentrations tendedto correspondto mining rateswith a time lag of appmximatelyfive years,ptobably reflectingthe rate of oxidation and metal leachingfrom the exposedrock
Steffen Robertsonand Kirsten 166004 - Britannia Mie Site Page 3-4 From a descriptionof eachof the main orebodiesand the wall rockspresented by James(1929) both me ore and wall rocks have abundantpyrite and other sulphideswhich are potentially acid generating. It would appearthat oxldation was noted in severalamas throughout the workingsalthough the description was somewhatunclear, ” ...Pyrite is more msistantthan other minerais,but it is invarlably corrodedby quartz,and is not stable...”(James, 1929).
The contribution of surface disturbancesto contaminantloadings was also noted durîng operations. Correspondencefmm Anaconda(1974) indicated that two surfacesources, rather than the mine workings, were msponsiblefor the elevatedmetal levels in JaneCxeek.
an old mine wastedump located “... below and to the southof JaneBasin, on the steepslide area of the west side of the valley.” The wasterock was discardedfrom.the nearby 1200portai; from which thexewas no drainageat the time of observation.Jane Cmek at that time did howeverflow by this dump beforeentering Britannia Cm&. The dump was thoughtto containboth pyrhe and chalcopytite; ii) the original mining townsite atea was located in the “...generalJane Basin area...“. Mining activity from the undergroundworkings ceased in 1957but surfacemining continuedperiodically untiI 1974. Within the basin ama thereforethete are reportedly bath exposedworkings and extensiveslides. One slide was descrlbedas extendingfrom the Basindown to BritanniaCreek with a significantquantity of mineralixedrock distributedover the mountainside.
A samplingprogram in 1974included Jane Cmek immediately above the confluencewith BritanniaCmek The resultsindicated minor concentrationsof heavymetals and near neutral pH, howeverthe samplmg was conductedin Januaryand March. Flows in the hvo samplingperiods were 600 and 200 IGPM (38 and 13 Us). Metal concentrationswere 4.6 mg/L Cu, cl.3 mg/L Zn, 0.05 mg/L Fe, ami 52 mg+/LSOds. It is not clear whether these aredissolved or total metal concentrations;total solids in solution were 10.4 mg/L. . An excellentoverview of the more mcenthistory of the Britannia acid mine drainageptoblem, together with a summaryof the impactson Howe Sound is provided in the review by Goyette and Ferguson (1985). Two intemal reportsfor the Ministry of Environment(Moore, 1985;Moore and van Aggelen, 1986)provide detailed analytical results of investigationswith respectto water quality and environmentai impact. Thesereports provided usefitl analyticaland fiow data that were usedin tteatmentplant design for this study.
The mview by Goyetteand Fergusonhas been summarizedbelow, with respectto acid generationand water quality:
Steffen Robemon and Kirsten 166004 - Britannia Mine Site Page 3-5 Water quality
. ail minewater was diverted to the “Beach” treatmentplant in 1972 and then dischargedto Britannia Cmek,untii the deepoutfall was constructedin 1978; . flows of 65 m3/dwith low dissolvedcopper concentrations (0.43 mg/L) werefotmd from the 2200 level in 1980; . at this tinte the copperconcentration in the drainagefrom the 4100 level was 14 mg/L, indicating contaminatedminewater was still divertedfrom the 2200level. In 1983however significant flows of contaminatedmine water had emergedfrom the 2200 level; . elevatedtmatment plant copperconcentrations corresponded more to high influent concentrations than to large flows, howeverbath arecontributing factors. Overallcopper removal efficiency was 19 percentduring the early 1980s; . similar water quality wasnoted in BrinumiaCmek to 1976with 1.6 mg& dissolvedCu, 37 mgL dissolvedZn, and 40 mg/L dissolvedFe recordedat the mouth. Concentrationswere xeducedby an order of magnitudein 1980 with the diversion of minewaterto the deep outfall discharge, althoughmetal concentrationsin the creekincreased again in 1983/1984with the reintroduction of the 2200 portal drainage; . samplingin 1983/1984of the minewaterand selectedsites along BritanniaCreek mdicatedthe water was acutelytoxic to fish. Britannia Creekwas probablyacutely toxic to fish over most of the mine life; . copperconcentrations in the drainagef?om the 4100 portal have decteasedfrom about 66 mg/L in 1966to 17 mg/L in 1984.
Contaminantloading
. high flow periodscorrespond to high copperloadings and concentrationsindicating a large store of solubleoxidation products are containedin the workings; . historically water quality in Britannia Creekbas beenimpacted by the high metal loadingsfrom contaminateddrainage. Surveysin 1972 indicatedthat the 2200 portal drainagewas tbe only signifïcantsource of copperto BritarmiaCreek several hundred mettes upstream of its confluence with Mineral Creek. There was an unidentifiedsource, however, between this stationand below Minerai Creek. Tmatedminewater fiom the plant contributed61 percentof the copper(253 kg/d) to the Creekwith unidentifiedsources wntributing the test; . pH, sulphateand metal loadingsto Britannia Creek were lower in 1984&n 1972; . the mean copperloading from the 2200 portai in 1984 was 124 kg/d; . estimatedmean dissolved copper load to Howe Soundvia Btitannia Creekin 1972was 417 kg/d; . loadings from the treatedmmewater and plant bypassesfrom 1980 to 1984 varied from 50 to 700 kg/d with peaksoccurring duting June/Julyand NovemberDecember,corresponding to high
Steffen Robemon and Kirsten . 166004 - Britamia Mine site Page 3-6 minewaterflows. Thesewere lessthan the 1972loadings in the Creek,however, the mine water in 1980to 1984did not includethe 2200portal drainage,which could be a significantcomponent.
3.4 Water Treatment
In 1924a recoveryprocess was developedto precipitatedissolved copper onto scrapiron. A plant was installedin the JaneFlats areaalong with a numberof small plants. During most of the mine life, acidIi drainagefrom the mine workingswas collected for treatmentin two trearmentplants: one at the Townsite or 2200 levd in a plant constructedin 1928, and rhe other at the 4150 or “Beach” level constmctedin 1955. The 2200 level plant was shut down in early 1972. The drainagefrom the 2200 level portai. pteviouslytreated in this plant, was diverted intemally to the 4100 level.
Copperproduction from this pmcessreached one million pounds(453,600 kg) a year dtig the eariy 1930s. The predictedrecovery in 1970 was 262,ooOpounds (118,840 kg). This declinein production would suggesta decreasein copperleaching fmm the mine drainage. It might also reflect changesin the water flow pattems,flushing of the workings, and effectivenessof the cementationplant.
The treatmentprocess is basedon the electmchemicalreduction of copperin solutionto coppermetal with shnultaneousoxidation and releaseof iron fiom scrapiron. Copperpnzcipitates on the iron scrapsand cariultimately be nzcoveredby smeltingif desired. The dischargefrom the cementationprocess is routed to the deep water outfall. The cementationprocess does not removeany appreciableamount of acidity and cannotreduce copper to levelsachieved with conventionaltxeatment systems based on neutralization and precipitationof copperhydmxide.
The cementationprocess is particularly suitable for small waste flows since long contact times are requhed,but doesnot effectively treat high flows at low copperconcentrations which are encounteredat certaintimes of the year. The recoveryof copperfMm the mine drainagewaters varied over the year, with the highestcomr Rcoveryduring the highestprecipitation periodsz fall minsand sptig nmoff. This reflectsthe increasedarea of the workingsflushed during the high precipitationevents, which renlaindry or infnzcluentlyflushed during the dryer seasons.Goyette and Ferguson(1985) reportedthat more than 70 percentof the copperwas recoveredin the treatmentplant when influent concentrationsexceeded 80 mg/L, howeverremoval efflciencies are less than 50 percentat concentrationsless than 40 mg&
Investigationswere conductedin the early 1970sto evaluateremoval of the iron and copperfrom acidic mine water and preventprecipitation of metal hydroxidesupon dischargeinto Howe Sound(Drake and Robertson,1973; Anaconda correspondence, 1974). A neutralizationcircuit wasconsidexed for treatment of the mine effluent after the cementationplan& or dilution with mill water. This work was not pursued as the mine closedshortly thereafter.
Steffen Robertsonand Kirsten 166004 - Britannia Mine Site Pagu 3-7
TABLE 3.1 SUMMARY -OF FLOWS, COPPER CONCENTRATIONS, AND COPPER LOADiNG FROM THE 4100 PORTAL, 1983-1989
Average How Average [CU] CU Loading Year m’h m@ kg/d 1983 664 19.7 313
1984 561 18.4 247
1985 396 16.1 153
1986 494 19.6 233
1987 597 17.8 256
1988 475 18.5 211
1989 442 15.3 162
AVERAGE 518 18.0 225
Steffen Robertsonand Kirsten TABLE 3.2 SUMMARY OF ASSAY INFORh4ATION ON 4100 AN-D 2200 PORTAL FLOWS.
Parsmeter (mg/L)
Location 2200 2200 2200 4100 4100 4100 4 100 4 100 4100 4100 4100 Date 21/06/83 06/12/83 21/04/04 21/06/63 13/07/03 15/08/03*00/09/83 06/12/03 21/04/84 21/05/05 20/06/05
PH 2.9 3.5 2.7 3.4 3.5 3.2 3.8 3.9 Acldlty (pli 8.3) 445 109 494 367 306 277 239, 258 sulphate 880 293 895 1620 1700 1620 Diesolved metah Al 31.3 8.05 36.4 39 37.6 35.3 30.6 B 0.02 0.01 0.17 0.17 0.31 0.34 0.25 0.28 0.20 Cd 0.17 0.06 0.16 0.19 0.14 0.14 0.11 0.14 0.0058 0.12 0.16 Ca 129 53.2 121 441 411 418 478 419 450 387 CO 0.17 < .l 0.22 0.22 0.14 0.3 0.29 0.35 0.1 0.1 CU 51.4 12.3 43 31.7 30.3 23.6 22.5 18.3 14 11.1 18.1 Fe 36.8 3.16 45.1 11.3 17.1 50.6 56.1 17.1 14 10.8' 4.74 Pb 0.12 < .l 0.16 0.22 0.14 0.22 0.09 0.23 0.2 0:2 Hs 38.5 11.3 39.4 88.6 82.4 100 115 83.4 94.3 81.7 Mn 2.6 0.9 3.12 5.47 6.21 0.4 9.2 7.52 7.66 5.98 Ni. 0.07 < .05 * 0.05 0.11 0.08 0.15 0.09 0.07 0.07 0.06 2n 26.1 8.21 31.6 41.9 30.9 27.1 27.3 26.1 0.21 28.1 30.8
Flou estlmate 210 l Acidity In mg/L equiv. CaCO3; flow in m3/h
. 166004 - Britannia Mine Site Page 3-9 The availabletmatment plant datahave been compiled to mdicatetypical concentrationranges and flow rates and estimatemquired plant capacity(Moore, 1985;Moore and van Aggelen, 1986; Goyetteand Ferguson,1985; MOE treatmentplant performancerecords). These data am summarizedin Table3.1 and Table 3.2. They are further discussedin Chapter6, and presentedgraphically as Figure 6.11 ; 6.13.
While there is a downward trend in copper tenor of the solutions since the mine closed in 1974, Figure 6.11 showsthat the averageof the coppertenors over the period 1983* 1989provides an adequate estimateof copperproduction for studyof the potentialfor metalrecovery. Similarly,Figure 6.12 shows that averagehourly flows vary fiom 400 to 675 m3/h,there is no significanttrend in flow and an average flow basedon this period is adequatefor this phaseof study.
It is notedfiom this dataFigure 6.13 that them appearsto be an incteasein coppertenor with flow rate; probably due to gmater fhtshing and better wetting of sulphidesurfaces dukg wetter years. The regmssioncoefficient for the line shownis not smtisticallydifferent from zerohowever, SO the statement cannotbe madein certainty. This correlationwas also notedby Goyetteand Ferguson(1985).
While thereis a downwanitrend m coppertenor of the solutionssmce the mine closed,Figure 6.13shows that the averagingof the ‘coppertenors over the period 1983 - 1989provides an adequateestimate of copperproduction for studyof the potentialfor metal recovery.
3s Existing Environmental “Regulation”
The BritanniaMine was permanentlyshutdown in November1974. Anaconda,the pmviousoperator, appliedfor permit underthe ProvincialPollution Comm1Act in May 1973that includedprovisions for tmatmentof wastewater from a propertyusing a lime tmatmentpmcess. The permit Dischargecritexia appliedfor May 1973confonned to the Level “C” Objectivesfor Marine Dischargelisted in “Pollution Control Objectivesfor the Mining, Mine-Milling Smelthq and AssociatedIndustries” published by the WasteManagement Branch in Match 1973. Acidic minewaterfxom the 2200’ Level was divertedwithin the working to the coppermwvery plant at 4100 level after 1972. The plans for tmalmentof acidic drainagefiom the 4100 level portal includedwith the permit applicationwere not hnplementedsince the mine was shutdownin 1974before the applicationapproval pxocess was wmpleted.
The operationof the treaunentplant and minewaterdischarge qualityis wntrolled by an order issued January29th, 1981,f’rom the dimctor of the WasteManagement Branch (B.C.M.OE.) to CopperBeach Estates.The orderrequhes that all mine wateris wllected anddixtxted to the 4100 level, andthen to the “tmatment”plant (wpper rewvery) if the dissolvedcopper is greaterthan 15 mg./L. The order also pmvidesfor bypassof minewaterif the dissolvedwpper is lessthan 15 mg/L.
Steffen Robemon and Kirsten 166004 - Britannia Mine Site Page 3-10 The 4100 level copperrecovery plant continuedin operationafter shutdown After 1978all minewater wascollected and discharged through a 100ft deepoutfall into Howe Sound.Responsibility for operation of the pollution connol works was tmnsferredto CopperBeach Estates Ltd. (CBE) and is controlledby an onier issuedby the Director of the WasteManagement Branch to CBE in January,1981. This order rquires that all mine drainagebe directedto the 4100 level copperrecovery plant if the dissolvedcopper concentrationexceeds 15 ma. Bypassis allowedif dissolvedcopper concentration is lessthan 15 mg/L.
Surveysconducted by both EnvironmentCanada and Ministry of Environmenthave resultedin the following basicobservations regarding the level of compliance, . 0 recordedbypasses occur regularly when the copperconcentrations exceed 15 mg/L, (bypassesare usedto protectthe plant from washoutduring periodsof excessivemine flows); ii) overall copperremoval in the plant is low; iii) comamim@dminewater is dischargedto BritanniaCrack fxom the 2200 portaJ&ing h@hflow periods;ami, iv) operationof ‘the treatmentsystem’ is erraticallycontrolled
Steffen Robertsonad Kirsten 166004 - Britannia Mme Site Page 4-l 4.0 EMSTING ENVIRONMENT
4.1 General
An initial site visit wasconducted August 30,199O by SRK andGPE personnel to developan appreciation of the site, identify the scopeof the field investigationsand define samplingrequirements and locations. Mr. Eric Beresford(MEMPR), Dr. John Enington (MEMPR) and Mr. Dan Cummii (CopperBeach Estates)conducted a tour of the site, including surfaceworkings up to the EastBluff and Janepits, and undergroundfrom the 2200 portal. Accessto the upper pit amas(Empress ami No. 5 pits) was not possibledue to road conditionsand time constraints.
Two Eeld investigationsof the Britannia mine site were undertakenon September21 and December6, 1990with the objectivesoE
. identifyhtg sourcesof acidic drainage;
. samplingand chemicallycharacterizing mine discharges,seeps and receivmgwater;
. measuringor estimatingdischarge flows for an assessmentof sitehydrology and the detennination of contaminantloadings;
. providing a basisto comparethe present(1990) situationto historicalconditions.
. The fbcus of the investigation was the Britannia Creek drainage ami contributing watercoursesin acconiancewith the temu of referencefor the project Accessto the Upperareas of the site, above2200 level, was not possibledue to road constructionand snow in tbe secondstuvey.
The samplinglocations sud resultsof theseinvestigations are discussedin Section4.2 through4.4, and presentedin Figures4.1 through 4.6. Detailed pxocedumsof investigationand msults are preséntedin Appendices1 and 2.
4.2 Mine Deveiopment
42.1 Pits
Openpit mining was conductedin Eve pits, as shownon Figure 4.1. The quantity of materialmmoved from eachpit is not known, howeverthe major@, pmbably in the order of 95 percent,was taken from the EastBluff andFairview pi& Photograph4.1. Therewas someinitial open pit mining during the early
Steffen Robertsonand Kirsten r / -L. 493,000 E CL-/ / ._
LEGEND - Stream. definite .- Stmom. indefinite - Cmvsl Roaa - Poved Road - Trails 0 Townsite
M,“lstlyCfmergy. Mmes ond Petroleum Resourcss I BRITANNIA MINE SURFICIAL MINE WORKINGS r 418.J. I STEFFEN ROBERTSON & KIRSTEN Conruttlng EnQ;neers
166004 - Britamia Mine Site Page 4-4 yearsof the mine,however most of the openpit mining occunedafter 1966. Somegloryholes, subsidence and early open pit mining had disruptedthe topographyprior to open pit mining in 1966. Glory holes wexedeveloped under all of the pits exceptthe Empress,however, underground mine developmenthas effectivelyreached the surfacein this ama. Subsidenceami erosionhas since filled all of the glory holes leavingsteep sided cane shaped depressions, except for the Fairviewpit which still hasan openconnection to the undergroundmine.
The 1050level headingis exposedm the Lower JaneEit, ami the 850 level headingis exposedin the East .Bhtff Bit (Note: Elevation4300 ft = 0 level in the mine, mine level increasesby 100foot with each 1flO dmp in elevation). Essentiallyall of the disturbedamas titfiin the pits have confinuingslope instability as patchyvegetation has re-establishedin only a few amas. Above the Janepit, and in the ama of the 1915landslide, there appearsto be a scatpwhich may be indicative of ongoingsubsidence. Essentiaily all of the pit walls appearto be acid generating,based on observedmineralogy and the pmsenceof oxidationproducts. .
4.2.2 Underground
Undergmundmining has been the main sourceof ote at the BritanniaMine, accountingfor in the order of 95 percent of the ote, and has exploited seven oxebodies. Gm extractionused several methods, principahy:timber supportedopen stopes,tut and fill, ami sub-levelcaving, It is believedthat most of the flll wascyclonedtailings. Gther mining methodsmay have beenused. The proportion or location of the stopeswhich am backfïlled is not known at this time. The mine is shown.ina compositesection in Figez 42. It is tmderstoodthat thereare many vent raisesto surface,none of which are shownon this ggme, however, it is expectedthat most of them are near the area of the open pits except for any associatedwith the Victoria camp. Thesevent raiseswould be locatedin the Furry Creekvalley.
It is understoodthat in many amasof the mine that the timbershave totted andthe openingsam collapsed. Someof the are passesare also believedto be partiahy collapsed(Klohn Leonoff, 19&4). The a&ess drifts in the mine anzbeUeved to be appmimately thnx by tiuee metresin section. The condition of theseheadingsandtheacces~~~throughoutthemineisnot~o~ Itisunderstoodthatatmine clos& all mine entranteswem caved,although this doesnot seemto apply to the 2200 level portai in JaneCreek, where only a partial water diversionexists. An examinationof the detailedmine plans will be quired to identify the location of ail pot%& and vent mises.
Acidic wastewater curmntly drains from the mine. The principle sourcesof the acidity from the mine workings are probablythe sublevelcave stopes aud any stopeswhere backiïll was used.
Steffen Robertson and Kirsta~ LEGEND - Levels 7 Waier Table - Topogrûphy
SECTION LOOKING NORTH
Approwimote current woter level drlI r . Notas, Fiqwe derived from l COPPC’ Bscch Estotes I -- - r=- 1 - Section is o %mplified i tiomestoke projection of the mine I workings
Ministry of Energy. Mines and Petroleum Rssources BRITANNIA MINES UNDERGROUND MINE WORKINGS - 1 ,. I 4.L ROBERTSON & KIRSTEN, Consultlng Eng;neers 166004- Britannia Mine Site Page4-6 4.23 Waste Dumps
There are threemain amaswhere waste rock has appamntlybeen dumped:
. in JaneCreek adjacent to the East Bluff pit, . at the 4100 level porta& . 2200 level portaL
Theseareas are shown on Figure 4.1. The quantity of material at eachsite is not known A rough estimateof the wastedump geometryadjacent to me East Bluff pit indicatesab&t 700,000tonnes of waste. Estimatesof the quantityof wastedumped at the 2200 level and 4100 level havenot beenmade, howeverthese quantities appear to be in the order of 30 and 10 percentmspectively of the estimated 700,000 tonnes located at the Bluff Fit. These estimatesare basedon interpretationof high level ahphotos,the orighraltopographie data and mine records.Field measurementswill be necessaryto obtain more accumteestimates.
Most of the wasterock is contahxd in the dump adjacentto the East Bluff pit. A small portion of the wasteat EastBhrffpit waspmduced from the undergroundmine developmentand early openpit minhrg and may be up to 50 yeamold The balanceof the wastewas pmducedbetween 1966 ami 1973. The wasteappears to be an acidgenerating material based on observationsof its mineralogyand the pmsence of oxidation pmducts. ABA tests have not been conductedon this material. Based on airphoto interpretationthis wastedump partially overliesthe debrisof the 1915landslide.
Wastehas beendumped at the 4100 level portai ama including...~ the amasouth of the mill ami the dock anz~ Mostofthewasteappearstobecontainedinthe~asouthofthemilland probablyconsistsof non-acidgenerating material pnxluced dming developmentof the 4100 level ami an overlyinglayer of spilled are ami low gradematerial, which appeamto be acid generatingbased on the bon oxide staining. The wastedumped at the 2200level portal is believedto be developmentwaste only andis probablyacid genemhg, althoughABA testinghas not beenconducted. Historical refexences (Ramsey, 1967) describe somelandslides which travelledfxom tire JaneBasin to Btitannia Cmek Although thesecould not be identified in the airphotos,it is probablethat they underliethe wasteat the 2200 level portaL Britannia Cmekhas been subject to periodicflooding (1921,1989)and thesefloods haveprobably emded some of the wastedeposited at this location
Basedon photographieevidence (Ramsey, 1967), waste has alsobeen dumped at the 1800portal on the Furry Creekside near the Victoria Camp,however, it hasnot beenidentified in the air photosas the area has naturaUyrevegetated.
Stefkn Robmson and Kirsten 166004- BritanniaMine Site Page4-7 4.2.4 Tailings
Essentiallyall of the tailings wem either dischargeddinxtly into Howe Soundor wem cyclonedto yield a coax-sefraction for use in backfill with the fines being dischargedinto Howe Sound. However,some material,possibly tailings, was dischargedto a taillngs pond abovethe tteatmentplant at 4100 level, as shownon Figure4.1 andPhotograph 4.2. This wasapparently an emergencypond, or settlingpond. This pond may also have receivedeffluent from the 2100 treatmentplant during operation,and servedas a settlingpond.
The quantityof materialcontait& hereis not lmown,but basedon plan dimensionsof 20 x 40 m and an estimateddepth of 5 m, the pond containsapproximately 8000 tonnes of waste. Recentroad construction has resultedin road flll material overlying a portion of the tailings pond. Placementof the road fill material over the tailings has not resuhedin slope faihues which implies that tire tailiqs are highly consolidatedand/or self cementedwith iron oxide. Thesetailings are aisobelieved to be acid generating fiom the oxidizedsurface appearance.
Unconfirmedreports suggest there may also be sometailings depositionin the beachama on the north side of BritanniaCmek.
4.2.5 Roads
Many toadshave been developed in the BritanniaCmek valley. It appearsthat ail of the roadshave been constructedusing tut ami fill techniquesand that imported mine waste has not been used in mad constmction,except for roadswithin tbe pits ami on the wastedumps. Oniy thosemads near to the pits are likely to bave beenconstructed of acid generatingmaterif It doesnot appearthat any of the other mds involved cuts deeperthan a few metressud are therefomunlikely to have exposedfresh acid generatingmaterial.
4.2.6 Landslides
Therehave beenat leasttwo hWancesof landslidesin the JaneCreek area. The first slide occurredon March 22,1915. Basedon the records@amsey, 1967) ami airphotointerpretation, this slide originated near the cnxt of the west side of JaneBasin along a shearzone oriented roughly north-south. It is not clearhow largethis slide was,however based on photographsof the damage,the reportedsize of several million tonnesis ptobably high by a factor of ten. The acid generationon characteristicsvalue of this materialis not known, howeverslide debriswas suspect&historlcally to contrlbutedissolved metals to JaneCxeek as descrlbedin Section3.4.
SteffeaRobeztson and Kkstea Photograph 4.2 Pond at 4200 level above treatment plant 166004 - Brima Mine Site Page 4-9 The secondlandslide was probablydue to the failure of a wastedumps near the JanePortal at the 1050 level producedduring the early undergroundmine developmentand openpit mining. The recordsare unclearregarding the dateor the exactsource or quantityof materialinvolved. Accordingto the records, the debris fmm the landslideforms part of the acid generatingmaterial deposited near the 2200 level Pol-Ql.
43 Hydrology and Hydrogeology
4.3.1 Catchment Developments
Developmentswithin the study amathat have significanteffect on the existinghydxology comprise:
0 alterationsof surfacedrainage patterns,
ii) dischargesof mine water fiom portaisand
iii) abstractionsfor water supply.
Figures4.1 aad 4.3 show currenthydrological mgime and locationsof thesedevelopments.
The alterationof surfacedrainage pattems is due to the existenceof both the surfaceand underground workings. Most of this aherationis cox&ed to an amaknown asJane Basin, which comprisesthe Upper reaclxs of JaneCmek and a small amaalong the drainagedivide sharedby Janeand Furry Cmeks. The existingtopography and catchments of JaneBasin are shown in Figure4.4. The obviousimpact of surface mining on the drainagepattems was to alter to~gmphy and thembychange stmam courses and drainage divides. However,the impact is accentuated.by the existenceof welldrained undergroundworkings directly beneaththe openpits. Due to cavingin the underground,the rock at the bottomof the openpits is probablyhighly fiactuxedand therefomhas high infiltration capacity. Also, vent misespxobably exist that increasethe effective infiltration. The coupledinfluenœ of the surfaœ and undergroundmining pmbably causesmost of the nmoff from Jane Basin to be funnelled into the undergroundworkings thmughthe perviousbases of the openpits. This makesthe JaneBasm essentially an encloseddrainage basinthat likely contributesto the stmamflowin the lower reachesof JaneCreek and to Furry Creek. The contribution,however is not consideredto be significant
Steffen Robextsonand Kirsten Legend
494.0Wm E
BRITANNIA MINES Carrent Topogrophy ond Droinoge 4..3 SEFFEN ~WXVSON & KIRSTEN. Consulting E-,ginaen J 4.4 STEFFEN ROBERTSON 8 KIRSTEN, Consulting Enginctrs 166004 - Britannia Mine Site Page 4-12 The drainageof mine water fiom the undergroundworkings represents a secondimpact on the mine site hydrology. As explainedin Section3.1, most of the water from the Britanniaunderground drains at the 4150 foot level wheteit is subsequentlydisposed of thmugh a submergedoutfall to the depthsof Howe Sourd. The next largestsource of mine water is believedto flow frorn the 2200 ponal which discharges to JaneCxeek. The flow of mine waterfrom this portaihas been obsexved to be seasonal,occurring only durhrgperiods of high flow. Mine water is known to dischargefiom at leasttwo other sources,namely the 2700 portal in the catchmentof Mineral Creekami a portal in the amaof EmpmssCreek.
Abstractionsare made from at leasttwo locationswithin the catchmentarea of BritanniaCmek, both of which are relatedto the water supplyof the townshipat Britannia The high pressurewater systemfor the townshipof Britanniais suppliedfrom Tunnel Dam in BritanniaCreek. A penstock,once used for generationof hydroelectricpower, diverts water fiom Tunnel Dam to a reservoirfor the high pressure system. Ovefflow fiom this reservoirmakes its way to Thistle Creek,a small streamthat discharges directly into Howe Sound. The potablewater supplyis obtainedfmm a small dam on Mineral Creek. This dam is locatedabove the inflows from the 2700 portaL
An additional influence on the mine site hydrology could be drawdown of groundwatercaused by undergroundworkings. This could mducebase flows below naturallevels for streamsthat drainthe mine
4.3.2 Available Data
During the field trips conductedon September21, 1990 and December6, 1990,spot measummentsof sheamflowwenz made at severallocations within the drainagebasin of Britannia Creek. Spot flow measurementswere alsomade by othersin earlierfield investigationsof the Britanniame axea.These data are valuablefor the assessmentof cantaminantloadings catried by the mine site streamshowever, they axetoo spaxsefor accuratelycharacterizing the pmsentdayhydrology of the studyama streams. The data are discussedin detail in Section4.4. .
Although few stmamflowmeasurements are availablean excellentflow recordhas beenkept on mine drainagefiom the 4150 level discharge.The flows axegauged by two -hall flumes,one locatedon a chantre1leading to the tmatmentplant amithe otheron a bypasschantre1 leading dimctly to the submetged outfall. Stagemeasumments are made on a weeklybasis. The flow recordat the two flumescommences in March 1978and is completeup to the pmsent.
A recordof infrequentflow measurementshas alsobeen made of the mine drainagedischarging from the 2200 level portaL
Steffen Robertsonand Kirsten 166004 - Britarmia Mine Site Page 4-13 4.33 Present-dayHydrology
Section 22.3 ptovides estimatesof the Mural hydrology at key points within the study area. The following discussionoutlines the extentthe abandonedmine development has altered the naturalhydmlogy at thosesame key points.
Within the study ama,the gmatestdisturbance to the surfacehydtology has occurmd on JaneCreek. As explainedabove, it is believedthat most of the runoff fmm the Upperreaches of JaneCmek is trapped by ami then funnelledthmugh the open pits, or glory holes,into the undergroundwodcings. Figure 4.4 showsthe outline of the encloseddrainage basin commandedby eachof the open pits within the Jane Basin. The total axeacovered by encloseddrainage basins, including the small areawithin the Funy Cxeekcatchment, amounts to 1.19km2.
The total runoff from the encloseddrainage basins was estimatedusing mgional analysis. At a median elevationof about 1250m, the unit MAR was estimatedto fall within the rangeof 3500 to 4500 mm. Figure4.5 showsa high andlow estimatefor the averagemonthly distribution of runoff generatedby the encloseddrainage basins. For compatisonsakes, the averagemonthly flows measuredat the 4150 portal are supimposed on this figure. The measumdmine flows compareremarkably closely to the estimated nmoff fiom the Jane Basin. Although not aJl of the mine drainageexists at the 4150 port& the correlationsuggests that surfacerunoff from JaneBasin may be the singlelargest source of mine water.
With the flow from the Upperreaches essentially tut off, the stmamflowsin JaneCmek at its mouthhave beendrastically reduced from the pre-miningcondition. The effectivecatchment atea for JaneCreek at its mouth is now about0.59 lon2,or 35 percentof îhe original size. Thus, the flows in JaneCmek have probably been reducedby a similarpmpotion, Mine drainagefrom the 2200 portai only partially compensatesfor the lost contributionof nmoff from the Uppermaches of JaneCreek.
The hydrological regime of Minerai Creek, another tributary of Britannia Cmek, has experienced disturbanwsdue to mine developmenLSeveral tunnels daylight within the catchmentof Mineral Cm&, and at least one of these,the 2700 or 2750 porta&is a sourceof mine water. The 2700 portal was not visited during the 1990field hips as accessto this amawas not possible,however, it is understoodfrom site personnelthat the flows are relatively smalL The other impact on the hydrologyis the abstraction for the BritanniaBeach water supply. Furtherdata would be requiredto quantifythe differencein flows betweenpresentday and naturalconditions.
SteiTenRobextson and Kirsten Mean Monthly Runoff and Mine Drainage Distribution
Mean Monthly Discharge (L/s) 350 1
50 I I I I I I l I l I :AN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Month
- Measured tlowa from + Low estfmate for * Hlgh estlmate for 4150 Porta& 1983-1990 Jane Basin Runoff Jane Baaln Runoff Figure 4.5 166004 - Britannia Mine Site Page 4-15 During the operationalphase of the BritanniaMine, the flow xeghneof BritanniaCreek at its mouth was pmbably significantlyaltexed due to the operationof the hydtoelectricdevelopment. This is no longer the caseas pmsentdayhydrology ptobably resemblesnatural hydtology fairly closely. The alterations of flow on the two tributariesof Minerai and JaneCmeks are relatively small compamdto the nmoff genemtedby BritanniaCxeek as a whole. Also, the damsremaining from the hydmelectricscheme have minimal influenceon the flows of BxitarmiaCmek at its mouth. The abstractionfxom Tunnel Dam, effectively an interbasintransfer to Thistle Creek is alsorelatively smalL
Within the catchmentarea of Furry Creek,the mine developmenthas causedminor disturbanceto the hydrologyof EmpmssCmek and someneighbouring unnamed stmams. One of the openpits in the Jane Basinstraddles the dividebetween Brida andFurry Cmeks.Another two openBits No. 5 andEmpress are located in the EmpmssCreek drainageami may act as encloseddrainage basins. The resulting reductionof catchmentarea of Furry Cmekis small. As with MhreralCreek, the flow of EmpressCreek and its neighbomingstreams has been supplementedby the dischargeof at least one portaL More informationwould be requiredto assessthe impactof man’sactivities on the hydrologicalregimes of the Fuq Cmek tributariesthat dmin the mine atea. At the mouth of Furry Cmek, the alterationto the stxeamflowsby the mine developmentis expectedto be imperceptible.
4.4 Water Quality
4.4.1 Sampling Program
Two water quality samphnginvestigations were conductedby SRK to identify the major sourcesof contaminantloadhrg to BrinumiaCreek. The two samplingperiods reposent extmme flow events:the Septembersamplhrg during a low flow period ami the Dzcemberduring a high fiow petiod. Accessto the site waslimited duringthe fall periodby landslidesand resuham highway closums between Horseshoe Bay and BritanniaBeach. Pmcipitationdata for the SquamishAhport is pmvidedin Table 4.1.
Measuredflows at the mouth of Britannia Creek were 97 and 1770 L/s duxing the Septemberami Decembersampling, mspectively. For the determinationof all potentialsources of comamim#ddrainage, the high flow samplingperiod pmbably indicates more accuratelypotemial drainage sources. The results from the Decemberinvestigation will be pmsentedin the following discussionswith the resultsof the Septemberinvestigation following in parentheses.
Steffen Robexuonand Khtem 166004 - Brittmnia Mme Site Page 4-16
TABLE 4.1 MONTHLY PRECIPII’ATIONAT SQUAMISHAIRFORT (mm)
MONTH 1951-80 1990 % OF NORMAL NORMAL JAN 3132 415.9 133 234.3 386.8 165 MAR 188.9 136.9 72 APR 149.1 67.1 45 MAY - 77.2 56.5 73 68.5 1182 173 52.3 34.0 65 AUG 73.0 . 51.5 71 SEFT 127.0 29.8 23 OCT 301.3 329.0 109 NOV 314.4 929.1 296 DEC 347.8 396.5 114
2247.0 2951.3 131
Samplingsites were selected along Britannia Cmek and on the contributingwater courses such that source axeascould be isolated ami the loading contributionsfiom specific amascould be calculated. The locationsof the samplingsites are shown in Figure 4.6a and 4.6b. The msultsof the water quality samplingprogram are summarizedand compamdwith historical data in Tables4.2 through 4.7 and provided in detail in Appendix A. The water quality and waterflow data has been compiled in a GeographicInformation System (GIS) and is displayedgraphically in Figure4.6a and 4.6b.Compilation of the data in this format allows graphicalpmsentation of any individual parameter,and with input of histoxicaldata, comparison of trendswith respectto placeor time.
BritanniaCmek was sampled at six locations. Backgtoundwater quality, that is upstreamof the influence of mining areas,was detenninedat site Bl at appmximately2200 ft elevation. During the September samplingmad work was being done in this ama and accessto the north side of the creekwas limited. In December,the Creekcxossing at the 2200 level was washedout,
Samplingwas conductedalong the length of the creekto idem.@sources of loadingalong the Cxeekand spedically to addressknown and suspectedsources:
Steff~ Robertsonand Kirste.n LEGEND - Stream. definite ‘- Streom. indafirh - Gmvel Road - Poved Road - Troils m Mined3 a Townsits 8 Wat?r +ality Monhnng Station
L Ministry of Enerw. Mines ond Petrolsum Rssoxcss “or&. 1991 -- 6600. BRITANNIA MINE - WATER QUALIN RESULTS for SEPTEMBER m4 ,5fl, STEFFEN ROBERTSON L KIRSTEN, Consult:ng Enginccrs Britanrb Brac LEGEND - Stmom. definite .- Strsom. indsfinite - Gravel Rood - Paved Road - Trails m Mhesits II1 ownsite 8 WotTr +7lity thxtonng Station
, Mines ond Pstroleum Rcsourzos
WATER QUALITY RESULTS for DECEMBER TABLE 4.2 WATER QUALITY DATA, SEF’TEMBER 1990
Britannia Jane 2200 Jane Britannia Britannia Hineral Britannia 4100 Treatment Treatment Britannia Creek Creek Porta1 Creek Creek Creek Creek Creek Porta1 Plant Plant Creek Bl Jl 52 B2 B3 B5 In out B6 CALC PR 1.02 7.37 4.29 7.56 NA 6.98 7.23 6.92 4.46 4.55 4.38 6.98 Acidity CaC03 1 4 142 3 NA 15 2 3 266 254 242 2 Sulphate SO4 3 36 559 31 27 28 44 16 1740 1730 2030 18 Dissolved Metals Copper D-CU (0.001 0.100 13.5 0.100 0.620 0.570 0.008 0.092 15.4 15.3 13.8 0.073 Iron D-Fe TABLE 4.3 WATER QUALITY DATA, DECEMBER 1990 Britannia Jane 2200 Jane Jane Britannia Britannia Britannia Minera1 Britannia 4100 Furry Creek Creek Porta1 Creek Creek Creek Creek Creek Creek Creek Porta1 Creak Bl Jl 52 53 B2 B3 84 - Ml 86 PR 7.02 7.49 3.49 3.99 3.97 6.97 5.41 5.12 7.93 6.42 4.24 8.36 Acidity CaC03 2.7 3 764 184 181 5.3 20 10.4 2 5 332 *1 Sulphate SO4 Cl.0 30.9 1470 390 391 10.2 44.1 30.1 12.8 19.4 1930 Total and dissolvedmetal (CU, 2%) concentrationsare similar, indicating most of the metal load is dissolved. Total iron vahres,however, are higher than the dissolvedin BritanniaCreek at sitesB3 and B4; whexeJane Creek joins Britannia. Metal pmcipitationwas evidentalong the cmekin this area,and pH valuesare higher than in the upstmamdrainage, ranging tlom 5.4 to 7.0. The total imn load is probably due in part to physicaImobilization of some of the iron oxide and hydroxide precipitates. Sodiumconcentrations were typically less tban 1.5 mglL but wete elevatedin the drainagefrom the poxtaIs(up to 11.4 rn& fmm the 4100 level) and sIightly elevated(2.3 mg/L) in Mit@ral Cnxk suggestingdrainage from the 2700 portai was conhibutingBritannia Cmek in December. In September,total amidissolved copper values in the tmatmentplant influent were 15mg/L, approaching the lower designlimit for this plant. Someof the flow throughthe tmaunentplant was divextedinto the setdingpond below the plant, at variousstages along the courseof the cementationlaundem. Copper concentrationsin the tmatmentplant effluent were similar at 14 mg/L. Iron concentrationshowever increasedfrom 1.4 to 12 mg/L Fe @SS.)from infiuent to effluent, hrdicatingcementation mactions were occuning. The initial flushingof oxidationzones after a prolongeddry periodtends to resultin high concentrations and metal loadingsdue to storedoxidation products. Samplingwas not possibleat the Bxitanniasite in the initial weeksof heavyrainfall dueto roadclosures along the Squamishhighway which linmed access fmm Vancouver.The Decembersampling trip wasconducted after appxoximatelytwo monthsof rainfall. Steffen Robmon aqd Khten TABLE 4.5 COMPARISON OF BRITANNIA CREEK AND MAJOR DISCHARGES 1972,1976,1980,1983/84,1990 Parameter Year Flow PH SO4 T.CU T.Zll T.Fe DCU D.ZIl D-Fe Creek U/S 72 60.1 6.7 1.6 0.047 0.03 0.07 - 80 0.03 0.02 The variation in flow rates and concentrationfiom each of the drainagesources evident in this and previoussurveys mdicates the need to addmssseasonal fluctuations in drainagewater quality. Such variationsmust be understoodfor the designof any treatmentpmcess. The objectiveof the sampling programdescribed herein was to identify andcharacterize the majorsources of loadingto BritanniaCnxk. In order to accuratelyquant@ the total ammalcontributions of eachsource, and identify sourceswhich may not have been distinct during theseperiods, a more extensivesmvey on at least a monthly basis would be requiredover at least a one year period, including two springrunoff periods. 4.4.5 Contaminant Loadings Flow data we= usedto calculatechemical mass loadings for each of the samplingprograms. These resultsare summarizedin Table 4.6 and 4.7 and shown graphicallyfor key parametemin Figure 4.6a and 4.6b. The waterquality samplingdata have been hrcorporated into a GeographicInformation System (GIS). Detailedrtmlts of the loadiugcalculations are pmsentedin AppendixA. Thesemsults indicatethe major sourceof contaminantloading is the drainagefmm the underground workings. In December,88 % of the total copperloading in BritanniaCreek was contributed by the 2200 portai drainage. This drainagealso had the highestcopper concentration at 97 mg&, and the flow from the poxtal reptesentedless than 1 96 of the total flow of BritarmiaCreek at the mouth. It must be recoguizedhowever that slow liom the undergroundworkings which dischargesat the 4150 level is dischargedto Howe Soundeither dimctly, or throughthe tmatmentplant Flow wasnot issuingat a measurablerate front the 2200portai duringthe Septembersurvey however the drainagehad low pH (429) with elevatedacidity at 142 mg&. Dissolvedmetal concentrationswere; 13.5mg/L Cu, 3.8 mg& Fe, ami 11.7mg/L Za It would be expectedhowever that, when flowing, this drainagewould contributesignificantly to the metal loadingsin Janeaud BtitanuiaCmeks. The total copperloading to Howe Soundfrom BriuumiaCmek calculatedfor eachof the two sampling periodswas 0.9 kg/day (Sept) and 128 kg/day (Dec.). Dischargedimctly to Howe Soundfi-ont the 4100 level and tmatrnentplant dischargewas 51 kg/d Cu (Sept.)ami 289 kg/d (Dec.bypass of the txeatment plant due to high flows). Thesedata are summarlzedin Table 4.8. Steffen Robemon and Kirsten p Brittania Mine Site Sulphate And Acidity Levels, Sept & Dec Concentration (mg/L) 2000 1500 1 1000 500 Bl Jl 2200 52 53 B2 83 84 Ml B5 B6 4100 Sample Station - Acldity, Sept 1990 -C Sulphate, Sept 1990 - Acldity, Dec 1990 + Sulphate, Dec 1990 Figure 4.7 Britannia Mine Site Copper and Zinc Concentrations 12. Concentration (mg/L) r Bl Jl auO2200 J2 53 B282 83 84 Ml BS B6 4100 Sample St’ation -- ICul, Sept 1990 + IZnl. Sept 1990 * ICul, Dec 1990 * hi, Dec 1990 Figure 4;8 TABLE 4.6 CALCULATED LOADINGS, SEPTEMBER 1990 Britannia Jane 2200 Jane Britannia Britannia Minera1 Britannia 4100 Treatment Treatment Britannia creek Creek Porta1 Creek Creek Creek Creek Creek Porta1 Plant Plant Creek Bl Jl 52 B2 B3 BS In : out B6 CALC Estimated Flou L/s 58 4.2 0 4.2 39.8 44 0 92 42 42 42 97 PB 7.02 1.31 4.29 7.56 NA 6.98 7.23 6.92 .4.46 4.55 4.38 6.98 Sulphata SO4 16.0 13.2 0.0 13.5 94.0 107.6 30.3 127.2 6314.1 6277.8 7366.5 150.0 Dissolved Metala Copper D-CU 0.00 0.04 0.00 0.04 2.1 2.2 0.01 0.13 55.9 55.5 50.1 0.61 Iron D-Fe 0.00 0.00 0.00 0.00 4.9 4.9 0.00 0.29 5.0 4.9 43.5 0.00 Sodium D-Na 6.2 0.54 0.00 0.54 4.4 5.0 1.6 11.2 42.5 ’ 42.0 42.1 12.6 Zinc D-IA 0.00 0.20 0.00 0.29 2.4 2.7 0.03 1.9 110 112 110 1.9 Total Hetals Copper T-CU 0.00 0.05 0.00 0.11 2.7 2.9 0.01 0.07 56.6 55.9 50.8 0.92 Iron T-Fe 0.00 0.00 0.00 0.05 6.5 6.6 0.00 1.0 13.2 15.0 48.6 1.1 Zinc T-Zn 0.00 0.20 0.00 0.31 2.5 2.8 0.03 1.9 110 118 110 1.9 Sesults are expressad as kilograms per day except where indicated otherwise. ( I Less than detaction limit TABLE 4.7 CALCULATEiD LOADINGS, DECEMBER 1990 Britannia Jane 2200 Jane Jane Britannia Britannia Britannia Minera1 Britannia 4100 Furry Creek Creek Porta1 Creek Creek Creek Creek Creek Creek Creek Porta1 Creek 81 Jl 52 53 B2 83 B4 Ml B6 Estimated Flou L/B 560 56 13 69 69 661 730 1040 130 1770 '160 NA PB 1.02 7.49 3.49 3.99 3.97 6.97 5.41 5.72 7.93 6.42 4.24 8.36 Sulphate SO4 0.0 150 1651 2325 2331 583 2781 2705’ 144 2967 26680 NA Dissolved Hatals Copper D-CU 0.73 1.5 109 140 138 23 156 156 .D.lS 124 216 NA Iron D-Fe 0.00 0.00 44.1 57.9 50.4 20.3 10.8 11.5 1.0 1.0 108 NA Sodium D-Na 30.5 6.2 3.1 9.2 9.5 31.1 41.3 70.1 10.6 129 158 NA Zinc D-In 0.39 3.9 52.8 15.1 15.1 15.1 87.7 89.1 0.48 83.2 505 NA Total Hetals Copper T-CU 0.73 2.20 109 140 138 25.9 157 157 0.2 128 289 NA Iron -T-Fe O.OQ D-.20 41.0 62.6 54.4. 23.6 64.3 63.1. 1.3 32.4 129 -NA Zinc T-En 0.39 4.1 55.1 11.5 75.7 15.1 90.0 91.7 0.51 83.5 541' NA Results are expressed as kilograms per day except where indicated otherwise. < - Less than detection limit 166004 - Britannia Mine Site Page 4-33 TABLE 48 CALCULATED LOADINGS TO HOWE SOUND BRITANNIACREEK 4100 LEVEL TreatmentPlant Direct Discharge Discharge Total CopperLoading (kg/day) September 0.9 51 -- December 128 m- 289 Total Zinc Loading (lcg/day) September 1.9 110 SI December 84 s-s 541 Zinc loadingsto Howe Soundaxe significant, and appearto be higherthan m pmvioussuxveys. Copper loadingsto BritanniaCreek are less than historicalvalues (during operations) however are similar to, or slightly higher than, copperloadhqs in the early 1980s(Section 3.1.3). The mlativelyhigh concentrationsand loadings from the portai drainagesamples in the Decembersmvey a&x prolongedhigh precipitationindicates there is a significantstore of dissolvedor solubleoxidation productsin the undergroundworkings. A high precipitationevent tends to flush amaswhich nonnally remain“dry” andstore oxidation products. It would be expectedthat the initial drainage conta%&higher colons thanthis sampling,,@er approximatelytwo monthsof high precipitation.At a Conservative estimatethërefore, the combmeddrainage from Britannia Cmek and the 4100 level contributedover 24 tonnes of copperto Howe Sound during the two month period p&xding the sampling. The stored oxidationproducts would tend to provide a “slug” of umu&nants in runoff and drainageimmediately following precipitationperiods. Metal precipitateformation was evidentalong Jane and BritauniaCreeks and drainage channels frorn the pottals. Iron stainingwas evident along the Upperreaches of BritanniaCreek to approximatelystation B4. As shownin Photograph4.8 at stationB3, therewas appamntlypoor mixing of the two stmams,and the &aracteristi~~orange-yellow pnxipitate was evident along the banks but a white precipitate,possibly sulphatesalts, dominatedin the centre of the stream. Thesemetal oxide and hydroxideprecipitates representa store of potentially mobile ptoductswhich could be flushed during high flow periods,or leachedwith acidic flow ami reportedas a “slug” of elevateddissolved or total metal contamination. SteffemRobeswn and ICMen 166004 - Britxmnia Mme Site Page 4-34 Three “othei’ sourcesof drainagecontributing to BritanniaCxeek were identitïedfrom the hydrological balance. Based on the chemical mass loading calculatedfor the Creek, apptoximatemetal ami concentrationswere calculatedfor eachof thesedrainage sources. SourceSl (see Section4.4.3) was the most contaminatedsource contributing 101 L/s of flow with dissolvedmetal loadings of 22 kg/dayCu, 20.3 kg/dayFe, 14.7kg/day Zn, and583 kg/daySOds (2.1 kg/d Cu, 4.9 kg/d Fe, 2.4 kg,/dZn and 78 kgfd SOhsin the Septembersampling despite no apparentincrease in flow). Theseincreases in loadingwere notedbetween Bl and B2, upstreamof the confluenceof Jane Cmek with BritanniaCmek. Possiblesources of contaminantsat this level include: . drainagefrom the wasterock materialamund the old cote shackand powerhouse; . wasterock dumpson which thesefacilities were constructed; . seepagefrom the 2200 level portai or abovedinxtly into BritanniaCreek, or throughthe wasteat the 2200 level into the Cmelr; e acid generationbelow the 2200 level site and aboveor within the debrisaccumulated at Tunnel Dam. The flow rate and concentrationsat this site were estimatedfrom sitesB3 and 52. SourceS2 appeamdto be “fmsh” water ami did not conttibutecomammams to the Creek. SolutionpH valueshxxeased slightly fiom StationB3 abovethe sourceto B4 below the source,and sulphatedecnxsed awy* SourceS3 did not appearto be severelycontamhnued ahhough sulphate loading incmased slightly from B4 to B6. SolutionpH incmasedfrom 5.7 to 6.4 and dissolvedCu and Fe loadingsd ecreased slightly, possiblydue to precipitationof metalsat more alkalinepH values. Sulphatewas howevercontributed fiom this source;approxhnately 120 kg/d (23 kg/d). Steffen Robertsonand Kirsten Photograph4.8 Britannia Creek Phatograph4.9 Tunnel Dam above SamplingStation B3 Station B2, B3 and 53 166004- BritamiaMine Site Page5-l 5.0 ENVIRONMENTAL CONSIDERATIONS 5.1 Phgsical/Geotechnical Cumzntand future physicalimpacts at the BtitanniaMine will occur primarily in the JaneBasin. These Will con& of subsidenceof the ama abovethe undergroundworkings, failums on the pit walls, and ravellingof the wastedumps. A glory hole is presentin the bottomof me Fairviewpit andthe areabelow the EastBluff pit is the zonewhem most of the undergroundmining was conducted,therefoxe cominued subsidenceis likely in theseamas, eqxiaJly as undergroundtimbers continue to rot. A scatpappears to be pmsentabove the Janepit indicatingtbe possibilityof ongoing subsidencein this area. This should be verifkd by a groundtraverse. The limits of subsidenceto datecannot be accummlyestimated because only high level airphotoshave beenexamined. Portionsof the pit walls axestill actively erodingand becausesubsidence is continuingit’is Jikely that theseareas will not stabilizewithin the next decade. Txeesare not likely to establishon theseslopes becauseof the lack of soil and activeslope ravelling. Vegetationis beginningto establishon the waste dumpsand shouldhelp to teducefuture erosion. Otherareas whete physical impacts may occur aretbe wastedump at the 2200 level portai andthe roads intheJaneBasin. Erosionofthewastedumpmayoccurasaresultofafloodeventorchangeintbe cmek channelof BritanniaCreek. Any erodedmaterial would be depositedfurther downstmam.Some of the roadsin the pit area are eroding as the fill ravels and the ditchesbecome blocked. This is a relativelyminor impactrelative to the othersdescribed above. 53 Dr&age Water 5.2.l Sourcesof Water Entry ‘lb majority of the slow into the Britanniaunderground workings is believedto dischargeat the 4150 port& Smalleramounts of mine waterare known to flow from at leastthree other portais (namely, 2200 level, 2700 level and at leastone within the Futry Cmekdrainage). A detailedrecord of flow measmements has beenmaimahxd of the mine drainageemerging fiom the 4150 portaL The data reveala long-u& averageflow rate of about 130 L/s. Only spot measumments or visual estimatesare availablefor assessingthe dischargesfrom the other threeportais. Basedon tbis sparsedata set, the combinedflow from the thme portaisprobably amountsto somethingless than 10 pemnt of the dischargefiom the 4150 portaL Stefh Robexrsonand Kirsten 166004 - Britamia Mine Site Page S-2 The prhnarysource of waterentry to the undergroundwokings is consideredto be the ateaknown asJane Basin, The effectsof surfaceand undergroundworkings in this generalaxea have combined to produce conditionsthat maximizeinfiltration to the underground.The bottomof the openpits in JaneBasin may be suffïcientlypermeable that ail nmoff flowing into the openpits subsequentlyseeps to the underground workings. Indimt evidencefor the abovewas found by compatingthe estimatedrunoff into the openpits with the measuredflows out of the 4150 portal. The total catchmentarea commanded by the openpits is about 1.2 km2. For this size area,the meanannual nmoff wasestimated to lie within the range130 to 170 L/s, or valuesvery similar to the measuredmine drainageflow. As shownon FQure4.1 this compaxisonis also valid on a monthly basis. 533 Sourcesof Loading The major sourcesof comaminamloading to BritatmiaCmek were identifïed by reviewof historicaldata, discussionwith thosefamiliar with the area,observation of the site and metal stainingalong active ami dry creek beds and seeps,and two site samplingsurveys. These sourcesate discussedin detail in Sections3.1 (historical)and 4.3 (curmnt). Drainagethmugh the open pits, exposedsurface workings, underground workings ami water coursesis contaminatedwith acidity and metalsfmm thme major sources: 0 oxidationproducts generated by contimdngacid generationand metal leactig teactions; ii) fhshing of storedoxidation pnxiucts; iii) fhtshingami dissolutionof saltswhich pmcipitated,as a resultof dilution/neutralizationmactions along the drainagepadx The relativecontribution of eachis diflïcult to quanti@with the existingdata however. 0 it would appearthat the rate or extentof oxidationhas decreased since the mine was operational by mducedconcentrations in the portai drainage. This is probablydue bath to a reductionof disturbedareas which reducesexposed ftesh minerai surfacesfor oxidation,and, a reductionin fine particles which would contribute to elevatedtotal metal levels during operation. The consumptionof availablesulphides, and therefore long-tenn potential for contaminantgeneration cannotbe predictedfrom availabledata; Steffen Robertsonand Kirsten 166004 - Britaunia Mi Site Page 5-3 ii) thereis a considerablestore of oxidixedproducts within the undergroundworkings based on the elevatedconcentrations and loading after an extendedprecipitation period (fall of 1990); iii) bon andcopper pmcipitates wem evidentalong both Janeand BritanniaCreeks, but not Mineral Creekin the areaof the road crossin~ iv) pmeipitationof metal oxides and hydroxidesalong drainageflowpaths could serveto coat the flowpath andlimit flushhrgof potentiallyoxidixing areas. Suchprecipitation was evidentalong the 2200 portal dminagechannel. The major sourcesof metal and acidity loading fîom the mine workingswhich were identifïed in this smveyinclude: 0 Extensivelyacidixed open pit and glory hole walls which drain primarily into the underground workings; ii) 2200 poltal drainage iii) 4100 portal dminage. Suspectedor potentialsources of contaminateddrainage from the mine woricingswhich wemnot sampled or not connibutingsignifmam loadings during thesesampling periods include: 0 drainagefrom the 2700 portai into Minerai Crue~ ii) drainagefmmthe1800portalintotheFurryCreekdrainagebasin. Somm of loadingfrom-the wasteswhich were not specifïcallyidentiged from seeps,but appeamdto contributecontaminants curmntly or historicall~ 0 wastedumps at the East Bluff pit ama. Wastein the miU area(Beach level) may be generating coxuamhantsbut would probablydrain dimctly by gmundwaterflow into Howe Soundand not be apparentin samplingof Britannia Cre& ii) mine wasteat the 2200 level includingrock, timbemand structural material at the 2200’ level on which the old powerbouse,tore shackand road am located; Steffen Robertsonand Kimen 166004 - Britannia Mine Site Page S-4 iii) landslideswete not specificallyidentified ami major seepswere not evidentfmm areasof slide debrisin this ptogram. Historicalrecords however suggest that at one time surfacedrainage from the JaneBasin amacontained contaminants fmm the slide debris. Potentialsources of contaminantsftom facilitiesand wastes have been identifled from a reviewof the site, and understandingof geochemistry.These sites axe classified as “potential”as they were either not: 0 contributingdrainage to BritanniaCmek at the time of the study,or werebeyond the scopeof this investigation,i.e. werenot in the BritanniaCreek watershed, or ii) contribtig to Howe Sounddirectly or requhingdetailed hydmgeological investigations. Theseamas should be addressedif further investigationsare conductedat the Btitia site, and include. 0 settling pondsand facilities at the former water treaunentplant at the 2100 level. It would be expectedthat drainagefmm this area would dischargeinto the Cmek near site B4. From the resultsof the massloading calculations for the Cmek,it did not appearto contributecontan&ants fxom sutfaceor subsurfacenmoff at the time of sampling ii) settbg pond at the Beachlevel tmatmentplant; iii) pond at the 4150 level which was appamntlyan emergencystorage or tailhqs pond, receivmg contributionsfiom the mill and the 2200 level cementationplant Surfacewater front the pond would decantinto the tmatmentplant; iv) tailings depositionon the lxach near the mouth of &hannia Cmek (uncontlmmd); VI portaldrainagetotheFurryCreekdminagebasin. Steffen Robertsonand Kirsten 166004-BrimmiaMileSite Page 64 6.0 REMEDIATION OPTIONS There are tbreeappmches to the comrol of acid rock drainage: 0 control of acid generationxeactions; ii) contxolof migrationof comaminantq iii) collectionand treatmentof acid drainage, Control of acid generationmactions is the most desirableapproachz preventing the onsetof rapid acid generationby early identificationand contml of potentially acid genemtingmaterials. Oncethe acid generationneactions are established.me approachmust be to contml the movementof the oxidation productsand minimizethe dischargeof theseproducts to the receivingenvironment. In somecases this caribe accomplishedby the useof coversand seals, and diversion of surfaceami gmundwaterto minimize the movementof thesecontamhrants. Altematively, for somesites the most practicalalternative is to wllect the contamWed drainagefor tmatmentprior to discharge. Thesethme approachesare not exclusivehowever, and a combiion of thesemeasures is generallythe mosteffective and ewnomically acceptablesohuion. The data wntained within this review of the Britanniasite indicatethat rapid acid generationhas been establishedboth on surfaceand within the undergroundworkhqs thtoughoutthe site. Controlof further acid generationmay be feasiblein someamas, however them appears to be a significantstore of oxidation products. The approachto remediationof the site is thereforeseen to be a combinationof the latter two approaches.Where possible, the migrationof contaminantswould be limited by wntrolling the flushing ami infiltration of surfacewater by wvers or surfaceand groundwater diversions. It is mcognizedthat there is a significantstore of oxidationpxoducta comamed witbin the surfacewaste and the surfaceand undergroundworkings,andthatintheshorttennatleastsomeformoftreatmentmaybe~dto pmducewater quality suitablefor discharge. If physicalwntrol measumsare adoptedfor control of surfacewater, treatment may alsobe requimddut@ wnstmction and hnplementationof thesemeasures. Any surfacedisturbance in areasof oxidationor d&urbed materialmay msult in the mleaseof both total and dissolvedmetal values, deleterious to water quality. The possibleappxoaches to wntrol and remediationof the Britannia site are describedin the following sectionsand summarizedin Table 6.1. This table provides a generaldiscussion of the approach, advantagesami disadvantages and relative wsts of eachremediation option wnsideredindependently. It is recommendedhowever that a wmbination of control measuresis considexedfor the Britatmiasite, as describedin Section6.0. Steffen Robeatwnad Kirsta TABLE 6.1 PROPOSED REMEDIATION OPTIONS FOR BRITANNIA MINE l lower available dilution l Ilmit furthcz acid generation l fhuhing of storcd poducts l net positive water balsnce l locate openings to surfa& therefore discharge ultimately l grotmd conditions i . identify specitïc sounxs of l fboding with alkaline l complexation and pecipitation l qttantity of alkali reqttired l extent of underground of stored oxidation products l potential for subsequent l liitation of futther acid remobilixation of precipitate l provide storage of acid drainage plior to treatmmt plant l reduce infiltration and l locations and stored volumes in migration of contaminane wsste dumps not known l lowa volume of water to be l accessto dumps (location and l cost - depending on location store wastes below l materials handlin Remediation * Advantares Diiadvantaees Further Studies II 4. Taihngs l installation of covers l reduce flushing and migration l availability of caver materials and diversion of surface of conmminams water l removal to tmderwater l remove possible source of l release of stored pmdtu4s l altemate disposai amas storage elther in Howe contaminants l cleanup required of c-turent l volume of material Sound or in l imptove physical stability in storage area l potential for water caver underground workings emagency pond area l locedng appropriate storage l predictions of tailings location deposition patterns for submarine disposai 5. Draiuage Water l reduction in total volume to be l constmction and maintenauceof (overview for site treated divasim ditches (slope specific instability), leakage discussion!isee l considerableprecipitation occurs Section 6.2) as snow - mping witlt snow pack l limitations of topography l centralization of comaminated l construction and maintenauce drainage l identificadon of sources l pumping and piping requirements l prevention of diiarge to l identification all surface B&annir and Mineral Creeks openings and intetnal diversions l potential physical instability of underm-ound workines l collection sud l conttol of discharge water l long term maintenance and treelment ww operation requirements and costs l removal of contaminants l sludge stabihty l sludge disposal l collection system and upstream surge control * each of these remediation options is evaluated iraîependently. It is recommendedthat a combiition of measuresmay ptove most effective, as described kt Section 6.0. At this tinte it appeau that the shaded items should be pursued in the near future. 166004 - Britamia Mine Site Page 6-4 6.1 Water Management- Diversion 6.1.1 Pits Them are hvo optionsfor mducingwater flow over the pit surfaceix 0 diversionof nmoff aroundthe pits, and, ii) placingcovers to pmmoterunoff and xeduceflushing of pit walls f?omdirect precipitation. There t is potemialfor divextingnmoff aroundthe eastside of the EastBluff pit andaround the westside of the EastBluff and Janepits. Reducinginfiltration to the pits throughthe useof coversis not recommendedbecause ongoing subsidence would destxoythe integrltyof the covers.Fmthermore, the topographysud pmsenceof glory holeswould makeany caver very difficult to place. Location of potential diversionditches and msultantcatchments are shown on Hgme 6.1 and cari be companxi to the curmnt catchmentareas shown in Figure 4.3. These diversionscould reducethe catchmentwhich drainsinto the undergroundmine fiom 12 km2by a maximumof 0.15 ami 0.55 km2, respecdvely.Factors such as the feasibility of ditch locationand seepageunder the ditchesthmugh talus will reducethe efficiencyof the ditches. On the eastside diversion a cost savingsin ditch constructioncari be achievedby upgradingthe madsso that the upstreamedge becornes the diversion dit&, howeverthe diverted area would be only about 50 percentof that areadiverted if a ditch was locatednear the pit crest. It is difficult to determinethe bestlocation for a diversionon the west sideof the EastBhrffpit becausethe availabletopographie maps are not sufficiently accumteand the distribution of talus, mine waste, and slide debris influencethe practicalityof ditch location. It may be necessaryto constructlined ditchesto preventlosses into talus and subsidencecracks. The Empresspit lies in the Fmry Creekwatershed and is not part of the scopeof work for this project. As noted in Section4.2.1, the Empresspit may be hydraulicallyconnected to the undergroundmine. 6.13 Underground Workings There are hvo options for limiting the flow of water through the undergroundworkings. The options include: 0 divert runoff fiom the points of entry, and; Steffen Robertsonand Kirsten CATCHMENT BOUNDARY FOR AREA COMMAI’JXD ;~T~~;?SION 6.1 STEFFEN ROBERTSON 8 KIRSTEN, Constilting Engineerr _- __.___.-_- 166004 - Britannia Mine Site Page 6-6 ii) flood the undergroundworkings to the upper most levels. Diverting runoff from the points of entry, as discussedin Section6.1.1 will be limited becauseof the pit areacatchment. Divexting runoff fmm around the pits, as desctibedabove, could mduceinflows by approximately50 percent. Reducingthe flushingof contaminantscari be achievedby flooding the undergroundworkings. It should be recognized,however that there could lx in the short tenu, au initial slug of loading frorn pmviously unftushedareas. Rroposed locations for bulkheadsate shownin Figure6.2. Detailsof preliminaiydesign of bulkheadtequirements for flooding are ptesentedin AppendixA. A modificationof the flooding option that has beenimplemented at the abandonedBethEnergy Mine in WestVirginia, U.S.A.,incorporates alkahne additives to the flooding water(House and Willison, 1986). The undergroundworkings wem sealedand flooded with alkaline water, and apatite (phosphate)was dustedon the surfacesunderground which would not be flooded. Alkahnity wasadded as lime andcaustic soda(NaOH). Prier to this flooding, contamMed drainagewas collectedand tteatedat an annualcost ($1985) of $480,000. At the lime, the pmsentvalue of this cost on a projected40 year treatment requinment was $4.7 million (10 percentdiscount rate). The cost of flooding was $1.3 million. It has not beenpossible to obtain any further informationto date,however the paperreports that: . withh~four momhsof beghmingflooding (1984) dischargepH increasedfmm 3.9 to 7.0 and remainsat 7.0 (1986) . itondecmasedfrom133ppmtoflppm. . alkahnityhasincmasedf’kmOto350mg/Landacidityd ecreasedfiom 470 to 20 mg/L. . at an annualflow of 512 x ld gallons(US.) per year, an equivalentflow of four teplacement volumesof water haverun thmugh the mine wotlkigs sinceflwding, and no addhionalsurface water tnxtment hasbeen requimd. This approachmay havemerit at Brhanniahowever would xequhecamful consideration of the natureand amountof storedptoducts, and the requiredtype and amountof alkali for metal removal(notably zinc). Steffen Robertsonand Kirsten - Topography is projected onto section Topogrcphy is proje LEGEND - Levels 13 Recommended Bulkheo’ Locat;ons 7 Wottr Table - Topography SECTION LOOKING NORTH v .Appro.Kifnotecurrent aoter k?vel 0 L I Notes: Figure is derived n / ç r- -- from Copper Beach Estates Section is a simplified Homestake projection of the mine .ivork;ngs I Ministiy of Energy. Mines ond Petroleum BRITANNIA MINES PROPOSED BULKHEAD LOCATIONS - 6 2 STEFFEN ROBERTSON b KIRSTEN, COnSUltlnQ hQ:tWWS 166004 - BritamCa Mine Site Page 6-8 6.13 Waste Dumps There are three options for reducinginfiltration into the waste dumps;diversion ditches, covers, and removalfor disposaleither underwateror within anothercatchment such as the pits. The thxeeareas of concemare: the main wastedumps adjacent to the EastBluff pit, the wasteat the 2200level portai, and the wastein the miU area. In the caseof the wastedumps adjacent to the pits thereare two generalapproaches for remedi$on, The flrst is to leavethe wastein placeand reduce the infiltration with diversionditches and a caver. This may not be suffïcientto reduceenvironmental impact to acceptablelevels and somefonn of collection and treatmentmay be xequired. Basedon a plan axeaof 38,000m’, a caver 1 m thick, and allowing for recontomingof up to 10,000m3 of waste,the cost of constructinga caver would be in the order of $1.2 million (Assumingcosts similar to Mt. Washingtonat (K. Ferguson,review comments, 1990) $30/m3 for importedand compactedfill, and $2/m3for nzcontotig). The other option is to xemoveand disposethe wastein the pits. It is not likeli that much of the waste could be dumpedso that it would be below the flood elevationin the undergroundand workings and consequentlythe wastewould continueto generateARD. The benefit of this approachis that the total volumeof waterto be treatedcould be decreased.A concemis that rehandlingwïll pmmoteflushing of ARD productstim the wasteand may also createnew acid generatingsurfaces, both of which would result in incxease+Iloadings to the heatmentfa&@. The cost of this appmach,based on a total of 700,OOO’tonnesand a unit costof $2/tonne,the total costwould be in the orderof $1,400,000.Additional data and a cost benefit analysisis necessaryto determinethe best option for xemediationof this waste dump. The characterand quant@of wastestoxed and usedfor 5Il and constructionat the 2200level cannotbe detenninedfmm smfaceobservation, consequently, it is diffïcult to identify suitableremediation options. However, given that this waste is not located near to a site where underwaterdisposai could be hnplemented,it appearsthat someform of drainagewater diversionand caver will be rhe most cost effectivesolution. protectionagainst future erosionby BrltanniaCreek is a concem.Fmther information will lx requhd to quantify ami cost remediationfor this source. Wastewhich hasbeen dumped at the 4100 level nearthe mill has a suifaceslope at or near the angleof reposewhich would make placementof a wver very difficult. This materlalis not locatednear to a suitableunderwater disposal site, exceptfor Howe Sound which is not xewmmendedbecause of the short-tennpotential for releasingstored ARD pxuductsin waste. Funher data are requiredto identify potentialremediation options. Skffen Robertsonand Kksten 166004 - Britannia Mine Site Page 6-9 6.i.4 Taiiings Optionsfor reducingcontaminated drainage from the tailings pond includereduction of in.tïltrationinto the tailings throughdiversions or covers,or temovalof the tailings. The following discussionrefers to the pond near the mill, and doesnot include other amasof possiblehistoric tailings deposition,such as along the shorelineof Howe Sound. Constructionof diversionditches around the pond area,in conjunctionwith placing a syntheticcaver, could signifrcantlyreduce the infiltration, possibly by as much as 90 percent.. A syntheticcaver is pmbablyless expensive to placeover the tailingsthan a soit caverbecause of the soft natureof the tailing material,additionally a syntheticcaver would be more effectiveat reducinginfïltration. A 40 mil low densitypolyethylene (LDPE) caver over the pond would costapproximately $7,000, installed. Allowance for regularreplacement of the caver would be xequired.The existingtailings pond could be upgradedto ensurethat a permanentwater caver is maintained. The natureof the existingembankment containing the tailings is not known so it is diffïcult to estimatecosts for xehabiitationof the structure. This approachcould effectively limit the formation of ARD pmducts fiom the tailings, however, further treatmentof the drainagewater might be quired to removeARD productsflushed out of the tailings. Optionsfor disposaiof the tailingsinclude underwater disposal in HoweSound, where most of the tailings wen placedduring operationor placementunderground in the mine. Placementof the tailings in Howe Soundis not recommendedbecause this would liberatethe accumulatedARD pmductsin the taïlings. Removaland placement underground would probablyrequire taking the materialinto the 2200 level. The cost of this approachcould be in the order of $lO/tonneor $80,000because either specialtrucks would be requimdto enterthe mine, or doublehandnng would be requind. Underwaterdisposal in the mine would limit furtherARD, howevertemporary increases in metalloadings to the tmatmentplant may occur due to flushixigof storedptoducts. 6.15 Roads At this tinte it is assumedthat acid generationfrom the toadsis not a problemand that measuresto divert water ftom the toadsare not requited. 6.2 Drainage Collection Systems 63.1 Pits Options for implementingdminage collection for the pits in Jane Basin are hmited to allowing the drainageto exit via the undergroundmine becauseof the limits of topographyand the presenceof the Steffen Robertson and Kirsten 166004 - Britannia Mine Site Page 6-10 glory holes. Drainagefmm the Empxesspit could be monitored and if acceptablereleased to the environmentor otherwisepumped up to the No. 5 pit whereit would flow into the undergroundmine. 63.2 Underground Mine The geometryof the undergroundmine is well suitedfor drainagecollection and routingto the 4100level portai, as is the currentpractice. Drainagefrom the 2200 level mustbe effectivelydiverted back irito the undergroundworkings or, if requin& this drainagecould be pipeddown BritanniaCreek to the treatment plant. Seasonalvariations in metalloading and drainagevolume will needto be reducedin orderto effectively run the treatmentplant Sometype of flow pond must be considered.The two optionsfor this are to constructa retention pond in the vicinity of the outfall, or to use the stomgecapacity within the undergroundworkings. It is estimatedthat up to 0.4 x 106cubic meters of storagewould be requiredfor an averageprecipitation year. The geometryof the site is not suitablefor a retentionpond of this size. TO usethe underground workingsas a retentionpond would require: i) effectiveblocking of any portaiswithin the zoneof water storage and fluctuation; ii) control of water volumes exiting the mine at the 4150 level. If the undergroundworkings were flooded, these structures would be requiredat all the mine porta.&.Flooding the minewould havethe advantageof reducingthe formationof ARD products,but it mayresult in higher initial ARD loadingto the tmatmentplant It is possiblethat undergroundstorage of watermay accelerate subsidenceof that portion of the mine which is in the zoneof the fluctuatingwater level. If rtxphed, drainagefiom the 2200 level portal amacould be either piped down BritanniaCxeek to the treatmentplant, or pumpedmto the mine at the 2200 1eveL This may requirea high pressurepump if the mine is flooded. A pipe along BritanniaCmek would drain by gravity and would avoidthe needfor a power supply. 6.23 Waste Dumps 1 Optionsfor collectionof wastedump drainage,assuming that the wasteis not relocated,is limited to providing a collectionpond downhill of the variouswaste dumps. Someof the drainagefrom the waste adjacentto the East Bluff pit may be dmining into the undergroundmine. Drainagefrom the dumps which is collectedcould be monitoredand if acceptabledischarged to the environmentor routedto the tmatmentplant Drainagefrom the JaneBasin waste dumps would be mosteasily routed to the tmatment plant, if mquired,with a pump systemto raisethe water to whereit could drain into the underground mine. It may be diicult to providepower to this locationto run the pumps. Steffen Robertsonand Kirsten 166004 - Britannia Mine Site Page 6-11 Drainagefrom the 4100 level mill areawaste could be collectedin ditchesand pumpeddirectly to the treatmentplant 6.2.4 Tailings Collectionof drainagefmm the tailingspond would be mosteasily conducted with a ditch excavatednear the toe of the embankment.The drainagecould be then piped to the treatmentplant. 6.25 Roads It is assumedthat the roadsin BritanniaCreek are not sourcesof ARD and that collectionof drainageis not mquired. 63 Treatment 63.1 General In developinga treatmentstrategy for an acid mine drainagesituation, a logical sequenceof activitiesis followed. Theseactivities are listed to provide an overviewof the approachadopted in this study. . identify maximumand averageflows . characterizefeed as well as possible . Selectthe probableoptimum processing concepts . test proposedconcepts at lab scale . developconceptual designs based on lab data . completethe detailedengineering for best concept . build the plant 63.2 FIows Fiow data for the period 1983to 1990 at the 4100 portal was analyzedto generatebistorical maximum and averagedesign flows. Theseresults, presented in Section6.6, were in tum usedto generatecapital and operatingcosts pmsented in Sections6.9.4 and 6.95. The designflow assumesthat diversionof surfacewater abovethe pits will mducepeak flows and that the pluggingof the portais and vent mises usingconcrete bulkheads will equalizehydraulic loading. The maximumdesign flowrate used to sizethe equipmentwas 690 m3/hwhile the meandesign flow usedfor operatingcost estimateswas 635 m3/h. Steffen Robertsonand Kimten 166004 - Britannia Mine Site Page 6-12 6.33 Raw Water Characteristics The chemicalcharacteristics of the potential feed to a treatmentplant were detenninedby galyzing samplescollected from the 4100 and2200 poxtals on November28 and December6,199O. The chemical characteristicsof the two sample-sare provided in Tables6.2 and 6.3. Thesetwo sampleswere used for the initial benchtests presented in this report. The 2200 portal samplehad considerablyhigher acidity ami dissolvedmetals than the 4100 portal sample. Both samplescontained elevated levels of dissolved copper,zinc, iron and aluminum. In addition, a samplefrom the 4100 poxtal was collectedon March 13, 1991 to conductthe prucess simulationwork. The resultsfrom this sample,which indicatea lower acidity than the November28, 1990sample, are providedalong with the test resultsin Table 6.7. 63.4 ProcessTestwork Description A seriesof benchtests has been conducted to screenalternative processes. The purposeof this work was to provide a basis for assessmentof the relative technicaland economicfeasibility of each. Process selectionwill ultimately involve trade-offsbetween costs, effluent quality and alternativesfor upstream mitigation. Testworkwas initially conductedon samplesfrom both the 4100 and 2200portals due to the markeddifference in their chemicalcharacteristics and uncertainty regarding future blending ratios for the drainages.The final test serieswas conductedon an additionalsample fmm the 4100 level sinceaccess to the 2200 level was difficult, and the contributionof the 2200 level solution appeaxsto be minor. In addition,the 2200 solutionwill likely be redixectedto the 4100 level within the mine prior to the onset of treatment,SO that its chemicalcharacteristk wilI be kdifkd in any case. The following processeswere evaluatedon a labratory amenabiitylevel: 1) Lime Pnxipitation 2) SodaAsh Precipitation 3) SulphidePrecipitation 4) Lime and SodaAsh Addition 5) Ion Exchange 6) SeawaterDilution 7) LimestoneTreatment The nmlts are reportedin the following sectionstogether with descxiptionsof the processesthat were considered,and our evaluation. Test detailsare providedin AppendixC. Steffen Robextsonand Kirsten Table 6.2 Raw Water Characteristics - Physical Test, Anions and Nutrients 2200 Porta1 4100 Porta! Date of Collection Dec 6/90 Nov 28/90 Physical Tests ITotal Dissolved Solids 1170 2480 1 Hardness CaC03 610 979 PH Units 3.49 3.51 Total Suspended Solids 21 26 Conductivitv umhoslcm 37Rrl Dissolved Anions Acidity CaC03 764 343 Alkalinity CaC03 Cl <1 Chloride CI CO.5 CO.5 Fluoride F 0.85 1.52 Sulphate SO4 1470 1850 Nutrients Ammonia Nitrogen N 0.14 0.043 Nitrate Nitrogen N CO.005 CO.005 Nitrite Bitrogen N KO.001 co.oo1 Total Phosohorous P 0.038 0.017 Results expressed as mg/L except where noted < = less than Table 6.3 Raw Water Characteristics - Metals 2200 Porta1 4100 Porta1 Date of Collection Dec 6190 Nov 28/90 Total Dissolved Total Dissolved Aluminum Al 61.8 35.3 33.3 Antimony Sb <0.0001 CO.2 <0.2 Arsenic As 0.0011 <0.2 -CO.2 Barium Ba 0.012 0.012 Berytlium Be <0.005 All results expressed as mg& < = less than 166004 - Britannia Mine Site Page 6-15 6.3.4.1 Lime Neutralization The conventionaltmatment plant for acidicdrainage is basedon neutralizationand precipitation to mmove acidity andheavy metals tiom solutior~Lime is addedto misethe effluentto a pH whexethe heavymetal hydtoxidesare sufficientlyinsoluble to ptoducea dischargeableeffluent. The systemwould consistof a milk of lime mixing systemto which hydratedlime (calciumhydroxide) ami water would be addedto make a 15-20weight percentslurry. Lime sluny would be dosedfrom a ring main to the acidic feed in one or more stirred tanksunder pH control. At the appropriatepH, the metalswould precipitate. The precipitatewould need to be removedin a settling devicewhich could rangefrom a simple sludgepond to a fairly sophisticalédthickener and/or filter. Iron removalwould dependin part on the successof iron oxidationin the lime mactor,which would be achievedby means of an air sparge. It is likely that use of an organicflocculant chemical would be specifiedas well, to assistin the settling of the precipitates.The flocculant systemwould requim a mixing tank and a stock tank, togetherwith a metexingpump and ptediIutionsystem to makeme appropriateadditions. The NaOH basedneutralixation cmves are provided in Figures 6.3 and 6.4 for the two samples. Equivalent curvesbased on quicklime are provided in Figures 6.5 and 6.6. These latter plots are calculatedbased on the equivalentbasicity of 1.43 for causticsoda compared to high calciumquicklime (CaO) at a basicity of 1.0. Reagentconsumption is expmssedas kg/1000 m3 which is numerically identicalto concentrationexpressed as ma. Lime consumption(CaO) to pH 7.0 wasapproximately 410 and 150 kg/1000m3 for the 2200 and 4100 portai drainagesmspectively. Ca0 consumptionto pH 9.5 increasedto 490 and 220 kg/1000m3 for the 2200 and 4100 portai drainagesmspectively. The resultsof the lime ptecipitationtests on the two portal drainagesare pmsentedin Table 6.4; .The testworkbas indicatedthat a lime dosageof 227 kg Ca&X) m3 was mquimdto reducethe soluble metalsto acceptableconcentrations, based on the samplefrom the 4100 portal collectedin November, 1990,while the equivalentlime dosagefor the 2200 portai was 643 kg CaO/lOOOm3. 6.X4.2 Iron/Alum Coagulation In the lime process,removal of the metal hydroxidesin the settling device might not be sufflciently effective owing to the gelatirmusand colloidal nature of hydroxideprecipitates, and the low levels at which they would be present. Settlingof the pxecipitatedsolids could be enhancedby the additionof a coagulantsuch as ferrlc or aluminumsulphate. Iran or al~inum havethe additionalcapability of Steffen Robextsonand Kirsten Table 6.4 Lime Precipitation Test Results I Location 2200 Porta1 4100 Porta1 Dec 6190 Nov 28190 0 700 850 1000 0 200 300 500 0 530 643 757 0 151 227 378 2.92 6.6 8.7 10.09 3.51 7.13 8.57 9.9 Dissolved Dissolved Metals Metals Aluminum Al 61.8 CO.2 0.49 1.47 33.3 CO.2 <0.2 0.87 Antimony Sb :0.001 X0.2 <0.2 CO.2 CO.2 CO.2 CO.2 <0.2 Arsenic As 3.0011 <0.2 CO.2 CO.2 CO.2 <0.2 CO.2 CO.2 Barium Ba CO.1 CO.1 CO.1 0.012 CO.01 CO.01 CO.01 Beryllium Be CO.005 <0.005 CO.005 CO.005 CO.005 <0.005 a.005 Bismuth Bi 0.173 Ail results expressed as mg/L <=lessthan Neutralization of 2200 Porta1 Drainage Sodium Hydroxide Dec 6190 Sample . PH 12 I I I 400 600 800 1000 kg NaOH/lOOOm3 Figure 6.3 Neutralization of 4100 Porta1 Drainage Sodium Hydroxide Nov 28/90 Sample 200 300 kg NaOH/lOOOm3 Figure 6.4 Neutralization of 2200 Porta1 Drainage High Calcium Quicklime Equivalent Dec 6/90 Sample PH 12 7 a 6 0 100 200 300 400 500 600 kg CaOAOOOm3 Figure 6.5 Neutralization of 4100 Porta1 Drainage High Calcium Quicklime Equivalent Nov 26190 Sample PH 12 ! a 6 I I I I I 2- I 0 50 100 150 200 250 300 350 kg CaO/iOOOm3 Figure 6.6 166404 - Britannia Mine Site Page 6-19 coprecipitatinga wide rangeof ions. T~US,tbeir use would both imptove settling and xeducethe total dissolvedsolids by adsorbing/coprccipitatingadditional quantities of undesirableions. The processmodifications mquired to use tbesemagents would consistof a mixing and a stock tank, togetherwith a meteringpump to add the reagentsolution to the lime reactor. The reagentsconsume somelime as part of their lïmction, so additionallime capabilitymight be required. Bath iron and alum arc presentin tbe feed to the precipitationprocess (Table 6.3) and constitutea signifïcantportion of me metalloading. Consequently,it wasnot felt necessaryto augmentthe quantities naturallypresent, SO that this variant of the lime precipitationprocess is alreadyreflected in the current ttXtW0l-k. 63.43 Soda Ash Sodaash cari be usedfor neutralixationand precipitationas an alternativeto lime. This processrelies on the pxecipitationof metals as both hydroxidesand carbonates.Pmcipitation of zinc carbonateunder neutralpH conditionsis feasibleas an alternativeto tbe pH 9.0 to 9.5 conditionsrequired to removezinc as a hydroxide. Altematively,in a pmdominantlylime-based pmcess, tbe mquimdlime dosagewould be lower than that requimdto precipitatezinc as a hydmxideif carbonateaddition msults in the formation of insolublezinc carbonatesor basiczinc carbonatesunder neutral pH conditions.Potentially this process would allow completezinc removalwithout the aeedto increasepH to pmcipitatezinc hydroxide,themby minimizing total alkali consumption. The resultsfor sodaash addition are provided in Table6.5. For both feeds.the bigherdosage was capable of removingboth copperand zinc to acceptablelevels, while the lower dosagesleft residualdissolved zinc in solution. The nsults indicatethat the removalwas due to the precipitationof zinc under high pH conditionsas opposedto pmcipitationof zinc carbonate.The calculatedCa0 equivalentfor both samples indicatesthat partial sodaash substitution has a higher equivalentdosage than solely quicklime,perhaps dueto the lossof CO, duringneutralizatioa Neutralixationto pmcipitatemetals as their hydroxideswould not be attractiveusing sodaash alone due to its higher cost comparedto lime. However,soda ash may have an applicationto precipitatebasic cartx~~tes when usedin conjunctionwith lime. The resultsof experimentsusing a sequencedaddition of lime and sodaash are providedin Table 6.6. Comparativeresults with lime only are also includedin this table. Steffen Robertsonand Kirsten Table 6.5 Soda Ash Neutralization Tests 2200 Portai - 4100 Porta1 Soda Ash Dosage Na2C03 0 720 1056 0 320 546 0 381 559 0 169 289 2.92 7.76 9.15 3.51 8.07. 9.17 Dissolved Dissolved Metals Metals Aluminum Al ‘CO.2 <0.2 33.3 CO.2 <0.2 Antimony Sb CO.2 CO.2 CO.2 CO.2 <0.2 Arsenic As CO.2 CO.2 CO.2 CO.2 CO.2 Barium Ba CO.1 CO.1 0.012 All results expressed as mg/L c = less than Table 6.6 Lime Precipitation and Soda Ash Addition Tests 2200 Porta1 4100 Porta1 Lime Dosage . mg/L Ca(OH)2 0 700 700 0 200 200 300 300 500 Ca0 Equivalent ko/l OOOm3 0 530 530 0 151 151 227 227 378 (Soda Ash Dosage 1 mg/L Na2C03 t 0 40 0 20 0 80 0 Ca0 Equivalent 0 21 0 11 0 42 0 kg/1 OOOm3 Total Ca0 Equivalent *530 551 151 162 227 269 378 kg/1 OOOm3 DH 2.92 6.6 7.1 3.51 7.13 6.56 8.57 7.39 9.9 Dissolved Dissolved Metals Metals i~u~~liiiitii~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~““““:: . . :::::.:.:::...l’i’:.:.:.:.:.~..~:.~.:.:.~::.:.:.:.~.:..,._:.:::.::..:.:.:.:.:.!.:.:.:.:.:.:.~.:.:.:.:.:.~.:::::.:.~.:.:.:.~.:...... :...: ...... :..::.:.:...... 0.. . . ~~~~~‘t~ijiji~i~i~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~a~~. . . . .,...... :._.:.:.: ...... _ ...... ::..:..::. ..::.::::...... :., Antimony Sb For both samples,the additionof sodaash at?er lime dosingwas capableof reducingsoluble zinc to low levels under neutral pH conditions,whereas the comparativelime-only result reponed a measurable quant@ of zinc in solution. In the caseof the 4100 portal sample,the total equivalentlime dosage calculatedusing basicity factorswas less for the 2 reagentprocess than the requiredlime dosagewhen no other reagentwas added. 63.4.4 Additional Lime and Soda Ash Prkess Evaluation Results In order to confïrmthe screeningtest resultsfor the lhne and lime plus sodaash alternatives, a seriesof follow-up testswere conductedon a sampleof 4100 portal drainagecollected on March 13, 1991. The purposeof thesetests, reported in the Appendixas Experiments 9 and 10,was to simulatethe coagulation, flocculationand sedimentationaspects of the lime and lime plus sodaash alternatives. The resultsof thesetests, mported in Table 6.7, indicatethat the lime pxocesswas successfulat a lime dosageof 250 mg/L CaO,while the lhne plus sodaash combination was not as efficient in tennsof zinc removalat a lime dosageof 125mg/L and a sodaash dosage of 25 mg/L. Possibly,a higherdosage of either lime or soda ash would be requimd to improve the performanceof the lime ‘plus soda ash alternative. The data generatedduring thesetests were used to assemblethe operatingcost estimatesreported in Section6.6. Lie consumptionmsults from the testswem convertedto a lime to acidity ratio in order to estimatethe requireddosage at a higher acidity concentration. In the caseof the lime/sodaash combmation,the estimateddosages were increasedto 150 mgL Ca0 and 40 mg/L Na&O, in order to providea consexvativeestimate of the Ragentconsumption prior to calculatinga reagentdosage to acidity ratio. 63.45 Sulphide Precipitation In this process,a solutionof an inorganicor organicsulphide, or even a sluny of groundixon sulphide, could be addedto the effluent afkerneutralization. The sulphideions would reactwith the heavymetals presentto pxecipitatethe respectivesulphides. If iron sulphidewere added,the surfaceof the sulphide particleswould becomecoated with the heavymetal sulphides(especially copper) driven by the greater insolubiity of the respectivesulphides compared with that of h-onsulphide. The iron would corneinto solution,and might needto be oxidizedand precipitatedsubsequently. Stefkn Robertson and Kirsten Table 6.7 Lime and Soda Ash Treatment Process Simulation Test Results 4100 Porta1 Sample Collected March 13,1991 Raw Lime Lime & Soda Ash ILime Dosage 0 331 165 0 250 125 25 250 178 3.63 9.2 7.95 285 25.5 24 2520 2520 2540 Total Dissolved Total Dissolved Total Dissolved Aluminum Al 32.3 27.9 0.72 0.6 CO.2 CO.2 Antimony Sb <0.2 CO.2 CO.2 CO.2 CO.2 CO.2 Arsenic As 0.21 <0.2 CO.2 CO.2 X0.2 CO.2 Barium Ba <0.010 All results expressed as mg/L <=lessthan 166004 - Britannia Mine Site Page 6-24 The sulphidesproduced wouid be removedby senlingor fïltratio~~Use of coaguhmtsmight enhancethis process,but might requin the additionof akalinity (lime) to maintaina suitablefinal pH. Recycleof the pre~pitatedsolids could be requiredto enhancesolid/liquid separationpmperties. Rrecipitationof metalsby sulphiderequins the @xence of a significantconcentration of sulphideion, S’. At increasinglyacid pH, S’ is convertedto HS’ or H$, reducing its availability for metal pnxipitation: S’ + al+ - &y- (1) - (2) The concentrationof sulphideion requimd to precipitatea given metal is dependenton the relative insolubilityof the sulphide;thus, copper is pmcipitatedby very low levelsof sulphideion, while zinc and imn requirehigher levels. This theory was borneout by the testing:at low pH, copperwas successfully pnxipitated by sulphideaddition, but much larger additionswere requiredto removezinc. As shownby equations1 and 2, the additionof sulphideion to acidic effluent consumesacid (H+),and thus, its use in large quantitiesis tantamountto using it as a neutralizingagent rather than as a highly specificprecipitant. When comparedwith lime or soda ashin this capacity,and assumingaddition as sodiumsulphide, it is not economicallycompetitive. As well, usedin this way, significantquantities of highly toxic hydrogensulphide gas may be evolved. The test resultsare pxovidein Table 6.8. In both casesthe highestsulphide dosage was requimd to precipitatezirtc while iron remainedin solution Copperwas precipitated out at the lowesttest additions; i.e., 313 mg/L in the caseof 4100 level and 1254mg/L with the 2200 sample. The msultsindicate that a high sulphideto metalratio is xequimdin all casesto precipitatemetals, making this processunattractive unlessa sourceof sulphidesuch as a sulphidenotation concemratewere readily available. 6.3.4.6 SeaWater Dilution The watersof Howe Soundare a convenientlarge xepository of availableakalinity. Althoughthe volume is large,the akalinity is not high. Garmlsand Christ (1965)have calculated the molality of bicarbonate as 0.00’24,and carbonateas O.MlO27. Steffen Robertsonand Kirsten Table 6.8 Sulphide Precipitation Tests 2200 Portai 4100 Portai - Na2S Dos.age mg/L S= 0 313 627 1254 2090 0 313 627 1254 Na2S.l OH20 Equivalent kg/1 OOOm3 0 2524 5055 10110 16851 0 2524 5055 10110 DH 2.92 2.95 2.98 3.1 4.14 3.51 3.67 4.76 Dissolved Dissolved Metais Metals ...... ~~~~~i’~!ii!l!iiiiial:iliiij iii~i~iijiiliiiiiii~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ii;~i~iii~iiii~:~~~~~~~~~~~~~~~~~~~~~~~~ . .:t.:.: ‘.‘:‘;. , : ...... iii:..:.. -...... :...... :::::. . . :. : . :‘:‘:‘:‘:‘:‘: ...... : . : . :‘:‘:‘:‘:‘:‘: ...... t: . :‘...... , . :?. .. . : :::...:..~...i.i:~:i:~:~...~..~...:.:.:.:.:.:...~..?...... Antimony Sb :0.001 CO.2 CO.2 CO.2 CO.2 CO.2 CO.2 CO.2 <0.2 Arsenic AS 0.001 CO.2 CO.2 CO.2 CO.2 KO.2 CO.2 X0.2 CO.2 Barium Ba CO.1 CO.1 CO.1 CO.1 0.012 CO.01 KO.01 CO.01 Beryllium B0 CO.005 CO.005 KO.005 CO.005 0.005 CO.005 CO.005 CO.005 Bismuth Bi All resultsexpressed as mg/L < = less than 166004- BritanniaMine Site Page6-26 The testing(Table 6.9 and Figures6.7 and 6.8) showedthat for the 4100 level sample,a dilution ratio of 15:l was requiredto machbackground seawater pH (7.58), suggestingan equivalentalkabnity of about 22 mg/L CaCO,,or about 0.00024molal. For the 2200 sample,a ratio of about 55:l was nquired, suggestingan equivalentalkalinity of about 14 mg/L CaCO* This comparisonillustrates the difficulty of using standardtests such as acidity and alkahnitytitrations to pmdict treatmentchemistry in some situations. Dissolvedzinc levelsresulting from thesetests wete aboveconventional discharge levels. Only 50 % of the reductionin solubleconcentration is due to pmcipitationduring neutralixation.The kineticsof xinc ptecipitationvia seawaterdilution arenot favourable.In additionthe precipitatesfonned are colloidal and may not necessarilyhave beenretained on 0.45 micron filter paper. 6.3.4.7 Ion Exchange This processoperates using plasticreshr beads that arepenneable to the effluent solution As part of the plastic structure,organic chemical groups are incorporatedthat are capableof exchangingone ion for another. Thus, for example,in a heavymetal solution,they might exchangehydrogen ion for metal ion (a cation exchangeresin). The loaded” resinbeads cari be regeneratedperiodically by washingwith an acid solution. The beadswould be chargedto a packedor fluidixed bed and the effluent passedthmugh, in batch or wnth-mousmode. When the resin was loaded,it would be dischargedand regenemted. For batch operation(most common),at least two parallel beds would be required one on line ami the other in the ptocessof being rejuvenated.The pxoce&ngwould be underthe contml of a programmable logic contmller (computer)which would sequencea set of valves acconlingto a thned progmmor in iesponseto an on-line analyticalsignal. In continuousoperation, at leasttwo columnswould be requin& one for treatingeffluent, and the other for mgeneration.Fully loadedand fully regeneratedresin would be transferredat leastsemi-continuously betweenthe columns.The spentregenerant would be a relativelyconcentrated solution containing ail the cxmamhnts that had been mmoved. This would needto be tteatedfurther (e.g.,by limmg) or to be shippedtoasafedisposalarea. Onemason for wnsideringion exchangeis that it wuld providea necessarywncentration step as a front- end to a solventextraction process for wpper recovery. The resultsof the ion exchangeexperiment aie providedin Tables6.10 ami 6.11.The dissolvedvalues for zinc andcopper are plotted in Hgums 6.9 and 6.10 on a bed volumebasis. SteffenRobemon and Kirsten Table 6.9 Seawater Dilution Test Results 2200 Porta1 Drainage 4100 Portai Drainage .- .. Dilution Dissolved Metals Dilution Dissolved Metals Ratio pH Copper Zinc Iran Ratio pH Coppet- Zinc lron 0 2.85 , 97.10 47.00 39.30 0 3.58 22.9 42.4 5.95 1 3.42 1 4.89 2 4.35 2 5.37 3 4.90 3 5.83 4 5.10 4 6.11 5 5.30 5 6.28 2.19 5.75 0.073 6 5.52 6 6.43 7 5.71 7 6.54 8 5.91 8 6.60 9 6.02 9 6.70 10 5.87 4.94 3.72 0.08 10 6.79 0.873 3.14 0.086 15 6.29 3.39 2.62 0.10 11 6.84 20 6.49 12 6.95 25 6.75 1.68 1.46 LO.015 15 7.58 0.69 2.17 0.092 30 6.92 35 7.03 40 7.17 45 7.27 50 7.39 0.78 0.87 0.12 55 7.44 0.52 0.89 LO.015 All results expressed as mg/L L i less than Table 6.10 Ion Exchange Test Results - 2200 Porta1Drainage Resin - Dowex MSC-1 Strong Acid Cation Bed Diameter I 10 mm Resin Volume 25.12 ml 0.000025 m3 Bed Depth 320 mm 0.32 m Bed Area 0.000078 m2 Flow Rate 10 mUmin 0.00001 m3/min Surface Loading . 7.64 m3lm2ih 3.31 gpmlft2 I Sample Bed Dissolved Metak l”ime Volume Volumes PH Zinc Copper Calcium Magnesium min 10 100 4.0 5.82 20 200 8.0 5.71 0.058 0.069 LO.05 0.131 30 300 11.9 5.70 40 400 15.9 5.45 0.036 0.073 0.782 0.098 50 500 19.9 5.08 -60 600 23.9 5.70 0.032 0.057 0.904 0.077 70 700 27.9 5.00 80 800 31.8 5.48 0.059 0.088 0.941 0.134 iii~i~!i:~~iii~ii~~~~~~~~~~~:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.. ..:.:...::.:...... >...... :::::::::...... :..:..::.: ,...... ,..... :...:...... 3 .. . . . :::.: ...... :...\ .. . . . ::.: 110 1100 43.8 3.17 0.391 0.562 0.246 0.767 120 1200 47.8 3.08 I 130 1300 51.8 2.76 1.35 1.83 0.655 2.53 Ail concentrations in mg/L Table 6.11 Ion Exchange Test Results - 4100 Porta1 Drainage Resin - Dowex MSC-1 Strong Acid Bed Diameter 10 mm Resin Volume 25.12 mL 0.000025 m3 Bed Depth 320 mm 0.32 m Bed Atea 0.000078 m2 flow Rate 10 mL/min 0.00001 m3/min Surface Loading 7.64 m3Im2lh 3.31:. arlm/ft2 Sample Bed Dissolved Metals Time Volume Volumes pH Zinc Copper Calcium Magnesium 10 100 4.0 5.39 20 200 8.0 5.65 0.024 0.016 LO.05 0.084 30 300 11.9 5.79 40 400 15.9 5.83 0.012 0.013 LO.05 0.098 50 500 19.9 5.88 60 600 23.9 5.77 70 700 27.9 5.90 0.014 0.021 0.453 0.069 80 800 31.8 5.78 90 900 35.8 5.72 0.028 0.109 0.318 0.082 100 1000 39.8 5.60 rtr~!l~i~lrlB~~nii~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ::::::::::::::y:.:.;.:.:.:.:::*:...... p..:.:.:.:.:...: ...... :.::: ...... 120 1200 47.8 4.45 130 1300 51.8 3.95 140 1400 55.7 3.50 150 1500 59.7 3.28 411concentrations in mg/L Neutralization via Seawater Dilution 2200 Porta1 Drainage 0 1 2 3 4 5 6 7 8 9 10 15 20 25 30 35 40 45 50 55 Dilution Ratio Seawater/Sample Figure 6.7 Neutralization via Seawater Dilution 4100 Porta1 Drainage PH -0 1 2 3 4 5 6 7 8 9 10 11 12 15 Dilution Ratio Seawater/Sample Figure 6.8 Cation Exchange Test Results 2200 Porta1 Drainage Concentration mg/L 20 30 40 50 60 Bed Volumes -- Zinc + Copper Figure 6.9 Cation Exchange Test Results 4100 Porta1 Drainage Concentration mg/L 4 f 3.5 3 I I ! 2.5 ! ! ! / 2 1.5 1 0.5 0 Bed Volumes - Zinc + Copper Figure 6.10 166004 - Britannia Mine Site Page 6-32 In our testing,the resinswere sucwssfulin picking up the metals,break tbrough occurredat 40 bed volumesin the caseof the 2200 samplewhile breakthroughoccurred at 44 bed volumesin the caseof the 4100 portal sample. The probableapplication of ion-exchangeto the Britannia situationis discussed further in Section6.4.3.2. 6.3.4.8 Carbon Adsorption Carbonadsorption is a pmcessthat would operatein a similarmanner to ion exchange,but usingactivated carbonas the adsorbingmedium. Although activatedcarbon cari adsorbmetals, the adsorptionisotherm has a low X/M ratio (which measuxesthe quantity adsorbedin relationto the concentrationin solution). As a xesult, loadings will be low, and the application of activated carbon given the discharge concentrationsat Britanniais not judged practical No testingwas completedon this option. 63.49 ReverseOsmosis This is a ratherhigh cost processthat is more suitedto smalleroperations whem mcoveryof valuesis important(e.g. plating shopwastes) and for desalinationprojects. It is not usedfor tmatinghigh volume effluents. The procas involvesforcing waterthrough a membranewith high pressure.The membraneis permeable to the watermolecules, but not to the salt ions, which remainon the “salt” side of the membrane.Thus, the impuritiesare rejectedas a salty solution ratherthan as a precipitatewhich cari be dischargedto a tailingsimpoundment. The solutioncari be recycledif a processis availableto useit, but the impurities wili build up, usuallywith detrhnentaleffects on the treannentptocess (greater pressure will be requin& and fouling is likely). No testingwas completedon reverseosmosis. &4 Contaminant Disposaland Sludge Stabiiity The treatmentpxocess will removecontaminants from the effhrent There remainsthe questionof how to disposeof thesecontaminants without hannfuUy reinnoducing them into the environment.This section considersboth the possibiitiesfor recoveringsaleable pnxlucts, and the optionsfor permanentlydisposing of the pxocesspmducts. Steffen Robextsonand Kirsten 166004- Britia Mme Site Page633 6.4.1 MetaI Reeovery The metal content representsthe most significant proportion of the contaminantsremoved. It is conceptuallyattractive to considerrecovexing them for sale. This approachis consideredin more detail for copperin Seçtion6.4.3. MacDonalds & (1989)have summarkd someof the considerationswhen xecyclingzinc sludgesto a conventionalelectrolytic zh~c smelter (as at Trail, for example). Impuritiescontained in the sludgemay interfete with the elecholysispmcess. In particular,iron in the sludgebecomes a disposalproblem for the smelter.The watercontent of sludgesmay alsogive ptoblemsin handlingthe sludges,and on the zinc plant water balance. Given thesefactors, and the low level of xinc encounteredin suchsludges, it is unlikely that any payment would be xeceivedfrom the smelterfor the metalcontent. In fact, a fee might be chargeablefor accepting the mate&& in additionto the cost of transportingit to the smehersite. MacDonald-t (1989)have provided cost estimatesfor alternativesto conventionallime treatmentthat inwrporate metal recovery. Ah the altemativeswill msult in signilïcantcost increasesto the mineral industry, but ion exchangeand solvent extraction costs are lower in some casesthan combined conventionallime precipitation,sludge dewatering, and disposai Ion exchangeand solvent extraction are evaluatedspecifically in the Britanniacontext in Section6.4.3.2. ._ 6.4.2 Remaining Contaminants In addition to copperami xinc. other contaminants(such as iron ami cadmium)will be presentin the emueritin insufficientquantities or will baveinsufkient valueto justiQ recoveryby known technology. These would be rejectedfiom the treatmentprocesses described above as sludgesor concentrated solutions. Metal ions in solution are highly mobile, and so solutiondisposal would not be considered suitablefor final placement. The dissolvedmetals likely would have to be convertedto a solid form whete their mobility was restrictedto a level tolerableto the depositionenvironment, and this process would likely msult in the formationof a metal-containingsludge. The stabiity of the sludgedepends on the modeof storage. The sludgeshould contain some ptotective akalinity, which will latgely pxeventleactig of the pmcipitatedcomaminants. However, the akalinity (calciumcarbonate - calciumhydroxide) has a sohibility in water, as do the pnxipitated contamhnts. Changesin the sludge’saqueous environment provide the opportunity for continual leaching of rhe alkalhity and metalsto meet their respectiveequilibria, and eventually,with the akalinity gone, pH swingscould msult in heighteneddissolution of contaminants. SteffenRobertson and Kirsten 166004 - Bitannia Mine Site Page 6-34 Thus, the sludge should be depositedin a way that immobilizesthe water in its immediatevicinity, discmragingleaching of the sludgeconstituents. This shouldnot be too difficult to achieve,since the precipitatesare very fine, and over lengthyperiods should consolidate to a relativelyimpermeable mass. Local dissolutionand reprecipitation of hydmxidesand carbonates may help to “cernent”the masstogether over the long tenn. Situationsto be avoidedate thosewhere the sludgemay periodicallybe resuspended and resettled(e.g., shallow ponds), as this providesa changeof water and pxeventsconsolidation. Solidificationof the sludgeusing (for example)a cernentbinder is an expensiveoption that may have to be consideredin specificcircumstances. Sludge solidification is an areaof intensiveresearch, and several proprietarysolidification systems are available. Dewateringof the sludgeand disposalon the Britanniasite may be possible. With sufficientcontait& alkalhity resultingfrom unreactedlime, the sludgeis unlikely to be a SpecialWaste as detenninedby the SWEPleaching test, It could thus be depositedin a pmperly designedlandfill at Btitannia,or possibly underground if non-contactwith acidic liquo~can be assured. Once dewatemd,it could also be transportedto a tailing disposalarea at one of the minesitesin B.C. whemsuch sludges are aheadybeing deposited,for exampleEquity Silver,or preferablyan abandonedtailings impoundment closer to Britannia. Acceptabledisposition of the Fquity sludgeafter closmehas yet to be detennined,but whateversolution is adoptedmight also accommodatesludge fiom Britannia. 6.43 Potentiel for Enhancementand Copper Recovery 6.43.1 Copper Cementation The fact that metallic copperhas been recovemdby cementationat Britannia raisesthe possibility of updatingthis processand usingthe copperproduced as a sourceof revenueto offset treatmentcosts. Copperis being producedfrom bacterialdump leachoperations at severallocations in the southwestem U.S., as well as at Gibraltar in B.C. The pmcesshrgsequence used is solvent extractionfor copper concentrationand purification, followed by electmwinningto wimbargrade cathode copper. Cementation is no longer widely practiseddue to the low paybackmceived for cementcopper and the relativelyhigh cost of scrapsteel The solventextractio~electrowinnin g pmcessis shnply better and more economic technologyfor the situationswhere cementation formerly was practised. In situationswhere cementationwas practised,the solution feed gradewas much higher than is now presentat Britannia. When the mine was operatig, the solution gradewas in the range30 - 105 ppm copperfor the BeachPlant, and 100 - 175 ppm copperfor the Mt. Sheerplant (The Anaconda(Canada) CO.,1965). At the low gradeexpetienced now, the “cari factoi’ which measumsthe iron consumption Steffen Robertsonand Kirsten 166004 - Britamia Mine Sita Page 6-35 relativeto the copper productionbecomes large and the quality of the cernentis poor dueto contamhation with impuritiesfrom the large amountof iron that is nqtired. A cari factor of 2 to 4 kg carisper kg copperprecipitated was a ntle of thumb for cementationplants (Spedden gai, 1966);Btitannia-achieved about2.2 kg of carisper kg of copper. The cari factor increaseswith low fend gradebecause the side reactionsthat consumeiron (e.g. with sulphuricacid, ferric iton, and atmosphericoxygen) becorne significant relative to the amountof copper that is macted. Thus,the plant simply contributesferrous imn to the effluent, while nmoving copperin an hradequatemanner. At low copperconcentrations, the reactionrate of the copperis slow and ptecipitationefficiency is poor. The mcentrecords for B&annia showlittle removalof copperfmm the effluentduring its passagethrough the launders,although the hnptessionis that the laundersate somewhatneglected. The low quality cernentmust be transportedto a smelter,which in the caseof Britanniawould pxobably meanJapan. Whenthe mine wasoperating, it was easyto add the cementto the concentratewhich was aheadybeing shippedto a smelter. Now, the bestoption would be to determineif it could be addedto concentratesfiom one of the operatingB.C. copper mines as they passedthtough the tenninaJsin Vancouver. Genemlly,thete would not be much incentivefor the concentrateownets to acceptit, since it has low copJxzrcontent, high water content, and poorly controlled impur@ content due to the uncontrolledsources of the scrapsteeL Net smeltermtum on this materialwould be expectedto be low. T~US,copper recovery is dealt with in the next section by consideringthe alternativesother than cementationfor the effluent asit occurs,with adjustmentfor a rxdttctionof flow to 60 percentof curmnt averagesto be achievedby diversionof sourcesentering the mine in the JaneBasin area. Themafter,the potentialfor increasingthe amountof copperleached by techniquessuch as tedistributionof solution, crushingthe mmainingwaste and replacingit, in situ blasting,etc. is considemd. The basii for this analysisis the flow datasummarized in Table 6.12 and the analyticaldata pmvided in Table 6.13, andvaries somewhat fxom the dataused to developthe costestimates in Section6.6 sincethe hydrologicalanalysis was not completeat the time the work xeportedhem was done. The conclusions fiom the analysisremain valid. 6.433 Other Copper RecoveryApproaches Flow and copperassay information for the period 1983 to 1990 was ptovided by the Minishy. This informationwas compiledwith the data from Moore and van Aggelento determineplant capacity. The data is summarizedin Table 6.12 and 6.13. Steffen Robemon and Khten Table 6.12 - Summary of Flows, Copper Concentrations and Copper Production from the 4100 Portal, 1983 - 1989 Year Avg Fiow Aw W CU Production m3/h ma/L kald 1983 664 19.7 313 1984 561 18.4 247 1985 396 16.1 153 1986 494 19.6 233 1987 597 17.8 256 1988 475 18.5 211 1989 442 15.3 162 IAveraae 518 18 225 I Table 6.13 - Summary of Assay Information on 4100 and 2200 Porta1 Flows ocation 2200 2200 2200 4100 4100 4100 4100 4100 4100 4100 4100 late 21106/83 06/12/83 21/04/84 21106183 13/07/83 15/08l83 08109l83 06/12/83 21104184 21/05/85 20/06/85 H 2.9 3.5 2.7 3.4 3.5 3.2 3.8 3.9 cidity (pH 8.3) 445 109 494 367 306 277 239 258 krlphate 880 293 895 1620 1700 1620 rissolved metals Al 31.3 8.05 36.4 39 37.6 35.3 30.6 f3 0.02 0.01 0.17 0.17 0.31 0.34 0.25 0.28 0.20 Cd 0.17 0.06 0.18 0.19 0.14 0.14 0.11 0.14 0.0058 0.12 0.16 Ca 129 53.2 121 441 411 418 478 419 450 387 CO 0.17 <.l 0.22 0.22 0.14 0.3 0.29 0.35 0.1 0.1 CU 51.4 12.3 43 31.7 30.3 23.6 22.5 18.3 14 11.1 18.1 Fe 36.8 3.16 45.1 11.3 17.1 50.6 56.1 17.1 14 10.8 4.74 Pb 0.12 <.l 0.16 0.22 0.14 0.22 0.09 0.23 0.2 0:2 Mg 38.5 11.3 39.4 88.6 82.4 100 115 83.4 94.3 81.7 Mn 2.6 0.9 3.12 5.47 6.21 8.4 9.2 7.52 7.66 5.98 Ni 0.07 < .05 0.05 0.11 0.08 0.15 0.09 0.07 0.07 0.06 Zll 26.1 8.21 . 31.6 41.9 30.9 27.1 27.3 28.1 0.21 28.1 30.8 :low estimate 210 * Acidity In mg/L equiv. CaC03, flow in m3/h, concentrations In mg/L .- 166004 - Brittmnia Mine Site Page 6-38 While thereis a downwardtrend in coppertenor of the solutionssince the mineclosed, Figure 6.11 shows that the averagingof the coppertenors over the period 1983 - 1989 providesan adequateestimate of copperproduction for studyof the potentialfor metal recovery. Similarly,Figure 6.12 showsthat there is no significanttmnd in flows, and thus averageflows basedon this period are adequatefor the study. It is noted(Figure 6.13) that thereappeats to be an increasein coppertenor with flow rate,and this could be explainedby gmaterflushing and better wetting of sulphidesurfaces during wetter years. However, the regressioncoefficient for the Uneshown is not statisticallydiffemnt from zem,so the.statementcannot be madein certainty. Perhapsa significantcorrelation could be achievedif the datawere analyzedon a monthly basisrather than on an annualbasis. Suchan activity was outsidethe scopeof this study. During the periodJanuary 1,1983 to December31,1989 the averagehourly flow from the 4100level was 518 m3/hcarrying an averageof 225 kg/day copperfor an averageconcentration of 18 mg&. We have only one measurementfor the 2200level flow, at 210 m3/ltin June,1983, when the 4100 level flow was 927 m3/h. Proratingthis to the average4100 level flow, we could say that the average2200 level flow was 117 m3/b. The total averageflow xequiringtreatment would then be 635 m3/h. The averageplant feed assaywould be a flow-weightedaverage of the two sources.Assume a reasonable fhst approximationwould be to averagethe given data. When this is done,we get: 2200 4100 Flow-weighted Average Acidity: 349. 289. 300. sulphate: 689. 1646. 1470. - COppeC 36. 18. ‘il. Iron: 28. 23. 24. zinc: 22. 31. 29. The averagecopper production (100 SQrecovery) would then be 320 kg/day. For processdesign, we must sixethe plant somewhatabove the avemgeflow, sincestorage will not be enoughto com~nsatefor annualvariation in flows. The factor to apply will dependon the storagewe cariprovide to averagethe monthlyflow variations,together with the variationin annualflows, which we assumecannot be averaged.For this study, we assumethat monthly flows cari be averagedby storage behind a bulkheadat the 4100 level, and thus we look at historical data to determinethe maximum varlability in annualrunoff. This indicatesthat the maximumrunoff would be twice the average,so the plant should be sizedto tmat 1270m3/h. (Analysissubsequent to this study indicatesthat more flow averagingcapabihty is available,and the treatmentplant designis basedon a substantiallysmaller flow.) Steffen Robextsonand Kirstm Trend in Copper Tenor Comer (mg/L) 23 22 21 20 19 18 17 18 15 14 13 12 1983 1984 1985 1988 1987 1988 1989 Year Based on flow-weighted averages from 4100 Por tal Drainage Figure 6. I I Trend in Average Hourly Fiowrate Flow (m3/h) r 700 -/ 650 -J‘ Ï / 600 ->’ f 580 -?’ ,..’ 500 -/ / 450 -.>’ ...- 400 -,.’ ,..‘ 350 -..’ / 300 1 - 1983 1984 1985 1986 1987 1988 1989 Year Based on 4100 Porta1 Drainage Figure 6. 12 Correlation Between Copper Tenor and Average Annual Hourly Flowrate 1983 - 1989 Copper (mg/L) 24 22 20 l 18 16 . 14 -.~ 12 ----- l I I I 10 I I 350 400 450 500 550 600 650 700 Average Annual Hourly Flowrate, m3/h Copper concentration based on flow-weighted mean - 4100 Porta1 Figure 6. 13 I 166004 - Britannia Mine Site Page 6-41 Two major difficulties arisewith this concept first, evenwith a reductionof total flow to 60 % of the curmntrate by appropriatecivil works,the plant fend concentrationis only 35 ppm copper,worth about $.08/m3. Organiclosses to mffïnate in a solventextraction process, even with very camfûl recovery ptocedurescould hanily be less than 25 ppm (50 ppm is a conventionalrule of thumb). The organic phaseis vahtedassuming a 5 % solutionof extractantin a proprietarydiluent, with extractantat $16 /kg, and diluent at $.45/kg: Extractant 43 kg $688 Diluent 807 kg 363 Total 850 kg $1051/m3 At 25 ppm @y weight),organic losses total 25 g/m3of aqueousraffinate, or 29 x 106m3 of the organic mix. The valueof this lossis $0.03/in3 of effluentheated. Thus,nearly 40 percentof the revenueis lost ..- -. in the effluent before any other provisionfor operatingor capital costsis made. The seconddifficulty is that the averageproduction rate of 0.32 tonne copperper day is substantially below the,levelof about5 tonnesper day considereda minimumeconomic plant size. Fmm standardcost curves,if a plant werebuilt for Btitannia,the capitalcost would be of the otder of $3.5 million, with the bulk of the capitalin the solventextraction plant, owing to the large flow (this designassumes only the averageflow, not the maximumfloi). If we assumea 15 year plant life at 15 % hueres&the annual capitalcharges would be about$600,000. The annualcopper production might be 105tonnes, so the cost would be about$6 per kg’of copperptoduced, twice the curmnt spot price. An ion exchangeplant could be addedto the ftont end of the plant to preconcentratethe copperand therebyconttol organicreagent losses. Àt an assumedproce&ng rate of 24 n& (10 USGPM/@),the columnswould requirea cross-sectionalarea of 26 m2(average slow only), ami the systemwould costof the otder of $1.5 million Their presencewould reducethe size,but not eliminatethe solventextraction plant, sinceconventional ion-exchangers do not offer the selectivity(copper purification capability) that the solventextraction reagents do. Chelalingtes& offer better selectivity,but providea shorterlife, and cost approximatelyten times as much (MacDonaki,a&, 1989). The regenerantwould likely needto be chlotiderather than sulphatebased, to preventbuild up of calcium fiom causinggypsum fouling of the resin(calcium is the major cationin the AMD). Thus,either sodium chlorideor hydrochloricacid could be considered.Recovery of pure copperfrom chlotide solutionsis an emergingtechnology, but cannotnow be considemdpmven commercially. An alternateto solvent extractionand electrowhmingwould needto be sought. Steffen Robemon and Kirsten 166004- BritanniaMine Site Page6-42 Another major constituentof the plant feed is iton. A SigniEcantportion of this will be in the ferrous form owing to its contactwith sulphidesin the mine. After adsorptionby the cation exchangeresin, it may becomeoxidized and precipitatewitbin the,tesin as fenic hydroxide. This is a major sourceof fouling in cation exchangeresins (Pelosi and McCarthy,1982). AU the cations,including all the heavymetal contamhrants,would havebeen removed, but there would be little economicoffset in reducedtreannent costs. The metal cations(other than copper,assuming it was removedby solventextraction) would needto be precipitatedfrom the strippingsolution, and this would mostlikely be doneby raismgthe pH to causemetal hydrolysis. The acid remainingin the treated AMD would not have beenextracted and would mquireneutralization. It thereforeappears that recoveryof the coppershould not be mcommended.For the abovescheme, neutralixationof the effluentwould still be required,while the technicaland economic feasibility of copper recoveryfrom the strlppingsolution is questionable.There is no precedentfor tbis type of processon low-stmngthcopper sulphate waste streams. Alternativessuch as precipitatinga bulk copper-zinc-iron sulphide do not achievesigniEcant purhïcation, and thetefore ptoduce a low-value ptoduct whose marketabilityis questionable.The availablemetal to be pmducedby any schemeis too smallan amount to provide recoveryof the amountsof capitallikely to be required. The alxwe work haa assumedan enhancedfend concentrationdue to mduceddilution inflow, while maintainingthe metalproduction fiom the mine at recentrates. In fact, the evidenceto datesuggests that the concentrationmay be reducedat reducedfIows due to less effective contactingof solution with oxidizedminerai TO achievethe assumedconcentrations, there would thus needto be an improvement in solutiondistribution patterns accompanying the reducedflows. This might be achievedby spnnkling in the glory holes as suggestedby Hooper(1970). Carefulthought would needto be appliedto the designof sucha system;the simplescheme proposed by Hoopermay not demonstratethe desimdeffectiveness. A better alternativemay be the flood and drain sequencepractised by DenisonMines and mcommendedby Wright Bngineersfor CopperBeach Bstates in 1983. Theseand other alternativesfor enhancedcopper production are considerednext. 6.433 EnhancedMetal Production Rates Bnhancedcopper production will msultfxom the eliminationof bottlenecksconstrai&g higherproduction rates. In principle,two major activitiesmust take place in orderfor copperto reportin the mine effluent: SteffenRobextson and Kirsten 166404 - Britannia Mine Site Page 6-43 the sulphidescontaining the coppermust be oxidizedto nnder the copperwater-soluble, and the resulting coppersulphate must be dissolvedand transportedaway fiom the reactionsite. Oxidationof tonner SUbhideS The mechanismsof oxidationof coppersulphides in dumpshave been described by Murr (1980). Both direct attackby bacteriaand indirect attackby bacterlally-producedferric ion are believedto occur, but the requirementfor bacterialinvolvement to achieveobserved rates is not doubted. Thus, optimization of coppersulphide oxidation requites optimization of the conditionsfor bacterialgrowd~ The bacteria are generallypresent in all circumstancesami do not needto be supplied. The needsof the bacteriaare: l a sourceof energyfor growth, usuallyferrous iion, varloussulphides, or elementalsulphur. l a sourceof oxygen. The combiition of the oxygenwith the energysource is the reactionproducing the quimi energyfor bacterialprocesses. l a sourceof carbonand nitrogenas building blocks for synthesisof biomass. l sufficient water to provide a suitableenvironment for the aqueous-phasebiosynthetic and energy ptoducmgmactions, as well as to removethe ptoductsof bacterialmetabolism. A pH of 2-3 in this aqueousmedium surrounding the bacteriais optimal,ami pmducts of metabolism(e.g., cupric ion) must not rise to toxic concentrations. l maximumbacterial activity takesplace at temperatumsaround 35 OC. In a wastedump situation, the energysources are the iron andsulphide.content of the mineralization.The oxygenis providedby circulationof air throughthe dump (and to a muchlesser extent by oxygenated waterpasshrg through the dump). Carbonis pmvidedby bacterialfixation of atmosphericcarbon dioxide, as well as by carbonatesthat may be dissolvedin the dump water. Nitrogenis suppliedas ammonium ion which may be pxesentfrom breakdownof organiccompounds or fiom blastingagents. Water is suppliedby the dump operator,with gtoundwaterptoviding an additional sourcein some situations. The opemtormay acidify the water if the bactexiaate not ableto keepthe pH down with the productsof their metabolism. Temperatureis not usuallycontrolled, and rarely is optimal. Dumpsthat ate activelyoxidizing may rise well abovethe optimaltemperature due to the heat of reaction,while thosein a moredormant state may be too cold. Steffea Robextsonand Kirsten 166004 - Britatmia Mme Site Page 6-44 T~US,to enhancethe oxidationrate at Britannia,it shouldbe determinedwhich factorsare limiting, and then stepsshould be takento hnprovethe appropriateconditions. Exposedarea of oxidizablesulphides is doubtlessone importantfactor, and the reasonwhy the copperproduction rates have droppedsince mining stoppedis probablythat the availablesulphide surface is decmased,both by consumption,and by blinding with mactionproducts. Wright Engineers(1983) concludedthat size reductionof the in-place reservesto exposemore surface would be impractical,as material reclamation, crushing, and replacement would be requimd. Basedon experiencewith other sulphidedump leach situations,the other probablerate-limiting factors a~ accessto oxygenand water. Oxvgen As a moult of detaileddump modmg, Cathles’ami Schlitt (1980) concludedthat the opthnum dump height shouldbe roughly 15 m, and the optimum width about 30 m. Beyondthese hmits, convective tra&er of oxygenis insufficientto pxovidefor maximumleaching rates, and mdeed, in low oxygenareas, coppercari be mpmcipitatedfrom the leach solutionsby contactwith sulphides. Obtainingadequate convective flow in enclosedstopes located between the 2200 and 4100 foot levels at Britanniaseems unlikely without the establishmentof an extensivesystem to mechanicallyhmoduce air. While this cari be ttied as an enhancementapproach, it could result in the leachingcomponent of the processhaving a significantoperating cost, whemasour @itial conceptis that the leach solutionsare availableessentially for tîee. As an altemative,a systemcould be setup whexethe stopeswem periodicallyflooded and drained. This cycling would draw air ht0 all the intersticeshaving greaterthan capillarydimensions, ensu&g at least someexposure to both oxygenand water. In the Wright Engineexsconcept, the cycle would take place oncea year,with the flooding owuning during mn-off, and the drawdown occurdngover the remainder of the year. TO operatea cycle on any shortertime fiame would mvolve provision of large storage capableof holdhtgthe entireflooded solution inventory of the mine, togetherwith pumphtgfacilities for high rate solutionmovement Room for such storagepmbably could not be found at the site. The volume of solution(and air) that could be exchangedin such a schemewould be the void volume of the broken rock in the stopes. We cari calculatethat the oxygencontent of the h~hoducedsolution would have a neghgibleequivalence in copper. If the in-placerock hasa densityof 2.6 tomeslin’, andthe swell factor on mining is 1.5, the bulk density of brokenrock would be 1.7. The availablecopper rese~~es in the mine are stated(Hooper, 1970) to be Steffen Robertsonad Kirsten 166004 - Britam-daMme Site Page 6-45 245 million pounds(Fairview and WestBluff only), and an averagegrade has been assumed to be 0.4 % (Stern, 1966). Wright Engineersrefer to a C.M.S. report completedin 1980which esrimatedreserves availablefor leachingof about 200 million poundsof copper. It is not clear whetherthis reserveis currentlyall bmken. Assumingit is, and usingthe 245 million poundestimate at 0.4 % copperithe rock availablefor enhancementwill be 28 million tonnes occupyinga volumeof 11 million m3if unbroken, 16 milhon m3 if broken. The volume of air to be exchangedannually is 5 million m3, containing 1 million m3or 45,000kg-moles of oxygea * The oxygenwill be usedto oxidixe sulphidesto sulphate,which appearsin the leachsolution. From our historicaldata, the sulphatelevel is 1470mg/L when the copperlevel is 21 mg/L. Smce1 kg-moleof oxygenis equivalentto 0.5 kg-moleof sulphate,the sulphatewhich could be producedas a resultof the air exchangewould be 22,000kg-moles, or 2140 tonnes. Pmratingby cunent solutionconcentrations, the copperthat would accompanythis would be about30 tonnesper year,or 80 kg/day. This doesnot representan enhancementover currentpmduction The abovecalculation is basedon very rough data and is opento criticism. The exchangedair doesnot representthe only sourceof oxygen,as caribe seenliom the on-goingacid productionin the absenceof enforcedexchange. Some sulphate that is producedmay be depositedin the mine asjarosite and gypsum. Nevertheless,there doesnot appearto be great scopefor oxygentransfer enhancement thmugh cyclic OperatiOrL Water Solution managementis consideredcrltical in the operationof heapsand dumps. Since no special activitiesare completed at ptesentto ensurecareful solution distribution, it is assumedthat enhancement shouldbe possiblein this area. Onemeans of ensu&g completewetting of ah the rock is the flooding appmachdiscussed above. Shrce only one cycle per year seemsfeasible, the productivityof this approachis relatedto the ability of the bacterlato carry on oxidationdming the dry cycle, at which tinte concentrationsof metalsin the pore water surroundingthe bacteriacould rise to inhibitory levels. If the 28 million tonnes of rock assumedabove drained to 10 percentmoistum, the pore water would contain2.8 million kg of copperat 1 g/L concentration.Ifentirely flushedduring eachyear, this quantity would representa copperproduction of 7.7 tonnesper day,which would likely be an economicproduction rate. $effen Robertsonand Kirsten 166004- BritanniaMin~ Site Page6-46 The bacteriaare known to be ableto tolerateconcentmtions much higher than this, so this appxoachcould be feasibleas a water distributionmethod. The Wright Engineersreport questionsthe ability of a plug at the 4100 level to withstandthe pressures that could be reachedwith a periodic flooding concept. Theserelate to the strengthof the rock usedto hold the plug in place. Shouldperiodic floodhrg appear desirable, a detailedengineering investigation of this problemwould be necessary. If it were desirableto obtain a flow through systemfor air in the stopesin order to ensureadequate oxygenfor the oxidationmactions, a percolationsystem might be necessary.Certamly, vertical air flow would be mstricteddming any tinte the stopeswem not completelydrained. Hooper(1970) planned to use this approachin his feasibiity study. While the runoff and groundwatercould not be captumdfor redistributionand percolation,a recycle streamwas proposedas a meansof enhan&g solution contact. Recycleof leach solutionafter copper recoveryis mutinely employedin dumpleachhrg to makeuse of the acid it contains,thereby ensuring the necessarylow pH for metaldissolution and bacterialactivity. The iron contentmay alsobe beneficialto the bacteria,who will oxidize ferrous to ferric in pmferenceto other substrates.FAy. it contains bacteria,and thereby servesto mdistributethe organismsami provide a good distribution of activity thtoughoutthe dump. A bleed from the recycleloop equivalentto the amountof runoff ami groundwaterwould be taken for copper recoveryand subsequenttreatment and dischargein order to maintain a water balanceon the leachingsystem. ‘lhee difficulties cari be fomseenwith this appxoach.First, the stopesapparently are hrclinedtiom the vertical. There is thus a hangingwall, and ail are locatedbeneath this would have poor accessto the pexwlating solutionswhich tend to move vertically downward. Second,the vertical depth for percolationis much greaterthan is encounteredin most dump leach situations. Oncethe solutionhas been distributed at the brokenore surfacein the stope,it is no longer in the operator’s control, and the formation of chant& which take most of the flow has been demonstratedin pilot testing (Murr, 1980). The greater the percolationdepth, the gmater is the opportun@for maldistributionof ue solution As an extremeexample, it has been found that packed columnsin chemicalpxocess plants (which are designedto facilitate welldistributed percolation)should incorporatesolution redistribution mechanisms at intervalsof at leastevery 6 or 7 m (Treybal,1980). StefknRobemon and Kirsten m 166004 - Brhmia A&meSite Page 6-47 Third, as the solutionspercolate through the brokenare, migrationof the fines contentand precipitates resultsin the formationof impermeablelayers in the waste(Bruynesteyn and Cooper, 1974). This results in areaswhich are limited in accessto bath oxygen and solution. Mur-r (1980) observesthat “dump flufiing” by blastingto incxeasepermeability results in a decrease,not an increasein penneabili~ty.T~US, this shouldnot be a useful strategyat Britannia. . Summarvof conter oroductionenhancement The possibilityof incxeasingcopper production to economicrates is intriguing, andwhile questionshave beenraised especially in the amaof oxygenavailability, we feel the ideacannot be rejectedout of hand. A full scaletest is requiredto determinewhat caribe achievedby appmachessuch as outlinedabove. The down sideis that attemptsat enhancementwill eliminatethe gradualdecline in coppertenor in the effluent that has occunedsince the mine close& The ability to “walk away” from the AMD problemwill thus havebeen postponed (if it cari ever be achieved). 63 ProposedTreatment Plant Design The designsequence consists of the following steps: review testwork,experience of others w decide on a pmcessconcept; i.e., high density sludge versus straight thmugh, lime versus limestone,etc. w determinethe processflowsheet to meetthe concept w balancethe flows, chemistryon the flowsheet w list the major equipment basedon the processflows and des@ criteriaestablished in testing,calculate the equipmentsize w makequipment layout drawingsthat defmethe major structuraland mechanicalquirements m completedetailed engineering as required to specifyand procure the equipment,Select contractors and build the plant The engineeringdoes not necesszuilypmceed in asdefïned a sequenceas laid out above;in reality, there is usuahysome iteration, as layout constram&may alter the flowsheet,etc. However,the lime treatment pmcessis fairiy stmightfonvard,so that few complicationswould be expected. ‘Ihe pqosed processflowsheet is given in Figure 6.14. The des@ assumesa combmedlime and soda ash treatmentsystem or a two-stagelime treatmentsystem. The following sectionsoutline the design selectedand discusssome of the pertinentconsiderations when settingthe processconcept and selecting and sizing the major equipment. Steffea Robextsonad Kksten DRAINAGE I Lime or Soda Ash Polyelectrolyts - FLASH MIXER TREATED NEUTRALIZATION EFFLUENT’ REACTORS SLUDGE RECYCLE 1 Fil-t& Press +.,,,,+- PUMP SI udge Pump I I Cake TREATMENTPROCESSFLOW DIAGRAM TO Disposa1 FIGURE 6.14' 166004 - Britamia Mine Si Page 6-49 65.1 ReagentMixing and Storage 65.1.1 Lime Slaking Bumed quicklhneis usually mceivedin bulk truckloadsas minus 6 mm matetial It is pneumatically cmveyedto a silo, which is equippedwith a baghouseto temovethe lime dust fmm the transportingair. Lime slakingis usuallyaccomplished in one of threeways: detention slakers, paste slakem, or lime mills. These alternatives,and some others are describedin the National Lie AssociationBulletin 213 (Anonymous,1976). Pasteslakers are said to provide a higher yield of slakedlime owing to the higher temperatureat which they operate.Lime mills offer the advantagethat grit removalis not requimd,smce it is groundup and dischargedwith the productshury. The current desiguincorporates a paste slaker,but this is not a final choice. The relative costs and benefitswould be weighedin arriving at a final choiceas part of the pumhasingprocess. 6.5.1.2 FlOCCUhUltS Flocculantsused in lime heatmentplants usually will be of the polyacrylamidetype, although some natural pmductsare usedas well. They axequite solublein water,but their long chainpolymeric nature makes the solid paniclestend to stick togetherif initially wet in a mass,SO that so-called“fisheyes” are fonned in the stocksolution. Thesemay take a considerabletime to completelydissolve. Themfore, proprletary mixing equipmentis sold by the chemicalsuppliers and others, which is designedto individuallywet each flocculant particle befote dischargingit into the mixing,vesseL Theserange fiom simple futmels on educatorsconnected to the fend water flow to complexcompletely automated pneumatic feeders with wettedwall col-. For this design,a fblly automaticpreparation unit is included. As an altemative,floccuIants cari be purchasedas premixed fluid dispersionswhich combinereadily with water. The long chainnature of the polymersmakes the solutionsvery viscous,and thus stocksolution strengths are limited to about 0.2 to 0.5 percent. At this stmngth,the solution may be storedfor a day or so; eventuallyit degradesdue to polymerhydrolysis. Before additionto the proce&,the solutionis dlluted to 0.05 percent,which allows the polymerto fùlly “unwrap”ami hydrate for maximumeffectiveness. Ideally, 30 minutesmsidence tinte shouldbe provided after dilution to allow this hydrationto proceedprior to addhrgthe solutionto the pmcessstream. Steffen Robemon and Kirsten 166004 - Britarmia Mine Site Page 6-50 In onier to minimizepolymer chain breakage, shearing of floccuhmtsolutions is minimizedat all stages. This is a considerationin agitatorselection as well as pumpin~ typically, pmgressingcavity pumps’am used. Flocculantsare not conosive,and specialmaterials selection for the handlingequipment are not requixed. 6.5.1.3 Soda Àsh Sodaash is availablein bulk ttucks or in bags. For the loadings considemdin the Britannia design, purchasein bags (approximately25 kg each)would lead to unreasonablyhigh levels of labour, SOthat bulk purchasewould be prefermd. Discussionswith local chemicalsuppliers suggest that the most economicmeans of delivery could be in 1 tonne bags,which could be unloadedinto a small hopperas requin% Ahematively,unloadhrg of bulk trucks or rail cars to a silo is done pneumaticallyas for quicklime. Soda ash dissolvesreadily and usually may be handledwithout any specialmate&& of constructionconsiderations. 6.53 Oxidation and Precipitation Reactorsand Agitators The tanksare sixedto providethe requimdmsidence time, typically in the range30 to 60 minutes. The residencelime will be more effectivelyused if at leasttwo tanksare co~ected in series to defeatshort circuiting. Addition of intemalfeed and/or exit bafflescari help ehminateshort circuiting as well, but cari causeproblems for descaling. Best practicewill keepthe xeactorintemals as simpleas possible. Detailed designof a mactor in which air is to be dispemedfor. oxidation is a very complexsubject, involvhIg estimationof requireddissolved oxygen level, oxidationrates, and masstransfer coefficients. This type of analysisis ramly undertakenin practice. Instead,a chemicaldemand for oxygenis calculatedbased on the reactionsdesimd, and the rate at which they must proceedto be completein the desiredresidence thne. This rate is usedwith a rule of thumb oxygenutilisation from dispersedair (typically 10-20pement) to estimatethe rate at which air must be supplied. Tank geometryis usually selectedsomewhere near a “square”design (tank diameterequals liquid depth)which pennits goodmixing with a singleimpeller. Four antiswirlbaffles wiil be included, equalto approximatelyl/lO tank diameter.Agitator vendom are asked to recommendan agitatorthat will dispersethe quimd amount of air in the mactor, comfortably below the flooding point Solids suspensionis not usuallya major considerationin thesedesigns, as the solidsare typically very fine and suspendeasily. More likely, the selectionwill be govemedby gasdispersion. Steffea Robextwn and Kirsten 166004 - Britamia Mine Site Page 6-51 Agitator vendors cari provide recommendationson the best arrangementfor spargingair under the impeller. Oncethe feed is neutralized,its corrosiveproperdes diminish. lkpending on the pH at which the fïrst stageis operated,it may be possibleto constructall the tanks in mild steeL Altematively,it may be desirableto makeat leastthe first stageof stainlesssteel. Polymerlinings or fme-standingPRP are not considered,as they would be damagedby periodic descalingoperations. 6.53 Clarifier Sel&on and Sizii Select-ionof the type of clarifier will be tbe msult of the experienceand preferenceof tbe designer,the recentexperience of otherswith similarplants, and an economicevaluation based on solicitationof quotes from vendors.Where the effluentquahty is specifledin termsof total metalsrather than dissolvedme&, an effective clarifier is essential,and post-filtration may be a useful option to ensum continuous achievementof discbargespecifications. Post ftltration is not proposedfor Britannia. In the high densitysludge process, flocculation is critical to successlülperformance, and thus, separate reacto~~may be providedfor “flash” mixing of flocculantwitb the feedfollowed by gentleagitation while the flots form and consolidate.Altematively, tlash mixing and flocculantmay be providedby addition of the flocculamto a pipelineor launderupstmam of tbe clarifier. Sometimessome experimentation with the additionpoint and methodis mquimdafter start up, since the hydraulic conditionsin a pipeline or laundercari be hardto define. Recommendationsfor des@ of flash mixing and flocculationfacilities am given by the U.S.E.P.A.(Anonymous, 1975). The clarifter is sizedbased on rise rate to achieveoverflow clarity, and residencetime/sludge depth for underflow density. Test work is completedto v&ify that standarddesign factors for tbis type of applicationapply, but might not be used directly in sixing the equipment,especially for smallerunits. Testworkresults for a rise determinationusing the lime treatmentpmcess are providedin Figure 6.15. This pmdictsan overflow rate of 1.4 m/h (0.57 USGPW. Rake mechanismsare selectedwith assistancefrom the vendor based on the anticipatedsludge characteristics.A featurethat may be includedis a lifting device(of greatestconcem when high density sludgesare being sought)which may be manuallycontmlled or instrumentedto actuatebased on torque. Otherdetails vary with the designseiected. Vendors should give assistancein undemtandingthe various featutesthat shouldbe evaluatedin arrlving at the final specification Steffen Robemon and Kksten -. .4 Settling Test Results Lime Treatment Process Interfacial Heiaht- (ml-. 0 2 4 10 12 14 nrne (min) Figure 6.15 166004 - Britannia Mie Site Page 6-5 Bath positivedisplacement and centrifugalpumps are usedin pumpingunderflows. The sludgecari be abrasive(inclusion of somelime grit, for example),and so the pumpshould be designedfor fine-abrasive shnry service. Rubberlined centrifugalpumps, and air or mechanicallyoperated diaphragm pumps are common. Diaphragmpumps offer the advantagesthat their periodic motion cari help to “fluidixe” the thixottopic sludgeand keep it flowing out of the tank; and pumpingrate is easily controlledto allow balancingof a suitablerecycle rate with obtaininga desiredsludge density in the clarifier. Flow rate variationwhen using centrifugal pumps may be achievedby variablespeed drives, or by automaticvalves on the pump discharge. . Thesepieces of equipmentare handlingneutralised shnries in which the fluid is supposedlydischarge quality; materialsof constructionselection is thereforenot restrictive. Mild steel or concretetanks and steelmechanisms are adequate;various internals such as lamellapacks may be fabricatedfxom plastics if desired(e.g., to give a surfacewith a low friction coefficient). 6.5.4 Instrumentation 6.54.1 Reagentdosing systemand control Lime is addedas a shury,which make-scontinuous conholled addition at low ratesdifficult. TOmaintain adequatevelocities periodic additions at full flow are often used. The controllermay set the frequency of pulseor pulselength or bath. Automaticvalves should be selectedsuitable for slurry service. Branch lines are shott and pxeferablycorne vextically off the ring main so that solids settleback hrto the main when flow is shut off The valve is then mountedin a horixontalrun so that a Columnof solidscannot settleon the contxolelemenh preventing its funclioning. Controlof pH andminhnixation of supersaturationwhich carilead to scalingwill be enhancedby staged additionof lime in a seriesof stirredtanks. Conhol also requiressuf&ient tank msidencethne to give stableoperation. A minimumof 20 minutesper tank is suggested. Makeupof the sodaash solution to the desiredsttength quires either instrumentationto weigh out the reqired amountto makea batchof teagentsohnion, or a mix tank sixedto acceptthe entixecontents of a 1 tonnebag. For Britannia,a systemusing weighinginsaumentation is specifred. Sodaash solution addition rate may be automaticallycontrolled to maintaina desiredpH leavingthe last stageof the process,or it may simply be set at a constantdosage to matchthe feed rate (which is not expectedto vary much in the short ter-m). Steffen Robemon and Kirsten 166004 - Brhnia Mine Site Page 6-54 Plocculantaddition is not usually automaticallycontmlled. The diluted flocculantsolution is metemd thmgh a needlevalve, and its additionrate is monitoredwith a rotameter.Plocculant performance will be enhancedif dilution is accomplishedwith sufficient residencetime (30 minutes)to allow complete hydrationof the polymerbefore addition to the ptocess. 6.5.4.2 Turbidity measurement . Pmess upsetsin AMD and similar typesof heatmentplants are commonlyassociated with an incmase in the level of suspendedsolids in the effluent. The conditioncari be monitomdusing an on-lineturbidity metercoupled to an alarmsystem. Sampling and analysesof effluent samplesduring start-upcari provide a correlation betweensuspended solids, turbidity and other parameters. In this way, a masonably instantaneousmeasurement of generaleffluent quality cari be provided, and seriousupset conditions avoided.Regular maintenance and recalibration of the turbidity meteris essentialin orderto pxovidegood quality data. The use of an on-line instrumentsuch as a turbidity meter cari mducethe amountof samplingand analyticalwork requiredfor processcontml and for regulatorycompliance. Automaticconnol cari be usedto ptovide an alann, and to divert the ptoduct stmamback to the feed sourcewhen turbidity specifïcationsare exceeded. 65.5 Andytical support At the Britannia treatment plant, analytical capability will probably be limited to transmission spectrophotometry(not atomicabsorption spectrophotometry), and simpletitrations. Plant operatorscari be trainedto completethis type of analysis,but the levelsof detectionachievable are often not adequate for monitoring treatedsolutions. Clean facilities are mquired to avoid contaminationof assays,ami independentlydetemGned msults cari be more cmdible for extemalreporting. ‘Ihus, normal analytical supportconsists of a mixtureof on-sitedetenninations for day to day plant control,together with extemal assaysfor reporting purposes. Commerciallaboratories have equipmentsuch as Muctively coupled plasmaspectrophotometers (ICP) that cariperform multi-element assays more quickly andcheaply. These labs also have personneltrained in the more diflïcult wet techniquesrequimd for somecimumsnmces. The ffequencyof samplingwill be specifiedin the permitunder which the facility operates.Beyond tbis, when a treatmentplant is in stableoperation, samples once a shift are the most that might be xequimd, andthis might be reducedto daily samplingor evenless frequently when feed flow andchemical makeup do not vary quickly, as shouldbe the caseat Britannia. The flow path tbroughthe mine, togetherwith storagecapacity to be providedbehind the 4100 bulkheadwill help to evenout the plant loading. Steffen Robertsonand Kirsten 166404 - Britannia Mine Site Page 6-55 6.6 Capitai and Operating Cost Estimates 6.6.1 FIow and Loading Critical to the sizing and costingof the treatmentpmcess are the flow rate and acidity loadingused for des@. 6.6.1.1 Geotechnical/IIydrologicalAnaiysis The meanaunual flow of a 100 year wet year with half of JaneBasin catchmentdiverted and 100 % diversionefficiency gives 396 m3/h. Use of a diversionefficiency of 70 % and assumptionof surgesin flow at 10 % abovemean to allow for inflow exceedingstorage at somepoint in the yearprovides a mean annualflowof511m3/handapeakflowof576m3/h. Loading Assumingdiversion of surfacewater at the open pits, with all drainagedixected to the 4100 level and meanannuaI flow of a 100 year return wet year,the calculatedloading fhm availabledata compaxedto “typical” long texmslow as shownin December1990 sampling, the coppr loading will be 233 kg/day, and the zinc loading will be 413 kg/day. 6.6.13 Historicai Data In Secdon6.6, the flow andloading data fxom the 4100 portal wexereviewed for the period 1983to 1989. It wasConcIuded that alIowingfor a contributionfkom the 2200 flow, the meaucopper 1eveI wouid be 21 mg& with tbe relatedacidity at 300 mg/L of CaCG eqyivalent,in a fiow averaging635 m3/h. The analysisshowed that the predictedaverage copper production was 320 kg/day, so the associatedacidity loading would be 4.6 toms/day CaCO,equivaleti The geotechnicalprediction of loadingis lower owing to the assumptionof the applicationof diversions to the water enteringthe mine. However,although a reductionin loading is expectedto accompanya reductionin water enteringthe mine, this is an uncertainpredictio~~ For plant design,a conservative assumptionwould be no changein thehistodcal loading. The ge-otechnicalpredictious should then be examinedas a sensitivitycase. Stcffen Robextsonand Kimten 166004 - Britannia Mine Site Page 6-56 6.63 Des@ Basis The peak 100 year retum flow estimatedwill serveas the designbasis for sizmgequipment where size is dependenton flow rate. Whereequipment size is dependenton loading@agent preparation and dosing equipment),the historicalloading of 4.6 tonnes/dayCaCq plus a designfactor will be used. A plant shouldnot be designedto operatefor any significanttinte exactly at its ultimate capacity;this leavesno flexibility to cormctproblems or allow for down tinte. Consideringthe uncertaintyin the data, we themforefeel it prudentto apply a 20 8 designfactor. The designconditions for eouinmentsizmg Will thereforebe: m 576 m3/hx 1.20 = 690 m3/h Loading 4.6 tonneshiayx 1.20 = 5.5 tonnes/dayCaCO, For the oneratingcost estimate,reagent consumption will be estimatedbased on the historicalloading of 4.6 tonnes/dayCaC03 (no contingencyincluded), with the pmdictedreduced loading due to application of diversionconsidered as a semitivity. 6.6.3 Equipment List The flowsheetwhich is the basisfor this estimateis shownin Figure6.14, ami an equipmentlist is given in Table 6.14. If an all lime systemwere selected,it is likely that the soda ash facilities would be retained,as the additionto capital cost is not large, ami the flexibiity to add the secondreagent could provide secuxityshould the effluent chemistrychange. Acid mine drainageis suppliedfrom behindthe bulkheadat the 4100 level at a controlledrate to the first of two treatmenttanks in series. Each tank has been sixedto provide a tesidencetime of 30 minutes basedon feed fiow. Lime is addedto the fimt tank to maintaina controlledpH which may be set in the rangeof 5 to 7. Underflow sludgefrom the clarifier is recycledto this reactorto increasethe solids concentrationand impxove flocculant effectiveness. Sodium carbonate solution is addedto the secondtank at a rate which is ratioedto the feed flow rate to providea dosageof 242 kg/tonneCaC03 acidity in the feed. Slurty overfiowingthe secondtank flows by gravity to a flash mixer of 30 secondsresidence tinte, whete diluted flocculant solution is dosedat a rate of 1.5 ppm. Fxomthis mixer, it passesto three lamella clariiïersin parallel. Steffen Robertsonand Khsten Table 6.14 - Major Equipment List - Britannia Water Treatment Plant Item No. Description HP/- Conn; Total No. Req’d unit HP Cost 1 2 Neutralization tanks, 21 ‘x23’ 0 0 184,000 2 2 Agitators, SS 30 60 45,000 3 1 Air biower 100 cfm 10 10 7,000 4 1 Clarifier mech. 87’ cs 5 5 91,000 5 1 Clarifier tank, 87’dia. cs 0 0 210,000 6 1 Piiter press, 100 ft3 1 1 123,000 7 4 Diaphr. pumps 0. 0 38,000 8 1 Lime siio/slaker/storage pckge 15 15 180,000 9 2 Hor. cent. pump, srl, 2” 5 10 6,000 10 1 S. ash bin, 5 t, c/w scr. conv. 3 3 18,000 11 1 Soda ash mix tank, 9x10’, cs 0 0 10,000 12 1 Agitator 3 3 6,000 13 1 Soda ash stock soln tank, 9x10' 0 0 10,000 14 2 Metering pump, O-5 USGPM 1 2 9,000 15 1 Ploc mixing unit 3 .3 24,000 16 1 Mix tank, 4x6, pe 0 1,000 17 1 Agitator 1 1 2,000 18 -2 Moyno transfer pump 3 6 7,000 19 1 Stock tank 8x8 cs 0 0 7,000 20 2 Moyno process feed pump 3 6 7,000 21 1 Plant air compresser, 500 cfm 150 150 36,000 22 1 Chain hoist 0 0 1,000 23 4 Submersible pumps, 8’ 50 200 57,000 Total 475 $1,079,000 166004 - Britamia Mine Site Page 6-58 The clarifiershave been sixed based on an industrystandard loading of 0.5 USGPM/ft?rise ratefor water treatment-typehydroxide sludges. This is a lower rise rate than demonstratedin testing,but a design factor is necessaryto providean operatingrange for the equipment.Most of the sludgeis withdrawnand recycledto the first reactortank. As requimdto mahitaina constantsludge inventory, a portion is fed to a filter pressusing an air-operateddiaphragm pump (an additionalpump is providedfor spamcapacity). The filter pmssis a caulked,gasketed, recessed plate unit sizedto handlethe mquimdshrdge volume in four batchesper 24 hour day. The cakeis dischargedat a densityof 35 percentsolids and is truckedto disposalat a site to be determined. Clarifier overflow is continuouslymonitored for turbidity. If turbidity rises,the plant feedis stopped,and the ovefflow is ncycled to the first reactorfor retreatment Clear ovefflow is directedto one of three monitoring ponds, whem it is held until analytical msults verify that it meets dischargecriteria. Submergedpumps then dischargethe pond throughthe existingoutfall mto Howe Sound. The costsfor the monitoringponds are addedin Table 6.15, after the factorsfor piping, etc. havebeen applied. Burnedpebble quicklime is delivemdin tankertrucks and pneumatically conveyed to a 45 tonnelime silo. It is slakedas required,with the milk of lime bemg stand in a tank fiom which a mchculationloop is pumI& Milk of lime is dosedto the pmcessas mquimdto maintainthe set pH. Sodaash is delivemdto the plant in 1 tonne bags which are emptiedinto a hopperas mquired. It is conveyedto a mix tank to makebatches of sodaash solutionin water. The sodaash solutionis dosed to the pmcessby a meterhigpump whose rate is automaticallyadjusted to maintaina constantratio to the feed rate. $6.4 Factored Capital Cost Estimate The purchasedequipment cost has beenfactomd into a fixed capital cost as shownin Table 6.15. This estimateis of the type describedas a StudyEstimate by Weaverand Bauman(1973) and is expectedto bewithin3Opercentofthecosttobuildtheplantdescribed. The capitalcosts shown do not includeGST. We havenot investigatedthe tax positionof the plant. The overall capitalcost would mcmaseby about7 percentif the GSI’ is applicable. The estimatedfixed capital cost for the plant is $3400,000. TO this would need to be addedowner’s costs,lhming charges,head office costs,and other costs as dictated by the ownexs’accounting methods. This estimateis basedon all new equipment,and significant savings might be realixedif appropriateused equipmentbecame available at the time purchasingcommenced. Steffen Robeztsonand Kimen Table 6.15 - Factored Capital Cost Estimate for Britannia Treatment Plant lesign Flow 690 m3/h .- rota1purchased equipment 1,079,000 nstallation at 25% 269,750 Mat installed equipment 1,348,750 Piping 15 % 202,313 Electrical 12 161,850 Instrumentation 7’ 94,413 Buildings, struct. 20 269,750 728,325 rotai Physical Plant 2,077,075 donitoring ponds 456,000 Zapital spares 5% 53,950 Startup and commissioning 2% 21,580 531,530 2,608,605 3g. and Construction 18 46 469,549 3,078,i 54 >ontingency 10 % 307,ai 5 rota1plant fixed cost 3,385,969 Say $3,400,000 ------m-s- 166004 - Brhnnia Mine Site Page 6-60 The factor assumedfor structuresassumes that a building would be providedto housean office, control room, control and switchgear,reagent storage and pmparationequipment, pressure filter, air blower, rudimentarymaintenance facilities, and the plant air compresser.The lime silo, processtankage and clarifier would be outside. 6.65 Operating Cost Estimate 6.65.1 Lime Treatment System The operatingcost based on treatmentwith lime (no sodaash) is summarizedin Table 6.16,and amounts to $0.16/m3treated at the historical mean operatingflow of 635 m3/h. Reagentusage assumes the txeatmentof 1669 tonnesacidity (as CaCO&per year, and a lime dosage/acidityratio derived from teslwork of 0.88 kg pebblelime/kg CaCO,. The major cost items are for lime, soda ash,labour, and shrdgedisposal. This coversonly the costsat the site, and doesnot allow for any costsassociated with managementof the facility beyonda generalforeman. Chemicalvendom have advised us that GST would apply to thesepurchases, and this hasbeen included at 7 percent. Lime consumptionhas beencalculated fîom the loading assumingthat the purchasedpebble quicklime would have92 8 activelime content,and in the gypsum-saturatedsolution, would reactto an extentof 82 96. This leavesmsidual alkahnity to stabilize’the shrdge. Operahg labour has beencosted at $18.oO/h,withallowance of 30% for payroll burdensand 10 % for overtime. The foremanis assumedto be paid an annualsalary of $45,000,phrs burdens at 27%. Power is chargedat an averagecost of 5 centsper kWh. Maintenancesupplies are included at 3 % of purchased equipment;operating supplies are aliowedat $51,006/y. Lime is quotedat $118/tonne FOB Britatmia. GST is additionalto the quotedprices. 6.653 Lime and Soda Ash Treatment System Basedon the use of conservativelime and soda ash dosages,them is an operatingcost advantageof approximately$2O,OOO/yr at the operatingflow of 635 m3/h. (Sodaash is quotedat $0.28/kg for 1 tonne bags,FOB Britannia.) Steffen Robesson aad Kirsten Table 6.16 - Operating Cost Estima& Conditions Fiow 635 m3lh Mean Copper 21 mg/L Equivalent Acidity 300 mg/L CaC03 Acidity Loading 4.57 tonnelday 1669 tonne/yr Sample Acidity 285 mg/L CaC03 Lime Treatment Option Lime Dosage 250 mg/LCaO Ratio Lime Dobage/Acidity 0.88 kg CaOlkg CaC03 Percent Reacted Lime 85 % Annual Lime Consumption 1722 tonne/yr Lime Cost :i:i:i:i’:.:.:::::.:::,:::‘:‘:‘I:I126 $/tonne F.O.S. Srittania Annual Lime Cost i;i;i~i;$g~@~#xg nd Soda Ash Treatment Option Lime Dosage 150 mg/L Ca0 Ratio Lime DosagelAcidity 0.53 kg CaOlkg CaC03 Percent Reacted Lime 90 % Annual Lime Consumption 976 tonne Annual Lime Cost $122,963 Soda Ash Dosage 40 mg/L Na2C03 Ratio Soda Ash DosageIAcidity 0.14 kg Na2C03/kg CaC03 Annual Soda Ash Consumption 234 tonne Soda Ash Cost 300 $/tonne FOB Brittania Annual Soda Ash Cost $70,264 ~~~~~ae3i~j~~~ Total Cost Lime and Soda Ash ._..._..._..._..._._...:.:.:.:ii:i Percent Savings 11.0 Polvelectrolvte Consumptbl Percoll56 Dosage 1.5 mg/L . Daily Consumption 22.86 kgtday Ratio Poly/Acidity 5.0 kg/tonne Annual Consumption 8343.9 kg cost 5 Wkg iiifi;i;ifi~~~~~~ Annual Cost :::::::::::.: .\ .: I Summafy of Operating Cost EstImates Lime Lime + Soda Ash Labour $223,891 24.5Ybj $223,891 25.1%/ Total Reagent Cost Supervision Contract Maintenance $25,000 2.7 Maintenance Supplies Op.Supplies Assay Power Sludge Disposai ITotal Annual Operating Cost 1 $914,331 1 OO.OO/t $890,565 100.0%1 166004 - Britamia Mine Site Page 6-62 Opthnizationof this systemwould mquhe additionalpmcess development work, especiallyin termsof evaluatingthe benefitsof recycle,i.e. relief of gypsumsupersaturation, The treatmentsystem design that has beenpxoposed would be sufficiently flexible to accommodateadditional reagents such as sodaash A systemusing lime and sodaash may be pmfembleto a lime-basedsystem due to the hrherentstability of copperand zinc carbonatescompamd to the equivalentmetal hydroxides. For this report,the use of operatingcost estimatesbased just on lime is wan-antedsince this representsproven technology. 6.6.6 Jmpact of Acidity Ibad Reduction on Operating Costs Diversionof surfacewater ànd partial flooding of the workingsmay msult in a reductionin the acidity loadingsthat the treatmentplant would be requimdto pmcess. In order to evaluatethe hnpactof load reductionson operatingcosts a seriesof calculationswere conducted to generateFigures 6.16 and 6.17. Figure 6.16 is a plot of total operatingcost in 1991dollars versus percentage of acidity load reduction, using data in Table 6.16 as the basecondition. Two casesam provided;the first case,which mcludes sludgedewateting and off-site truckingand disposal (“Complete Sludge Cost”) and the secondcase whem sludgedisposaJ costs have been elhnim&d. The secondcase would applyif the dischargeof a thickened sludgeto the undergroundworkings is feasible. Figure 6.17 is a plot of operatingcost reductionversus loading teductionexpressed as percentage,again , using Table 6.16 data as the basecondition. Comparativedata for lime and lhne plus soda ash are included. As expected,reductions in loadingcari signifïcantly reduce reagent costs. However,other costs suchas labour ami power axenot as sensitiveto loadingreductions. For example,based on Figure 6.17, a 50 95 reduction in loading reducesthe operating cost by approximately15 96 (for the case of undergrounddeposition of sludge). 6.7 Discussion Continuouspilot plant operationis neededto btter definesequential lime/sodium carbonate requirementa, generatesufficient sludgefor m-cycle,settling, pressureEhration, and sludgestability tests. Potential savingsfiom using lim&oda ashvs straightlime shouldbe vetied in continuousoperation. A pilot plant could be set up as a demonstrationof the technologybemg applied by the mining mdustry to solution of the acid mine drainageproblem. An oppottunityexists to combinethis pilot work at the Britanniasite with the summerseason at the Minhrg Museum. The exhibit could be expandedto include demonstmtionsof other apptoachesas well. Steffen Robeztsonand Kirsten Evaluation of Operating Cost _ Annuai Operating Cost vs Load Reduction - Operating Cost ($1 1000 j j 1 900 800 700 600 500 A00.-- 0 20 LoaY ioGnO 80 100 Reduct (%) Based on Lime Treatment Option Figure 6.16 Evaluation of Acidity Load Reduction Operating Cost vs Load Reduction Opeyajing Cost Reduction (%) :f. 50 -.. 40 25 35 50 SO 70 80 90 Acidity Load Reduction (%) m c/w Sludge &%! w/o Sludge Based on Lime Treatment Option Figure 6.17 166004 - Britamia Mine Site Page 6-64 The costshown is basedon the historicalloading of 320 kg Cu dischargedper day. Becausethe operatig costcontains significant elements that axenot relatedto loading,the changein operatingcost with loading reductionis mode& and may not justify sometypes of expendihuesto reduceloading. Labouris a significantcomponent of operatingcost. Themis a needto havea responsibleperson present or nearbyat all thnesto dealwith alarmsand upsets,make up magents,and clean the filter press. In fact, cleaningthe pressis a job betterdone with two operators,and this may dictatea switch to an automatic ptessat aboutthme times the capitalcost. A potentiallabour savings could be obtainedif somelabour could be associatedwith the Mining Museum or the teal estatedevelopment. Perhaps the plant could be a showcasefor mdustrymitigation activities, althoughlime p-ses axeinhexently a bit messyfor public exposure. Furtherinvestigation into fate of the sludgeis tequited. Truckingis a sign.iEcantexpense, so that study of fmther dewateringmeasums would be worthwhile. An addedbenefit of an automaticfilter pressis the probablehigher solids contentachievable in its product filter cake,with consequentteduced transport costs. The sludgeis not expectedto be a Special Wastedue to its residualalkahnity. Thus,disposal in a landGll at Britanniais an option, if an appropriatesite cari be found. The quant@,at about 9000 tonneswet weightper yearis not beyondaccommodation in fhis type of facility. The bestsolution would be to pump the clarifier underflowto depositin the workingsbelow the 4100 level. This would eliminatethe need for the filter press,elimi&ng an operatingheadache, reducing the needfor labour andmaintenance. TO justiQ this, knowledgeabout water flows andchen&ty in the areaof the proposeddeposition would need to be developedand interpreted. The provision of monitoringponds for the plant dischargempresents a sigrrificantcapital expenditum (nearlyone-third the equipmentcost). The costsshown for theseare based on the volumeof materialto be excavatedami the areato be lined, but do not representmore than an order-of-magnitudeestimate. With a tutbidity meterinstalled on the clarifier overflow to detectprocess upsets, consideration should be givm t0 eliminatingthese ponds in favour of a direct dischargeto Howe Soumi tbm@ a sea-wa&r dilution chamberas an aid to dispersion. If flow equalizationby storagewithin the mine turns out not to be feasible,the plant sixe might be doubled. Using a standard2f3 power law scalefactor, the capitalcost might be expectedto increaseby a factor of 1.6. Due to the small size of the plant, and the fact that the lime systemquoted to us is alreadysignificantly oversized, the increasein cost might not be as great as ptedictedby this factor. Steffen Robertsonad Kirsten 166004 - Britada Mie Site Page 6-65 The GST positionof the plant needsto be clarifïedto makeboth the capitaland operating cost estimates more certain 6.8 Permit Conditions and Monitoring 6.8.1 DischargeStandards In the original termsof mfexenceit was requestedthat considemtionbe given to the curmntpermit, and to futuxedischarge critetia. Upon review of the draft report,it was agmedthat this is the responsibiity of the mgulatorsand the companyand will be developedwith the mmediationplan The following discussionis ptovidedfor information,ami as an initial approachto dischargecriteria. Smcethe dischargeis not undera WasteManagement Permit and is not an operatingmine it theomtically fa& outsidethe jurisdiction of the ProvincialObjectives established under the WasteManagement Act. Assumingthat it wasan activemine it would be regulatedacconiing to the critetiapmvided in Table6.17. Under FederalRegulations the FisheriesAct which conttolsthe mleaseof deleterioussubstances would be the only legislationthat applies. Sincethe effluent is toxic to fish then it would legally be deemedto be in contraventionof the Fisheriesact. Howeversince the previousowner,is no longer msponsiblefor operationof the fscility it would be diffïcult for FederalFiiheries to advancea caseunder the Fisheries Act that would in fact resultin any hnprovementin the currentstatua. The Metal Mines Liquid Effluent Regulationsdo not apply in this casesince Britannia is no longer an activemine. If Britanniawem an activemine then it would be conttolledby the Metal Mine Liquid EffhrentRegulations established under the F&er& Act (Table 6.17). Once mmedialmeasums such as installationof a treatmentplant are completethen it will possibleto brhrg the d&chargeinto compliancewith both Federalami prmrincial regulationsand objectivesami issuea permit Dischaqe Standardscari be set by hvo methods,either at the point of dischargeor on a receivingwater basis. MMLER criteriaor Level “A” ProvincialObjectives would apply if the dischargeis regulatedon a “end of pipe basis”. Criteria basedon the receivingenvironment could utilize criteria such as the CREEM guidelines. In this casethese criteria would apply outsidea specifïczone of hrfhznce of the discharge.This zoneof influencecould be defined spatiallyas a specifiedoffset both horizontallyami vertically from the point of discharge.The use of receivingwater criteria may result m a less shingent dischargecriteria than “end of pipe” specifications,especially if the allowedzone of innuenœis largedue to the fact that the teceivmgenvironment is alreadyheavily impacted.Based on studiesconducted by EE in 1985 (Goyette& Ferguson)the cmrent dischargeis having a significanthupact on the Howe Souud in that elevatedcopper levels are evident in oyster and musse1tissue over a wide spatial distribution. Howeverit shouldbe pointed out that the dischargeof tailings and cycloneoverflow at the mouth of BritanniaCmek over a 50 year period may be responsiblein part for the tissuemetal levels noted. Steffen Robemon ad Kirstm 166004 - Britamia Miue Site Page 6-66 Table 6.17 Effluent Water Quality Regulationsand Objectives muent ReceivingEnvix&nent r I Parameter MMLER* Provincial CCREM Objectives*** Objectives** PH 5 6.5-85 6.5-9.0 Total SuspendedSolids 2550 25 - 75 cl08 increase Toxicity loo-80% 100% Cyanide 0.1-0.5 0.005 AmmoniaN 1.0-10 1.4-2.2 Metals Allmlimml 0.5-1.0 0.al5-0.1 ANSliC 0.5-1.0 0.05-0.25 Cadmium O.Ol-o;l o.ocND0.0018 Copper 0.3-0.6 0.05-0.3 0.002-0.004 h-on 0.3-1.0 0.03 Lead’ 0.2-0.4 0.05-0.2 0.001-0.007 Manganese 0.1-1.0 Nickel OS-l.0 0.05-0.5 0.025-0.015 ZillC OS-l.0 0.2-1-o 0.03 Al1 concem&ns in mglL unlessothenvise specified * Metal Mines Liquid Effhent Regulations- FisheriesAct 1970 ** Pollution Control Objectivesfor the Mining, Smeltingand RelatedIndustries of B.C. (1979), Pollution Control Board,Mïnistry of Envhwunent,Victoria *** CanadianWater Quality Guidelines, 1978, Task Forces Water Quality Guidelines of the Canadian Council of Resourceand Envinxunental Ministers (CRREM), 1987 Steffen Robemon and IGrsten 166004 - Britannia Mine Site Page~~67 The establishmentof future dischargestandards will be a function of threefactoxs: 0 receivingwater objectives; ii) compliancewith existingregulations established under the WasteManagement Act; iii) availabilityof the technologyto meet the desimdeffluent quality. In regardsto tic availabletechnology it caribe assumedthat if a treatmentsystem is hxtalled suchas one that involvesthe useof lime, the incrementalcosts associated with meetinga specific“end of pipe” ctiteria aresmall relative to the total capitalcost of the facility andbaseline operating costs. Someother treatment optionssuch metal mcovety w/o neutmlizuionmay however mquire some flexibility in uxmsof discharge standards. In summaryit is mcommendedthat “end of pipe” criteria be establishedfor this facility. Thesecriteria shouldconsider both the receivingenvironment and the treatmenttechnology used. 63.2 SurveillanceMonitoting Requirements Acidic drainageis curmntly originatingfrom both the 2200 and 4100 port& Diversionof the 2200 drainagewill be essentialto minimizethe impacton BritanniaCreek. Potentiallya tmatmentfacility could be wnshuctedin the vicinity of the 4100 portai or the existingcopper recovery plant in orderto tmat all acidic drainagefiom the property. Oncethese treatment faciities are in place it will be necessaryto monitor the successof the diversionand drainagecollection system. This will potemiallyinvolve the establishmentof a surveillancenetwork that would be includedas patt of the petmit. The networicwould include stationsboth upstmamand downstreamof the property. The network would be monitomdon a regular basis to deternmrewhether the collection and diversionfacilities are functioning as designed. Stationswould be monitomdvia samplecollection and the useof portablehu%ruments. Trends in the data would in mm be usedto evaluatethe efficiencyof collectionami diversion. A secondarypurpose of the surveillanceprogram would be documentationof huptovementsin water quality in the drainagebasin relativeto both historic informationand data collectedas part of this program. The sweillauce networlcwould be monitoredfor physical parameterssuch as pH, conductivity and suspendedsolids as well asacidity and sulphate plus both total anddissolved aluminum, cadmium, copper, h-on,lead, nickel and zinc. Surveillancewould be conductedmonthly at most stationsthat are accessiblehowever it would not likely bé necessaryto conductall the analyseson a fiequentbasis since in many casesphysical measurements Steffen Roktson and Kirsten 166004 - Britannia Mine Site Page 6-68 caribe usedfor assessmentonce a mlationshipbetween items suchas dissolvedmetals and conductivity are established. The location of the surveillancenetwork stationswould mirror that conductedas part of this program. Designof a surveillancepmgram will dependto someextent on the availabiity of fùnds and personnel to conductthe work. 6.83 Description of Available Monitoring Equipment The surveillancenetwork described above would rely on the use of both samplesand on-sitemonitoring equipment,Analyses of metalswill dependon the collectionand analysesof samplesusing commercial labs while someof the physicalmeasumments cari be conductedusing either hand held instrumentsor portableequipment. Physicalmeasumments that cari be madeusing portableequipment include, . PH . turbidity . COlldUCtiVi~ . dissolvedoxygen Theseinstnunents are madily availablecommercially at a nxsonablecost, The useof instrumentsdoes howeverrequire some training regardingoperation and maintenance. pH would be used in specifïcamas to determineif acidic upstreamdrainage is machingthe mceiving environmentand whetherthem is any deviationfrom baseline conditions lkrbidity measumments cari be usedto measumthe impactof bank erosionin the Upperportion of the drainagebasin on downstmamwater quality. Pïeld turbidity data cari be correlatedwith lab suspended solid8data. Conductivitycari be usedto detectedthe pmsenceof contaminatedgtoundwater msulting fiom acidic drahuge. since the pmsenceof dissolvedsalts msulting from the generationof acid will hrcmase conductivityreadings abve background. Dissolvedoxygen cari be usedto assessthe impactof acidicdrainage on the mceivingenvixonment since thesedrainages cari contain oxygen demanding materials, however in mostcases changes in conductivity would be more sensitiveto the pmsenceof acidic drainagein a particularstream. Diisolved oxygen would be of moresignificance to documentingthe statusof a streamin regardsto waterquality for aquatic habitat Steffen Robertsonand Khten 166004 - Britamia Mime Site Page 669 Instrumentationwould naturallybe includedin the installationof a tnzatmentfacility. Chemicaldosage of reagentssuch as lime would be controlledby a combinationof flow me-ment and pH while final efnuent quality would be monitored usiug on-line turbidity. The level of sophisticationof the instrumentationshuMled in the plant will be controlledby the pmcessused and the availabilityof trained operators.Expetience has indicated that instrumentationcari significantly hnprove performance and reduce the fquency and severity of upsets.~However it is essentialthat operatorsbe trained to operateand maintainiustrumentation to maximizeplant pelformauce. Steffen Robemon ad Kirsten 166004 - Brimnia Mine Si Page 7-l 7.0 CONCLUSIONS AND RECOMMENDATIONS 7.1 Conclusions The following discussionof conclusionsand recommendationsis basedon the investigationscompleted to date. The site assessmentwithin the scopeof this investigationhas been completed, and the amasin which remedi+ionmeasums for acid drainageare mquimdboth in the short and long tenn identifled. Potentialphysical and chemicalcontrol and remediationmeasums have been identified. The next stage of the investigationrequires more detalledinformation in specificamas than hasbeen available to date. These recommendationsfor further studies specifïc to the contml measureshave been included in Section6, Table 6.1. In someareas, further field investigationsare requiredto define technicaldetails and constructioncosts. As a result of the investigationto date,the following conchrsionsand recommendationsam indicatedz . acidgeneration and metal leaching is continuingfrom the Britanniasite msultingin elevatedmetal concentrations,notably copperand zinc, ami other metal loading to Brltannia Creekand Howe sound; . water quality data are limited from the site, metal loadscurrently discharged are lessthan those dischargedduring operation, they havehowever not significantlydecmased in the pastfive years; . variability in precipitationand runoff affectsthe sourcesand relativecontribution of fmsh water and contaminateddrainage, and the drainagequality and loadingsf?om, the mine workings. The fluctuationscari be bath seasonalami vary within shorterperiods. Long antecedentdry pexiods followed by high pmcipitationevents (such as the summer/fallof 1990)eau result in shortterm : high metal loading in drainagewaters; . the primarysources of metalloading appearto be drainagefrom the undergroundworkings: from the 2200 and4100 portaisand to a lesserdegree the 2700portal. Pit walls and wasterock above the 2200 level appearto be oxidizedand potentiallyconhibute oxidized pmducts to the drainage which entersthe undergroundwodtings; . there is a signiflcantstore of oxidation productswithin the undergroundwodcings and within wasterock tailings and flll materialused throughout the site; . the Britanniasite couldtherefote potentialIy continue to generatewntaminated drainage for many years. Physicaland/or chemical wntxol measureswould be requiredfor improvementin drainage Steffen Robertsonand Kirsten 166004 - Britannia Mine Site Page 7-2 water quality to BritanniaCreek and Howe Sound. It must alsobe recognizedhowever that in the short tenn, as conho measmesare implemented,drainage water quality may worsendue to physicaldisturbance of wastesand releaseof stomdoxidation products; acid generationis well establishedat the Britannia Site ami, given the extent of development underground,and surface openhqs (gloryholes) whichessentially act as“funnels” forprecipitation, contml of acid generationand comaminammigration are not feasible; diversionof surfacewater intlows is estimatedto potentiallyteduce the quantityof flow through the workingsby appmximately50 percent; flooding of all of the mine workingsis not feasible,however partial flooding may significantly reducethe volume and loadingto the heannentplant; diversionof inflows with ditchesand coversto the mine wasteat the pits and the 2200 level poti may be successfulat reduclnginflows for the controlof acidgeneration and metal leaching. Somecollection and treatment, removal of wasteor coveringmay be quired, dependingon the extent of the waste,and hydrogeologicalregim~ the undergroundworkings could be used for flow attenuationto the treatmentplant Partial flooding of the workingswould provide surge control prior to the treatmentplant, to allow control of the influent concentrationsand flow ratesto the tmannentplant; diversionof flow thmughthe mine wasteat the 4100 and mill levelsdoes not appearfeasible for control of ARD, althoughthe extent of the waste and drainagewater quality is not known. Collectionand treatmentmay be mquim& remediationor mclamationof the “tailings” pondnear the 4150level will probablyxequhe a caver and/or flooding if it is determhredthat this material is (or could potentially) contxlbute contaminantsto drainagewater. If flooding is selected,then the embankmentstability must be examine& an opportun@exists to test copperleaching enhancement and mcoveryif desired. The outcome of snchan activity cannotbe predictedwith certainty,but it shoulddelay eventual“bumout” of the acid forming reactionsif the enhancementis only moderatelysuccessful, copperrecovery from the presenteffluent is expectedto be uneconomic; Stetfen Robemon ad Kirsten 166004- BritamiaMine Site Page7-3 . significantreduction in copper,zinc and acidityloading aretechnically feasible by applicationof a lime or lime and sodaash treatment pxocess. The ca@talcost for sucha treatmentpxocess is esthnatedat $3,400,000assuming two stage lime or lhne plus soda ash treatment,with clarificationand sludge dewatering by fllter pmss. The annualoperating cost for the limë process is estimatedat $914,000assuming the historical 10-g. Capital expendituresto mducethe loading will bring aboutmodest reductions in ammaloperating costs. 73 RecommendedApproach to Future Work The mcommendedapptoach to fittuxework at the site oumed in the followhrg sectionincorporatesin a stagedapproach bath potential remediationoptions and specific investigations. More information is requhedabout the physicaland chemicalnature of the site which must be acquimdin the next year or two. Experiencewith site investigationsand remediationof abandonedsites has shownthe importance of thoroughlyunderstandhrg the speciflcsources of acid generationand contaminant loading, and relative contributionto drainagewater, prior to implementingmmediation measures. As mmediationmeasums are put in place,in the stagedprogram developed below, spec%cmonitoting must be conductedto determine the effect of the control measure,and refine the treatmentdesign and overallremediation requirements. The Britanniasite could alsoprovide a ratherunique opportunity for researchand investigation into ARD processesand controL The site is readily accessibleby road with a long historyof ARD potentiallyfrom all componentsof any mine site; openpits, underground,tailings, waste rock and constructionmatexials. Considerationshould be given to developingthe site as a researchfacility, and also as an oppottunityto disseminateinformation to the public. The waterquality informationand topographical information has beeninwrporated into a CAD packageand also a GIS system,providing an idealmedium for preparation of visual displaysof informationfor the public. More recemtopographical information is being acquited at this time, and incorporatedinto the GIS packagefor fûrther investigationinto the generalapplications of GIS to environmentalsite assessmentby SRK. ‘l’he potentialconttol optionsfor the Britanniasite and mquhedinvestigations specific to thoseoptions have beendescribed and tabulatedin Section6. Additional investigationsto more fully understandthe site and selectremediation measums are deflnedin the following discussion,with conttol measuresthat shouldbe consideredin the near future. Within the next year it is recommendedthat the followmg be implemented: . water quality monitoringshould be conductedon at leasta monthlybasis for a 14 monthperiod along Btitannia Creek,Jane Creek, and Minerai Cteek for key parametersmcluding flow, pH, acidity/alkahnity,conductivity, sulphate, and total and dissolvedCu, Fe and Zn, SteffenRobesrson aad Kirsten 166004 - Britamia Mine Site Page 7-4 . detailedseep surveys in the sprhtg(fmshet) ami fallrain periods. The amasaround which these surveysshould be concentratedare the wastedumps, pit walls, tailings and settlingponds, and in areaswhem wastehas beenused for Gl.h . surfaceinvestigations to identify and sampledrainage to the Furry Cmekbasin fmm undergmund. Accessto this amais reshictedhowever and it is not clearwhich aditsmay still extendto surface. If the 1800level adit is still fme draining,this would ptovide useful informationon the relative contributionof oxidizedpnxiucts over the depthof the undergroundworkings; . surfacesolids samplmg including acid-baseaccounting and shakeflask test fmm openpit/ glory hole walls, wasterock, tailings, and fmm underground(if accessis possible)to determinethe potentialfor further oxidation and the extentof storedptoducts; . geotechnicalinvestigation in Faitview ami EastBluff pit areato evaluateground conditions and availabilityof materialfor diversionof the Upperreaches of JaneCreek fiom enteringthe glory holes(open pits) andlimiting the downstmamcontribution to BtitanniaCreek near the 2200level; . . if feasible,design ami constructsurface water.divexsion(s); and, . conductdetailed monitoxing to evahtateeffect on drainagewater quality and flows; . reflne treatmentsystem design and ovemll remediationplan It is also importantto rexoutedrainage fmm the 2200 level portai away from Britannia Creek,as this drainageis a major sourceof 10-g to the Cmek. Investigationsby Klohn Leonoff (1983, and the provincialmines inqector haveindicated limited accessinto the 2200 level adit, and obstructionswithin a few hu&ed feet of the portaL The physicalstability of the workingsand obstructionsto flow mustbe investigatedto ensurethat pluggingof the poxtalwill not simply causethe drainageto issuefrom another opening. ‘Ibis type of investigationshould be conductedby qualifled mining/geotechnicalengh~~rs in cooperationwith the Mines Wpection Branchoffices. The availablerecords of the developmentof the undergroundworkings are limited (the CopperBeach Estates files andMuseum of Mining files werebath searched),and it may be necessaryto intetview formermine employeesand reviewtheir pemonnelfiles to developa betterundemtanding of the extentof the undergroundworkings and surfaceopenings. Another key issuethat shouldbe addressedwithin the next year is wasteat the 2200 level. The nature ami quantity of wastesat this level, must be quantifmdthrough original topography,survey of cunent elevationsand sampling(by trenching,test pits or drilling). A limited hydrogeologicalinvestigation to detennineflushing and contaminantloading to BritanniaCmek shouldbe considered. Steffen Robertsonad Kimen 166004 - Brhmia Mine Site Page 7-5 Diversionof surfacewater and e*tion of the 2200poxtal drainage should impmve the drainagequality andquantity to BritanniaCreek and Howe !Sou& Within the next yearhowever it would not be possible to identi@,design and install remediationand contml measuresthroughout the site; the site is simply too complex,with insufficientphysical, chemical and hydrologiedata available. In the shortterm therefore someform of collectionand/or chemical treatment may be requiredif an immediateimprovement in water quality is feasible. It shouldbe xecognizedhowever that if tnzatmentis selectedas the long term control for the site, this interim treatmentplant designmay not be appmpfiate._ Steffea Robettsonand Kirsten 166004 - Britamia Mine Site Page g-l 8.0 REFERENCES AnacondaMining CO.,1965. 1974correspondence, pp. 15-20. Anonymous, 1975. PtocessDesign Manual for SuspendedSolids Removal, U.S. Environmental ProtectionAgency (NTJS),Springfield, VA, January1975, pp. 5-1 to S-24. Anonymous,1976. Lime Handling,Application and Storage,National Lime Association,Bulletin 213, Washington,1976, pp. 48-69. B.C. Departmentof EMPR, 1890-1900,p. 16. Brodie, J.B., IndustrialDivision, Departmentof Lands,Fonxts and WaterResources, Pollution Control Branch Victoria,British Colmbia, letter,September 26,1974, Re: Requestfor updateddrawings to show detailsof referredto in letter of August 14, 1974. AnacondaCanada Ltd., Attentions J. Robertson. Bxodie,J.B., JndustrialDivision, Departmentof Lands,Fores& and Water Resources,Pollution Control Branch,Victoria, British Colmbia, letter, June25,1974, Re: Applicationfor PollutionControl Permit on Behalf of AnacondaCanada Lui. AnacondaBritannia Mines Lui. Attention J. Lovering. Bruynesteyn,A., and Cooper,JR., 1974. Leachingof CananeaOxe in Test Dumps,in Aplan, F.F., McKhmey,W.A., and Pemichele,A.D., (eds.),Solution Mining Symposium,AIME, New York. Cathles,LM, andSchlitt, W.J., 1980. A Model of the DumpLeaching Process That Jqqorates Oxygen Balance,Heat Balance,and Two DimensionalAir Convection. Chapter2 in Schlitt, W.J. (ed.), Leachingand RecoverhrgCopper from As-MinedMaterials, AIME, New York. Drake,J. ami J. Robertson,January 4.1973, Departmentof Mineral Engineering,University of British Columbia,preliminary Report on the Disposaiof Mine Effluents frum the BritanniaMine Ltd., BritanniaBeach, B.C., basedon a ReseaxhProject in Partial Fulfïhuentof the Requirementsof the Mlneral Engineering480 Course. Enington J. and Ferguson,K., 1987. Acid Mine Drainagein British Columbia- Today andTomorrow, Pxxmedingof the Acid Mme Drainage Seminar/Workshop,Environmental Canada, Halifax, Nova Scotia,Match 23-26, 1987,p. 19. Steffen Robemon and Kimen 166004 - Britamia Mine Site Page 8-2 Ferguson,K., 1985, Static and Kinetic Methods to Predict Acid Mme Drainage. Presentedat the InternationalSymposium on Biohydrometalhngy,Vancouver, B.C., August. Gamls, R.M., and Christ, CL., 1965. Solution, Minerals, and Equilibria. Fxeeman,Cooper, San Francisco. Geological SurveyBranch, 1990. Minefield ReportNo. 092GNWOO3,MineraI Resomces Division, B.C. Goyette,D., and Ferguson,K., 1985. EnviromnentalAssessment of the BritanniaMine - Howe Sound, Departmentof the Environment,EPS, Pacifie Region, February 1985. Hause,D., and Willison, LR., 1986. DeepMine AbandonmentSealing and UndergmundTreatment of PmcludeAcid Mine Drainage. Fxom7th Annual West Virginia SurfaceMine DrainageTask Force Symposium Hooper,M.J., July 1970,Feasibility Study to Jnvestigatethe Expansionof Jn-SituCopper Leaching at AnacondaBritannia Mines, BritanniaBeach, B.C. .r James,H.T., 1929, Britannia Beach Map-area,British Columbia. CanadaDepamnent of Mines, GeologicalSmvey of Canada Klohn Leonoff, 1984,Report prepamd for CopperBeach Estates Ltd. Klohn Leonoff Lui., 1985. IntemalMine Drainageat 2200 Level, reportfor CopperBeach Estates Ltd. Lanouette,K.H., 1977.Heavy Metals Removal. Chen&al Engineering,Gctolxx 17, 1977,pp. 73-80. Lovering, John, AnacondaBritannia Mines, Division of AnacondaCanada Limited, letter August 14, 1974, Re: ApplicationPursuant to Pollution Comm1Act 1967 on behalf of AnacondaCanada Limited, datedMay 8,1973, Director Pollution Control Branch,Parliament Buildings, Victoria, B.C. Attention: J.B. Brodie. Lovering,J., AnacondaBritannia Mines, Division of AnacondaCanada Limited. letter,April9,1974, Re: ApplicationPursuant to Pollution Comm1Act, 1967,on behalf of AnacondaCanada Ltd., dated May 8,1973, J.B. Bmdie,Department of La&, Forestsand Water Resources, Water Resources ServicePollution Control Branch,Victoria, British Columbia. Steffen Robeztsonami Kirsten 166404- BritarmiaMine Site Page8-3 MacDonaid,R.J.C., Kondos, P.D., Cmvier,S., Rubinsky,P., and Wasserlauf,Mk., 1989. Generationof, andDisposai Options for CanadianMineral Industry Effluent Tmatment Sludges. CANMET MSL 8945 (OP&) Draft McCullough 1968, Geology of the Britannia Mhieralized District British Columbia, West Section. Master’sThesis, Univers@ of Illinois. Moore, B., 1985. (Anaconda Britannia Mines) Copper Beach EstatesLtd. AE-2194 Receiving EnvimnmentSurvey, internai teport, Ministry of Envimnment,Region 2 WasteManagement. . Moore,B., ami van Aggelen,G., 1986. (AnacondaBritannia Mines) Copper Beach Estates Ltd. AE-2194 Environmental Impact Assessment1985/86 Update Survey, internai report, Ministry of Environment,April 1986. Murr, L.E., 1980. Theoryand Practice of CopperSulphide Leachhrg in Dumpsand In-situ, MineralsSci. Engng,VOL 12, no. 3, July, 1980, 121-189. Novak,J. F., AnacondaBritannia Mines, Division of AnacondaCanada Limited, letter January11,1974, Re: ApplicationPursuant to Pollution Control Act, 1967,on behalf of AnacondaCanada Ltd., dated May 8, 1973, J.B. Bmdie, Departmentof Land& Forestsand Water Resources,Water ResourcesSetvice Pollution Comm1Branch, Victoria, British Columbia. Pelosi,P., andMcCarthy, J., 1982. PreventhigFouling of Ion-exchangeResins - 1,Chemical Engineering, August 9, 1982.7578. Ramsey,B., 1967,Britannia - The Stoty of a Mine, BritanuiaBeach Community Club, B.C. Robettson,J., AnacondaBriunmia Mines, Gctober17,1974, Meeting behveenAnaconda and Pollution Control Board,Summary of Meeting Held in Victoria. Robertson,J., AnacondaBritannia Mines, May 24, 1974, Summaryof Viiit by the Pollution Control Branchto BritanniaMines. Spedden,H.R, Malouf, EE., and Prater, J.D., 1966. Cone-typePmcipitators for Imptoved Copper Recovery,Journal of Metals, October1966.1137-1141. Steffen,Robertson and Kirsten (B.C.) Inc., 1988, Acid Mine DrainageReseamh in British Columbia, AnaIysesof Resultsfrom Questionnaire,‘April. S&&I Robextsonand Kirsten 166004 - Britannia Mine Site Page 8-4 Stern,W.R., 1966. Leaching-in-place- Jane Basin Project, intemal Britannia memorandum, January 31, 1966. Talbott, G.P.P.,Southem Interior Section,Municipal Division, letter June 26, 1974,Re: Application Ptusuantto PollutionControl Act,, 1967,on behalfof AnacondaCanada Ltd., DatedFeb 6, 1973.. AnacondaCanada Ltd. The AnacondaCompany (Canada) Ltd., 1965.Britannia Operations. Treybal,RE., 1980. MassTrausfer Operations, 3rd ed., McGraw-Hi& New York, 1980. Venables,P. Eng., W.N., Director,Pollution Contml Branch,Department of Lands,Forests and Water Resources,Victoria, Pollution Control Branch,British Columbia,October 25, 1974,Letter Re: RequirementsPmsuant to the PollutionControl Act, 1967,covering discontinuance of operations at the AnacondaBritannia Mine, Britannia,Beach, B.C., AnacondaCanada Ltd. Weaver,J-B., and Bauman, KC., 1973. Costand Profitability Ekirnation, Section 25 in Perry’sChemical Engineen’ Haudbook,ed. by RH. Perry and C.H. Chilton. McGraw-Hi.&New York, p. 46. Wright EngineersLiiited, 1983. CopperBeach Estates Ltd. LeachingPotential, report for CopperBeach EstatesLtd., July, 1983. Steffen Robemon ami Kixste-n APPWIX A DETAILJZD REWLTS OF SITE ~TIGATION Steffen Robertson ~IKI Kirsten WATERQUALITY DATA BriC;Ui: Jane 2200 Jane Jane Brîtannia Britannia Brltannia Minera1 Britannia 4150 Furry Creek Porta1 Creek Creek Creek Creek Creek Creek Creek Porta1 Creek 81 Jl 52 53 82 83 84 Ml 86 1990 06-Dec 06-Dec 06-Dec OB-Dec 06-Dec 06-Dec 06-Dec OC-Dec 06-Dec 06-Dec oo-Dec 06-Dec Physical Tests Total Dissolved Sollds 10 1170 430 430 ii50 10 Hardness CaC03 37=t 610 196 197 lj27 3069 2S47 223s ;: 919 8.13 PH i.i9 3.49 3.99 3.97 6.97 S-il 5.i2 7.93 6.42 4.24 6.36 Total Suspendad Solids 4 21 20 17 5 6 5 Stcffen Rohtson and Kirsten CALCULATBD LCJADINGS (kg/d) Britannla Jane 2200 Jane Jane Brltannia Britannia Britannîa Minera1 Britannia 4150 Furry Creek Creek Porta1 Creek Creek Creek Creek Creek Creek Creek Porta1 Creek Bl Jl J2 53 82 83 B4 Ml 86 06-Dec 06-Dec OCDec OB-Dec 06-Dec D6-Dec 06-Dec 06-Dec 06-Dec 06-Dec 06-Dec 06-Dec Estlmated Flow L/s 560 56 13 69 69 661 730 1040 130 1770 160 NA talc Physlcal Tests Total Dlssolved Solids 404 242 1314 2563 2563 1142 3784 3594 337 4500 17280 NA Hardness CaCO3 363 180 685 1190 1174 7S2 1949 2309 255 ios9 13534 NA PK 7.02 1.49 3.49 3.99 3.97 6.97 5.41 5.72 1.93 6.42 4.24 8.36 Total Suspended Solids 0 19 24 119 101 286 370 449 0 765 180 NA Dissolved Anions Acldity CaC03 131 858 1097 1079 303 1261 935 765 4590 NA Alkallnity CaCO3 300 3:.3 0.00 0.00 0.00 217 0.00 0.00 104 0.00 Chloride Cl 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 IA Fluoride F 0.4 21.0 NA Sulphate SO4 SI 150 1% 23;: 2E hi 27;: 2kf 2983 26680 NA Nutrlents Amonia Nitrogen N 0.34 0.04 mO.16 0.22 0.20 1.03 0.95 1.17 0.08 1.68 0.04 Nitrate Nitrogen N 3.00 0.77 0.00 0.00 0.00 3.37 1.96 a.30 0.13 13.00 0.00 Ii Nitrlte Nltrogen N 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 NA Total Phosphorus P 0.15 0.01 0.04 0.05 0.08 0.11 0.25 0.27 0.04 0.31 0.12 NA Total MetalS Aluminum T-Al 3.58 4.25 69.4 92.4 91.8 26.7 111.0 106.9 1.06 67.3 445.1 Antimony T-Sb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 EA Arsenic T-As 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.02 0.00 0.02 0.01 Cadmium T-Cd 0.01 0.03 0.37 0.49 0.47 0.10 .0.62 0.58 .o.oo 0.47 2.75 ii Coepar T-CU 0.73 2.20 109 140 138 25.9 157 157 0.2 128 289 NA Iran T-Fe 0.00 0.20 47.0 62.6 54.4 23.6 64.3 63.1 32.4 129 Lead T-Pb 0.00 0.00 0.11 0.17 0.17 0.00 0.13 0.00 OlOi 0.00 3.32 Mercury T-Hg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0:oo 0.00 0.00 Selenlum T-Se 0.90 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Zinc T-W 0.39 4.1 55.1 77.5 73.7 15.1 90.8 91.1 0.51 83.5 541 Dt;;k:Ed Wetals D-Ca 142 61.4 133 275 275 242 524 647 916 3373 NA Corner D-CU 0.73 109 140 130 156 156 0.2 124 276 NA I&n D-Fe 0.00 0% 44.1 57.9 50.4 2023. 10.8 11.5 1.0 106 NA Lead D-Pb 0.00 0:DO 0.11 0.17 0.17 0.80 0.13 0.00 0.00 072 3.32 NA Magnesium D-UP 12.6 6.2 84 117 116 42 151 165 5.9 ie4 1215 NA Potassium D-K 1.2 0.52 13.5 21.4 25.2 Sodium D-Na . 3x 9.2 ii.3 3E 4x 70.1 19.5 128 158 Ii Zinc D-Pin 0.49 36:: 52:: 7517 7517 1s:1 0717 89.1 O.iS 83.2 505 NA Results are expressed as kilograms per day exqept vere indlcated otherwise* c - Less than detection limit Iteffem Robertson and Kirsten NATER QUALITY DATA Britannia Jane 2200 Britannia Jane Brltannia Uineral Britannia 4150 Treatment Treatment Britannia Craek Creek Porta1 Creek Creek Creek Creek Creek Porta1 Plant Plant Creek 81 Jl 52 83 85 In Out 66 CE 1990 21-sep 21-sep 21-sep Il-Sep 21-sep Il-Sep 21-Sep 21-Sep 21-Sep 21-Sep 21-Sep 21-sap Physical Tests Total Dlssolved Sollds 20 110 990 2S636 49.6110 130 3000 3400 Hardness CaC03 52.6 412 2*75 55.9 22Y 1400 1400 1380 23? PK 70s: 1.37 4.29 iA 7.56 6.06 7.23 6.42 4.46 4.55 4.38 6.913 Total Suspended Sollds Cl 5 14 10 6 10 Iron T-Fe CO.030 SteJfea Robatson and Kirstcn CAIAXLATED LOADINCS (kg/d) Br'~tW& Jane 2200 Brîtanni8 Jane Britannia klinerrl Brltannia 4150 Treatment Treatment Brltannia Creek Porta1 Creek Creek Creek Creek Creek Porta1 Plant Plant Creek Bl Jl J2 B3 BS In out 86 CA% 21-Sep Il-Sep 21-Sep 21-Sep 21-Sep Ol-Sep Il-Sep 21-Sep 21-Sep 21-Sep 21-sep Il-Sep Estlmated Flou L/B 58 4.2 0 39.8 4.2 44 a 92 42 42 42 97 Physical Tests Total Dissol;;wDjolids 100 226 266 397 181 10886 12338 , 503 Hardness 47 :09 : ., 90 :: 108 39 176 5080 5080 5008 194 PH 7.02 7.37 4.29 NA 7.56 6.96 7.23 6.92 4.46 4.55 4.38 6.98 Total Suspnded Sollds 0 2 0 36 2 38 0 32 39 7 61 17 D;C;o,:gd Anions CaC03 1.5 0.0 NA 1.1 57.0 1.4 23.8 965.3 921.7 16.8 Alkalinity CaC03 4::: 22.4 SS.8 59.5 Chloride Cl 0.00 OY OOOO 3.:: 0% 3.04 D98i 0.00 0°8i 0% 0.00 Fluoride F 0.25 0:02 0:oo 0.24 0103 0.27 0:or 0.48 4:68 4.75 0.59 Sulphate SO4 16.0 13.2 0.0 94.0 13.5 107.6 30.3 127.2 6314.1 6271.0 150.0 Nutrienta Asnnonia Nitrogen Y 0.00 0.00 0.00 0.16 0.00 0.16 0.00 0.00 0.17 0.16 0.16 0.00 Nitrate Nftrogen N 0.60 0.05 0.00 0.25 0.05 0.30 0.06 1.03 0.00 0.00 0.00 1.17 Nltrita Nltrogen N 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Total Phosphorus P 0.02 0.00 0.00 0.02 0.00 0.02 0.13 0.10 0.05 0.01 0.01 0.09 Total Metah Aluminum T-Al 0.20 0.00 0.21 0.01 102 103 104 Antimony T-Sb 0.00 x 0.00 03i0 0.00 034 0.00 0'8tl 0.00 0.00 0.00 0% Arsenic T-As 0.00 0:oo 0.00 0:oo 0.00 0:oo 0.00 0:oo 0.00 0.00 0.00 0:oo Cadmium T-Cd 0.00 0.00 0.00 0.01 0.00 0.01 0.01 0.45 0.45 0.42 0.01 coppar T-CU 0.00 0.05 0.00 2.7 0.11 2.9 i%. 0.87 56.6 55.9 50.8 0.92 Iron T-Fe 0.00 0.00 0.00 0.05 6.6 0.00 13.2 15.0 48.6 Lead T-PL> 0.00 0.00 0.00 0% 0.00 0.01 0.00 0'82 0.83 0.83 0.91 OY Mercury T-Hg 0.00 0.00 0.00 0:oo 0.00 0.00 0.00 0:oo 0.00 0.00 0.00 0:oo Selenium T-Se 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Zinc T-Zn 0.00 0.20 0.00 2.5 0.31 2.8 0.03 1.9 110 118 110 1.9 D;;;;;zd Xetals D-Ca 16.6 o.oP 27.5 33,.8 14.1 57.1 1526 1520 1506 63.3 copw D-CU 0.00 000: 0.00 2.1 0% 2.2 0.01 0.73 55.9 55.5 50.1 0.61 Iron D-Fe 0.00 0.00 0.00 0:oo 0.00 0.29 43.5 0.00 Lead D-Pb 0.00 0.00 0.00 0'80 0.00 040i 0.00 0.00 OY 14i2 1.02 0.00 Magnesium D-Mg 1.4 0.57 0.00 s.2 0.55 3.7 0.80 7.9 iO1 jo7 292 8.7 ~~~td~;ium D-K 0.70 0.09 0.00 0.07 0.36 D-Na 0.54 0.00 0.54 54 1.6 1x 42-2 426'ii 42'14 12-s Zinc D-M 0% 0.20 0.00 0.29 217 0.03 1:9 ii0 ii2 lio 1:9 ReSUlt8 are expressed as kilograma per day except were lndfcated otherwiae. c - Less than detectîon llmit . APPENDIX B PRELIMINARY BULKHEAD DESIGN ESIMATE Steffen Robertsonand ht+ 166004 - Britannia Mine Site Page B-l APPENDIXB PRELIMINARY BULKHEAD DESIGNESDMATE BULKHEAD DESIGN FOR PARTIAL FLOODING OF UNDERGRdJND WORKINGS Tlris approachwould require constructionof a concretebulkhead in all portals,vent raisesand shafts which daylight, below the maximumflood 1eveL Basedon a review of a compositesection of the undergroundmine and the locationof the pits, Figures4.1 and 4.3, it appearsthat it is possibleto flood up to the 1050level, which is approximatelythe lower edgeof the East Bluff pit. It will be necessary to review detailedmine plansto detenninethe numberof openingsto be sealed,however the available dataindicates that thereare at least6 openingsto be sealed,as shownon Figure4.3. The numberof vent raisesis not known, however,allowance for sealhigup to 5 of theseopenings should be made. It is assumedhere that sealingof the Upperadits in Mineral Creekand in the Fairwestdeposit ls not mquired ‘I&re are no specificcrlteria for the designof permanentbulkheads in mines,however experience in SouthAfrican minesindicates that the bulkheadshould be designedSO that the hydraulicgradient through the bulkheadis in the rangeof 790 to 1020 kPa/m,with the higher gradientbeing allowed when the surroundingrock is of a goodquality. In addition,the minimumlength of the bulkheadshould not be less than the width of the drift opening.,These criteria resuh in plug type bulkheadswhich do not mquim reinforcingsteeL In orderto achievean effectivebulkhead it is essentialto scaleall looserock’from the floor, walls and roof of the drift, and to pour the concreteso that it is tight againstthe roof. Oncethis is completethe rock all aroundthe bulkheadshould be pressuregmuted. In the caseof bulkheadsfor the BritanniaMine, sulphateresisting concmte is recommended.The requiredlength of bulkheadfor some levelsin the mine am shownbelow, basedon flooding up to the 1050level and installationin good rock Theselengthsassumethatthedriitsizeisnotgmaterthan3x3m. BulkheadLevel -em 4100 9 . 2700 5 2200 3.5 Basedon estimatesfor constructionof shnilarbulkheads at a proposedmine in B.C.,the averagebulkhead would cost in the order of $50,000. A total of 11 bulkheadswould cost $550,000. This cost doesnot hrcludeany costsassociated with gainingaccess to the amaswhere the bulkheadsshould be hrstalled.As someof the accessesto the mine werecaved durhrg mine closuresome additional costs would be incurred. The cost indicatedabove may be low for constructionof sealsin vertical openings,depending on the condition of the timbers. Steffen Robemon and Kirsten 166004 - Britaunia Mine Site Page B-2 It is estimatedthat it would talceapproximately 1.5 yearsto fiood the mine up to the 1050level, based on the following evaluation. A total of 47.8 x lo6 tonneshave been mhred fmm the BritanniaMine, of which, say 1.5 x 100tonnes was takenfkom the pits ami 5 x 10’ tonneswas mined from the Fairviewmine abovethe 1050IeveL Assumingthat this includesdevelopment waste and the meanspecific gravity of the material is 3.0, then this gives a total excavatedvolume below 1050 level of 13.77 x 106m3. Assumingthat 30% of the mine has been backfrlledand that the lower 20% of the mine is curmntly flooded there is 6.9 x 106m3 to flooded Basedon dischargexeconis from the 4100 level, the mean . annualflow throughthe mine is 150lps or 4.73 x ld m3/year.It is thereforeestimated that this flow rate would mquire 1.5 yearsto flood up to the 1050 level, however this estimateis basedon numerous assumptionsand could easily vary by a factor of two. The time to mach the 1050 level would be approximatelytwice as long if diversionditches were constructedin JaneBasin prior to the start of floodhlg. Steffen Robertsonand Kirsten AFmNDIx c RESULTS OF TESTING Steffen Robertsonand K2ste-n ;- 166004 - Brimmia Mine Site Page C-l APPENDIXc RESULTS OF TESTING Experiment # 1 - pH Neutralization Cur~es Objective Evalue tbe reqdrementsfor baseto neutralizeacidiQ in the two samples. Method 1 N NaOH was addedstepwise using incremm of 0.1 and 0.2 mL to 1 L stined samples. pH was measuxedcontinuously and tecordedafter equilibrationfollowing eachxeagent addition step. The NaOH based neutralization‘curves axe ptided in Fïgunz 6.3 and 6.2 for the hvo samples. Equivalent cames basedon quicklime are pmvided in Figures 6.5 sud 6.6. These latter plots axe calculatedbased on the equivalentbasicity of 1.43for causticsoda compared to high calciumquicklime (CaO) at a basicity of 1.0. Reagentconsumption is expn?ssedas kg/looO m3 which is numeri&lly identicalto concemmtionexpressed as mg/L. Lime consumption(CaO) to pH 7.0 wasapproximately 410 and 150 kg/1000m3 for the 2200 and 4100 pottat drainagesrqectively. Ca0 consumptionto pH 9.5 increasedto 490 and 220 kg/1000m3 for the 2200 and 4100 portal drainagesrespectively. St&m Robemon and Kirsten 166004- BriunmiaMme Site PageC-2 Experiment # 2 - Lime Precipitation Test Objective Evaluatebatch addition of lime to neutralixeacid and pmcipitatemetals. This processrelies on the pmcipitationof metalsas insolublehydroxides. Methods A 5 % slurry of hydratedlime, Ca(OQ, wasadded batchwise to a stined 1 L sample.Each sample was tested at thme dosages. The sampleswem allowed approxhnately15 minutesof teaction thne after nagent additiox~The~ samples were then flltered thtough 0.45 micron filter paperand retainedfor metal analyses.A spot test using 10% Na$ solutionwas usedon productfiltrate to mdicatewhether metals remainedin solution, A blackprecipitate fonned aroundthe dxopletif zinc or copperwere present. This procedumwas used thtoughoutthe bench test program to assistin selectingdosages. It was noted howeverthat iron in solutiondid not readilyform a blackpmcipitate until the samplewas allowed to stand for 1 ht-. ReSXllts The tes& for the lime precipitationexperhnents am ptovided in Table 6.4 for both the samples. The 2200 ptal samplewas testedat 1000,850 and 700 mg/L Ca(Om, while the 4150 samplewas tested at 500,300 and 200 mg/L Ca(OQ concemmtions. For the 2200 portai samplea dosageof 700 mg/L C!a(OIQ,e-quivalent to 530 kg/1000ht’ CaO,mmoved solublecopper. However,a measurablequantity of zinc remainedin sohttion. A dosageof 850 mg/L Ca(O& [643 kg/lOOOm’ as Ca01 was xequhedto reducezinc to low levels. A similar relationshipoccurmd with the 4100 portai samplein that a dosageof 300 mg/L Ca(OI-& removedall solublecopper but left a smallmsidue of xhz. A dosageof 500 mg/L Ca(OH&[378 kg/1000 m3 as Ca01 was xquired for completezinc xmovaL In bath cases,the testwork demonstmtedthat it was necessaryto incmasepH above 8.5 in order to adequatelyremove zinc, potentiallydue to the solubiity of tic hydroxideunder neutml pH conditions. AU other metals,mcluding ahunhmm and iton, wem mmovedby neutralixationto pH 7. Additional benchtests usmg conthmousor stagedlime addition would be mquimdto more accurately determinethe quired dosageusing the lime tmatmentprocess. SteffenRobextson and IC&sten 166004 - Britunnia Mine Site Page C-3 Experiment # 3 - Soda Asb Neutralization Objective TO evaluatethe useof sodaash for neutmhzationand pmcipitationas a alternativeto lime. This process relies on the precipitationof metalsas both hydroxidesand carbonates.Précipitation of zinc carbonate underneutral pH conditionsis feasibleas an alternativeto the pH 9.0 to 9.5 conditionsrequired to remove zinc as a hydrozide. An addedpurpose of the test is to evaluatethe role of carbonateduring hydroxide pmcipitation. Carbonatepnxipitation is generallyapplicable to the mmovalof cadmium,lead and nickel if thesemetals axe present. Howeverthese metals were at relativelylow concentrationsin bath the raw water samples. Method The procedm usedin Experiment# 2 was followed. A sodaash solution containing4% Na&O, was usai for the testwork. Sodaash dosages tested wexe 720 and 1056mg/L for the 2200 sampleand 320 and 546 mg/L for the 4100 portal drainagesample. The resultsare providedin Table 6.5. In both cases,the higher dosagewas capableof mmovingbath copperami zinc to acceptablelevels, while the lower dosagesleft residualdissolved zinc in solution. The . msultsindicate that the removalwas due to the pmcipitationof zhx underhigh pH conditionsas opposed to precipitationof zinc carbonate.The cakulatedCa0 equivaknt for both samplesindicates that partial sodaash substitution has a higherequivalent dosage than solelyquicklime, perhaps due to the lossof CO, during neutralization. Steffen Robemon and Kirsten 166004 - Briuamia Mme Site Page C-4 Experiment # 4 - Sulphide Precipitation Objective Evaluatethe use of direct sodiumsulphide addition to pnxipitate metalsin the acid pH rangewithout neutralization. Method The methodused in Experiment# 2 was followed, exceptsodium sulphide mplaced the use-oflime. A 10% solution of N%S was madeup by addition of 100 g of Na$9%0 to 1 L of Milli-Q water. This solution had a sulphideconcentration of 20.9 mg/mL basedon analysesof a diluted stock solution for sodium. The two poxtalchainage samples were tested at sulphideconcentrations of 313,627,1254 mg/L 8 for the 4100 sampleand 313,627, 1254 and 2090 mg/L S‘ concentrationfor the 2200 sample. The test resultsare pmvide in Table 6.8. In bath casesthe highest sulphidedosage was requimdto pnxipitate zinc while h-ontemahred in solution. Copperwas howeverprecipitated out at the lowest test concentrationsi.e. 313 mg/L in the caseof 4100 level ami 1254mg/L with the 2200 sample.The results indicate that a high sulphideto metal ratio is requhedin all casesto pnxipitate metals,making this pxocessunattmctive unless a sourceof sulphidesuch as a sulphideflotation concentratewere nxdily available. Steffea Robeztsoaaad Kirstea 166004 - Britannia Mine Site Page c-5 Experiment # 5 - Lime and Soda Ash Precipitation Objective TOevaluate the useof a combinationof lime and sodaash to neutralizethe sampleand precipitate metals. The basisof this altemateis that the requimdlime dosagewould be lower thanthat quired to precipitate zinc as a hydmxideif carbonateaddition results in the formationof insolublexh~c carbonates or basiczinc carbonatesunder neutral pH conditions. Potentiallythis processwould allow completezinc removal without the needto increasepH to pmcipitatexinc hydmxide,thereby minimi&g lime consumption. The ptocedumused in Experiment#2 was followed. Lime addition precededsoda ash addition in all CaseS. The msultsof theseexperiments are ptovided in Table6.6. Comparativemsults fiom Experiment# 2 with lime only are alsoincluded in the Table. For both samplesthe additionof sodaash afkr lime additionwas capableof reducingsoluble xinc to low levels under neutral pH conditions,whemas the comparativelhne-only msult reporteda measurable quantityof zinc in solution The total equivalentlime dosagein the caseof the 4100 portal samplewas less the requhed lime dosagereported in Expetiment#2. Additional testwork will be mquùed to accuately defïne the reagentrequirements for both lime ami soda ash if this alternativeis developed further. Steffen Robeasonand Kirsten 166004 - Britmnia Mine Site Page C-6 Experiment # 6 - Ion ExchangeTests Objective Evaluatethe use of ion exchangeto selectivelyremove metal in the acid rangeusing a cation exchange resh Method The experimentwas conductedusing a 100 mL bun%ewith a bed depthof 330 mm and bed volume of 25 mL. The min was suspendedin Milli-Q water prior to placing in the column. Samplewas fed tbmugb the columu by gravity at a rate of 10 mLhix~ Sampleswere collectedat 10 min imervals. Pexiodically.pH and responseto the sulphidespot test (describedin Experimeut#2) weredetermined for eachsample. Solutionfeed contiuueduutil the spot test yieldedpositive readiugs indicating that soluble zinc or copperwas present. The resultsof the ion exchangeexperiment a pmvided in Tables6.10 and 6.11. The dissolvedvalues for zinc and copperare plotted in Figures6.9 and 6.10 on a bed volumebasis. Breakthmughoccuned i at 40 bed volumesin the caseof the 2200 samplewhile breakthrougboccuned at 44 bed volumesiu the caseof the 4100 portai sample. Steffen Robemon and Kirsten 166004 - Britmnia Mine Site Page C-7 Experiment # 7 - SeawaterDilution Objective Determinethe telatioushipbelween seawater dilution ratio, pH, and dissolvedmetals. Evahtatethe pmcipitationof metalsin the acidic drainagevia reactionwith alkahnityin seawater.This alternative could be utilixed in conjonctionwith other processesthat temovesome dissolved metal prior to disposal via an outfall. Method The experimentwas conductedby addingseawater in hrcrementsto a fixed volumeof sample,folIowed by measurementof pH oncethe samplehad equilibrated.With the Ationship betweenpH and dilution ratio established,a seriesof dilutions were made,filtered, and the filtrates retainedfor metal analyses. The resultsanz provided in Table 6.9, while the uAationshipsbetsveen pH and dilution ratio for the two samplesare provided in Figures6.7 and6.8. The resultsmdicate that somemetal remahrs in solutionafter neutralizationby seawaterdilution. In the case of zinc, only 50 % of the mduction in soluble concenttationis dueto pmcipitationdming neutralization.The kineticsof zinc ptecipitationvia seawater dilution arenot favourable.In addition,the precipitatesformed are colloidal and may not necessarilyhave beenreu&ed on 0.45 micron Glterpaper. Steffen Robemon and Kirsten 166QO4- Britamia Mine Site Page C-8 Experiment # 8 - LimestoneNeutralization Objective Evaluatethe potentialuse of Iimestoneto accomplishpartial neutralixation and to precipitatemet& This alternativecould be usedin conjunctionwith a lime treatmentsystem. Method The experhnentwas conductedby addingpulverixed dolomitic limestoneto 1 L samplesof eachportal drainage. The initial dosagewas 20 g/L. In the caseof the 2200 portai drainagesample two additional 10 g batchesof pulverixedwem addedafter 20 minutesand 2 hoursof mixing. The samesequence was followed with the 4100 portai sampleexcept the two additionalbatches of pulverixedlimestone were addedafter 10 minutesand 1 hour of mixing. The total mixing lime for the samplewas 3 hours,after which eachslurry was filtered and the filtrate retainedfor metal analyses. The msults,provided in Table Cl, mdicatedthat the useof limestonedid misepH to a limited extentbut did not precipitatexinc and copper. Limestoneaddition did howeverassist in the removalof solubleiron probablydue the oxidationof ferrousixon. The useof excesslimestone did not appearto haveany added benefitin termsof neutralixation.It is assumedthat gypsumformation on the limestoneparticles blocked neutralixationvia limestone. The pH incmasegenerated by limestoneaddition might justify the use of a separatesystem for handhngand feedingpulverized limestone in conjunctionwith a conventionallime tmannentsystem. Steffen Robertsonand Kirstm 166004 - Brhmia Mme Site Page C-9 Experiment # 9 - Process Simulation - Lime Treatment System Objective The puxposeof this experimentwas to simulatethe useof a lime treatmentsystem for treatingthe 4100 Portal Drainage. Following the results obtained with the previous series of tests using lime, this experhnentwas conducted to refinedosage estimates, predict supematant quality anddemonstmte the use of sludgerecycle. Method A sampleof 4100 Portai Drainagewas obtainedon Match 13.1991 in order to carry out the tests. The neutralizationcutve (Figure Cl) for the sample(using NaOH as describedin Experhnent#l) was determinedin order to comparethe xesuhswith data generatedusing the November28 sample. A series of two - 2 L samplesof portai effluent wastreated using hydrated lime. 0.6638of dry hydratedlime was addedto the fimt 2 L sample,to incmasepH to 9.5. .Tbiswas equivalentto a dosageof 251 mg/L as quicklime (CaO). After 15 minutesof mixing, 2 mg/L of Percol 156 was addedusing 4 mL of 0.05% polyelectrolytesolution. 4.4 mL of 15 $0lime slurry was addedto the second2 L aliquot, At this point the treatedsamples wete combmed. 6 mL of 0.05% polyelectrolytewas addedto flocculatethe sohds. The sluny was allowed20 minutesof settling time, after which the supematantwas discardedand tbe sludgeretained. The 6OOmLof sludgewas then combinedwith a 1 L sampleof 4100 PoxtalDrainage. 2.2 mL of 15%lime slurry was addedto the combinedsample followed by floccuktion using2 mg/L of Percoll56 as before. The flocculatedshury was then usedin a settlingtest to predict clarifier overflow rates. A supematantsample was collectedand retainedfor analyses.The sludgewas also retainedfor total metalsanalyses. Results The resultsof settlingtest areplotted in Figure6.15. The tesultspredict an overflow rateof 1.4m/h (0.57 USgpm/ft2). The analyticalresults are pt~vided in Table 6.7. The tesultsindicate that the lime tteatment systemshould be capableof meetinglow copperand zinc criteria at a dosageof 250 mg/L CaO. Steffen Robertsonand Kirsten 166004 - Britannia Mine Site Page C-10 Experiment # 10 - ProcessSimulation - Lime and Soda Ash Treatment System Objective The purposeof this experimentwas to simulatethe use of a lime and soda ash treatmentsystem for treating the 4100 Portai Drainage. This experhnentwas conductedto refrne dosageestimates, predict supernatantquality and demonstratethe use of sludgerecycle. Method A seriesof two - 2 L samplesof portal drainagewas treatedusing bath hydratedlime and soda ash Sufficient lime was addedto the first sampleto increasepH to 6.94. Secondly,1 mL of 5% Na&O, solution was addedto increasepH to 7.9. 8 mL of 0.05% Pemol solution were then acldedami the resultantslurry was allowedto seuleof 25 minutes. The resultantsludge was retainedfor subsequent testhg. The second2 L samplealiquot was treatedin the samemanner as the first using lime followed by sodaash. The shrdgefrom the first aliquot was then combinedwith tbe secondaliquot prior to the additionof 8 mL of 0.05%Percol156. The samplewas allowed25 minutesof settling-time. akr which the supematantand sludgewere tetainedfor analyses. The analyticalmsults for the supematantsample are providedin Table Cl along with the resultsusing lime- The Nuits hdicate that a lime-sodaash systemshould be capableof tmating pottal drainageto meet a 1.0 mg/L zinc criteria at the dosagesmported. Howevera bigher sodaash dosage would likely be regdred to produceresults equivaknt to the lime-only system A detailedevaluation of tbe pmcess would requiresome pilot testingin orderto f’ully assesstbe benefitsof recycleand detennhrethe optimum lime and sodaash combhUons. Steffen Robertsonand Kixsten Table C.l Limestone Addition Testwork - Britannia Pulverized Dolomitic Limestone Reacted for 3 Hours Continuous Agitation Provided by Mixer Location Limestone pH Alkalinity Sulphate Dissolved Metals Dosage Initial Final mg CaC03/L g/L Zinc Copper Iron 2200 Porta1 40 2.85 4.02 Ll 973 41.2 79 0.96 4100 Porta1 40 3.31 4.83 10.4 1230 37.6 17 0.582 Note:Lack of reactivity assumed due to gypsum coating of Jimestone particles Neutralization of 4100 Porta1 Drainage High Calcium Quicklime Equivalent March 13191 Sample DH 12 10 8 ! &.--.-- 1 1 I 1 I l 0 50 100 150 200 250 300 360 kg CaO/lOOO m3 Figure C.1