Acid Mine Drainage in the Bakers Creek Waste Rock Dump, Hercules, Western Tasmania

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1 Acid Mine Drainage in the Bakers Creek Waste Rock Dump, Hercules, Western Tasmania Sophie Elizabeth Smith (B.Sc.) UNivERshy of TASMANiA A Research Thesis submitted in partial fulfilment, of the requirements of the Degree of Bachelor of Science with Honours Centre for Ore Deposit Research (CODES SRC) School of Earth Sciences University of Tasmania November 1998

2 UNIVERSITY OF TASMANIA... School of Earth Sciences &c. Centre for Ore Deposit Research DISCLAIMER This thesis was prepared as part of an Honours course in geology at the University of Tasmania. The author; the Geology Department, the Centre for Ore Deposit Research, and the University do not accept any liability for or in respect of any expenses, losses, damages or costs arising out of reliance by any person or body on the contents of the paper or any conclusions expressed in it. If you intend to use any part of the paper, you should get independent advice before relying in any way on the contents of the paper or the conclusions expressed in it. \

3 ABSTRACT Mining has occurred at the Hercules Ag, Au, Cu, Pb, Zn VHMS deposit in western Tasmania, almost continuously for the last 100 years. Mining activity has degraded the local environment, through clearing of vegetation, enhanced erosion and the formation of acid mine drainage (AMD). Of significant concern is the Bakers Creek waste rock dump, situated in a waterfall in the upper reaches of Bakers Creek. This steep, unstable sulfidic rock pile cannot be readily removed or engineered, and is an on-going source of AMD. To allow rehabilitation options for the waste rock dump to be devised, the contribution of AMD from the Bakers Creek waste rock dump needed to be ascertained. Long term and intensive water sampling programs have been implemented to characterise and quantify AMD emanating from the waste rock dump, and to investigate climatic controls on water quality of Bakers Creek. Water samples were collected from ten sites along Bakers Creek, where field analyses of ph, Eh, conductivity and temperature were conducted. Water samples were collected for laboratory analyses of major and trace element concentrations, sulphate, chloride and alkalinity. The ph of the drainage waters vary from 5.6 (upstream of mining activity) to 3.0 (foot of the waste rock dump). Maximum metal concentrations were measured at the adit, or the base of the waste rock dump. Major contaminants are Fe (43.8ppm), Pb (19.2ppm), AI (8.47ppm) and Sulfate (1440ppm) and Zn (82.2ppm). During base flow, approximately 47.6 T/yr of Zn is discharging from Bakers Creek into Ring River, (98% of which is contributed by the waste rock dump). Other contaminants contributed by the waste rock dump, represented at least 95% of the total contamination in Bakers Creek including AI (2.87 T/yr), Cu (0.77 T/yr), Fe (1.54 T/yr), Pb 1.9 T/yr, and Sulfate, (199T/yr). The maximum mass loads were recorded during storm events (measured at the base of Bakers Creek). The maximum mass load for each contaminant was T/yr Zn, 13.9 T/yr AI, 0.33 T/yr Cd, 3.95 T/yr Cu, 65.4 T/yr Fe, T/yr Mn, Pb T/yr, and 756 T/yr sulphate. These metal mass loads are high enough to consider metal recovery strategies. To remediate Bakers Creek, a combination of treatment strategies are probably required. Diversion of Bakers Creek upstream of the waste rock dump, combined with the installation of a biosulphide metal recovery plant to treat Zn, have potential to reduce metal and sulphate concentrations to acceptable levels, and to increase ph. A major

4 advantage would be the metals can be extracted from solution and sold to create revenue to offset costs incurred from installing and operating the plant. Diversion of Bakers Creek combined with a wetland filter system at Williamsford, could be an alternative remediation strategy if a biosulphide treatment is not viable. ii

5 CONTENTS Abstract i Figures vii Tables ix Plates xi Acknowledgements xii SECTION 1.1NTRODUCTION AND BACKGROUND INFORMATION Chapter 1 INTRODUCTION PREAMBLE AIMS Thesis Structure HERCULES MINE Environment Physiography Climate Vegetation Geology and soils Recent Mining Operations HERCULES LEGISLATIVE REQUIREMENTS 1.4 PREVIOUS WORK Chapter2 ACID MINE DRAINAGE INTRODUCTION ELEMENTS OF ACID PRODUCTION ENVIRONMENTAL INFLUENCES ON ACID GENERATION Physical Chemical iii

6 2.2.3 Biological ENVIRONMENTAL IMPACTS SOURCES OF AMD AMD PREDICTION AND TESTING Static and Kinetic Tests ACID-CONSUMING REACTIONS Reactions with Carbonates Reactions with Silicates SCOPE OF THE AMD PROBLEM SECTION 2. EVALUATION OF AMD AT HERCULES Chapter3 SAMPLING AND ANALYTICAL TECHNIQUES INTRODUCTION WATER SAMPLING Long Term Sampling (Low Flow) Intensive Sampling (Storm Flow) Sampling Procedures Field Measurements ph Redox Potential (Eh) Conductivity (K) Flow (Q) Analyses Water Analyses Alkalinity, Sulphate and Chloride ICP-EOS Other Analyses Environmental Scanning Electron Microscope (ESEM) Bacteria iv

7 Chapter4. WATER QUALITY OF BAKERS CREEK INTRODUCTION CONTMINANTS Ficklin Plots Long Term Sampling Physiochemical Parameters Elemental Concentrations Spatial and Temporal Variations in Water Chemistry ntensive Sampling Results MASS LOADING CALCULATIONS Low Flow Storm Flow BACTERIA Introduction Results SECONDARY PRECIPITATES Site F (Base Waste Rock Dump) Site C (Adit) SUMMARY ChapterS. GEOCHEMICAL MODELLING INTRODUCTION PREDOMINANT SPECIES SATURATION INDICIES MINERAL STABILITY FIELDS COMPARISONS WITH ESEM SUMMARY v

8 SECTION 3. REMEDIATION AND REHABILITATION Chapter6. REMEDIATION AND REHABILITATION OPTIONS INTRODUCTION REMEDIATION OBJECTIVES CONTROL AND TREATMENT TECHNIQUES REMEDIATION OF BAKERS CREEK Waste Rock Dump Remediation Remediation and minor point source contributors to Bakers Creek SUMMARY Chapter 7. CONCLUSIONS AND RECOMMENDATIONS INTRODUCTION WATER CHEMISTRY REMEDIATION AND REHABILITATION OPTIONS RECOMMENDATIONS REFERENCES Appendix 1 Geology, Mineralisation and Alteration of the Hercules Orebody Appendix 2 Calibration solutions for field equipment Appendix 3 Summary of Thiobacillus Enrichment Media Appendix 4 Water Sampling Concentration Appendix 5 Rainfall at Mt Read Appendix 6 Mass Loading Calculations Appendix 7 Geochemical Modelling results with PHREEQC Appendix 8 Control and Treatment Options Appendix 9 Biosulphidation Metal Recovery- internet data Appendix 10 Rock Catalogue VI

9 LIST OF FIGURES Figure 1.1 Location map of Hercules mine. Figure 1.2 Location of Hercules mine, Bakers Creek, Ring River, Williamsford and the Bakers Creek waste rock dump (BOM, 1998). Figure 1.3 Average monthly rainfall at Mt Read from (BOM; 1998). Figure 1.4 Average monthly maximum and minimum temperatures at Rosebery. Figure 3.1 Location map of water sampling sites along Bakers Creek. Figure 4.1 Ficklin plot of all of the water samples analysed in this study. Figure 4.2 Ficklin plot of the samples at each sampling site. Figure 4.3 Drainage compositions as a function of distance along Bakers Creek A: ph; B: conductivity; C: temperature; D: redox; E: sulfate; F: Ca; G: Mg; H: Na; 1: locality map. Figure 4.4 Drainage compositions along Bakers Creek A: chloride; B: Mn; C: Fe; D: AI; E: Si; F: trace metals; G: As; H: Cd; 1: Cu; J: Pb; K: S; and L: Zn. Figure 4.5 Rainfall at Mt Read during long-term sampling. Figure 4.6 Intensive sampling results, A: ph B: conductivity, C: Redox; D: Temperature; E: AI, F: As, G: Ca, H: Cl, 1: Cu, J: Fe, and K: K. Figure 4.7 Intensive sampling results, concentration with hours since rain; A: Mg, B: Mn, C: Mo, D: Na, E: Pb, F: S, G: Si, H: Zn, 1: sulphate, J: trace metals, K: salts, and L: chloride. Figure 4.8 Flow of Bakers Creek at Site I (as measured by the monitoring station), and the times at which the samples used to calculate mass loads were taken. Figure 4.9 Flow at Site I and rainfall measured at Mt Read. Figure 4.10 Time on intensive sampling (Sep) relative to the flow rate at Site I Figure 4.11 Mass loads and concentrations of metals during the September intensive sampling. Figure 4.12 The sum of intensive metal mass loads plotted with the flow rate. vii

10 Figure 4.13 Spectral analyses of precipitates and interpreted mineralogy at Site F in August. Figure 4.14 Continued SEM spectral analyses of precipitates from Site C in July. Figure 5.1 Figure 5.2 Figure 5.3 Figure 5.4 Figure 5.5 Figure 5.6 Figure 5.7 Figure 5.8 Intensive-low redox (Site I) Fe speciation. Intensive- low redox (Site 1), As speciation. Intensive- low redox (Site 1), Cu speciation. Intensive - high redox (Site I), As speciation. Intensive- high redox (Site 1), Cu speciation. Intensive - high redox (Site I), Fe speciation. Long term- August (Site F), Fe speciation. Long term, August (Site F), Cu speciation. Figure 6.1 Figure 6.2 Remediation strategies for Bakers Creek including, diversion, wetland filter system and biosulphide treatment plant. General biosulphide process configuration, modified from viii

11 LIST OF TABLES Table 1.1 Table 1.2 Common Vegetation in the Pasminco Rosebery Mine mining lease (Pasminco, 1995 unpub). Emission concentrations into inland waters and for those from metalliferous mines (from EPA, 1973). Table 2.1 Stages of pyrite oxidation (Hutchison and Ellison, 1992). Table 2.2 Physiological types of bacterial able to oxidise reduced sulphur compounds (Holt et al., 1994) Table 2.3 Bacteria commonly associated with AMD (Ragusa and Madgwick; Gould et al., 1994; Shrenk et al., 1998). Table 2.4 Typical environmental impacts of AMD (modified from Ritchie, 1994). Table 2.5 Examples of static tests commonly used in Australia (OSS, Harries 1997). Table 3.1 Table 3.2 Sampling sites and reasons for their inclusion. Equipment types to take filed measurements. Table 4.1 Table 4.2 Table 4.3 Table 4.4 Table 4.5 Table 4.6 Table 4.7 Attributes covered by the ANZECC/NWQ water quality guidelines that are relevant to this study. Maximum and minimum values of the attributes studied in the long term sampling program. Maximum and minimum values of physiochemical parameters and element concentrations. Average calculated mass loadings for background low flow rates at Site I (Bakers Creek Gauging Station). ML = Mass load. Mass loadings at Sites A, D and I during low flow conditions on 31st August. Mass load contribution from the waste rock dump (WRD) during low flow conditions on 31st of August. Mass load contribution from the WRD on 22nd September (storm flow). ix

12 Table 5.1 Speciation of intensive samples at low and high redox and a long term sample form site F (Aug). Table 5.2 Saturation indices of water samples (31/8 long term sample at Site F, and intensive samples from 28th July at 2pm and 2:30pm)calculated using PHREEQC. Table 5.3 Equations for supersaturated minerals from the predominant species. Table 6.1 Table 6.2 Summary of physical chemical and biological remediation strategies for control of AMD (Sengupta, 1993; OSS, 1997; Taylor et al, 1997). Summary of possible treatment options for AMD (Sengupta, 1992: OSS, 1997; Taylor et al., 1997). X

13 LIST OF PLATES Plate 1.1 Plate 1.2 Plate 1.3 Bakers Creek as it flows through the waste rock dump during a particularly dry period. View of Bakers Creek with Williamsford in the Ring River valley below. The Hercules Mine offices and Bakers Creek. Note the lack of vegetation in the vicinity of the mining area. Plate 3.1 Plate 3.2 Plate 3.3 Site A (Weir) located at the start of Bakers Creek used for base line data. Site C (4 level Adit) discharges directly into Bakers Creek (Seen to far right in this figure). Site D (waterfall) located directly before the start of the Bakers Creek waste rock dump. Plate 4.1 Plate 4.2 Plate 4.3 (a) Bakers Creek (Site G) with Mt Hamilton in the distance. Note the amount of waste rock that has washed down from the waste rock dump upstream, (b) The ad it just upstream of site G that was mined directly in Bakers Creek (c) and (d) are typical examples of the sulphidic waste rock at Site G. (A) precipitates located at the base of the waste rock dump at site F; (b) precipitates deposited outside the mouth of the Ad it at Site C. The drainage from the adit flows directly into Bakers Creek. (a) Euhedral pyrite crystals from Site F. (B-E) are of the various fine grained platey aggregates found at Site C. xi

14 AKNOWLEDGEMENTS I would like to thank the following people for their help throughout the year: My supervisor Dr David Cooke for his continual support, encouragement and enthusiasm. I would also like to thank Dave for his role as honours coordinator, as he did a fantastic job. Pasminco Rosebery mine for logistical support, and for answering continual streams of questions and providing supervision. I would especially like to thank Graham Hawes, Nick Brady, and Richard Chapman. The Tasmanian Government, for luring me here in the first place with a Tasmanian Government Mining scholarship. Colleen Ferguson and all the girls at the Rennison labs for sulfate, chloride, analyses and use of their lab equipment for filtering and titrations. Caroline and Peter Glover from the Mt Black Lodge, who were fantastic hosts while I stayed in Rosebery. Lois Koehnken, for her wonderful knowledge and advice which helped me to formulate my remediation options. Leah Hawkes who tried to identify my thiobacilli bacteria. Mark Johnston from the HEC for his monitoring station information, especially those flow measurements. A big thank you must go to my fellow honours students, especially Mark, Dave, and Nicole, for helping to make this such a great year. Anyone who offered me help or support but I have failed to mention I would also like to thank. Finally I would like to thank my family and my friends (especially Damian, Udara, and Nick) back in South Australia, for their support, encouragement, and advice throughout the year. xii

15 SECTION 1 INTRODUCTION AND BACKGROUND INFORMATION

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CAMBRIAN INTRUSION-RELATED COPPER MINERALISATION AT THE THOMAS CREEK PROSPECT, SOUTHWESTERN TASMANIA

CAMBRIAN INTRUSION-RELATED COPPER MINERALISATION AT THE THOMAS CREEK PROSPECT, SOUTHWESTERN TASMANIA UN I VF.RS TTY OF TASMANIA By Robert Reid (B.Sc. Hons) A thesis submitted in partial fulfillment of