Brukunga Mine Site Water Monitoring Report – 2010 EPA Licence 10577 Mine Completion Program Mining Regulation and Rehabilitation Branch Minerals and Energy Resources Division Department of Primary Industries and Resources (PIRSA) Final Report December 2011 BRUKUNGA MINE 2010 WATER QUALITY MONITORING REPORT ACKNOWLEDGEMENTS The Brukunga Mine Water Monitoring Report is a combined effort, drafted and edited by the following individuals: PIRSA: Michael McLeary PIRSA: Chris Henschke AWQC: Darren Hicks (Macroinvertebrate section) Staff and companies that have provided valuable services / and or assistance with the collection, analysis, collation, interpretation and presentation of data include: Peter Grindley (PIRSA) Mark Seifert (PIRSA) Ross Stevens (PIRSA) Australian Water Quality Centre (AWQC) Water Data Services (WDS) ii BRUKUNGA MINE 2010 WATER QUALITY MONITORING REPORT EXECUTIVE SUMMARY The Brukunga Mine operated between 1955 to 1972, quarrying iron sulphide (pyrite and pyrrhotite) from the site of two steep hills in an open pit. The concentrated ore was converted to sulphuric acid, and subsequently used in the manufacture of superphosphate fertiliser. The pyrite and pyrrhotite minerals that remain on site naturally oxidise in air to form acid and the resultant acid and metalliferous drainage (AMD) dissolves other minerals causing heavy metal contamination of the local watercourse. The land is freehold title held by the Minister for Mineral Resources Development on behalf of the Crown and has been managed by the Department of Primary Industries and Resources - Minerals and Energy Resources Division since 1998. The key work undertaken on site is the interception and treatment of acid seepage with lime to prevent acid and metals from entering and polluting the local watercourse. The AMD is neutralised in a plant to remove the soluble heavy metals before the cleaned water is released back to Dawesley Creek. The water monitoring program, undertaken in accordance with conditions of the Environment Protection Authority (EPA) site licence No.10577, provides a measure of the success of the interception and treatment program. In 2003 a major improvement in water quality in the creek downstream of the mine site was achieved primarily due to the construction of a 1.7 km creek diversion drain. In 2005 upgrading of the lime treatment plant was completed, effectively doubling its capacity to treat AMD from the site. These two initiatives have resulted in a marked improvement in downstream water quality, compared to levels measured prior to 2003. Key points relevant to 2010 include: • There is consistency with 2010 results as compared to other years (post diversion) which are markedly improved over pre-diversion values. • Rainfall measured in 2010 was approximately 17% above the long-term average. This resulted in a marked increase in the volume of water treated during 2010. • Flushes of low pH and high metals are observed downstream of the mine following the drier summer months, but can also be observed to varying degrees sporadically in the wetter months. • Water quality downstream of the mine generally improves (relative to analytes measured against ANZECC guidelines) with distance (from the mine) in terms of livestock standards. Exceeded trigger values generally relate to sulphate, aluminium and cadmium. • Eight events were notified to EPA (largely resulting from overflows during or subsequent to periods of heavy rain) iii BRUKUNGA MINE 2010 WATER QUALITY MONITORING REPORT Table Of Contents ACKNOWLEDGEMENTS .................................................................................................................. II EXECUTIVE SUMMARY .................................................................................................................. III 1 LICENCE INFORMATION ...................................................................................................... 1 2 INTRODUCTION .................................................................................................................. 2 2.1 Background .............................................................................................................. 2 2.2 Forward Program ..................................................................................................... 4 2.3 Hydrology .................................................................................................................. 5 3 MONITORING ..................................................................................................................... 8 3.1 Monitoring Objectives ............................................................................................. 8 3.2 Monitoring Plan ........................................................................................................ 8 3.2.1 Flow Monitoring and Composite Sampling..................................................... 10 3.2.2 Biological Monitoring ...................................................................................... 11 3.2.3 Grab Sampling ............................................................................................... 11 3.3 Reporting Trigger Values and Thresholds .......................................................... 12 3.4 Analytical Methods and Limits of Reporting ....................................................... 12 3.5 Evaluation of Quality Control/Quality Assurance ............................................... 12 4 RESULTS & DISCUSSION .................................................................................................. 14 4.1 Flow Monitoring and Composite Sampling ......................................................... 14 4.1.1 Annual Flow Volumes ..................................................................................... 14 4.1.2 Annual Load ................................................................................................... 15 4.2 Biological Monitoring ............................................................................................ 18 4.3 Grab Sampling ........................................................................................................ 18 4.3.1 Spatial Variations for Key Analytes (Zone of Influence) ................................. 18 4.3.1.1 pH .............................................................................................................. 19 4.3.1.2 TDS ........................................................................................................... 19 4.3.1.3 Sulphate .................................................................................................... 20 4.3.1.4 Aluminium and Manganese ....................................................................... 21 4.3.1.5 Cadmium ................................................................................................... 22 4.3.1.6 Copper, Iron and Zinc ............................................................................... 22 4.3.1.7 Lead, Nickel, Chromium and Arsenic ........................................................ 23 4.3.2 Temporal Variations at Each Site (Monthly Pollutant Concentrations) .......... 23 4.3.2.1 Brukunga US (Peggy Buxton Road) ......................................................... 23 4.3.2.2 Brukunga DS ............................................................................................. 24 4.3.2.3 Melbourne Bridge ...................................................................................... 24 4.3.2.4 Downstream Nairne Junction .................................................................... 25 4.3.2.5 SE Freeway ............................................................................................... 26 4.3.2.6 Mt Barker Creek ........................................................................................ 26 4.3.2.7 Bremer River ............................................................................................. 26 iv BRUKUNGA MINE 2010 WATER QUALITY MONITORING REPORT 4.3.2.8 Nairne Creek (Control) .............................................................................. 27 4.4 Additional Monitoring ............................................................................................ 28 4.4.1 Rainfall............................................................................................................ 28 4.4.2 Water Treatment Plant ................................................................................... 28 4.4.2.1 Water Quality............................................................................................. 28 4.4.3 Tailings Storage Facility ................................................................................. 30 4.4.4 Plant Efficiency ............................................................................................... 34 5 NOTIFIED EVENTS ............................................................................................................ 36 6 CONCLUSION AND PROPOSED ACTIONS ........................................................................... 37 6.1 Conclusion .............................................................................................................. 37 6.2 Actions from 2010 .................................................................................................. 37 6.3 Proposed Actions for 2011 .................................................................................... 37 7 REFERENCES .................................................................................................................