ANNUAL ENVIRONMENT REPORT 2014

Transcription

1 ANNUAL ENVIRONMENT REPORT 214 ISO 141 Certified Environmental Management System

2 Barrick Porgera Annual Environment Report 214 BARRICK PORGERA OPERATIONS: Barrick (Niugini) Limited PO Box 484, Mt Hagen, Western Highlands Province PAPUA NEW GUINEA Barrick (Niugini) Limited PO Box 484, Mt Hagen, Western Highlands Province, PAPUA NEW GUINEA Telephone: (675) Fax: (675) Charlie Ross Environment Manager Prepared by: Barrick Porgera Environment Department Date: July 215 Document No: POR ENV 1/15 Cover Photo: Macroinvertebrate sampling at Ambi, upstream of SG3 on the Strickland River, 214. Photo is courtesy of Wetland Research & Management.

3 Land and Water New Illawarra Road, Lucas Heights NSW 2234 Locked Bag 27 Kirrawee, NSW 2232, Australia Telephone: (2) Facsimile: (2) ABN Charlie Ross Manager, Environment Barrick Porgera P.O Box 484, Mount Hagen WHP Papua New Guinea 23 July 215 Dear Charlie, Re: Porgera 214 Annual Environmental Report Dr Graeme Batley and Dr Simo Apte have reviewed a draft of the 214 Porgera Annual Environmental Report (AER) and provided detailed comments for consideration. Overall, the draft report was found to be technically sound, however, as might be expected with a report of this size, a number of minor recommendations were made for improvement. Barrick Porgera responded positively to the review team s recommendations and the report was revised in the light of the comments made. The revised report was assessed again by the review team and found to be satisfactory. We commend your Department on their considerable efforts in producing this comprehensive report. Sincerely Dr Simon Apte Senior Principal Research Scientist Dr Graeme Batley Chief Research Scientist

4 Barrick Porgera Annual Environment Report 214 EXECUTIVE SUMMARY Barrick Porgera Gold Mine is located in the Porgera Valley of Enga Province in the Papua New Guinea highlands, approximately 13 km WNW of Mt Hagen. The operation consists of an open cut and an underground mine, waste rock dumps, processing facility, gas fired power station, a water supply dam, limestone quarry and lime plant, and ancillary infrastructure. Operations commenced in 199 and are expected to continue until 225. The site employs approximately 28 local, national and expatriate staff and contractors, and produces approximately 5 koz of gold per annum. The operation has a number of unique economic, social and environmental aspects. The environmental aspects are managed through implementation of an Environmental Management System (EMS). The objectives of the EMS are to ensure methodical, consistent and effective control of the mine s environmental aspects so as to ensure compliance with legal and other requirements, mitigation of potential environmental risks, and continual improvement of environmental performance. The EMS was certified to the ISO141:24 standard for EMS in December 212. A critical element of the EMS is the environmental monitoring and reporting program. The program provides feedback on the effectiveness of the EMS for achieving the stated objectives, and therefore allows the operation to confirm management techniques that are working well, and more importantly identify those which require attention so that corrective action can be applied. The purpose of this Annual Environment Report (AER) is to provide an assessment of the overall environmental performance of the mine during the previous calendar year (214) as well as since the commencement of operations. The objectives of this report are aligned with those of the EMS and are to assess: 1. Compliance with legal and other requirements; 2. The level of risk and impact to the condition of the receiving environment posed by the mine operation; and 3. The environmental performance of the operation. Legal and other requirements are imposed predominantly by the two environmental permits, issued to the mine by the Papua New Guinea Conservation and Environmental Protection Authority (CEPA). The methodology for risk and impact assessment has been developed by Barrick Porgera in accordance with international guidelines and in consultation with external technical experts. The risk assessment stage is based on the comparison of physical and chemical environmental indicators at those sites potentially impacted by the mine (test sites) against risk assessment criteria or trigger values derived from baseline data, reference sites and international guidelines. It should be noted that the derivation of trigger values from the statistical distribution of baseline and reference site data, rather than "effects-based" trigger values, limits the assessment to only a "screening level" for identification of risk and potential impacts. A physical or chemical indicator (i.e. total suspended solids (TSS), cadmium or zinc) measurement at the test site that falls below the trigger value indicates low risk of environmental impact, while above the trigger indicates the potential for environmental impact and triggers further investigation to determine whether impact is actually occurring. The impact assessment stage is based on the comparison of biological indicators at test sites against biological indicators at reference sites. When the performance of biological indicator values at the test site is below that of the reference site, it indicates that environmental impact is potentially occurring (i.e. species diversity at a test site lower than at the reference site). If the same performance of biological indicators is observed at both the test i

5 site and the reference site then it indicates no potential impact is detected or there is a system-wide change that is not related to the mine. Tests of statistical significance were performed on the monitoring data to provide a statistical basis for drawing conclusions about differences within and between Test Site and Reference Site indicators, and therefore for determining whether risk or impact may exist at a particular test site. The first section of the AER quantifies the mine operations and associated activities during 214 as well as since the commencement of operations that have the potential to interact with the environment (i.e. the environmental aspects). Next, background environmental conditions are summarised to quantify the natural, or non-mine related changes within the receiving environment. Then assessments are made of compliance, risk, performance and impact, followed by a discussion of the findings and finally an outline of recommendations for improving the environmental management system and the environmental monitoring and reporting program. Background Environmental Conditions Rainfall during 214 was approximately 1% above average in the upper reach of the Strickland River catchment. Rainfall data were incomplete in the middle and lower reaches of the catchment due to equipment vandalism. In general, river flows were about 3-4% below average in the upper reach, about 15-2% above average in the middle reach and 5-1% above average in the lower reaches. Background conditions for environmental indicators; water quality, sediment quality, metals within the tissue of fish and prawns (tissue metals) and ecosystem health (abundance, richness, biomass and condition of fish and prawn communities), have been established using data collected from test sites prior to the commencement of mining operations (i.e. baseline data), and since operations began from sites within the receiving environment that are not potentially influenced by the operation (i.e. reference sites). Water quality of local creek reference sites within the Porgera Valley is typical of undeveloped catchments with limestone geology, exhibiting elevated ph and alkalinity, generally low TSS and low dissolved metal concentrations. However, these creeks are subject to episodic elevated TSS events due to landslides and/or high rainfall, and additionally detectable levels of mercury and selenium throughout the historical record are noted. Pre-mine baseline water quality data collected from the current upper river test site locations (SG1 SG3 on the Porgera, Lagaip and Strickland Rivers) indicate that prior to the mine being established, concentrations of TSS, total and dissolved copper, total lead, total and dissolved nickel and total and dissolved zinc were elevated compared to upper river reference sites. Baseline concentrations of dissolved copper and zinc exceeded the Australian and New Zealand Environment and Conservation Council Guidelines for Fresh and Marine Water Quality (ANZECC/ARMCANZ 2) for 95% species protection on some occasions. High baseline TSS concentrations are typical of higher order highland rivers, and elevated metal concentrations are typical of rivers draining naturally mineralised catchments, such as that which hosts the Porgera Gold Mine. Although concentrations of physical and chemical parameters are generally lower at the upper river reference sites than the baseline data from the upper river test sites, the reference sites do exhibit moderate TSS concentrations and detectable concentrations of total arsenic, chromium, nickel and zinc. This indicates that tributaries to the Lagaip-Strickland system have the potential to contribute non-mine derived TSS and some metals to the system. Lower river test site baseline water quality data indicate elevated TSS and dissolved nickel compared to the lower river reference sites, and both the baseline data and reference site data exhibit detectable concentrations of total chromium, copper, nickel and lead and total and dissolved zinc, however none ii

6 of the dissolved metal concentrations exceed the ANZECC/ARMCANZ (2) guideline for 95% species protection. Trends for ph, TSS and dissolved metals at the upper and lower river reference sites display no statistically significant changes over time. Lake Murray baseline data display elevated total and dissolved cadmium, compared to reference site data, and dissolved cadmium exceeded the ANZECC/ARMCANZ (2) guideline for 95% species protection. All other parameters are consistent between baseline and reference conditions and are all relatively low. Trends for ph, TSS and dissolved metals at the Lake Murray reference sites display no statistically significant change over time. Concentrations of total extractable metals (total digest; TD) and Weak Acid-Extractable metals (WAE, the bioavailable fraction) in benthic sediments at reference sites in the Upper River, Lower River and Lake Murray are low and all fall below the ANZECC/ARMCANZ (2) Interim Sediment Quality Low Guidelines. Concentrations of total digest copper and nickel in sediment from upper river reference sites, nickel and selenium in the lower river reference sites and chromium at the Lake Murray reference sites display a statistically significant increasing trend over time. Total digest concentrations of all other metals in sediment display no statistically significant changes over time. Baseline data for tissue metals are available only for fish flesh. These data show that baseline concentrations of metals in fish flesh in the upper and lower Strickland generally were higher than current levels at the regional reference sites. At Wankipe on the Lagaip River and at Tiumsinawam on the lower Strickland, baseline concentrations of arsenic, copper, nickel, lead and zinc in fish tissue exceeded the concentrations at the respective reference sites. Metal concentrations in the tissue of prawns and fish at regional reference sites for the upper and lower Strickland catchment and Lake Murray are low and below the relevant food quality guidelines. Increasing trends were observed for selenium in fish tissue at the upper river and Lake Murray, but overall the concentrations have remained low throughout the history of the monitoring program. Copper concentrations in prawn abdomens at the upper river reference sites, and copper and selenium in fish flesh and mercury and zinc in fish livers at the Lake Murray reference sites display a statistically significant increasing trend over time. All other metals at all reference sites display either a statistically significant decrease or no statistically significant change over time. Biological indicators show a statistically significant increasing trend in fish abundance, fish biomass, prawn abundance and prawn richness over time at the upper river reference sites, and a statistically significant increasing trend in prawn condition at the lower river reference sites. All other biological indicators at the upper river, lower river and Lake Murray reference sites display no statistically significant change over time. Mine Operations and Environmental Aspects The significant environmental aspects of the operation are riverine tailings disposal, waste rock generation, water extraction and discharge, transport, storage and use of hazardous substances, and waste management. Overall in 214, there was no material change from recent years to the scope or magnitude of the mine s environmental aspects. There was no change to the total area of land held by the Porgera mine during 214, ore and gold production increased from 213 but was consistent with previous years. iii

7 Water extraction was compliant with permit limits and consistent with previous years, and improvements in both water and energy efficiency were achieved compared to 213. The volume of competent waste rock produced in 214 remained consistent with recent years, with the majority being placed in the Kogai dump. The quantity of incompetent waste rock produced in 214 was significantly less than in 213 due to reduced volumes of mud trucked from the open cut mine, and the majority of erodible waste was sent to the Anawe erodible dump. The condition of the Anawe erodible dump has remained relatively stable in 214 with the exception of some material accumulation and valley wall erosion in the lower dump tract. The Anjolek erodible dump continues to be in a phase of erosion, with the majority of the material loss occurring from the toe of the dump, while the head and the body of the dump remain largely static. Tailings production also was consistent with previous years, and a significant proportion (8.2%) of the coarse fraction of tailings was diverted from riverine disposal and used for cemented backfill in the underground mine. Tailings quality achieved 1% compliance with the internal site-developed end of pipe criteria for ph and cyanide. Suspended sediment concentrations were lower than previous years. Concentrations of TSS, dissolved cadmium, copper, mercury, nickel and zinc, and total silver, arsenic and lead in tailings discharge were elevated compared to upper river reference conditions. Concentrations of dissolved cadmium, total chromium and dissolved zinc exhibit an increasing trend since operations began, and all other metals are either stable or decreasing. Contact rainfall runoff from the site is typical of neutral mine drainage and exhibits elevated sulfate, alkalinity, TSS and dissolved concentrations of cadmium, copper, nickel and zinc. Discharge of treated effluent from sewage treatment plants (STP) met compliance limits for BOD 5 and faecal coliforms throughout the year. However TSS concentrations exceeded the permit criterion on a number of occasions. The total volume of sediment discharged to the river system from rainfall runoff, waste rock dumps and tailings was less than in 213 due to the lower volumes of erodible waste produced, but was comparable with previous years. Compliance The operation achieved compliance with 94% of the conditions of its two environmental permits issued by the PNG Government. Non-compliance related to instances of elevated TSS in discharge from the sewage treatment plants and incorrect storage of hydrocarbons at particular locations around the site. Barrick is implementing improvement programs to correct and achieve compliance with all permit conditions. Monitoring results confirmed compliance with all of the environmental permit water quality criteria applied at SG3 (164 km from the mine) throughout 214. It should be noted that upstream of the compliance point, water quality at SG2 (42 km from the mine) met all of the SG3 criteria, and water quality at SG1 (8 km from the mine) also met all of the SG3 criteria with the exception of dissolved cadmium and dissolved zinc. Environmental Risks and Performance The total area held by the Porgera Mine did not change during 214. The total area of disturbance with in all the lease areas increased by 15.7 ha to 2,31ha due to incremental expansion of the mine, waste rock dumps and construction of the Kogai diversion drain. The total area under progressive rehabilitation as of December 214 is ha. iv

8 Ambient air quality monitoring was conducted at Panadaka and Kulapi Villages adjacent to the mine, and at the boundary of the Hides Power Station. The results indicate that air quality at all three sites exceeded the Australian National Environmental Protection Measure (NEPM) for Ambient Air Quality guidelines for particulate matter (PM 2.5 ). The composition of the fine particulate matter indicated significant inputs from wood burning, organics and wind-blown dust, with higher concentrations recorded at Kulapi which is located closer to the open cut mine than Panadaka. The particulate lead concentrations were very low at each of the three locations sampled and well within the NEPM guideline for lead. There were 27 zero-flow events of more than one day at Waile Creek Dam spillway during 214, however environmental flow immediately downstream was maintained by seepage from the base of the dam wall. Flow was maintained in Kogai Creek throughout 214 downstream of the extraction point for the water supply to the grinding circuit. Participatory sampling of drinking water supplies was conducted at 25 locations within Apalaka, Kulapi, Panandaka and Yarik villages adjacent to the mine and the results were assessed against the PNG Raw Drinking Water Standard. The sampling found that one site did not comply with the criterion for ph and two sites did not comply with the criterion for total coliforms. Results at all sites complied with all criteria for metals. The non-compliance results are not associated with mining activities. ph Water discharged from the lime plant exhibited elevated ph, however the volume of water discharged from this location was relatively small and the influence of elevated ph was limited to the immediate downstream environment. The ph values of all other discharges from the operation were consistent with upper river water quality TVs and so posed low risk of environment impact to the receiving environment. This was confirmed by the risk assessment results for ph in the upper and lower rivers where all sites were within the upper and lower TVs. ph measured at Kukufionga and Zongamange oxbows exceeded the Lake Murray and Off River Water Body (ORWB) TV, which is most likely due to the inflow of water from the Strickland River. This exceedance was an artefact of the TV being derived from baseline and reference data from Lake Murray, since there was no baseline or reference data available for the ORWBs, which may not fully reflect the natural variation of ph in the ORWB environment. TSS The tailings discharge, water discharged from Wendoko Creek downstream of Anawe North competent waste rock dump and the Yunarilama Portal all contributed elevated concentrations of TSS to the receiving environment. The risk assessment results indicated that elevated TSS in water posed a potential risk at SG1 in the upper river and at Bebelubi in the lower river. Elevated TSS at Bebelubi, which is located some 3 km downstream from the mine, was unlikely to be due to mine influence.the risk posed by elevated TSS was not due to increases in maximum TSS concentrations, but rather the constant nature of the mine contribution which maintains an elevated average TSS concentration in the receiving environment and prevents or reduces episodes of low TSS from occurring, as they would in a natural system. Biological monitoring is not conducted at SG1. Elevated TSS was potentially contributing to potential impact at Bebelubi indicated by some of the biological data. Silver Silver is contributed to the receiving environment in the tailings solids. The concentration of total digestible silver in the tailings solids exceeded the TV for WAE silver in the benthic sediments of upper rivers and exceeded the 8%ile of TD silver at the upper river reference sites. While the TD and WAE v

9 values were not directly comparable due to the influence of the different analytical techniques, in the absence of WAE data for tailings solids, the comparison provides an indication that tailings solids are the dominant source of silver from the mine to the receiving environment. Porgera will begin WAE analysis of tailings solids in 215. The risk assessment indicated the potential for elevated dissolved silver in water to cause environmental impact at SG1, Wasiba and SG3. It should be noted that the 214 median concentrations of silver at these sites were equal to the analytical limit of reporting, but the finding of potential risk applied because some concentrations within the 214 data set exceeded the TV. However, the CSIRO ultratrace sampling in 214 reported that dissolved silver concentrations at all test and reference sites were less than 1 nanogram per litre (ng/l). Therefore it is concluded that the finding of potential risk is an artefact of the analytical limit of reporting and the risk of impact from dissolved silver is highly unlikely. Arsenic Elevated concentrations of total digestible arsenic were measured in the tailings solids. In the receiving environment, arsenic was not elevated in water or sediment at any of the test sites. However, arsenic concentrations in fish flesh and prawn cephalothorax at Wasiba and Wankipe in the upper river, and in fish liver and prawn cephalothorax at Bebelubi in the lower river, exceeded their respective TVs, indicating the potential for environmental impact. Elevated arsenic in the tailings solids is potentially contributing to the bioaccumulation above that measured at the reference sites and the potential impact indicated by some of the biological data at Wasiba, Wankipe and Bebelubi. There is an inconsistency between the low concentrations of arsenic in water and benthic sediment within the receiving environment the bioaccumulation above that measured at the reference sites which suggests an alternative pathway of exposure to arsenic is possibly present within the receiving environment. Cadmium Contributions of dissolved cadmium in water to the receiving environment are occurring from the tailings, Kogai stable dump toe area and Wendoko Creek downstream of Anawe North stable dump. The latter two are the discharge points of water draining from within the Kogai and Anawe North stable waste rock dumps respectively. Within the receiving environment, median concentrations of dissolved cadmium in 214 exceeded the TV in water only at SG1 and SG2. At all test sites downstream from SG2, the median concentrations of dissolved cadmium in water and WAE cadmium in benthic sediments were not elevated. However, cadmium exceeded the respective TVs in fish liver, prawn abdomen and prawn cephalothorax at Wasiba, Wankipe and Bebelubi, and in fish flesh, fish liver, prawn abdomen and prawn cephalothorax at Tiumsinawam. The bioaccumulation above that measured at the reference sites indicates the potential for cadmium to cause environmental impact at these sites indicated by some of the biological data. The data suggest that the dominant exposure pathway for cadmium is dissolved cadmium in water in the upper catchment. However, as with arsenic, there appears to be an inconsistent trend between the low concentrations of dissolved cadmium in water, WAE cadmium in sediment, and accumulation in the tissue of fish and prawns, within the upper and lower river, suggesting an alternate exposure pathway may be present. Chromium None of the discharge points from the mine exhibited elevated chromium. However, elevated chromium was detected in fish flesh and fish liver at Wasiba, fish flesh and fish liver at Wankipe, and vi

10 fish flesh at Tiumsinawam. In all cases the 214 median concentration was equal to, or close to the analytical limit of reporting, although one or more results within the 214 data set from each site have exceeded the TV during 214, resulting in the finding of potential impact. However, as is the case with silver, this finding is the result of a conservative approach to risk assessment, and it is considered unlikely that elevated chromium is contributing to potential environmental impact within the receiving environment. Copper Elevated dissolved copper was evident in tailings and in water sampled at Wendoko Creek that receives drainage discharged from the Anawe North competent waste rock dump. In the receiving environment, elevated copper was detected only in fish liver at Bebelubi. Mercury Mercury concentrations were low in tailings and other discharges from the mine, as well as in receiving environment water and sediment. However, elevated mercury was detected in fish flesh and prawn cephalothorax at Wasiba, in prawn cephalothorax at Wankipe, in fish flesh and fish liver at Bebelubi, in fish liver at Tiumsinawam. The bioaccumulation above that measured at the reference sites indicates that mercury has the potential to cause environmental impact at these sites as indicated by some of the biological data. Mercury was not elevated in water or sediment within any of the upper or lower river sites, again suggesting an alternative pathway of exposure may exist. Nickel Dissolved nickel in water was elevated in tailings and in water sampled at Wendoko Creek that receives drainage discharged from the Anawe North competent waste rock dump. WAE nickel in sediment at Wasiba exceeded the TV, which indicates the potential for nickel to cause environmental impact at this location. However, the exceedance of WAE nickel in sediment at Wasiba was not accompanied by elevated nickel in the tissue of fish and prawns. Nickel in prawn cephalothorax at Bebelubi exceeded the TV which indicates the potential to contribute to potential environmental impact as indicated by some of the biological data at this location. Lead Total digestible lead in tailings was elevated compared to the WAE lead TV for the upper rivers. Within the receiving environment downstream of the mine, concentrations of dissolved lead in water were low at all test sites. WAE lead concentrations in benthic sediment appeared to behave conservatively and decreased with increasing distance downstream from the mine, and exceeded the TV at SG1, SG2, Wasiba and Wankipe. Lead concentrations exceeded the respective TV for prawn abdomen and cephalothorax at Wasiba, prawn cephalothorax at Wankipe, fish liver and prawn abdomen and cephalothorax at Bebelubi, and prawn cephalothorax at Tiumsinawam. WAE lead in benthic sediment at Zongemange exceeded the respective TV. The results indicate that lead has the potential to cause environmental impact at these sites. Lead is potentially contributing to potential impact indicated by some of the biological data at these sites. The data suggest that the dominant exposure pathway of lead to fish and prawns is via benthic sediment. Selenium The concentrations of selenium in discharges from the mine were not elevated in comparison to the upper river reference TVs and concentrations of dissolved selenium in water and WAE selenium in vii

11 benthic sediment were consistently low throughout the river system. However, selenium in the receiving environment exceeded the respective TVs in prawn abdomen at Wasiba and Wankipe, and in fish liver, prawn abdomen and cephalothorax at Bebelubi and Tiumsinawam, indicating the potential for selenium to cause environmental impact at these sites. Potential impact associated with elevated selenium is indicated by some of the biological data. Additionally, the low concentrations of selenium in water and benthic sediment suggest an alternative pathway of exposure may exist. Zinc Elevated concentrations of dissolved zinc were observed in tailings and in the water discharged from Kogai stable dump toe area and sampled at Wendoko Creek that receives drainage discharged from Anawe North competent waste rock dump. Dissolved zinc in water at SG1 and WAE zinc in benthic sediment at SG1, Wasiba and Wankipe exceeded the respective TVs. Zinc concentrations in prawn abdomen and prawn cephalothorax at Wasiba, in fish flesh and in prawn cephalothorax at Wankipe, in fish liver at Bebelubi and zinc in fish liver at Tiumsinawam exceeded their respective TVs, indicating the potential for zinc to cause environmental impact at those sites. The data indicate that zinc in benthic sediment is the dominant exposure pathway within the receiving environment, which suggests that after being discharged in dissolved form in water, zinc precipitates or is adsorbed to particulate matter, benthic sediment or suspended sediment. Bioavailability and Bioaccumulation Pathways The results of the environmental risk assessment indicate inconsistencies between low concentrations of dissolved metals in water and WAE metals in benthic sediment, and bioaccumulation of metals in the tissue of fish and prawns. In 214, Barrick Porgera engaged CSIRO to perform a parallel sampling program within the receiving environment downstream of the mine. The program employed ultratrace sampling and analysis techniques to measure metals at extremely low, sub parts-per-billion, concentrations. The program also investigated the relative contribution of dissolved metals in water, metals in benthic sediment, and additionally, metals in suspended particulate matter. The results of the CSIRO ultra-trace sampling (Angel et al, June 215) were in general agreement with the Barrick Porgera monitoring program, confirming the accuracy of the Barrick Porgera program, and confirming the very low concentrations of dissolved metals in water and WAE metals in benthic sediment within the receiving environment. The results also indicated that metals associated with suspended particulate matter have the potential to contribute to the concentration of bioavailable metals within the receiving environment. Barrick Porgera and CSIRO will conduct a more detailed investigation of bioavailability and bioaccumulation pathways in 215. Recommendations for Improvement Recommendations are proposed to improve the certainty of the findings of future reports; the assessment methodology; environmental performance; communication of the findings to the many stakeholders, and to reduce environmental risk and impact. Note that as a result of implementing a new approach to the AER in 213, the 213 AER was completed and submitted late in 214. A number of the recommendations from the 213 AER are still in progress and appear in the list below in addition to new recommendations raised from this year s AER. viii

12 Findings and Assessment Methodology 1. Sample sediment from contact runoff sites for contaminants of concern; 2. Analyse tailings solids for WAE metals; 3. Investigate options for increasing the frequency of TSS sampling in lower river, Lake Murray and ORWB reference and test sites; 4. Continue to investigate potential bioaccumulation pathways for contaminants of concern within the receiving environment; 5. Continue to improve the methods for sampling fish and prawn populations to improve catch rates, reduce within-site variability, therefore improving consistency and increasing statistical power; 6. Continue to conduct an annual macroinvertebrate survey to establish a robust data set, with the aim of incorporating macroinvertebrates as an additional indicator of impact into future annual environment reports; 7. Revise the QA/QC procedures associated with tissue metal sampling; 8. Continue to investigate the validity of certified reference material as a form of QA/QC. 9. Assess the adequacy of the water flow leaking from the base of Waile Creek Dam for maintaining environmental flow downstream of the dam spillway. Reduce Environmental Risk and Impact and Improve Performance 1. Investigate options for reducing the bioavailability of metals within the receiving environment; 11. Implement the Waste Rock Management Plan to minimise the release of metalliferous drainage from the competent waste rock dumps. Communication and Engagement 12. Continue to develop and apply a communication plan to the AER each year, including a presentation to the PNG Conservation and Environmental Protection Authority and a Report Card on the river system. ix

13 Table of Contents 1 INTRODUCTION MINE OPERATIONAL HISTORY AND DESCRIPTION Staged Development History of the Mine Mining Operations Overview Processing Operations Overview 4 2 AER METHODOLOGY ASSESSMENT FRAMEWORK THE ENVIRONMENTAL MONITORING PROGRAM Schedule and Execution QA/QC ENVIRONMENTAL ASPECTS RECEIVING ENVIRONMENT MONITORING Indicator Parameters Monitoring Locations ENVIRONMENTAL RISK AND IMPACT ASSESSMENT 14 Stage 1 Risk Assessment 14 Stage 2 Impact Assessment Establishing Risk Assessment Trigger Values Establishing Impact Assessment Trigger Values ENVIRONMENTAL PERFORMANCE ASSESSMENT Testing for Statistical Significance 32 3 BACKGROUND ENVIRONMENTAL CONDITIONS CLIMATE Rainfall in Strickland River Catchment Hydrological Context Rainfall Summaries HYDROLOGY Strickland River Catchment SG3 (Compliance site) BACKGROUND WATER QUALITY Local Sites Upper and Lower River Background Water Quality Lake Murray and ORWBs Background Water Quality BACKGROUND BENTHIC SEDIMENT QUALITY Upper and Lower River Background Sediment Quality Lake Murray and ORWBs Background Sediment Quality BACKGROUND TISSUE METAL CONCENTRATIONS Upper and Lower River Background Tissue Metal Lake Murray and ORWBs Background Tissue Metal BACKGROUND AQUATIC BIOLOGY 74 x

14 3.6.1 Upper and Lower River Background Aquatic Ecosystem Condition Lake Murray SUMMARY OF BACKGROUND ENVIRONMENTAL CONDITIONS Climate and Hydrology Background Water Quality Background Sediment Quality Background Tissue Metal Concentrations Background Aquatic Biology 78 4 MINE OPERATIONS AND ENVIRONMENTAL ASPECTS PRODUCTION Mining and Processing Operations Total Ore Processed Gold Production GREENHOUSE GAS AND ENERGY WATER USE LAND DISTURBANCE Land Disturbance WASTE ROCK PRODUCTION Kogai Competent Dump Anawe North Competent Dump INCOMPETENT WASTE ROCK DISPOSAL TAILINGS DISPOSAL Riverine Tailings Disposal Tailings used as Underground Mine Backfill TAILINGS QUALITY SEDIMENT CONTRIBUTIONS TO THE RIVER SYSTEM OTHER DISCHARGES TO WATER Treated Sewage Effluent Oil/Water Separator Effluent Mine Contact Runoff POINT SOURCE EMISSIONS TO AIR CLOSURE PLANNING AND RECLAMATION Mine Closure Plan Life of Mine Mine Closure Vision and Objectives Key Closure Environmental and Social Issues Mine Closure Consultation and Stakeholder Identification Progressive Closure and Reclamation NON-MINERALISED WASTE COMPLIANCE ENVIRONMENTAL RISK, PERFORMANCE AND IMPACT ASSESSMENT LAND DISTURBANCE 121 xi

15 6.2 HYDROLOGY AND ENVIRONMENTAL FLOWS SEDIMENT TRANSPORT AND FATE OF SEDIMENT RIVER PROFILES LOCAL WATER SUPPLIES Sampling and Analysis AIR QUALITY WATER QUALITY RISK AND PERFORMANCE ASSESSMENT Upper and Lower River Lake Murray and ORWBs SEDIMENT QUALITY RISK AND PERFORMANCE ASSESSMENT Upper and Lower River Lake Murray and ORWBs TISSUE METAL CONCENTRATIONS RISK AND PERFORMANCE ASSESSMENT Upper and Lower River Lake Murray AQUATIC BIOLOGY IMPACT ASSESSMENT Upper and Lower River Lake Murray DISCUSSION AND CONCLUSIONS MINE OPERATIONAL HISTORY AND DESCRIPTION AER METHODOLOGY MINE OPERATIONS AND ENVIRONMENTAL ASPECTS BACKGROUND ENVIRONMENTAL CONDITIONS COMPLIANCE RISK, PERFORMANCE AND IMPACT ASSESSMENT Contaminants of Concern RECOMMENDATIONS REFERENCES 16 APPENDIX A. BOX PLOTS EXPLAINED 161 APPENDIX B. QA/QC 162 B.1 WATER AND SEDIMENT QUALITY 162 APPENDIX C. BOX PLOTS AND TRENDS OF MINE AREA RUNOFF WATER QUALITY APPENDIX D. WATER QUALITY RISK AND PERFORMANCE ASSESSMENT DETAILS OF STATISTICAL ANALYSIS AND BOX PLOTS 191 APPENDIX E. SEDIMENT QUALITY RISK AND PERFORMANCE ASSESSMENT DETAILS OF STATISTICAL ANALYSIS AND BOX PLOTS 219 APPENDIX F. TISSUE METAL RISK AND PERFORMANCE ASSESSMENT DETAILS OF STATISTICAL ANALYSIS & BOX PLOTS 242 xii

16 List of Tables Table 2-1 Monitoring compliance to plan and data recovery in Table 2-2 Environmental aspects & monitoring parameters 1 Table 2-3 Receiving environment monitoring parameters 11 Table 2-4 Test sites, applicable reference sites and indicator parameters 12 Table 2-5 Assessment of reference site suitability 18 Table 2-6 Water quality TVs 22 Table 2-7 Risk assessment matrix water quality 22 Table 2-8 ph TVs 23 Table 2-9 Risk assessment matrix ph 24 Table 2-1 Sediment quality TVs 25 Table 2-11 Risk assessment matrix sediment quality 26 Table 2-12 Tissue metal concentration TVs 27 Table 2-13 Risk assessment matrix tissue metal concentrations 27 Table 2-14 Drinking water, air quality and river profile TVs 28 Table 2-15 Risk assessment matrix drinking water, air quality and river profiles 28 Table 2-16 Interpretation of Spearman Rank Test results 29 Table 2-17 Impact assessment matrix biology 3 Table 2-18 Environmental performance criteria 31 Table 2-19 Performance assessment matrix water, sediment and tissue metal 32 Table 3-1 Summary of meteorological data recorded at Anawe plant site during Table 3-2 Summary of median daily flows in m 3 /s for riverine stations in Table 3-3 Local site monitoring points 44 Table 3-4 Summary of total metal concentration trends in mine area runoff as tested by Spearman Rank Correlation (D = Dissolved and T = Total concentrations) 53 Table 3-5 Summarised water quality for upper river reference sites for baseline and for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) default TV for 95%species protection provided for comparison. All data reported as µg/l except where indicated 55 Table 3-6 Summarised water quality for lower river reference sites for baseline and for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) default TV for 95%species protection provided for comparison. All data reported as µg/l except where indicated 56 Table 3-7 Performance criteria for water quality at upper river reference sites (dissolved) as determined by Spearman Rank correlation against time 57 Table 3-8 Performance criteria for water quality at lower river reference sites (dissolved) as determined by Spearman Rank correlation against time 57 xiii

17 Table 3-9 Summarised water quality data for Lake Murray and ORWB river reference sites for baseline and for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) default TV for 95%species protection provided for comparison. All data reported as µg/l except where indicated. 59 Table 3-1 Performance criteria for water quality Lake Murray and ORWBs as determined using Spearman Rank Correlation against time 6 Table 3-11 Summarised sediment quality data for upper river reference sites for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) ISQG-Low values are provided for comparison. All data reported as mg/kg. 62 Table 3-12 Summarised sediment quality data for lower river reference sites for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) ISQG-Low values are provided for comparison. All data reported as mg/kg. 63 Table 3-13 Performance criteria for sediment quality for upper river (total digest) determined by Spearman Rank correlation against time 64 Table 3-14 Performance criteria for sediment quality for lower river (total digest) determined by Spearman Rank correlation against time 64 Table 3-15 Summarised sediment quality data for Lake Murray and ORWBs reference sites for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) ISQG-Low values are provided for comparison. All data reported as mg/kg. 65 Table 3-16 Performance criteria for sediment quality Lake Murray and ORWBs (total digest) determined by Spearman Rank correlation against time 66 Table 3-17 Summarised tissue metal data for upper river reference sites for previous 24 months (As-Cu), presenting median and 8%ile of data for each site. All data reported as mg/kg. 67 Table 3-18 Summarised tissue metal data for upper river reference sites for previous 24 months (Hg - Zn), presenting median and 8%ile of data for each site. All data reported as mg/kg wet except where indicated. 68 Table 3-19 Summarised tissue metal data for lower river reference sites for previous 24 months (As-Cu), presenting median and 8%ile of data for each site. All data reported as mg/kg wet except where indicated. 69 Table 3-2 Summarised tissue metal data for lower river reference sites for previous 24 months (Hg-Zn), presenting median and 8%ile of data for each site. All data reported as mg/kg wet except where indicated. 7 Table 3-21 Performance criteria of metals in fish flesh for upper river reference sites determined by Spearman Rank correlation against time 71 Table 3-22 Performance criteria of metals in fish liver for upper river reference site determined by Spearman Rank correlation against time 71 Table 3-23 Performance criteria of metals in prawn abdomen for upper river reference site determined by Spearman Rank correlation against time 71 Table 3-24 Performance criteria of metals in prawn cephalothorax for upper river reference site determined by Spearman Rank correlation against time 72 xiv

18 Table 3-25 Performance criteria of metals in fish flesh at lower river reference site determined by Spearman Rank correlation against time 72 Table 3-26 Performance criteria of metals in fish liver at lower river reference site determined by Spearman Rank correlation against time 72 Table 3-27 Performance criteria of metals in prawn abdomen at lower river reference sites determined by Spearman Rank correlation against time 73 Table 3-28 Performance criteria of metals in prawn cephalothorax at lower river reference sites determined by Spearman Rank correlation against time 73 Table 3-29 Performance criteria of metals in fish flesh at Lake Murray and ORWB reference sites determined by Spearman Rank correlation against time 74 Table 3-3 Performance criteria of metals in fish liver at Lake Murray and ORWB reference sites determined by Spearman Rank correlation against time 74 Table 3-31 Performance criteria for fish at upper river reference sites determined by Spearman Rank correlation against time 76 Table 3-32 Performance criteria for prawns at upper river reference sites determined by Spearman Rank correlation against time 76 Table 3-33 Performance criteria for fish at lower river reference sites determined by Spearman Rank correlation against time 76 Table 3-34 Performance criteria for prawns at lower river reference sites determined by Spearman Rank correlation against time 76 Table 3-35 Performance criteria for fish at Lake Murray reference site determined by Spearman Rank correlation against time 77 Table 4-1 Mine production and environmental aspects summary 79 Table 4-2 Areas of cumulative land disturbance and reclamation to December Table 4-3 Total quantities of waste rock placed in each dump Table Median dissolved metal concentrations in tailings discharge 214 (µg/l) 97 Table 4-5 Median total digest metal concentrations in tailings solids 214 (mg/kg) 97 Table 4-6 Tailings discharge quality trends Table 4-7 Summary of incompetent waste rock and tailings disposal tonnages in 214 and Table 4-8 Estimates of particle size distribution of material sampled at erodible dump toe 16 Table 4-9 Summary of long-term dump mass balance from survey data 17 Table 4-1 Estimate of sediment discharge from erodible dumps and tailings during Table 4-11 Estimated volumes of contact runoff from mine lease areas Table 4-12 Mine contact runoff monitoring sites 111 Table 4-13 Contact Water Quality- 214 median values (µg/l) 112 Table 4-14 Summary of water quality trends in mine area runoff (as tested using Spearman Rank Correlation) 114 Table 4-15 Point source emission metal concentrations 213 (mg/m 3 ) 115 xv

19 Table 4-16 Mean monthly sulfuric acid mist (as SO 3 ) emissions from the autoclaves (g/m 3 ) 115 Table 4-17 Species of tree seedlings planted in Table 5-1 Compliance Summary 119 Table 5-2 Summary table Corrective Actions 119 Table 5-3 Compliance Assessment at SG3 and Water Quality at Upper River Test Sites 214 (dissolved µg/l) 12 Table 6-1 Land disturbance footprints from 21 to 214 (ha) 121 Table 6-2 Sampling sites for Local Village Water Supplies 132 Table 6-3 Physiochemical concentrations at drinking water sites, showing compliance/noncompliance against PNG Raw Drinking Water Quality Standard. 134 Table 6-4 Metal concentrations at drinking water sites, showing compliance/non-compliance against PNG Raw Drinking Water Quality Standard 135 Table 6-5 Average airborne particulate matter concentrations for December 213 to December 214 (μg/m 3 ) showing compliance/non-compliance against National Environmental Protection (Ambient Air Quality) Measure (NEPM 1998) 137 Table 6-6 Risk assessment median water quality results at upper river test sites in 214 compared against UpRiv TVs showing which indicators pose low and potential risk (µg/l) 138 Table 6-7 Risk assessment Median water quality results at lower river test sites in 214 compared against LwRiv TVs showing which indicators pose low and potential risk (µg/l) 139 Table 6-8 Risk Assessment Median water quality results at Lake Murray & ORWB test sites in 214 compared against LMY and ORWB TVs showing which indicators pose low and potential risk (µg/l) 14 Table 6-9 Risk Assessment Median sediment quality results at upper river test sites in 214 compared against UpRiv TVs showing which indicators pose low and potential risk (mg/kg WAE whole sediment) 141 Table 6-1 Risk Assessment Median sediment quality results at lower river test sites in 214 compared against LwRiv TVs showing which indicators pose low and potential risk (mg/kg WAE whole sediment) 141 Table 6-11 Risk assessment median sediment quality results at Lake Murray and ORWB test sites in 214 compared against LMY and ORWB TVs showing which indicators pose low and potential risk (mg/kg WAE whole sediment) 142 Table 6-12 Risk assessment median tissue metal results at upper river test sites in 214 compared against UpRiv TVs showing which indicators pose low and potential risk (mg/kg) 144 Table 6-13 Risk assessment median tissue metal results at lower river test sites in 214 compared against LwRiv TVs showing which indicators pose low and potential risk (mg/kg) 145 Table 6-14 Impact assessment based on the trend of the annual median of biological indicators at upper river test sites relative to the trend of the annual median of biological indicators at upper river reference sites throughout the history of the operation using Spearman Rank Test. 147 xvi

20 Table 6-15 Impact assessment based on the trend of the annual median of biological indicators at lower river test sites relative to the trend of the annual median of biological indicators at lower river reference sites throughout the history of the operation using Spearman Rank Test. 148 Table 6-16 Impact assessment based on the trend of the annual median of biological indicators at Lake Murray and ORWB test sites relative to the trend of the annual median of biological indicators at Lake Murray and ORWB reference sites throughout the history of the operation using Spearman Rank Test. 149 Table 7-1 Summary of mine discharge water quality compared against respective TVs and receiving environment water quality risk assessment results, showing indicators in discharge and test sites that pose low and potential risk to the receiving environment. 156 Table 7-2 Summary of mine discharge sediment quality compared against respective TVs and receiving environment sediment quality risk assessment results, showing indicators in discharge and test sites that pose low and potential risk to the receiving environment. 157 Table 7-3 Summary of receiving environment tissue metals risk assessment results, showing indicators at test sites that pose low and potential risk to the receiving environment. 158 xvii

21 Barrick Porgera Annual Environment Report 214 List of Figures Figure 1-1 Location of Porgera Operation 2 Figure 1-2 Process flow chart 5 Figure 2-1 Receiving environment monitoring sites 13 Figure 2-2 Lake Murray monitoring locations 14 Figure 2-3 ANZECC/ARMCANZ Risk Assessment Framework (ANZECC/ARMCANZ Fig 3.3.1) 15 Figure 2-4 Risk assessment matrix water quality 22 Figure 2-5 Risk assessment matrix ph 23 Figure 2-6 Risk assessment matrix sediment quality 25 Figure 2-7 Risk assessment matrix tissue metal concentrations 27 Figure 3-1 Comparison of annual rainfall (214 data versus long term means) at sites in the Strickland Catchment 35 Figure 3-2 Residual mass plots Anawe rainfall station data 36 Figure 3-3 Anawe rainfall, SOI and PDO indices on 1-y moving average 36 Figure 3-4 Rainfall at Anawe Plant Site during 214 against long-term monthly means 37 Figure 3-5 Comparison of annual rainfall at Anawe Plant Site with long-term mean Figure 3-6 Rainfall at Open Pit during 214 against long-term monthly means 38 Figure 3-7 Annual rainfall at Open Pit Figure 3-8 Rainfall at Waile Dam during 214 against long-term monthly means 39 Figure 3-9 Rainfall at Suyan Camp during 214 against long-term monthly means 4 Figure 3-1 Rainfall at SG2 during 214 against long-term monthly means 4 Figure 3-11 Rainfall at Ok Om during 214 against long-term monthly means 4 Figure 3-12 Rainfall at SG3 during 214 against long-term monthly means 41 Figure 3-13 Rainfall at SG4 during 214 against long-term monthly means 41 Figure 3-14 Rainfall at SG5 during 214 against long-term mean means 41 Figure 3-15 Comparison of annual specific yield for main river gauging stations 42 Figure 3-16 Mean annual flow volumes for the main river gauging stations in Figure 3-17 Total daily flow (GL) at SG3 for Figure 3-18 Total monthly flow (GL) at SG3 during 214 against long-term monthly medians 44 Figure 3-19 ph in local creek runoff Figure 3-2 ph in local creek runoff Figure 3-21 Sulfate in local creek runoff Figure 3-22 Sulfate in local creek runoff Figure 3-23 Alkalinity in local creek runoff Figure 3-24 Alkalinity in local creek runoff xviii

22 Figure 3-25 TSS in local creek runoff Figure 3-26 TSS in local creek runoff Figure 3-27 Dissolved and total silver in local creek runoff Figure 3-28 Dissolved and total silver in local creek runoff Figure 3-29 Dissolved and total arsenic in local creek runoff Figure 3-3 Dissolved and total arsenic in local creek runoff Figure 3-31 Dissolved and total cadmium in local creek runoff Figure 3-32 Dissolved and total cadmium in local creek runoff Figure 3-33 Dissolved and total chromium in local creek runoff Figure 3-34 Dissolved and total chromium in local creek runoff Figure 3-35 Dissolved and total copper in local creek runoff Figure 3-36 Dissolved and total copper in local creek runoff Figure 3-37 Dissolved and total iron in local creek runoff Figure 3-38 Dissolved and total iron in local creek runoff Figure 3-39 Dissolved and total mercury in local creek runoff Figure 3-4 Dissolved and total mercury in local creek runoff Figure 3-41 Dissolved and total nickel in local creek runoff Figure 3-42 Dissolved and total nickel in local creek runoff Figure 3-43 Dissolved and total lead in local creek runoff Figure 3-44 Dissolved and total lead in local creek runoff Figure 3-45 Dissolved and total selenium in local creek runoff Figure 3-46 Dissolved and total selenium in local creek runoff Figure 3-47 Dissolved and total zinc in local creek runoff Figure 3-48 Dissolved and total zinc in local creek runoff Figure 4-1 Monthly and cumulative ore processed in Figure 4-2 Yearly and cumulative ore processed Figure 4-3 Monthly and cumulative gold production in Figure 4-4 Yearly and cumulative gold production Figure 4-5 Energy efficiency Figure 4-6 Water use efficiency Figure 4-7 Special mining lease and leases for mining purposes boundaries 84 Figure 4-8 Monthly tonnages of competent waste rock placed at Kogai Dump in Figure 4-9 Yearly tonnages of competent waste rock placed at Kogai Dump Figure 4-1 Monthly tonnages of competent waste rock placed at Anawe North Dump in Figure 4-11 Yearly tonnages of competent waste rock placed at Anawe North Dump xix

23 Figure 4-12 Monthly tonnages of spoil placed at Anawe Erodible Dump in Figure 4-13 Yearly tonnages of spoil placed at Anawe Erodible Dump July Figure 4-14 Area and volume of Anawe Erodible Dump based on LiDAR survey Figure 4-15 Monthly tonnages of spoil placed at Anjolek Erodible Dump in Figure 4-16 Yearly tonnages of spoil placed at Anjolek Erodible Dump Figure 4-17 Area and volume of Anjolek Erodible Dump based on LiDAR survey Figure 4-18 View downstream along the Anawe Erodible Dump 91 Figure 4-19 View upstream along Anawe Erodible Dump 92 Figure 4-2 Extract from survey plan showing erosion of the Anawe dump at the south boundary adjacent to Paiam Slopes and the north boundary between the Anawe Stable Dump and the toe 92 Figure 4-21 Kaiya Alluvial Fan well-vegetated and stable 93 Figure 4-22 Central Tract of Anjolek showing a dissected and relatively stable landform 94 Figure 4-23 Extract from survey plan showing toe location and changes to the northern boundary adjacent to Nikelama and Lepalama 94 Figure 4-24 Monthly discharge of tailings in 214 (m3) 95 Figure 4-25 Annual and cumulative tailings discharge (dry solids) ( ) 95 Figure 4-26 Tailings diverted monthly to underground backfill in Figure 4-27 Monthly ph in tailings discharge in Figure 4-28 Annual ph in tailings discharge Figure 4-29 Monthly TSS in tailings discharge in 214 (mg/l) 98 Figure 4-3 Annual TSS in tailings discharge (mg/l) 98 Figure 4-31 Monthly WAD-CN concentration in tailings discharge in 214 (mg/l) 99 Figure 4-32 Annual WAD CN concentration in tailings discharge (mg/l) 99 Figure 4-33 Monthly dissolved and total silver concentrations in tailings 214 (mg/l) 99 Figure 4-34 Annual dissolved and total silver concentrations in tailings (mg/l) 99 Figure 4-35 Monthly dissolved and total arsenic concentrations in tailings 214 (mg/l) 1 Figure 4-36 Annual dissolved and total arsenic concentrations in tailings (mg/l) 1 Figure 4-37 Monthly dissolved and total cadmium concentrations in tailings 214 (mg/l) 1 Figure 4-38 Annual dissolved and total cadmium concentrations in tailings (mg/l) 1 Figure 4-39 Monthly dissolved and total chromium concentrations in tailings 214 (mg/l) 11 Figure 4-4 Annual dissolved and total chromium concentrations in tailings (mg/l) 11 Figure 4-41 Monthly dissolved and total copper concentrations in tailings 214 (mg/l) 11 Figure 4-42 Annual dissolved and total copper concentrations in tailings (mg/l) 11 Figure 4-43 Monthly dissolved and total iron concentrations in tailings 214 (mg/l) 12 Figure 4-44 Annual dissolved and total iron concentrations in tailings (mg/l) 12 xx

24 Figure 4-45 Monthly dissolved and total mercury concentrations in tailings 214 (mg/l) 12 Figure 4-46 Annual dissolved and total mercury concentrations in tailings (mg/l) 12 Figure 4-47 Monthly dissolved and total nickel concentrations in tailings 214 (mg/l) 13 Figure 4-48 Annual dissolved and total nickel concentrations in tailings (mg/l) 13 Figure 4-49 Monthly dissolved and total lead concentrations in tailings 214 (mg/l) 13 Figure 4-5 Annual dissolved and total lead concentrations in tailings (mg/l) 13 Figure 4-51 Monthly dissolved and total selenium concentration in tailings 214 (mg/l) 14 Figure 4-52 Annual dissolved and total selenium concentrations in tailings discharge (mg/l) 14 Figure 4-53 Monthly dissolved and total zinc concentrations in tailings 214 (mg/l) 14 Figure 4-54 Annual dissolved and total zinc concentrations in tailings (mg/l) 14 Figure 4-55 Production of incompetent rock and tailings Figure 4-56 Total annual discharge volumes of treated sewage Figure 4-57 Average monthly TSS concentration in treated sewage discharge Figure 4-58 Average monthly BOD 5 concentration in treated sewage discharge Figure 4-59 Average monthly faecal coliform count in treated sewage discharge Figure 4-6 Average monthly total hydrocarbon concentrations in oil water separator discharges Figure 4-61 Mine area runoff sampling locations 113 Figure 4-62 Non-mineralised waste production by type 118 Figure 6-1 Daily flow duration curve (estimated) for Waile Creek Dam outflow 122 Figure 6-2 Daily flow duration curves for Kogai Creek 122 Figure 6-3 Mean monthly TSS and flow at SG3 for Figure 6-4 Estimated mean monthly suspended sediment loads for SG3 (Mt) 124 Figure 6-5 Estimated monthly suspended sediment load (black bars) with 3-month moving average at SG3 for full record (red solid line) 125 Figure 6-6 Historical average TSS Figure 6-7 Suspended sediment budget at SG3 since Figure 6-8 Estimated suspended sediment budget at SG3 expressed as % 127 Figure 6-9 Profile comparison (29 214) at Kaiya River downstream of Kogai Confluence 128 Figure 6-1 Profile comparison (29 214) for Kaiya River upstream of Yuyan Bridge 128 Figure 6-11 Profile comparison (29 214) for Kaiya River downstream of Yuyan Bridge 129 Figure 6-12 Time series of minimum bed elevations along the Kaiya River 129 Figure 6-13 Profile comparison (21 215) at Lagaip River at SG2 13 Figure 6-14 Profile comparison (2 213) at Profile Figure 6-15 Sampling Sites for Local Village Water Supplies 133 xxi

25 Figure 9-1 Cadmium in prawn cephalothorax upper river test sites 254 Figure 9-2 Chromium in fish flesh upper river test sites 254 Figure 9-3 Cadmium in prawn cephalothorax upper river test sites 254 Figure 9-4 Chromium in fish flesh upper river test sites 254 xxii

26 LIST OF ABBREVIATIONS AER: Annual Environment Report. ANSTO: Australian Nuclear Science and Technology Organisation. ANZECC/ARMCANZ: Australian and New Zealand Environment and Conservation Council and the Agricultural and Resource management Council of Australia and New Zealand. ANZFA: Australia New Zealand Food Authority. Baseline Data: Also called pre-operational data (studies); collected (undertaken) before development begins (ANZECC/ARMCANZ 2). BOD 5 : 5-day Biological Oxygen Demand. CIL: Carbon-in-leach. CIP: Carbon-in-pulp. CN: Cyanide. CO 2 -e: Carbon dioxide equivalents. Competent rock: Hard and durable rock that can be stacked in a stable dump configuration. CV-AAS: Cold vapour atomic absorption spectrometry. Dissolved metals: Operationally defined as passing a very fine (.45 µm) membrane filter. EL: Exploration lease. EMS: Environmental Management System. ENSO: El Nino Southern Oscillation. Environmental aspect: activities that have the potential to interact with the environment (ISO 141). Environmental Impact: A statistically significant adverse change in the ecosystem health of the receiving environment as a result of the operation s environmental aspects. Environmental Risk: The potential for adverse effects on living organisms associated with pollution of the environment by effluents, emissions, wastes, or accidental chemical releases, energy use, or the depletion of natural resources. (U.S. Environmental Protection Agency). Erodible waste dump: designed to temporarily store incompetent waste rock in a river valley while allowing the dump to gradually and progressively fail and some material to be eroded and transported downstream by the river system. GELs: Generally expected levels. ICP-MS: Inductively coupled plasma mass spectrometry. ISO141: International Organisation for Standardisation Environmental standard for Management Systems. ISQG: Interim Sediment Quality Guidelines. KPI: Key Performance Indicator. LMP: Lease for mining purposes xxiii

27 LOM: Life of Mine LOR: Limit of Reporting ME: Mining easement NMI: National Measurement Institute NOEC: No observable effects concentration ORWBs: Off-river water bodies PDO: Pacific Decadal Oscillation PLOA: Porgera Land Owner Association PNG: Papua New Guinea QA/QC: Quality Assurance and Quality Control Reference site: are sites within an ecosystem that are similar to and in the vicinity of the test site ecosystem, but are outside of the zone of potential influence of the operations environmental aspects. SAG: Semi-autogenous grinding SML: Special mining lease SOP: Standard Operating Procedure TARP: Trigger Action Response Plan Test site: are those sites at which the influence of the operations environmental aspects may occur Total metals: the sum of all the various compounds of a given metal in a sample (for example, the combined concentration of organic and inorganic mercury). TSM: Test Site Median TSS: Total Suspended Solids TV: Trigger Value WAD-CN: Weak Acid Dissociable Cyanide WAE: Weak acid extractable WWCB: West wall cut-back xxiv

28 Barrick Porgera Annual Environment Report INTRODUCTION The Barrick Porgera Gold Mine is located in the Porgera Valley of Enga province in the Papua New Guinea highlands, approximately 13km WNW of Mt Hagen. The operation consists of an open cut and underground mine, processing facility, gas fired power station, a dam, limestone quarry, lime plant, waste management infrastructure, workshops, warehouses, administrative and accommodation buildings. Operations commenced in 199 and are expected to continue until 225, the site employs approximately 27 local, national and expatriate staff and contractors and produces approximately 5 koz of gold per annum. The operation has a number of unique economic, social and environmental aspects. The environmental aspects are managed by operating in accordance with the sites Environmental Management System (EMS), which is certified to the ISO141 international standard for EMS. The objectives of the EMS are to ensure methodical, consistent and effective control of the sites environmental aspects so as to ensure compliance with legal and other requirement, mitigation of potential environmental risks and continual improvement of environmental performance. A critical element of the EMS is the environmental monitoring and reporting program. The program provides feedback on the effectiveness of the EMS for achieving the stated objectives and therefore allows the operation to identify management techniques that are working well, and more importantly identify those areas which require attention. The purpose of this Annual Environment Report (AER) is to provide an assessment of the overall environmental performance of the mine during the previous calendar year as well as since the commencement of operations. The objectives of this report are aligned with those of the EMS and are to assess: 1. Compliance with legal and other requirements; 2. The level of risk and impact to the condition of the receiving environment posed by the mine operation; and 3. The environmental performance of the operation. Barrick Porgera has continued to apply the risk-based frameworks/benchmarks that were developed for the 213 AER in a bid to optimise the evaluation of the large database of biophysical monitoring data. This gives better integration of the physical, chemical and biological monitoring data and a better indication of the environmental consequences of the mine operation than in previous environmental monitoring reports, and should improve the communication of findings to the many stakeholders. Legal and other requirements are imposed predominantly by the two environmental permits, issued to the mine by the Papua New Guinea Conservation and Environmental Protection Authority (CEPA. Monitoring data are compared against the permit conditions to assess compliance. The methodology for risk and impact assessment has been developed by Barrick Porgera in accordance with international guidelines and in consultation with external technical experts. The risk assessment stage is based on the comparison of physical and chemical environmental indicators at those sites potentially impacted by the mine (test sites) against risk assessment criteria or trigger values derived from baseline data, reference sites and international guidelines. A physical or chemical indicator (i.e. ph, cadmium or zinc) measurement at the test site that falls below the trigger value indicates low risk of environmental impact, while an exceedance of the trigger indicates the potential for environmental impact and triggers further investigation to determine whether impact is actually occurring. The impact assessment stage is based on the comparison of biological indicators at test sites against biological indicators from reference sites. When the performance of 1

29 biological indicator values at the test site is below that of the reference site (i.e. species diversity at a test site is reduced relative to a reference site), it indicates that environmental impact is potentially occurring. If the same performance of biological indicators is observed at both the test and reference sites then it indicates no potential impact is detected or there is a system-wide change that is not related to the mine. The first section of the AER quantifies the mine operations and associated activities during 214 as well as since the commencement of operations that have the potential to interact with the environment (i.e. the environmental aspects). Next, background environmental conditions are summarised to quantify the natural, or non-mine related changes within the receiving environment. Then assessments are made of compliance, risk, performance and impact, followed by a discussion of the findings and finally an outline of recommendations for improving the environmental management system and the environmental monitoring and reporting program. 1.1 Mine Operational History and Description Staged Development History of the Mine The Porgera mine and processing facilities located in Enga Province, Figure 1-1, were developed in four stages between 1989 and 1996 for optimisation of production. The original project approvals for the mine covered the staged development to a nominal processing capacity of 8,5 tonnes per day, which was subsequently increased to 17,5 tonnes per day. The four stages of project development are outlined below. Figure 1-1 Location of Porgera Operation Stage I construction of the mine commenced in July 1989 and comprised development of an underground mine, ore processing plant and associated infrastructure. The processing plant consisted of a crushing and grinding circuit, a concentrator to recover the gold-bearing sulphide portion of the ore and a cyanidation leach carbon-in-pulp (CIP) circuit. High grade ore from the underground mine was fed to the mill at a rate of 1,5 tonnes per day (t/day). The sulfide flotation concentrate was direct leached in the CIP circuit, recovering approximately 6% of the contained gold, followed by refining into doré on site. The CIP tailing containing the remaining 4% of the gold was stored in a 2

30 lined pond for later reclaim and processing through the pressure oxidation circuit. The barren flotation tailing was discharged into the river system. Stage I production commenced in September 199. Stage 2 of construction consisted of expanding the underground mine production and installation of the pressure oxidation circuit at the processing plant. The underground mine production was increased by addition of an ore crushing and hoisting system to convey the ore to the surface. In September 1991, commissioning was completed for the pressure oxidation autoclaves for processing the sulphide flotation concentrate and recovery of refractory gold. The sulfide flotation concentrate from the ore feed and the previously stockpiled Stage 1 CIP tailing were processed in the pressure oxidation circuit at 25 t/day. Gold liberated by pressure oxidation was recovered through the CIP cyanide leach circuit. The tailings neutralisation circuit was commissioned for combining the various processing waste streams (acid wash effluent, cyanidation tailing and flotation tailing) to detoxify and neutralise the tailing before discharge to the river system. Stage 3 was commissioned in September 1992, with mill throughput increased to 45 t/day. The underground ore was supplemented with ore from the open pit mine. Stage 4A of the project commenced in October 1993 and further expanded open pit mining operations and the mill facilities, increasing mill throughput to 85 t/day. In 1993, a major review of the project recommended expansion to a nominal capacity of 17,5 t/day for optimisation of mining and ore processing rates. Following the granting of project approvals, this additional expansion, known as Stage 4B, was completed in the first quarter of Stage 4B involved addition of a second semi-autogenous grinding (SAG) mill and a large ball mill, a 35 t/day oxygen plant, a 15 t/day lime kiln and increased flotation and leaching capacity. Process water storage and the Hides power plant generation capacity, together with other infrastructure also were increased to support this expansion. The open pit mining fleet capacity was expanded in 1997 from 15, to 21, t/day to provide for the increase in mill feed rates. Four Knelson concentrators were installed in the same year, to recover free gold ahead of the flotation circuit. In 1999, a further flotation expansion was installed to improve recoveries, and additional oxygen plant capacity was added to increase autoclave throughput. In 21, an Acacia reactor was commissioned to treat the Knelson gravity concentrate, and modifications were made to the grinding and CIP circuits. During 23 a contract secondary crusher was installed to optimise the capacity of the crushing plant and allow a better match between milling and oxidation capacity. In 29 a cyanide destruct plant was commissioned to reduce the concentration of cyanide in the tailings discharge and achieve compliance with the International Cyanide Management Code. Two years later in 211, a paste plant was commissioned for placement of the coarse fraction of tailing in the underground mine as cemented paste backfill. The paste plant has a nominal capacity of 8% of the tailings discharged from the processing plant Mining Operations Overview Barrick Porgera mining operations consist of open cut and underground operations. Open pit mining is a hard rock operation developed using drill and blast, load and haul techniques. The design utilises 1 metre benches, hydraulic face shovels and haul trucks to achieve a nominal material movement capacity in the order of 45 million tonnes per annum. A particularly challenging aspect to development of the open pit is the inherent instability of the western wall as a result of the presence of Brown Mudstone and inflow of water to the pit from surrounding catchments. Although mining continues despite the ingress of mud and debris, the ongoing wall failure does pose a risk to workers safety, equipment and inhibits access to and dilutes ore 3

31 at the bottom of the open pit. A number of mitigation and stabilisation measures, known collectively as the West Wall Cutback, are being investigated to stabilise the west wall and prevent the ingress of mud and water to the pit. High grade ore is transported to the crusher and low grade ore is transported to stockpiles for processing at a later date. Waste rock is classified into three categories and managed accordingly. An underground mine was first operated from 1989 to The underground mining operation was recommenced in 22 to extract underground reserves in the Central and North Zones. The original underground workings were subsequently maintained and developed to provide long-term drainage for the open pit, and to provide access for on-going exploration. The Underground Mine is accessed by a Portal adjacent to the Open Pit and mines ore both from outside and beneath the Open Pit footprint. The underground mining method used is long-hole bench stoping. Ore is recovered by drilling and blasting while retreating along the strike for the full length of the stope. The broken ore is progressively mucked to trucks on the lower level using a combination of conventional, remote and tele-remote control loader operations. Longer stopes are filled in stages with a combination of cemented and non-cemented fills to maintain hanging wall spans. After mining, open stopes in strategic places are filled with unconsolidated waste rock and cement aggregate and a cement-tailings aggregate, produced from the paste plant, to create crown pillars. The underground mine generates approximately 1 million tonnes of ore per annum. Ore is transported to the crusher, while the majority of waste rock produced from the underground mine is used as backfill to support underground development, the small quantity of waste rock that is brought to surface is stored in one of the competent waste rock dumps with waste from the open pit Processing Operations Overview A flow sheet describing the ore processing operations is shown in Figure 1-2. Run-of-mine ore is delivered by trucks to the dump pocket of a gyratory crusher. Primary crushed ore is conveyed to a coarse ore stockpile. A portion of the primary crusher product can be diverted to the secondary crusher circuit and the crushed product returned to the coarse ore stockpile. The secondary crushers are closed circuit with a screen producing a <25 mm product which reduces overall semi-autogenous grinding (SAG) feed size, this increases mill throughput particularly when treating harder ore. 4

32 Figure 1-2 Process flow chart An additional jaw crushing circuit is available to process waste rock for civil works and/or sticky ore. The circuit consists of a pan feeder, vibrating grizzly and jaw crusher which can deliver to either the coarse ore stockpile or provide <15 mm waste for the aggregate plant. The ore from the coarse ore stockpile feeds two parallel SAG mills (4.5 MW). The slurry discharge from each SAG mill passes over a vibrating screen and the oversize is conveyed to two Sandvik CH 66 pebble crushers where it is crushed prior to recycling to the SAG mills. The screen underflow is pumped to a distribution box where slurry is distributed to the ball mill cyclone feed pumps which operate in closed circuit with 3 cyclone packs. The cyclone underflow feeds three ball mills. A portion of the cyclone underflow from each cyclone pack feeds scalping screens with screen underflow feeding 4 Knelson concentrators to recover free gold. Knelson concentrate is transferred to an intensive leach reactor located in the gold room at Anawe. Overflow from the cyclone flows via gravity to the Anawe flotation concentrator via twin 2 km long pipelines. The flotation circuit consists of rougher, cleaner, and scavenger banks producing a final concentrate of 14% sulfur, and a throw away final tail. The flotation concentrate is combined with the Acacia reactor tail and reground to a size whereby 92% of the material is <38 µm, using three regrind ball mills operating in closed circuit with 2 sets of cyclones. Reground concentrate is pumped to a 35 m diameter concentrate thickener and then to the concentrate storage tanks, that provide approximately six days worth of production buffer storage between flotation and the oxidation sections. As required, flotation concentrate is pumped to a train of three carbonate reaction tanks, where the fresh feed is mixed with an acidic stream of recycled oxidized slurry to neutralise most of the carbonates in the concentrate, which limits the production of carbon dioxide in the autoclaves and thereby improves the utilization of oxygen. After carbonate destruction, the feed is directed to the four 5

33 autoclaves. The autoclaves are 4 m diameter, 27 m long, steel pressure vessels that are lined with lead and acid-proof brick. Agitation for the 6 compartments is provided by 6 x 1 kw motors. The autoclaves are operated at a pressure of 1,75 kpa and a temperature of 198ºC. The oxidation reaction can operate autogenously however steam is more often used to supplement the reaction. Water is added to each compartment of each autoclave to control the reaction heat balance. Approximately 98% of the sulfides are oxidized in this process. The oxidized slurry discharges from the autoclave via a choke valve into a flash vessel that is equipped with a gas scrubber to control acidic emissions. Acidic water is washed from the autoclave discharge of oxidised slurry using two stainless steel, 35 m diameter, high-rate thickeners. The wash circuit operates counter-currently, using concentrate thickener overflow as the wash water. The washed and thickened slurry is fed to the cyanide CIL (carbon in leach) circuit at 29% solids. The leach circuit consists of seven agitated leach tanks. Carbon is added to Tank (to negate the pregnant robbing nature of the ore) and flows with the slurry to tank 7 where an inter-tank screen is located. Slaked lime is added to the first tank (conditioning tank) to adjust the ph to 1.5. Sodium cyanide is added in the first CIL tank to a concentration of about 15 mg/l. Following the CIL step, a series of nine CIP (carbon-in-pulp) tanks recover the remaining gold from the slurry. Each tank contains about six tonnes of carbon, with four tonnes of carbon forwarded each day. The CIL and CIP recovery ranges from 86-92% depending on the ore type and the gold grade. The elution circuit comprises two pressurized vessels that each holds approximately 1 tonnes of carbon. The precious metals are eluted from the carbon using 15 bed volumes of eluate at 14ºC and 4 kpa. Barren carbon is regenerated in a rotary kiln and then acid-washed in a 3% hydrochloric acid solution prior to being returned to the CIP circuit. Gold and silver are electro-won from the pregnant strip solution in three banks of cells. Each bank consists of three cells containing 18 stainless steel wool cathodes and 19 stainless steel mesh anodes. At regular intervals, the cathodes are removed and the gold sludge is washed off, pressure filtered, and retorted to remove any mercury. The mercury is condensed and collected as a by-product and disposed to a licensed facility. The residue containing gold and silver is mixed with a flux of borax, soda ash, nitre, and silica, and smelted in an induction furnace to produce 5 oz. bars of doré bullion that average about 8% gold. Neutralisation of acidic autoclave wash water is achieved by using residual carbonate in the flotation tailing and slaked lime. Acidic wash water is pumped from the surge tank to 3 neutralisation tanks. Flotation tailings are distributed across the tanks depending upon flow rates between tanks. Slaked lime is added to the 4th tank, the first of two precipitation tanks, to increase slurry ph to 6.5 and precipitate metals. The CIP tails containing cyanide is processed through the cyanide destruction plant (INCO SO 2 Destruction plant) before being mixed with acidic wash thickener overflow. The final effluent from the neutralization circuit is discharged to the Porgera River, which in turn flows into the Lagaip River, the Strickland River, and the Fly River before entering the Gulf of Papua. Neutralised tailings is also utilised to generate a paste for underground backfill. Slurry is pumped from either of precipitation tank 1 or 2 to a cyclone pack. Cyclone underflow (43-53% solids) is pumped 1.6 km to the paste plant. Slurry is pumped from a 2 m 3 surge tank into one of two 3.81 m diameter 12 disc filters. Filter cake is conveyed to a paste mixer where cement, plasticizer and water are added to produce a paste of 73% solids and a slump of 24 mm. Cement is stored in 2 x 1 t bins. Paste flows via a surge hopper into a dual cylinder positive displacement Putzmeister piston pump and pumped 1.6km underground via a reticulated 16 mm diameter pipeline. Lime for neutralization purposes is produced from limestone quarried from a deposit 15 km south of the mine. The limestone is processed in two vertical kilns which use either waste oil or diesel as fuel. Quicklime is stored in a silo and trucked to the Anawe plant site and transferred into one of two lime silos. The quicklime is slaked in a lime mill and stored in an agitated tank. 6

34 Most of the water for the process plant is supplied by pipeline from the Waile Creek dam 2 km south of the mine site. Additional water is delivered to the Tawisakale grinding circuit from the nearby Kogai Creek. Electrical power is generated at Hides, 73 km south of the mine site using 9 gas turbines having a combined capacity of 72 MW and delivered to site via a 132 kv transmission line; this is supplemented by a 13 MW diesel power station at the mine site. 7

35 Barrick Porgera Annual Environment Report AER METHODOLOGY 2.1 Assessment Framework The environmental compliance, risk, impact and performance assessments are conducted in accordance with the following steps: 1. Identify those aspects of the operation that have the potential to interact with the environment (i.e. the environmental aspects) (Section 2.3). 2. Identify appropriate physical, chemical and biological parameters to serve as indicators of natural or mine-related change within the receiving environment. These indicators form the basis of the environmental monitoring program, and will be monitored at both the test and the reference sites. These data will provide the evidence upon which the compliance, impact and performance assessments will be made (Section 2.4.1). 3. Identify locations within the receiving environment where mine-related environmental impact may occur. These sites are known as test sites (Section 2.4). 4. Identify suitable reference sites within the receiving environment. These are sites that are similar in nature to the test sites but are not potentially influenced by mine operations (Section 2.4). Monitoring of environmental parameters at the reference sites is conducted to support development of risk assessment and impact assessment trigger values (TVs). 5. Establish risk and impact assessment trigger values for each indicator parameter by comparing the baseline and reference sites data sets with international guidelines and selecting the most appropriate value. 6. Describe the natural or background environmental conditions and any non-mine related changes to the condition of the receiving environment throughout the reporting period (Section 3). 7. Quantify the environmental aspects of the mine operation that have the potential to interact with the environment (Section 4). 8. Assess compliance against legal requirements (Section 5). 9. Determine the risk of mine-related environmental impact occurring at the test sites (Section 6). 1. Make a determination of environmental performance of the relevant mine operation control(s) for prevention or mitigation of environmental impact (Section 6). 11. Determine whether impact has occurred at the test sites and if so, to what degree has or is it occurring (Section 6). 2.2 The Environmental Monitoring Program The environmental monitoring program consists of sampling and measurement of physical, chemical and biological variables to quantify the operations environmental aspects, such as discharges and emissions to the environment, and the associated changes to the receiving environment. The monitoring program is detailed in the Porgera Environmental Monitoring, Auditing and Reporting Plan and associated Standard Operating Procedures. The spatial scope of the monitoring program is extensive, spanning from the mine site to SG5 on the lower Strickland River, approximately 56 river km downstream from the mine. 8

36 Many of the monitoring locations are in remote areas and require the use of helicopters to gain access. While all efforts are taken to conduct the monitoring program to schedule, high potential safety issues will sometimes prevent sampling from being undertaken. Safety concerns may arise from such issues as severe flooding, unsafe access, social unrest, threats against Barrick and threats against employees based on their area of origin Schedule and Execution Compliance with the monitoring plan is summarised in Table 2-1, overall the monitoring schedule was executed to plan, with some exceptions due to access, safety and equipment damage. Table 2-1 Monitoring compliance to plan and data recovery in 214 Discipline Compliance to Plan (%) Biology 95 Hydrology Spot Gauging 95 Chemistry QA/QC Barrick Porgera incorporates a quality assurance and quality control (QA/QC) program into the monitoring and reporting program to ensure the data being reported are accurate, representative and defendable. The QA/QC program consists of training and competency assessment, equipment calibration, method validation, field blanks, field duplicates, certified reference material, proficiency testing and interlaboratory analysis. Analysis of metals in water, benthic sediment and prawn and fish tissue is performed by the National Measurement Institute in Sydney, Australia. The results of the QA/QC program show that sampling and analytical techniques are providing representative and valid results for all water, sediment and tissue metal results. Some contamination of blanks and deviation from the required levels of recovery for duplicates and certified reference material was observed on occasion during the year. However, based on positive field blank, field duplicate and intra-laboratory QA/QC results, the data provided by the monitoring and reporting program, and subsequently presented in this report, are deemed representative and valid. Opportunities to improve the QA/QC program are: Completion of training and competency system development and implementation. Inclusion of field duplicates and field blanks with each tissue metal batch. More timely investigation of poor QA/QC results to allow for corrective action to be taken. Complete CSIRO led investigation of validity of certified reference material as a method of QA/QC. A full review of QA/QC performance is provided in APPENDIX B. 9

37 Barrick Porgera Annual Environment Report Environmental Aspects The significant environmental aspects of the Porgera operation are riverine tailings disposal, waste rock disposal, water extraction and discharge, hazardous substances transport, storage and use, and waste management. Each aspect must be monitored and quantified to determine the risk it poses, to determine whether the management techniques applied are effective in achieving the desired level of control and to determine whether actions taken to improve performance are effective. Table 2-2 provides an outline of the operation s environmental aspects and the associated physical and chemical parameters that are monitored to quantify each aspect. Table 2-2 Environmental aspects & monitoring parameters Environmental Aspect Physical Parameters Chemical and Toxicant Parameters Water extraction Volume extracted NA Discharge to air Emission rate, particulate concentration Metal concentration Discharge to land Volume discharged Metal concentration Discharge to water (including tailings and incompetent waste rock) Volume discharged, TSS concentration Metal concentration Land disturbance Area disturbed Not Applicable 2.4 Receiving Environment Monitoring In order to determine the scope and magnitude of the interactions of the operations environmental aspects within the receiving environment, it is necessary to identify suitable parameters to act as indicators of the interaction, to identify locations within the receiving environment at which the interaction is likely to take place (test sites), and identify locations within the environment where no interaction will take place (reference sites). This will ultimately allow a comparison of the same indicators between the test site and reference site and allow determination of the spatial extent and magnitude of mine related changes within the receiving environment Indicator Parameters The parameters monitored within the receiving environment have been selected based on their suitability for: Supporting assessment of compliance against legal and other requirements. Assessing the potential impact within the receiving environment as a result of the operations environmental aspects. Assessing the environmental performance of the operation, linked to environmental Key Performance Indicators (KPIs). Table 2-3 outlines the physical, chemical and biological parameters that are monitored at both the test sites and reference sites to support compliance, impact and performance assessments. 1

38 Table 2-3 Receiving environment monitoring parameters Environmental Aspect Indicator Parameters Physical Medium and toxicant Biological Water extraction Flow downstream of water extraction points NA NA Discharge to air Particulate concentration Air Quality - Metal concentration NA Discharge to land Volume Geotechnical characteristics Competency Geochemical characteristics - Metal concentrations, sulfur concentrations NA Discharge to water River profiling cross-sections Water Quality ph, EC, TSS, Metal concentrations in water Stream Sediment Quality Metal concentration Metal concentrations in fish and prawns Diversity, richness, biomass and condition of fish and prawns. Macroinvertebrates Land disturbance Area of disturbance NA NA NA - Not Applicable Monitoring Locations Receiving environment monitoring locations are categorised as test sites and reference sites. Test sites are those sites downstream of the mine, receiving discharge from the mine, where reference sites are in a similar geographical setting, generally adjacent to the test sites, but not receiving discharge from the mine. The test and reference sites at which receiving environment monitoring is conducted are listed in Table 2-4. The table also lists which reference sites are used as analogues for each test site. The locations of the monitoring sites are shown in Figure 2-1 and Table 2-4 shows monitoring locations within Lake Murray. 11

39 Table 2-4 Test sites, applicable reference sites and indicator parameters Reference Sites and Parameters Test Site Profile Water and Sediment Tissue Metal Diversity, Richness and Biomass Condition Upper River SG1 NAR 1 Ok Om Kuru Pori SG2 Ok Om Ok Om Kuru Pori NA 2 NA 2 NA 2 NA 2 NA 2 NA 2 Wasiba Ok Om Ok Om Ok Om Ok Om Ok Om Kuru Kuru Kuru Pori Pori Pori Wankipe Ok Om Ok Om Kuru Pori SG3 Ok Om Ok Om Kuru Pori Ok Om Kuru Pori Ok Om Ok Om Kuru Pori NA 2 NA 2 NA 2 Lower Strickland River Bebelubi NA 2 Baia Tomu Baia Tomu Baia Tomu Baia Tomu Tiumsinawam NA 2 Baia Tomu Baia Tomu Baia Tomu Baia Tomu PF1 NAR NA 2 NA 2 NA 2 NA 2 SG5 NAR Baia Baia Baia Baia Tomu Tomu Tomu Tomu Upstream of Everil Junction NA 2 Baia Tomu Baia Tomu Baia Tomu Baia Tomu Lakes and Off-River Water Bodies South Lake Murray Central Lake Murray SG6 Kukufionga NA 2 North Lake Murray North Lake Murray North Lake Murray North Lake Murray Zongamange Avu Levame Drinking Water Air Quality Villages surrounding Porgera Mine Hides Power Station boundary Villages surrounding Porgera Mine NA 2 NA 3 NA 2 NA 2 NA 2 NA 2 NA 3 NA 2 NA 2 NA 2 1 NAR No appropriate reference 2 NA Indicator not applied at monitoring site 3 NA Indicator at test sites compared against values derived from standards or guidelines not reference sites 12

40 Figure 2-1 Receiving environment monitoring sites 13

41 Northern Region N3 N28 N26 N25 N6 N18 N1 N9 Central Region N21 N2 N1 S7 S6 S5 Southern Region X7 X6 X5 X4 X3 S3 S2 X2 S4 S1 X1 Figure 2-2 Lake Murray monitoring locations 2.5 Environmental Risk and Impact Assessment The assessment of the environmental risks and impacts arising from mine operation are conducted in two (2) stages which are carried out concurrently: Stage 1 Risk assessment to determine the potential for impact to occur within the receiving environment based on levels of physical and chemical indicators at test sites within the receiving environment relative to trigger values; and Stage 2 Impact assessment to determine whether impact has actually occurred and to determine the magnitude of that impact based on biological indicators relative to impact criteria. Stage 1 Risk Assessment The purpose of the risk assessment stage is to determine the risk (potential or likelihood) that environmental impact has occurred or is occurring at the test site. A determination of risk is based on a comparison of physical and chemical indicators from each test site against risk assessment trigger values (TVs) in accordance with decision matrix (risk assessment matrix). Physical and chemical parameters are used to assess risk and not a determination of impact due to the complexity and variety of interactions between physical, chemical and biological functions within an ecosystem. Some ecosystems may function normally under conditions of elevated physical and chemical indicators, while the function of other ecosystems may be affected by relatively small changes to levels of physical and chemical indicators. TVs are established as the concentrations of 14

42 recommended that load-based guidelines be developed for nutrients, biodegradable organic matter and suspended particulate matter. The remainder of this section is divided into two parts: Section outlines the philosophy adopted in developing guidelines for physical and chemical stressors, physical and chemical indicators, which if exceeded, indicate that impact may be occurring. An exceedance while Section triggers further covers investigation the detailed using direct guideline indicators packages of ecological for condition each of in the form eight of biological indicators, to determine whether impact is actually occurring (the impact assessment). The issues considered. risk assessment trigger values have been developed using baseline and reference site data and default ANZECC/ARMCANZ (2) Guidelines, in conjunction with a decision matrix. The assessment framework is based on the ANZECC/ARMCANZ (2) framework and is presented in Figure 2-3 which is taken from the ANZECC/ARMCANZ (2) Guidelines. Define primary management aims (fig 3.1.1) Determine appropriate guideline trigger values for selected indicators (fig 3.1.1) Test against guideline values Compare key performance indicators with guideline trigger values for specific ecosystem type Decision framework for applying the trigger values a Low risk b Potential risk c Further site-specific investigations: Consider effects of ecosystem-specific modifying factors Comparison with reference condition Biological effects data (e.g. direct toxicity assessment) Low risk b High risk (initiate remedial actions) a Local biological effects data and some types of reference data (section 3.1.5) generally not required in the decision trees b Possible refinement of trigger value after regular monitoring (section 3.1.5) c Further investigations are not mandatory; users may opt to proceed to management/remedial action Figure 2-3 ANZECC/ARMCANZ Risk Assessment Framework (ANZECC/ARMCANZ Fig 3.3.1) Figure Decision tree framework (guideline packages) for assessing the physico-chemical stressors in ambient waters It should be noted that ANZECC/ARMCANZ (2) recommends further investigation of actual impact in cases where the median value of any indicator at the test site over a 12-month period (the test site median (TSM)) exceeds the TV, i.e. where the risk assessment TVs are exceeded. However, Barrick Porgera considers it prudent to conduct an impact assessment at all test sites, regardless of the risk assessment result, to provide confirmation of the risk assessment conclusions, a direct assessment of impact for ongoing performance monitoring and full transparency of the operation s interactions with the environment. e 3.32 Version October 2 15

43 Stage 2 Impact Assessment The purpose of the impact assessment stage is to confirm whether actual ecological impact has occurred, or is occurring within the receiving environment, and if so to determine the level or significance of that impact. The most significant potential impacts of the mine are associated with riverine discharge of tailings, erodible waste rock and associated mine-derived sediments to the Porgera-Lagaip-Strickland river system. Therefore, the impact assessment is based on direct assessment of the health of the aquatic ecosystem through the use of biological indicators such as abundance, richness, biomass and condition of resident aquatic fauna (fish and prawns). The impact assessment is conducted by comparing biological indicators from the test sites against impact assessment criteria developed using baseline and reference site data, with a decision matrix Establishing Risk Assessment Trigger Values The Australian and New Zealand Environment and Conservation Council Guidelines for Fresh and Marine Water Quality (ANZECC/ARMCANZ 2) nominate the following order of preference when establishing TVs for physical, chemical and toxicant indicators: 1. Using ecological effects data (physical and chemical only): For low-risk TVs, measure the statistical distribution of water quality indicators either at a specific site (preferred), or an appropriate reference system(s), and also study the ecological and biological effects of physical and chemical stressors. Then define the TV as the level of key physical or chemical stressors below which ecologically or biologically meaningful changes do not occur (ANZECC/ARMCANZ 2 Section ). Developing valid TVs using this method requires identifying a suitable reference site and highly controlled experimental conditions, consequently this method is rarely adopted. Barrick Porgera has not attempted to develop TVs using this method. 2. Using baseline or regional reference site data: Where there is insufficient information on ecological effects to determine an acceptable change from reference condition, the use of an appropriate percentile of the reference data distribution can be used to derive the trigger value (ANZECC/ARMCANZ 2 Section ). Baseline data are gathered from the test sites prior to disturbance and provide the best comparison of pre and post-disturbance conditions at the test site. Baseline data for Porgera Mine test sites have been compiled and validated and are used in comparison to support the development of TVs. A regional reference site is selected within an ecosystem that is similar to and in the vicinity of the test site ecosystem, but is outside of the zone of direct influence of the mining operation. Reference sites should be selected from the same biogeographic and climatic region, should have similar geology, soil types and topography, and should contain a range of habitats similar to those at the test site. (ANZECC/ARMCANZ 2 Section ) The suitability of regional reference site data as a basis for establishing TVs can be influenced by how well the reference sites reflect the pre-disturbance condition of the test site. If the predisturbance condition of the regional reference site and test site are different, then TVs based on reference data are unlikely to act as an accurate basis for assessment of post-disturbance change at the test site, and may over or under estimate acceptable levels of change and therefore risk at the test site. 16

44 Table 2-5 provides a qualitative assessment of the suitability of the regional reference sites for supporting development of TVs for physical, chemical and biological indicators. Variation between regional reference and test sites is usually more pronounced for catchments where mining projects occur due to naturally elevated mineralization in the test site catchment compared to surrounding catchments in which the reference sites exist. In general, ecosystems in reference sites adjacent to mining projects have evolved with lower levels of natural mineralization in water and stream sediment than those at the test-site prior to disturbance. Ideally, an assessment of pre-disturbance conditions at the reference sites and test sites will be conducted to assess the suitability of the reference sites for supporting development of TVs. If pre-disturbance conditions are similar, then the reference site is likely to be appropriate, but if pre-disturbance conditions are different, then the reference site is unlikely to be an appropriate analogue for assessment of post-disturbance change. Risk assessment criteria based on regional reference site data are calculated from the most recent 24 months of observations at the regional reference site(s). This approach will account for any non-mine related variations within the ecosystem condition at the reference site (ANZECC/ARMCANZ 2 Section ). Upper TVs are established for indicators that have the potential to cause impact at high concentrations (i.e. TSS, dissolved metals). Lower TVs are established for indicators that have the potential to cause impact at low levels (i.e. DO), and upper and lower TVs are established for indicators that have the potential to cause impact at either high or low levels (i.e. ph and DO). Where TVs have been developed from reference data, the preferred protocol is to compare the median of replicate samples from a test site with the trigger value. Statistically, the median represents the most robust descriptor of the test site data, while the reference percentile value represents the degree of excursion that the test site median is permitted before triggering some action. (ANZECC/ARMCANZ 2 Section ) 17

45 Table 2-5 Assessment of reference site suitability Suitability Assessment Reference Site Group Regional Ref Sites Test Sites Phys Phys, Chem and Toxicant Bio Comments Upper River Upper Lagaip SG1 SG2 Wasiba Wankipe SG3 Good Poor Poor Lower mineralization Naturally depauperate fish and prawn populations Fish and prawns potentially exposed to elevated metals if migrating between test and reference sites. Pori Poor Poor Poor Small tributary Lower mineralization Lower flows Lower suspended sediment Different habitat types Reference site biology potentially indirectly impacted (i.e. fish and prawn migration) Fish and prawns potentially exposed to elevated metals if migrating between test and reference sites. Kuru Fair Poor Poor Small tributary Lower mineralization Lower flows Lower suspended sediment Different habitat types Reference site biology potentially indirectly impacted Fish and prawns potentially exposed to elevated metals if migrating between test and reference sites. Ok Om Good Poor Fair Lower mineralization Fish and prawns potentially exposed to elevated metals if migrating between test and ref sites. 18

46 Suitability Assessment Reference Site Group Regional Ref Sites Test Sites Phys Phys, Chem and Toxicant Bio Comments Lower River Baia Bebelubi Tiumsinawam Fair Fair Poor Medium size tributary Lower mineralization PF1 Different habitat types SG5 Upstream Everil Junction Ref site biology potentially indirectly impacted Fish and prawns potentially exposed to elevated metals if migrating between test and ref sites. Tomu Fair Fair Poor Medium size tributary Lower mineralization Different habitat types Ref site biology potentially indirectly impacted Fish and prawns potentially exposed to elevated metals if migrating between test and ref sites. Lake Murray North Lake Murray Central LM South LM Good Good Good Nth Lake is potentially impacted. ORWBs North Lake Murray Kukufionga Zongemange Avu Levame Poor Poor Poor Nth Lake is potentially impacted by mine aspects. Different habitats in Lake and ORWBs. Different biological and biochemical and hydrological processing occurring in ORWBs than in Nth Lake. 3. Using ANZECC/ARMCANZ (2) default guidelines: The default approach to deriving trigger values for physical parameters has used the statistical distribution of reference data collected within five geographical regions across Australia and New Zealand (ANZECC/ARMCANZ 2, Section ). Most of the default trigger values for chemical parameters (referred to by ANZECC/ARMCANZ 2 as toxicants) have been derived from single-species toxicity tests on a range of species, because these formed the bulk of the concentration-response information. High reliability trigger values were calculated from chronic no observable effect concentration tests (NOEC). However the majority of trigger values were moderate reliability trigger values, derived from short-term acute toxicity data (from tests 96 h duration) by applying acute-to-chronic conversion factors (ANZECC/ARMCANZ 2, Section ). 19

47 The ANZECC/ARMCANZ (2) default trigger values derived using the statistical species sensitivity distribution method were calculated at four different protection levels, 99%, 95%, 9% and 8%. Here, protection levels signify the percentage of species expected to be protected at different concentrations of the toxicant (ANZECC/ARMCANZ 2, Section ). The 95% species protection level is used in most commonly used in monitoring programs. The guideline trigger values were derived primarily according to risk assessment principles, using data from laboratory tests in clean water. They represent the best current estimates of the concentrations of chemicals that should have no significant adverse effects on the aquatic ecosystem (ANZECC/ARMCANZ 2, Section 3.4.3). By their nature, the default trigger values provided by ANZECC/ARMCANZ (2) are inherently conservative assessment levels, not 'pass/fail' compliance criteria. Default TVs are to be applied to systems for which there are no baseline data or where baseline data are insufficient to adequately describe the natural or existing seasonal or annual fluctuations in water quality. Local conditions are naturally variable between river systems and because of this, ANZECC/ARMCANZ (2) recommend that TVs should be tailored to local conditions through the development of local guideline levels. The guidelines recommend site-specific derivation of guideline TVs, based upon comprehensive biological effects data, wherever this is possible. Such derived values will always be preferred over use of prescribed guideline defaults contained in ANZECC/ARMCANZ (2). Locally-derived TVs are also recommended for the situation where the default TV is consistently lower than natural background concentrations, in which case natural background data should be used to derive a site-specific TV. Locally-derived TVs are then compared to the median value of the subject water obtained from a monitoring programme (for further details see Sections and of ANZECC/ARMCANZ (2). ANZECC/ARMCANZ (2) recommended that site-specific TVs should be based on at least two years of monthly monitoring data. Operational TVs are usually set as condition targets in which to maintain a system (i.e. once the indicator values fall outside of the TVs, a level of disturbance may be inferred). TVs are usually set in terms of some quantum of change from reference condition, with the extent of allowable change sufficiently small as to minimise risk of significant disturbance to the ecosystem. ANZECC/ARMCANZ (2) has set the standard for developing such targets, whereby the guideline values for indicators are set at the 8 th percentile (8%ile) for upper TVs, and/or 2 th percentile (2%ile) for lower TVs, of the reference (or baseline) condition. This approach has been adopted widely in Australia for monitoring wetlands and river, and assessing ecological health (see Fukuda and Townsend 26, Storey et al. 27). The 8%ile and 2%ile are deemed to be approximately equivalent to ± one standard deviation around the median, and it is argued that this level of change is unlikely to result in risk of disturbance to the ecosystem (ANZECC/ARMCANZ 2) Risk Assessment TVs and Matrix Water Quality Water quality TVs for all parameters except ph, have been established by comparing the 8 th %ile value from baseline data at the test sites pre-mine, and the 8%ile value from the most recent 24- months regional reference site data against the respective ANZECC/ARMCANZ (2) default guideline for 95% species protection and then adopting the highest of the three values as the TV or local guideline level. The concentrations of dissolved metals in water from the baseline and regional reference sites are used to represent the fraction of metals that are bioavailable and therefore have the potential to cause a toxic effect. Where applicable, the ANZECC/ARMCANZ (2) default guidelines for 95% species protection have been hardness-modified prior to comparison with the reference site data in 2

48 accordance with Section of ANZECC/ARMCANZ (2). Hardness modification is done separately for default guidelines applied to the upper river, lower river, Lake Murray and ORWBs, conservatively using the 2 th %ile hardness value from all test sites within each of the respective groups. Adoption of the 2 th %ile value is considered a conservative approach as it assumes low buffering capacity throughout the entire year, and calculating a specific hardness modified trigger value for each of the different regions, will account for the different hardness within the upper river, lower river, Lake Murray and off-river water bodies (ORWBs) such as ox-bow lakes. This method has been adopted to avoid setting an overly-conservative TV, primarily due to the poor suitability of the reference site conditions as an analogue for the pre-disturbance conditions at the test sites. The differences that presently exist between the reference and test sites, and particularly the likelihood that the pre-disturbance test site conditions were characterized by naturally elevated mineralisation, means that blanket adoption of the reference site data is likely to result in overly conservative trigger values, and therefore an over-estimation of risk at the test sites. The comparison between test site baseline data, reference site data and the ANZECC/ARMCANZ (2) default guidelines for 95% species protection in the upper river, lower river, Lake Murray and ORWBs are presented in Section 5. A summary of the TV development method is provided in Table 2-6 and the decision matrix is shown in and Table 2-7. It should be remembered that the TVs are not intended as compliance levels, but as the name implies, if exceeded are a trigger for further investigation to determine if: 1. Exceedance is still within the historic range, or 2. Exceedance represents a short-term event with likely low risk to the environment, requiring no management intervention, or 3. Exceedance represents a longer-term trend with potential risk to the environment, requiring management intervention. Exceedance of a TV does not automatically imply increased toxicity and increased risk to the ecosystem. It does however, warrant investigation into the bioavailability of the analyte and the duration and frequency of elevated concentration. Biota may be unaffected by infrequent events that are of short duration, though this may need to be confirmed by supporting field ecological studies. Inherent in the use of 8%ile or 2%ile of baseline data to derive local TVs, is the fact that monitoring data may exceed the TV at least 2% of the time. Therefore, a statistical test is required to determine if the exceedance is statistically significant, rather than an artifact of variability within the dataset itself. This is shown in Table 2-6, where a non-parametric rank test is used to determine if monitoring data are significantly higher, lower or not significantly different from the trigger value derived from baseline data, reference data or ANZECC/ARMCANZ (2) default TV. It should be noted that in cases where the TV, the Test Site Median (TSM) or the entire test site data set upon which the TSM is based are less than the analytical limit of reporting (LOR), Wilcoxons test will find the TSM not significantly different from the TV which indicates the potential risk of environmental impact. However, in these cases given that the data set from the test site indicates that the concentration of a particular parameters does not have the potential to exceed the TV, and both the TV, the TSM and the TSM data set are equal to the LOR, it is considered appropriate to conclude there is low risk of potential impact rather than infer potential risk of environment impact. This scenario is captured in the risk assessment matrices. 21

49 Table 2-6 Water quality TVs Indicator Parameter TV Level Risk Assessment Trigger Value (TV) Water Quality Physical and chemical Toxicants Upper Whichever is higher: Baseline 8%ile, regional Ref 8%ile, or ANZECC/ARMCANZ default guideline for 95% species protection (hardness modified where appropriate) Figure 2-4 Risk assessment matrix water quality Table 2-7 Risk assessment matrix water quality Indicator Parameter Assessment Result Potential for impact to occur at the test site Action 214 Test Site Median (TSM) Water Quality TSM significantly > TV (P <.5) TSM not significantly different from TV (P >=.5), and TV, TSM Potential Risk Potential Risk Confirm assessment of risk by conducting impact assessment based on biological indicators. and TSM data set all LOR. TSM not significantly different from TV (P.5), and TV, TSM and TSM data set all < LOR. Low Risk TSM significantly < Trigger Value (P <.5) 22

50 Risk Assessment TVs and Matrix ph Upper and lower TVs for ph in the upper river were established by comparing the 8%ile and 2%ile test site baseline data, and the reference site values from the most recent 24-month data with the ANZECC/ARMCANZ (2) upper and lower limit respectively for ph for upland rivers in tropical Australia. Upper and lower TVs for ph in the lower river and Lake Murray and ORWBs were established by comparing the 8%ile and 2%ile Lake Murray baseline data and the North Lake Murray reference site values from the most recent 24-month data with the ANZECC/ARMCANZ (2) upper and lower limit respectively for ph for lowland rivers in tropical Australia. Comparisons between upper river test site baseline data, reference site data and the ANZECC/ARMCANZ (2) default guidelines for upland rivers in Tropical Australia are presented in Section 3.3. Comparisons between test site baseline data, lower river reference site data and the ANZECC/ARMCANZ (2) default guidelines for lowland rivers in Tropical Australia are presented in Section 3.3. A summary of the TV development method is provided in Table 2-8, and the decision matrix is shown in Figure 2-5 and Table 2-9. Table 2-8 ph TVs Indicator Parameter TV Level Risk Assessment Trigger Value (TV) Water ph Upper Whichever is higher: Baseline 8%ile, regional Ref 8%ile or ANZECC/ARMCANZ upper limit for upland rivers in tropical Australia Lower Whichever is lower: Baseline 2%ile, Ref 2%ile or ANZECC/ARMCANZ lower limit for upland rivers in tropical Australia Figure 2-5 Risk assessment matrix ph 23

51 Table 2-9 Risk assessment matrix ph Indicator Parameter Assessment Result Potential for impact to occur at the test site Action 214 Test Site Median (TSM) ph TSM significantly > Upper Trigger Value (P <.5) TSM not significantly different from Upper Trigger Value (P.5) Potential Risk Potential Risk Confirm assessment of risk by conducting impact assessment based on biological indicators. TSM significantly < Upper Trigger Value; and Low Risk TSM significantly > Lower Trigger Value (P <.5) TSM not significantly different from Lower Trigger Value (P.5) Potential Risk TSM significantly < Lower Trigger Potential Risk Value (P <.5) Risk Assessment TVs and Matrix Sediment Quality Sediment quality data from the reference sites were compared against the ANZECC/ARMCANZ (2) interim sediment quality guidelines (ISQGs). These guidelines were developed from United States effects databases (Long et al. 1995) and are termed interim because an understanding of the biological impacts from sediment contamination is still being developed (Batley and Simpson 28). The guidelines include ISQG-Low and ISQG-High values, which represent the 1th percentile (1%ile) and 5th percentile (5%ile) values for chemical concentrations associated with acute toxicity effects respectively. The ISQG-Low value is the default TV below which the frequency of adverse biological effects is expected to be very low, and if exceeded, should trigger further study. The ISQG-High value corresponds to the median effect concentration as detailed in Long et al. (1995), and indicates the concentration above which adverse biological effects are expected to occur. Pre-disturbance baseline conditions were not sampled at river test sites for sediment quality, however baseline conditions were sampled at Lake Murray, but the samples were analysed only for total extractable metals. TVs for sediment quality for all parameters except selenium (Se) have been established by comparing the 8%ile value from the most recent 24-month reference site data against the ANZECC/ARMCANZ (2) interim sediment quality high guideline value (ISQG-low), and adopting whichever is higher. ANZECC/ARMCANZ (2) does not provide sediment quality TVs for selenium, therefore the TV for selenium has been established from the most recent 24-month 8%ile from the reference data set. 24

52 The weak acid extractable (WAE) fraction from the whole of sediment sample is used to represent the bioavailable fraction of metals that may cause a toxic effect, and therefore the WAE results for whole sediment sampled from the reference sites is used to establish the reference site criteria. Similar to water quality, the lack of suitable reference sites, particularly due to the presence of natural mineralization in the test site catchment, means that TVs based on the reference site data alone are likely to be overly conservative. Comparisons between the upper river, lower river and Lake Murray and ORWB reference site data and the ANZECC (2) ISQG-low are presented in Section 5. Also similar to water quality it should be noted that in cases where the TV, the TSM and the entire test site data set upon which the TSM is based are less than the analytical limit of reporting (LOR), Wilcoxons test will find the TSM not significantly different from the TV which infers a potential risk of environmental impact. However, in these cases given that the data set from the test site indicates that the concentration of a particular parameter does not have the potential to exceed the TV, and the TV, the TSM and the TSM data set are equal to the LOR, it is considered appropriate to conclude there is low risk of potential impact rather than potential risk of environment impact. This scenario is captured in the risk assessment matrices. A summary of the TV development method is provided in Table 2-1 and the decision matrix is shown in Figure 2-6 and Table Table 2-1 Sediment quality TVs Indicator Parameter TV Level Risk Assessment Trigger Value (TV) Sediment Quality Upper Whichever is higher: Ref Site 8%ile WAE in whole sediment or ANZECC/ARMCANZ ISQG-low Figure 2-6 Risk assessment matrix sediment quality 25

53 Table 2-11 Risk assessment matrix sediment quality Indicator Parameter Assessment Result Potential for impact to occur at the test site Action 214 Test Site Median (TSM) Stream Sediment Quality TSM significantly > Trigger Value (P <.5) TSM not significantly different from TV (P.5), and TV, TSM and TSM data set all LOR. Potential Risk Potential Risk Confirm assessment of risk by conducting impact assessment based on biological indicators. TSM not significantly different from TV (P.5), and TV, TSM and TSM data set all < LOR. Low Risk TSM significantly < Trigger Value (P <.5) Risk Assessment TVs and Matrix Tissue Metal Concentrations Pre-disturbance baseline data are available for river and Lake Murray test sites, but only for fish flesh tissue samples. TVs for tissue metal concentrations in fish and prawns for all parameters, except selenium in fish flesh, have been established by comparing the reference site 8%ile value from the most recent 24-month data against the 8%ile of the test site baseline data and adopting the highest value. This method has been selected in the absence of any suitable effects based guidelines for use as a comparison against reference site data, and is considered conservative due to the lack of natural mineralization within the reference site catchments. However, reference site data could be elevated as a result of fish/prawns migrating upstream from Test sites. The trigger value for selenium in fish flesh has been established by comparing the reference site 8%ile value from the most recent 24-month data, the 8%ile of the test site baseline data and the United States Environmental Protection Agency draft tissue metal criterion for protection of aquatic life (USEPA 214). The USEPA 214, although still in draft form, is the best available toxic effects based criterion for fish tissue and is therefore deemed appropriate for use. Similar to water quality and sediment quality, it should be noted that in cases where the TV, the TSM and the entire test site data set upon which the TSM is based are less than the analytical limit of reporting (LOR), Wilcoxons test will find the TSM not significantly different from the TV which indicates the potential risk of environmental impact. However, in these cases given that the data set from the test site indicates that the concentration of a particular parameter does not have the potential to exceed the TV, and both the TV, the TSM and the TSM data set are equal to the LOR, it is considered appropriate to conclude there is low risk of potential impact rather than potential risk of environment impact. This scenario is captured in the risk assessment matrices. A summary of the TV development method is provided in Table 2-12, the decision matrix is shown in Figure 2-7 and Table

54 Table 2-12 Tissue metal concentration TVs Indicator Parameter TV Level Risk Assessment Trigger Value (TV) Tissue metals Upper Reference site 8%ile (most recent 24 months) or baseline 8%ile, whichever is highest. (For all parameters except selenium in fish flesh) Selenium in fish flesh Reference site 8%ile (most recent 24 months), baseline 8%ile or USEPA criterion, whichever is highest. Figure 2-7 Risk assessment matrix tissue metal concentrations Table 2-13 Risk assessment matrix tissue metal concentrations Indicator Parameter Assessment Result Potential for impact to occur at the test site Action 214 Test Site Median (TSM) Tissue Metal TSM significantly > Trigger Value (P <.5) TSM not significantly different from TV (P.5), and TV, TSM Potential Risk Potential Risk Confirm assessment of risk by conducting impact assessment based on biological indicators. and TSM data set all LOR. TSM not significantly different from TV (P.5), and TV, TSM and TSM data set all < LOR. Low Risk TSM significantly < Trigger Value (P <.5) 27

55 Risk Assessment TVs and Matrix Drinking Water, Air Quality, River Profiles Porgera has adopted the PNG Drinking Water Quality Guidelines (1984) as the default risk assessment TVs for drinking water quality. PNG has not enacted air quality legislation and therefore the relevant World Bank and Australian air quality guidelines have been adopted as TVs for air quality. Measurement of river bed profiles provides information on the changes in river bed due to sedimentation, which can affect water levels and flow conditions. A summary of the TV development method is provided in Table 2-14 and the decision matrix is shown in Table Table 2-14 Drinking water, air quality and river profile TVs Indicator Parameter TV Level Risk Assessment Guideline Drinking Water NA PNG Drinking Water Guidelines Air quality NA World Bank, or Australian Air Quality Guidelines River Profiles NA Change from historical record Table 2-15 Risk assessment matrix drinking water, air quality and river profiles Indicator Parameter Assessment Result Potential for impact to occur at the test site Action Drinking Water Test Site Median (TSM) TSM > PNG Drinking Water Guidelines Low Moderate Dependent on exposure Conduct Health Risk Assessment Air Quality Test Site Median (TSM) TSM > World Bank or Australian Air Quality Guidelines Low Moderate Dependent on exposure Conduct Health Risk Assessment River Profiles Qualitative assessment of change NA NA Establishing Impact Assessment Trigger Values The impact assessment is based on a direct assessment of aquatic ecosystem health through the comparison of biological indicators (abundance, richness, biomass and condition) of the resident aquatic fauna at the test sites against impact assessment criteria (TVs). ANZECC/ARMCANZ (2) recommends deriving impact assessment criteria from the most recent 24 months of observations of aquatic fauna at the reference site(s). This method is consistent with the approach used for physical and chemical parameters in previous sections in this report. However, the regional reference site data set(s) upon which this approach is based must achieve minimum quality requirements in order for the TVs to be valid. In 213, initial analysis of the ability of the Porgera data set to support this approach identified issues related to small sample size, high variability, low replication and poor catch rate, resulting in low catch numbers and narrow range in data collected. Small sample size resulted in low statistical power and poor catch rates resulted in narrow data range in results, which ultimately produced TVs with very low values, with sometimes zero catch at reference sites. These issues appeared to relate to a combination of sampling methods used, limitations of habitat availability, sampling difficulties, and naturally low diversity and abundance of fauna being 28

56 targeted. Therefore, it was concluded that the data being used to develop biological TVs using the 24month method were not suitable for supporting robust and accurate impact assessment. This issue was first identified in the 213 AER and since then Barrick Porgera has revised the prawn and fish sampling methods and has also investigated the validity of benthic macroinvertebrates as an additional biological indicator. However it is expected to take two to three years before either of these improvements yield a viable data set. These items are discussed further in Section 3.6, however to support the 214 AER, the alternative method of impact assessment developed for the 213 AER has been adopted based on the available data. The interim approach applied for the AER 213 and now 214 AER, uses the Spearman Rank Test was selected as a statistically conservative method of comparing temporal trends in biological indicators between test and reference sites. The approach involves applying the Spearman Rank Test (the test) to the test site data and then to the reference site data using the full historical data sets for each site. The test is capable of determining whether the given indicator is increasing, decreasing or remaining constant over the long-term period of monitoring to a pre-determined level of statistical significance, and thereby allows a comparison of the trend at the test sites against that of the reference sites. However, given the limitations outlined above of the reference site dataset within any single year, the long-term trend must similarly be treated with caution and therefore is considered suitable for use only as an indicator of potential impact. The Spearman Rank Test is run using Minitab software and produces a correlation coefficient (Spearman s rho), and a statistical probability (p) for each data set. The results of the Spearman Rank Test are interpreted in accordance with Table 2-16 and the impact assessment is conducted in accordance with the decision matrix presented in Table 2-7. Table 2-16 Interpretation of Spearman Rank Test results Indicator Parameter Spearman s rho sign Probability (P) Conclusion about indicator behaviour Abundance Richness Biomass Condition Positive sign (+) <.5 Significant increase over time Negative sign (-) <.5 Significant decrease over time Either positive or negative.5 No significant change over time (i.e. no statistically significant increase or decrease over time) 29

57 Table 2-17 Impact assessment matrix biology Indicator Parameter Reference site Test Site Potential Impact Level at the test site Trend of annual median from historical record using Spearman rank sign and significance for: Abundance Richness Biomass No significant change of annual median over time No significant change of annual median over time Significant decreasing trend of annual median over time No significant change of annual median over time Significant increasing trend of annual median over time No significant change of annual median over time No potential adverse impact indicated. Trend of annual median at test sites stable or increasing over time relative to reference sites. Condition Significant decreasing trend of annual median over time Significant increasing trend of annual median over time Significant decreasing trend of annual median over time Significant decreasing trend of annual median over time 1 Significant increasing trend of annual median over time Significant increasing trend of annual median over time 1 No significant change of annual median over time Significant increasing trend of annual median over time Significant decreasing trend of annual median over time No significant change of annual median over time Potential adverse impact indicated. Trend of annual median at test sites reducing over time relative reference sites. Significant increasing trend of annual median over time Significant decreasing trend of annual median over time 1 Indicates system-wide change and not mine-related, i.e. occurring at the reference sites and test sites 3

58 2.6 Environmental Performance Assessment Assessment of the operation s environmental performance is based on 4 criteria: 1. Reduction of the risk of environmental impact occurring within the receiving environment, or maintenance of low potential environmental impact conditions. 2. Reduction of the level of environmental impacts occurring, or maintenance of nil impact conditions. 3. Improved water and energy use efficiency. 4. Compliance with environmental permit conditions. The indicators, metrics, impact criteria and criteria for positive performance are presented in Table 2-18 and decision matrix presented in Table Table 2-18 Environmental performance criteria Indicator Indicator Metric Performance Criteria Positive Performance Water Quality Sediment Quality Tissue metals Spearman rank sign and significance of change in annual medians from the Test site Spearman rank sign and significance of change in annual medians from the Reference site See Table 2-19 Table 2-19 Air quality Ambient concentration World Bank Air Quality Guidelines Compliance River Profiles Bed level Historical record No significant change Water Use Efficiency Energy Use Efficiency Linear trend Previous years efficiency Negative trend Linear trend Previous years efficiency Negative trend Legal Compliance % Compliance with permit conditions 1% Compliance with permit conditions 1% Compliance 31

59 Table 2-19 Performance assessment matrix water, sediment and tissue metal Indicator Reference site Test Site Potential Level Impact Trend of annual median from historical record using Spearman rank sign and significance for: Water Quality Sediment Quality Tissue Metals No significant change of annual median over time No significant change of annual median over time Significant decreasing trend of annual median over time No significant change of annual median over time Significant decreasing trend of annual median over time Significant decreasing trend of annual median over time Low potential for impact indicated. Annual median concentrations at test sites stable or reducing over time relative to reference sites. Significant increasing trend of annual median over time No significant change of annual median over time Significant increasing trend of annual median over time Significant increasing trend of annual median over time 1 Significant decreasing trend of annual median over time Significant decreasing trend of annual median over time No significant change of annual median over time Significant increasing trend of annual median over time Potential for impact indicated. Annual median concentrations at test sites increasing over time relative to reference sites. No significant change of annual median over time Significant increasing trend of annual median over time 1 Indicates system-wide change and not mine-related, i.e. occurring at the reference sites and test sites Testing for Statistical Significance Tests of statistical significance are performed on the monitoring data to support both the risk and impact assessments. The tests provide a statistical basis for drawing conclusions about differences within and between test site and reference site indicators, and therefore for determining whether risk or impact may exist at a particular test site. It is important to apply a significance test to provide confidence that the data being used to support the assessment are sufficient to support a robust conclusion, and that the inherent characteristics of the data set under consideration are not influencing the accuracy of the assessment result. Using the statistical tests allows the assessment result to be described as significantly greater than, significantly less than or not significantly different from the relevant trigger value, and ultimately to provide confidence that the result is valid. The test used for determining statistical significance at the risk assessment stage and for impact assessment is the Wilcoxon Signed-rank Test with a probability threshold of P =.5. The Wilcoxon 32

60 test is a non-parametric statistical hypothesis test used when comparing two related samples which uses the rankings of the data and is independent of the absolute values. The test used for determining statistical significance of trends over time to support the performance assessment is the Spearman Rank Test, with a probability threshold of P =.5. This test also uses ranked data, and so is independent of the absolute values, but is ideal for use on data monotonically related, as it is not dependant on data having a linear relationship (as are linear regression or Pearson Product Moment Correlation). Both tests are performed with the Minitab software package. The procedure for determining significance involves integrating the significance test into the risk and impact assessment matrices. The procedures for testing significance in the risk and impacts assessments are shown as expanded assessment matrices in Appendix D. The results of the risk and impacts assessments are presented in Section 6 and detailed results of the significance tests are presented in Appendix D. 33

61 3 BACKGROUND ENVIRONMENTAL CONDITIONS The environmental conditions of all natural systems will change throughout time due to natural changes in climate, geography and biology. An objective of the AER is to determine how much change has occurred within the receiving environment of the Porgera Mine, how much of that change is caused by factors not related to the mining operation, and how much of that change is caused by factors that are related to the mining operation. Aspects of the operation that have the potential to interact with the environment (the environmental aspects) will be discussed and quantified in Section 4. The purpose of this section is to quantify the natural, non-mine related changes within the environment downstream of the Porgera mine. This information is then used to determine what degree of change observed at the test sites is attributable to natural change and what degree is attributable to the mine environmental aspects. The objectives of this section are to: 1. Quantify the climatic condition, meteorological and hydrological conditions at the mine site and within the receiving environment during 214; 2. Describe the background environmental physical, chemical and biological conditions of aquatic ecosystems not influenced by the operation (i.e. reference site condition) and identify and quantify the natural changes at those sites during 214 and over the history of mine operation; and 3. Establish risk assessment and impact assessment trigger values (TVs) and performance criteria for physical, chemical and biological conditions at Upper River, Lower River and Lakes and Off-River Water Bodies to support the compliance, risk, impact and performance assessments conducted in Section 5 and Section Climate Rainfall in Strickland River Catchment Figure 3-1 shows annual rainfall at stations in the upper, middle and lower Strickland catchments. The upper catchment can broadly be described as the reach of river extending from the mine site down to SG2, the middle extends from SG2 down to SG3, and the lower from SG3 to SG5 (near Lake Murray) and beyond to the Fly River. In general terms, rainfall in 214 was approximately 1% above average in the upper reach. In the middle and lower reaches, rainfall data were incomplete for SG2, SG3 (middle) and SG5 (lower) due to equipment vandalism. Data loss at SG2 was from April to July, SG3 from May to November and SG5 from June to August. 34

62 Rainfall (mm) Annual Rainfall 214 Vs Long-term Mean 6, 5, 4, 3, 214 LTM 2, 1, Anawe Open Pit Waile Pongema SG2* Ok Om SG3* SG4 SG5* *Incomplete data record due to equipment vandalism Figure 3-1 Comparison of annual rainfall (214 data versus long term means) at sites in the Strickland Catchment Hydrological Context In the context of longer term rainfall trends, Figure 3-2 shows the rainfall pattern of recent years and a residual mass plot of annual rainfall at Anawe (the station with the longest period of record). The plotted lines represent the cumulative deviation of each year s rainfall total from the overall median of the dataset. To interpret the graph, a downward sloping line represents below-average years, while an upward sloping line represents above average years. This demonstrates that since 1997, rainfall was notably higher than the period suggesting decadal scale variability. Figure 3-3 presents the Pacific Decadal Oscillation (PDO) index expressed as a residual mass in order to identify trends more clearly. The PDO is a pattern of Pacific climate variability that shifts phases on at least inter-decadal time scale, usually about 2 to 3 years. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 2 N. During a warm or positive phase, the west Pacific becomes cool and part of the eastern ocean warms; during a cool or negative phase, the opposite pattern occurs. The PDO is strongly related to El Nino Southern Oscillation (ENSO) episodes but operating over much longer timescales. Although ENSO events are strongly correlated to rainfall trends in parts of PNG, the Porgera rainfall also appears inversely correlated with the PDO on a decadal scale, although both indices are correlated with Anawe rainfall on a 1-year moving average basis. Although detailed analysis of rainfall trends is not the focus of this section, the analysis serves to highlight that rainfall (and, by inference, river flow and sediment transport) varies over both long and short-term timescales. 35

63 SOI/PDO Index (1-year moving av.) Anawe Rainfall 1-year moving av. (mm) Rainfall Cumulative Deviation from Mean Value (mm) Cumulative Deviation from Mean for PDO Index About-average years Generally below-average years Generally above-average years Pacific Decadal Oscillation Figure 3-2 Residual mass plots Anawe rainfall station data SOI PDO Anawe Rainfall Figure 3-3 Anawe rainfall, SOI and PDO indices on 1-y moving average 36

64 Rainfall (mm) Rainfall Summaries Anawe Plant Site Meteorological data are measured continuously at Anawe plant site. The parameters monitored are rainfall, temperature, humidity, evaporation, wind vectors, barometric pressure and solar radiation. Due to the orographic influence of the surrounding mountains there is minimal seasonal variability throughout the year at Porgera. Winds are katabatic (down-slope) in nature and generally tend from the east. Table 3-1 provides a summary of the meteorology data collected during the year. Table 3-1 Summary of meteorological data recorded at Anawe plant site during 214 Parameter Yearly total Daily max Daily min Daily mean Long-term daily mean Std dev. (%) Rainfall (mm) Max/Min Temp. ( o C) Mean Daily ( o C) Sunshine (hr) Evaporation (mm) Wind Run (km) The historical rainfall at Anawe is shown in Figure 3-4 and Figure 3-5. The highest annual rainfall recorded at Anawe was 4,594 mm in 211. Figure 3-4 shows monthly total rainfall at Anawe in 214 against long-term monthly means. Annual rainfall was 3,813 mm on 317 wet days, the long-term mean annual total is 3,761 mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 214 Long term Mean Figure 3-4 Rainfall at Anawe Plant Site during 214 against long-term monthly means 37

65 Rainfall (mm) Rainfall (mm) Annual Long term Mean Figure 3-5 Comparison of annual rainfall at Anawe Plant Site with long-term mean Open Pit Figure 3-6 shows total monthly rainfall at the Open Pit during the year against long-term monthly means. Annual rainfall was 4,819 mm on 33 wet days; the long-term mean annual total is 3,879 mm. Figure 3-7 shows the historical annual totals Long Term Mean 1 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 3-6 Rainfall at Open Pit during 214 against long-term monthly means 38

66 Rainfall (m) Rainfall (mm) Annual Total Long term Mean Figure 3-7 Annual rainfall at Open Pit Waile Creek Figure 3-8 shows rainfall at Waile Dam during 214 against long-term monthly means. Annual rainfall was 3,486 mm on 329 wet days, long-term mean annual total is 2,914 mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 214 Long term Mean Figure 3-8 Rainfall at Waile Dam during 214 against long-term monthly means 39

67 Rainfall (mm) Rainfall (mm) Rainfall (mm) Pongema Figure 3-9 shows rainfall at Suyan Camp during 214 against long-term monthly means. Annual rainfall was 3,367 mm on 318 wet days; the long-term mean annual total is 2,956 mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 214 Long term Mean Figure 3-9 Rainfall at Suyan Camp during 214 against long-term monthly means SG2 Figure 3-1 shows rainfall at SG2 (Lagaip River) during the year for the months data were available plotted against long-term monthly means. During April to June there was no rainfall data recorded due to equipment vandalism. The long-term mean annual total is 2,39 mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 214 Long term Mean Figure 3-1 Rainfall at SG2 during 214 against long-term monthly means Ok Om Figure 3-11 shows rainfall at Ok Om during 214 against long-term monthly means. Annual rainfall of 2,116 mm fell on 265 wet days; the long-term mean annual total is 2,121 mm Long term Mean Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 3-11 Rainfall at Ok Om during 214 against long-term monthly means 4

68 Rainfall (mm) Rainfall (mm) Rainfall (mm) SG3 (Compliance site) Figure 3-12 shows rainfall at the SG3 compliance site during 214 against long-term monthly means. An accurate annual rainfall measurement could not be obtained due to equipment failure between May and November; the long-term mean annual total is 1,86 mm Long term Mean 5 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 3-12 Rainfall at SG3 during 214 against long-term monthly means SG4 Figure 3-13 shows rainfall at SG4 in 214 against long-term monthly means. Annual rainfall of 3,759 mm was recorded against the long-term mean annual total of 3,736 mm Long term Mean 1 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 3-13 Rainfall at SG4 during 214 against long-term monthly means SG5 Figure 3-14 shows rainfall at the SG5 during the year against long-term monthly means. Total rainfall of 1,778 mm and fell on 17 wet days, the long-term mean annual total is 2,596 mm. There were no data recorded from June to August due to vandalism of equipment Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 214 Long term Mean Figure 3-14 Rainfall at SG5 during 214 against long-term mean means 41

69 3.2 Hydrology Strickland River Catchment The river systems downstream of, and potentially impacted by, the mine are the Porgera, Lagaip and Strickland Rivers. From a hydrological perspective these can be broadly be grouped into three regions of interest; upper catchment (Porgera Valley), middle catchment (SG2 to SG3) and lower catchment (SG3 to lowlands / floodplain). The Ok Om monitoring site is a reference and therefore not potentially influenced by the mine. In general, flows were about 3-4% below average in the upper region, about 15-2% above average in the middle region, and 5-1% above average in the lower regions, which is commensurate with rainfall being slightly above average. A summary of river flow data collected at the operational stations during the year is given in Table 3-2, while plots of yield and total flow for the main stations are provided in Figure 3-15 and Figure 3-16 respectively. Table 3-2 Summary of median daily flows in m 3 /s for riverine stations in 214 Station Days lost Max. Daily Mean Min. Daily Mean Daily Mean Long-term Daily Mean Std Dev. (%) SAG Mill Culvert Yunarilama SG Ok Om SG SG4 9453* SG * Flows at SG5 would be expected to exceed flows at SG4, however the max flow rate at SG4 exceeds that at SG5 in 214 as the max flow at SG4 occurred on one of the 18 days where data were not available for SG5. Figure 3-15 Comparison of annual specific yield for main river gauging stations 42

70 Figure 3-16 Mean annual flow volumes for the main river gauging stations in SG3 (Compliance site) The total flow for the year at SG3 of 23,85 GL was approximately 14% above the long-term average of 21, GL. September with 3,23 GL had the highest monthly flow while March with 1,39 GL had the least. Figure 3-17 shows the daily total flows for the year at SG3 while Figure 3-18 shows total monthly flows against long-term monthly averages. Figure 3-17 Total daily flow (GL) at SG3 for

71 Figure 3-18 Total monthly flow (GL) at SG3 during 214 against long-term monthly medians 3.3 Background Water Quality This section presents the water quality data collected from reference sites throughout the history of the operation. The sites are grouped into Local Sites, Upper River, Lower River and Lake Murray and Off- River Water Bodies (ORWBs). Data from all groups, with the exception of local creeks, are used to develop risk and performance assessment criteria for each of the respective groups. Risk assessment TVs are derived from the monitoring data for the previous 24 months and describe the current background conditions of the receiving environment. Performance assessment criteria are derived from the long-term historical data and are used to describe the long-term background conditions at each site. The TVs and performance criteria are used in Section 6 to support the environmental risk and performance assessments at the test sites. Data from local reference sites are presented only to describe the quality of non-mine related contributions to the receiving environment, they are not used to derive receiving environment TVs Local Sites Local Sites comprise the small highland creeks within the Porgera River catchment that are not affected by the mining operation. Water from these creeks joins with discharge from the mine to form the Porgera River, and so the quality of water within these creeks is important for providing the full context of inputs that influence downstream environmental conditions. The site names are presented in Table 3-3 and water quality results presented in Figure 3-19 to Figure 3-48, with long-term trends shown in Table 3-4. Table 3-3 Local site monitoring points Site Type Site Name Local sites Kaiya River upstream of Anjolek erodible dump ( ) Aipulungu River upstream of lime plant and quarry ( ) Waile Dam ( ) Pongema River ( ) 44

72 Water quality within local creeks is dominated by the surrounding limestone geology and relatively low level of development within the catchments. The ph is alkaline and typical of limestone geology, while TSS is generally low but has the potential to reach elevated levels particularly under high rainfall periods due to landslides and erosion within the steep valley catchment, and particularly in the Kaiya River catchment (Kaiya US Anjolek) and Aipulungu River. Metal concentrations generally are low, however, background mercury and selenium are at detectable levels throughout the historical record. Levels of ph and sulfate at Waile Creek, and alkalinity at Pongema have increased since monitoring began in The likely cause of the ph and alkalinity increases is increased exposure of limestone geology within the upper catchments. The concentration of all other parameters have either reduced or remained unchanged over the history of the monitoring program. The details of the statistical analysis for long-term trends are provided in Appendix C. 45

73 Barrick Porgera Annual Environment Report 214 ph levels for local creeks 214 ph levels for local creeks ph (standard units) ph (standard units) Aipulungu US Waile Dam Kaiya U/S Anj Pongema 6 Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-19 ph in local creek runoff 214 Figure 3-2 ph in local creek runoff Sulfate concentrations for local creeks 214 Sulfate concentrations for local creeks Sulfate (mg/l) 2 1 Sulfate (mg/l) Aipulungu US Waile Dam SITES Kaiya U/S Anj Pongema Aipulungu US Waile Dam SITES Kaiya U/S Anj Pongema Figure 3-21 Sulfate in local creek runoff 214 Figure 3-22 Sulfate in local creek runoff

74 Total alkalinity concentrations for local creeks 214 Total alkalinity concentrations for local creeks ALK-T (mg/l) 2 15 ALK-T (mg/l) Aipulungu US Waile Dam SITES Kaiya U/S Anj Pongema Aipulungu US Waile Dam SITES Kaiya U/S Anj Pongema Figure 3-23 Alkalinity in local creek runoff 214 Figure 3-24 Alkalinity in local creek runoff Total suspended solids for local creeks 214 Total suspended solid levels for local creeks TSS (mg/l) TSS (mg/l) Aipulungu US Waile Dam SITES Kaiya U/S Anj Pongema Aipulungu US Waile Dam SITES Kaiya U/S Anj Pongema Figure 3-25 TSS in local creek runoff 214 Figure 3-26 TSS in local creek runoff

75 Silver concentrations for local creeks 214 Silver concentrations for local creeks Dissolved silver (Ag).5 Total silver (Ag) 7.2 Dissolved silver (Ag) 5 Total silver (Ag) Ag (µg/l) Ag (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema. Aipulungu US Waile Dam Kaiya U/S Anj Pongema. Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-27 Dissolved and total silver in local creek runoff 214 Figure 3-28 Dissolved and total silver in local creek runoff Arsenic concentrations for local creeks 214 Arsenic concentrations for local creeks Dissolved arsenic (As) 2. Total arsenic (As) 5 Dissolved arsenic (As) 5 Total arsenic (As) As (µg/l) As (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema.5 Aipulungu US Waile Dam Kaiya U/S Anj Pongema 1 Aipulungu US Waile Dam Kaiya U/S Anj Pongema 1 Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-29 Dissolved and total arsenic in local creek runoff 214 Figure 3-3 Dissolved and total arsenic in local creek runoff

76 Cadmium concentrations for local creeks 214 Cadmium concentrations for local creeks Dissolved cadmium (Cd).5 Total cadmium (Cd) 5 Dissolved cadmium (Cd) 12 Total cadmium (Cd) Cd (µg/l) Cd (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema. Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-31 Dissolved and total cadmium in local creek runoff 214 Figure 3-32 Dissolved and total cadmium in local creek runoff Cr (µg/l) Dissolved chromium (Cr) Aipulungu US Chromium concentrations for local creeks 214 Chromium concentrations for local creeks Waile Dam Kaiya U/S Anj Pongema Total chromium (Cr) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Cr (µg/l) Aipulungu US Dissolved chromium (Cr) Waile Dam Kaiya U/S Anj Pongema Total chromium (Cr) Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-33 Dissolved and total chromium in local creek runoff 214 Figure 3-34 Dissolved and total chromium in local creek runoff

77 Copper concentrations for local creeks 214 Copper concentrations for local creeks Dissolved copper (Cu) 25 Total copper (Cu) 1 Dissolved copper (Cu) 14 Total copper (Cu) Cu (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Cu (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-35 Dissolved and total copper in local creek runoff 214 Figure 3-36 Dissolved and total copper in local creek runoff Iron concentrations for local creeks 214 Iron concentrations for local creeks Dissolved iron (Fe) 1 Total iron (Fe) 5 Dissolved iron (Fe) 6 Total iron (Fe) Fe (µg/l) Fe (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-37 Dissolved and total iron in local creek runoff 214 Figure 3-38 Dissolved and total iron in local creek runoff

78 Mercury concnetrations for local creeks 214 Mercury concnetrations for local creeks Dissolved mercury (Hg).5 Total mercury (Hg).8 Dissolved mercury (Hg) 6 Total mercury (Hg) Hg (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Hg (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-39 Dissolved and total mercury in local creek runoff 214 Figure 3-4 Dissolved and total mercury in local creek runoff Nickel concentrations for local creeks 214 Nickel concentrations for local creeks Dissolved nickel (Ni) 1 Total nickel (Ni) 2 Dissolved nickel (Ni) 16 Total nickel (Ni) Ni (µg/l) Ni (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-41 Dissolved and total nickel in local creek runoff 214 Figure 3-42 Dissolved and total nickel in local creek runoff

79 Lead concentrations for local creeks 214 Lead concentrations for local creeks Dissolved lead (Pb) 5 Total lead (Pb) 5 Dissolved lead (Pb) 1 Total lead (Pb) Pb (µg/l) Pb (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-43 Dissolved and total lead in local creek runoff 214 Figure 3-44 Dissolved and total lead in local creek runoff Se (µg/l) Selenium concentrations for local creeks 214 Dissolved selenium (Se) Total selenium (Se) Se (µg/l) Selenium concentrations for local creeks Dissolved selenium (Se) Total selenium (Se) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-45 Dissolved and total selenium in local creek runoff 214 Figure 3-46 Dissolved and total selenium in local creek runoff

80 Zinc concentrations for local creeks 214 Zinc concentrations for local creeks Dissolved zinc (Zn) 6 Total zinc (Zn) 6 Dissolved zinc (Zn) 1 Total zinc (Zn) Zn (µg/l) Zn (µg/l) Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema Aipulungu US Waile Dam Kaiya U/S Anj Pongema SITES SITES Figure 3-47 Dissolved and total zinc in local creek runoff 214 Figure 3-48 Dissolved and total zinc in local creek runoff Table 3-4 Summary of total metal concentration trends in mine area runoff as tested by Spearman Rank Correlation (D = Dissolved and T = Total concentrations) SITE ph Sulfate Aipulungu U/S Waile Dam Kaiya U/S Anj Pongema ALK - T TSS Ag As Cd Cr Cu Fe Hg Ni Pb Se Zn d T d T d T d T d T d T d T d T d T d T d T Decreasing or no change over time Increasing over time 53

81 Barrick Porgera Annual Environment Report Upper and Lower River Background Water Quality This section presents the results from pre-mine baseline water quality monitoring at upper and lower river test sites and current monitoring data (last 24 months) from upper and lower river reference sites. Baseline data were collected from the test sites prior to the commencement of mining. The purpose of this section is to describe the background or natural water quality conditions at sites that are not influenced by the mining operation, and by doing so, establish TVs as a basis for assessing risk and potential impact at those test sites which are influenced by the operation. Water quality risk assessment TVs for the upper and lower river reference sites are presented in Table 3-5 and Table 3-6 respectively. The TVs are derived by comparing the 8%ile of the baseline data at test sites, the 8%ile of the most recent 24-months data from all of the reference sites, and the ANZECC/ARMCANZ (2) default guideline for 95% species protection, and then adopting the highest of the three values for each analyte. With the exception of dissolved silver, copper and zinc in the upper river, silver in the lower river and silver and cadmium at Lake Murray, the baseline and reference site 8%ile values for all parameters are either equal to or fall below the respective ANZECC/ARMCANZ (2) value, therefore the default ANZECC/ARMCANZ (2) values are adopted. Where no ANZECC/ARMCANZ (2) guideline exists, the 8%ile of the most recent 24-months data from the reference site has been adopted as the TV. Water quality performance criteria from the upper and lower river reference sites are presented in Table 3-7 and Table 3-8 respectively and are derived from the full historical data set for each site. Concentrations of all parameters at the upper and lower river reference sites show no significant change over time. It should be noted that in some cases all of the results within the dataset have fallen below the analytical limit of reporting (LOR). In these cases the Spearman rank test is not capable of supporting a statistically significant result given that all of the data points are equal and cannot be ranked. However, given that all of the results are equal, a determination of no change has been assigned. Additionally, the LORs have changed over the history of the monitoring program as a result of changing analytical methodologies. In some cases this change has influenced the data so that either an increasing trend (where the LOR has increased) or decreasing trend (where the LOR has decreased) is indicated. These cases are noted in the respective tables and the result modified to reflect a finding of no change. 54

82 Barrick Porgera Annual Environment Report 214 Table 3-5 Summarised water quality for upper river reference sites for baseline and for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) default TV for 95%species protection provided for comparison. All data reported as µg/l except where indicated UpRiv Ref 24 month (n=92) SG1 Baseline (n=15) SG2 Baseline (n=24) SG3 Baseline (25) Baseline SG1,SG2 & SG3 (n=64) Parameter 2%ile Median 8%ile 2%ile Median 8%ile 2%ile Median 8%ile 2%ile Median 8%ile 2%ile Median 8%ile UpRiv REF UpRiv Baseline ANZECC/ ARMCANZ 95% ph* Sulfate* Alk-T* TSS* NA 296 Hardness* NA ND ND ND ND ND ND ND ND ND ND ND Ag-D ND ND ND ND ND ND ND ND ND ND ND ND Ag-T ND ND ND ND ND ND ND ND ND ND ND ND As-D ND ND ND ND ND ND As-T ND ND ND Cd-D ND ND ND ND ND ND ND ND ND ND ND ND.2 -.5**.5 Cd-T Cr-D ND ND ND ND ND ND ND ND ND ND ND ND Cr-T ND ND ND ND ND ND ND ND ND ND ND ND Cu-D ** 4.3 Cu-T ND ND ND Fe-D NA 75 Fe-T* ND ND ND Hg-D ND ND ND ND ND ND Hg-T ND ND ND ND ND ND Ni-D ** 28.2 Ni-T ND ND ND Pb-D ** 13.9 Pb-T ND ND ND Se-D ND ND ND ND ND ND ND ND ND ND ND ND Se-T ND ND ND ND ND ND ND ND ND ND ND ND Zn-D ** 21 Zn-T ND ND ND D=Dissolved fraction; T = Total; ph standard units; *Units in mg/l; **Hardness modified; NA = not applicable; ND = Not Determined Baseline data were data collected from the test sites prior to mine operations commencing UpRiv TV 55

83 Table 3-6 Summarised water quality for lower river reference sites for baseline and for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) default TV for 95%species protection provided for comparison. All data reported as µg/l except where indicated LwRiv Ref 24 Month (n=22) Baseline SG4 (n=36) Parameter 2%ile Median 8%ile 2%ile Median 8%ile LwRiv REF LwRiv Baseline ANZECC/ ARMCANZ 95% LwRiv TV ph Sulfate* ALK-T* TSS* NA 986 Hardness* ND ND ND Ag-D ND ND ND.2 ND.5.2 Ag-T ND ND ND As-D ND ND ND 1.1 ND As-T Cd-D ND ND ND.2 ND.4**.4 Cd-T Cr-D ND ND ND 1. ND Cr-T ND ND ND Cu-D ** 2.8 Cu-T Fe-D NA 75 Fe-T* Hg-D ND ND ND.1 ND.6.6 Hg-T Ni-D ** 22.2 Ni-T Pb-D Pb-T Se-D ND ND ND 1. ND Se-T ND ND ND Zn-D ** 16.1 Zn-T D=Dissolved fraction; T = Total; ph standard units; *Units in mg/l; **Hardness modified; NA = not applicable; ND = Not Determined Baseline data were data collected from the test sites prior to mine operations commencing 56

84 Barrick Porgera Annual Environment Report 214 Table 3-7 Performance criteria for water quality at upper river reference sites (dissolved) as determined by Spearman Rank correlation against time Water Quality Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Upper River Ref (Trend of Annual Median over time) ph No change over time TSS No change over time Ag-D No change over time As-D*.845. No change over time Cd-D*.815. No change over time Cr-D* No change over time Cu-D No change over time Fe-D No change over time Hg-D* No change over time Ni-D No change over time Pb-D No change over time Se-D No change over time Zn-D No change over time * The trend indicated by Spearman s rho and p of these tests are artefacts of a change (either upwards or downwards) of the analytical limit of reporting throughout the historical record and are not representative of an actual positive or negative trend. Therefore the finding has been corrected to indicate no change over time, which is representative of actual conditions. Table 3-8 Performance criteria for water quality at lower river reference sites (dissolved) as determined by Spearman Rank correlation against time Water Quality Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Lower River Ref (Trend of Annual Median over time) ph No change over time TSS No change over time Ag-D <LOR <LOR No change over time As-D <LOR <LOR No change over time Cd-D <LOR <LOR No change over time Cr-D No change over time Cu-D <LOR <LOR No change over time Fe-D No change over time Hg-D No change over time Ni-D <LOR <LOR No change over time Pb-D <LOR <LOR No change over time Se-D <LOR <LOR No change over time Zn-D No change over time LOR = Analytical Limit of Reporting 57

85 3.3.3 Lake Murray and ORWBs Background Water Quality The North Lake Murray sampling site was selected as the most appropriate reference site for the ORWBs and the middle and southern end of the lake. The 8%ile value from North Lake Murray site data set and the 8%ile value from the Lake Murray baseline data set have been compared with the ANZECC/ARMCANZ (2) default guideline for 95% species protection and the highest of the three values adopted for each analyte. With the exception of dissolved silver (Ag-D) and cadmium (Cd-D), the reference site 8%ile values for all parameters are either equal to or fall below the respective ANZECC/ARMCANZ (2) value. Where no ANZECC/ARMCANZ (2) guideline exists, the 8%ile value from the reference site has been adopted as the TV. Risk assessment TVs derived from the North Lake Murray reference site are presented in Table 3-9. Water quality performance assessment criteria derived from the North Lake Murray reference site are presented in Table 3-1 and show no change for all parameters. 58

86 Barrick Porgera Annual Environment Report 214 Table 3-9 Summarised water quality data for Lake Murray and ORWB river reference sites for baseline and for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) default TV for 95%species protection provided for comparison. All data reported as µg/l except where indicated. NORTHERN LAKE MURRAY (n=12) Lake Murray (LM1) Baseline (n=1) Lake Murray (LM2) Baseline (n=1) Lake Murray LM1 and LM2 Baseline (n=2) LMY ORWBs REF LMY ORWBs Baseline ANZECC/ ARMCANZ 95% Parameter 2%ile Median 8%ile 2%ile Median 8%ile 2%ile Median 8%ile 2%ile Median 8%ile ph Sulfate ALK-T* TSS* # NA 12 Hardness* ND ND ND ND ND ND ND ND ND Ag-D ND ND ND ND ND ND ND ND ND.11 ND.5.11 Ag-T ND ND ND ND ND ND ND ND ND As-D As-T Cd-D **.72 Cd-T Cr-D Cr-T Cu-D ** 1. Cu-T Fe-D NA NA NA NA Fe-T Hg-D ND ND ND ND ND ND ND ND ND.16 ND Hg-T Ni-D ** 7.6 Ni-T Pb-D ** 3.7 Pb-T Se-D Se-T Zn-D ** 5.5** Zn-T D=Dissolved fraction; T = Total; ph standard units; *Units in mg/l; **Hardness modified; ND = Not Determined NA = not applicable; # Derived from full historical data set Baseline data were data collected from the test sites prior to mine operations commencing LMY ORWBs TV 59

87 Barrick Porgera Annual Environment Report 214 Table 3-1 Performance criteria for water quality Lake Murray and ORWBs as determined using Spearman Rank Correlation against time Water Quality Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Lake Murray and ORWB Ref (Trend of Annual Median) ph No change over time TSS No change over time Ag-D No change over time As-D* No change over time Cd-D* No change over time Cr-D* No change over time Cu-D No change over time Fe-D No change over time Hg-D* No change over time Ni-D No change over time Pb-D* No change over time Se-D <LOR <LOR No change over time Zn-D No change over time LOR = Analytical Limit of Reporting * The trend indicated by Spearman s rho and p of these tests are artefacts of a change (either upwards or downwards) of the analytical limit of reporting throughout the historical record and are not representative of an actual positive or negative trend. Therefore the finding has been corrected to indicate no change over time, which is representative of actual conditions. 3.4 Background Benthic Sediment Quality This section presents the benthic sediment quality data collected from reference sites over the past 24 months and over the full history of the operation. The weak-acid extractable (WAE) metal concentrations from the whole sediment fraction have been used to develop the TVs. The WAE method is designed to replicate the ability of an organism s digestive system to liberate metals from sediment, and therefore represents the bioavailable fraction of metals within the sediment. The total digest (TD) method uses a stronger acid to liberate metals from the sediment and is likely to overestimate the concentration of metals to which an organism would be exposed from digesting the sediment. Baseline benthic sediment quality data for WAE metals from whole sediment are not available. Measurement of WAE metals in benthic sediment commenced mid-way through 213 which has reduced the sample size below the target of 24 monthly samples. In August 213, the analytical limit of reporting (LOR) for mercury was lowered from.2 mg/kg to.1 mg/kg by changing from analysis by ICP-MS to CV-AAS. Any data equal to the higher LOR have been excluded from the dataset which has further reduced the sample size for mercury. The TVs have been established by comparing the 8%ile values from the reference site data set against the ANZECC/ARMCANZ low Interim Sediment Quality Guideline (ISQG-low) and adopting the higher of the two values. There are insufficient long-term WAE data available for deriving performance assessment criteria for WAE metals. Therefore, the long-term historical trends have been established using total digest (TD) metals results. 6

88 3.4.1 Upper and Lower River Background Sediment Quality Sediment quality risk assessment TVs from the upper and lower river reference sites are presented in Table 3-11 and Table 3-12 respectively. The long-term trends for total metals in sediments are presented in Table 3-13 and Table 3-14 respectively. The data show an increasing trend in concentrations of chromium, copper and nickel at the upper river reference sites. An increasing trend of nickel and selenium concentrations and decreasing trends for cadmium and zinc were observed at the lower river reference sites. 61

89 Barrick Porgera Annual Environment Report 214 Table 3-11 Summarised sediment quality data for upper river reference sites for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) ISQG-Low values are provided for comparison. All data reported as mg/kg. Upper Lagaip Pori Kuru Ok Om UpRivs Ref 24 month UpRiv Parameter N Median 8%ile N Median 8%ile N Median 8%ile N Median 8%ile N Median 8%ile REF ANZECC/ ARMCANZ ISQG-Low Ag-WAE Ag-TD As-WAE As-TD Cd-WAE Cd-TD Cr-WAE Cr-TD Cu-WAE Cu-TD Hg-WAE Hg-TD Ni-WAE Ni-TD Pb-WAE Pb-TD Se-WAE NA.5 Se-TD Zn-WAE Zn-TD WAE = Weak-acid Extractable on whole sediment (i.e. the bioavailable fraction); TD = Total Digest on whole sediment; NA = Not Applicable Porgera UpRiv SEDs TV 62

90 Table 3-12 Summarised sediment quality data for lower river reference sites for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) ISQG-Low values are provided for comparison. All data reported as mg/kg. Baia Tomu LwRiv REF Parameter N Median 8%ile N Median 8%ile N Median 8%ile LwRiv REF 8%ile ANZECC/ ARMCANZ ISQG-Low Porgera LwRiv Sed TV Ag-WAE Ag-TD As-WAE As-TD Cd-WAE Cd-TD Cr-WAE Cr-TD Cu-WAE Cu-TD Hg-WAE Hg-TD Ni-WAE Ni-TD Pb-WAE Pb-TD Se-WAE NA.5 Se-TD Zn-WAE Zn-TD WAE = Weak acid Extractable on whole sediment (i.e. the bioavailable fraction); TD = Total Digest on whole sediment; NA = Not Applicable 63

91 Barrick Porgera Annual Environment Report 214 Table 3-13 Performance criteria for sediment quality for upper river (total digest) determined by Spearman Rank correlation against time Sediment Quality Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Upper Riv Ref (Annual median over time) Ag-TD* No change over time As-TD No change over time Cd-TD* No change over time Cr-TD.748. Increasing over time Cu-TD Increasing over time Hg-TD*.729. No change over time Ni-TD Increasing over time Pb-TD No change over time Se-TD No change over time Zn-TD No change over time * The trend indicated by Spearman s rho and p of these tests are artefacts of a change (either upwards or downwards) of the analytical limit of reporting throughout the historical record and are not representative of an actual positive or negative trend. Therefore the finding has been corrected to indicate no change over time, which is representative of actual conditions. Table 3-14 Performance criteria for sediment quality for lower river (total digest) determined by Spearman Rank correlation against time Sediment Quality Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Lower Riv Ref (Annual median over time) Ag-TD No change over time As-TD No change over time Cd-TD Decreasing over time Cr-TD No change over time Cu-TD. 1. No change over time Hg-TD No change over time Ni-TD Increasing over time Pb-TD No change over time Se-TD Increasing over time Zn-TD Decreasing over time Lake Murray and ORWBs Background Sediment Quality Sediment quality risk assessment TVs from Lake Murray and ORWB reference sites are presented in Table Total metals were measured in the baseline samples and are included for reference purposes. TVs are derived by comparing the reference site 8%ile from the previous 24 months WAE data set against the ANZECC/ARMCANZ (2) ISQG-low and adopting the higher of the two values. Sediment quality performance assessment criteria for total digest metals in sediments from Lake Murray and ORWBs are presented in Table The data show an increasing trend in chromium in the Lake Murray reference sites. 64

92 Barrick Porgera Annual Environment Report 214 Table 3-15 Summarised sediment quality data for Lake Murray and ORWBs reference sites for previous 24 months, presenting 2%ile, median and 8%ile of data for each site. ANZECC/ARMCANZ (2) ISQG-Low values are provided for comparison. All data reported as mg/kg. Northern Lake Murray (n=12) LMY Baseline (n=42) Parameter 2%ile Median 8%ile 2%ile Median 8%ile LMY and ORWBs Rivers REF ANZECC/ARMCANZ ISQG-Low LMY and ORWBs TV Ag-WAE ND ND ND Ag-TD ND ND ND As-WAE ND ND ND As-TD Cd-WAE ND ND ND Cd-TD Cr-WAE ND ND ND Cr-TD Cu-WAE ND ND ND Cu-TD Hg-WAE ND ND ND Hg-TD ND.1 ND Ni-WAE ND ND ND Ni-TD Pb-WAE ND ND ND Pb-TD Se-WAE ND ND ND.5 NA.5 Se-TD Zn-WAE ND ND ND Zn-TD WAE = Weak Acid Extractable on whole sediment (i.e. the bioavailable fraction); TD = Total Digest on whole sediment; NA = Not Applicable NA = Not Applicable; ND = Not Determined Baseline data were data collected from the test sites prior to mine operations commencing 65

93 Barrick Porgera Annual Environment Report 214 Table 3-16 Performance criteria for sediment quality Lake Murray and ORWBs (total digest) determined by Spearman Rank correlation against time Sediment Quality Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Lake Murray and ORWB Ref (Annual median over time) Ag-TD* No change over time As-TD No change over time Cd-TD No change over time Cr-TD Increasing over time Cu-TD No change over time Hg-TD.775 <.1 No change over time Ni-TD No change over time Pb-TD No change over time Se-TD No change over time Zn-TD No change over time * The trend indicated by Spearman s rho and p of these tests are artefacts of a change (either upwards or downwards) of the analytical limit of reporting throughout the historical record and are not representative of an actual positive or negative trend. Therefore the finding has been corrected to indicate no change over time, which is representative of actual conditions. 3.5 Background Tissue Metal Concentrations This section presents the tissue metal concentration data collected from baseline sampling at test sites pre-mine and from reference sites over the past 24months and over the full history of the operation. The baseline data are limited to tissue metal concentrations in fish muscle, the reference site data include tissue metal concentrations in muscle and liver of fish and in abdominal and cephalothorax tissue of prawns. Risk assessment TVs for metal concentrations in the tissue of fish and prawns were established by comparing the 8%ile value from the baseline data set, the 8%ile value from the combined reference site data over the most recent 24-month period and US EPA guidelines values where applicable, and selecting the highest value as the TV. Performance assessment indicators are derived from the long term historical data to provide an indication of the trend in the tissue metal concentrations. The TVs and performance indicators are then used in Section 6 to support the environmental risk and performance assessments Upper and Lower River Background Tissue Metal Tissue metal risk assessment TVs for the upper and lower river are presented in Table 3-17 to Table 3-2. Tissue metal performance assessment criteria for the upper and lower river are presented in Table 3-21 to Table The data show an increasing trend of copper in prawn abdomen at the upper river reference sites. All other metals at the upper and lower river reference sites for all tissue types either decreased or remained stable over time. 66

94 Barrick Porgera Annual Environment Report 214 Table 3-17 Summarised tissue metal data for upper river reference sites for previous 24 months (As-Cu), presenting median and 8%ile of data for each site. All data reported as mg/kg. Site Sample n As Cd Cr Cu Median 8%ile Median 8%ile Median 8%ile Median 8%ile Fish Flesh Pori Fish Liver Prawn Ab Prawn Ceph Fish Flesh Ok Om Fish Liver Prawn Ab Prawn Ceph Fish Flesh Kuru Fish Liver Prawn Ab Prawn Ceph Wankipe baseline Fish Flesh ND ND Upper River Ref 24 month Trigger Value Fish Flesh Fish Liver Prawn Ab Prawn Ceph Fish Flesh Fish Liver Prawn Ab Prawn Ceph ND = Not Determined; Ab = Abdomen; Ceph = Cephalothorax 67

95 Table 3-18 Summarised tissue metal data for upper river reference sites for previous 24 months (Hg - Zn), presenting median and 8%ile of data for each site. All data reported as mg/kg wet except where indicated. Site Sample n Hg Ni Pb Se Zn Median 8%ile Median 8%ile Median 8%ile Median 8%ile Median 8%ile Fish Flesh Pori Fish Liver Prawn Ab Prawn Ceph Fish Flesh Ok Om Fish Liver Prawn Ab Prawn Ceph Fish Flesh Kuru Fish Liver Prawn Ab Prawn Ceph Wankipe baseline Fish Flesh USEPA (214) Fish Flesh NA NA NA NA NA NA NA 2.36 (11.8 dw) NA NA Upper River Ref 24 month. Trigger Value Fish Flesh Fish Liver Prawn Ab Prawn Ceph Fish Flesh Fish Liver Prawn Ab Prawn Ceph ND = Not Determined; NA = Not Applicable; dw = dry weight; Ab = Abdomen; Ceph = Cephalothorax 68

96 Table 3-19 Summarised tissue metal data for lower river reference sites for previous 24 months (As-Cu), presenting median and 8%ile of data for each site. All data reported as mg/kg wet except where indicated. Site Sample n As Cd Cr Cu Median 8%ile Median 8%ile Median 8%ile Median 8%ile Fish Flesh Baia Fish Liver Prawn Ab Prawn Ceph Fish Flesh Tomu Fish Liver Prawn Ab Prawn Tiumsinawam baseline Ceph Fish Flesh Lower River Ref Stats 24 month Trigger Value Ab = Abdomen; Ceph = Cephalothorax Fish Flesh Fish Liver Prawn Ab Prawn Ceph Fish Flesh Fish Liver Prawn Ab Prawn Ceph 69

97 Table 3-2 Summarised tissue metal data for lower river reference sites for previous 24 months (Hg-Zn), presenting median and 8%ile of data for each site. All data reported as mg/kg wet except where indicated. Site Sample n Hg Pb Ni Se Zn Median 8%ile Median 8%ile Median 8%ile Median 8%ile Median 8%ile Fish Flesh Baia Fish Liver Prawn Ab Prawn Ceph Fish Flesh Tomu Fish Liver Prawn Ab Prawn Ceph Tiumsinawam baseline Fish Flesh USEPA (214) Fish Flesh NA NA NA NA NA NA NA 2.36 (11.8 dw) NA NA Lower River Ref Stats 24 month Trigger Value Fish Flesh Fish Liver Prawn Ab Prawn Ceph Fish Flesh Fish Liver Prawn Ab Prawn Ceph NA = Not Applicable; dw = dry weight; Ab = Abdomen; Ceph = Cephalothorax 7

98 Barrick Porgera Annual Environment Report 214 Table 3-21 Performance criteria of metals in fish flesh for upper river reference sites determined by Spearman Rank correlation against time Fish flesh Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Upper Riv Ref (Trend of Annual Median) As Decreasing over time Cd No change over time Cr <.1 Decreasing over time Cu No change over time Hg No change over time Ni Decreasing over time Pb Decreasing over time Se No change over time Zn No change over time Table 3-22 Performance criteria of metals in fish liver for upper river reference site determined by Spearman Rank correlation against time Fish liver Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Upper Riv Ref (Trend of Annual Median) As No change over time Cd No change over time Cr No change over time Cu No change over time Hg No change over time Ni No change over time Pb No change over time Se No change over time Zn No change over time Table 3-23 Performance criteria of metals in prawn abdomen for upper river reference site determined by Spearman Rank correlation against time Prawn Abdomen Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Upper Riv Ref (Trend of Annual Median) LOR = Analytical limit of reporting As No change over time Cd <LOR <LOR No change over time Cr No change over time Cu Increasing over time Hg <LOR <LOR No change over time Ni.3.37 No change over time Pb <LOR <LOR No change over time Se No change over time Zn No change over time 71

99 Table 3-24 Performance criteria of metals in prawn cephalothorax for upper river reference site determined by Spearman Rank correlation against time Prawn Cephalothorax Site Element Spearman s rho P-Value (P=.5) Reference Site Performance Upper Riv Ref (Trend of Annual Median) LOR = Analytical limit of reporting As Decreasing over time Cd No change over time Cr No change over time Cu No change over time Hg No change over time Ni No change over time Pb No change over time Se No change over time Zn No change over time Table 3-25 Performance criteria of metals in fish flesh at lower river reference site determined by Spearman Rank correlation against time Fish flesh Site Lower Riv Ref (Trend of Annual Median) Element LOR = Analytical limit of reporting Spearman s rho P-Value (P=.5) Reference Site Performance As Decreasing over time Cd <LOR <LOR No change over time Cr Decreasing over time Cu Decreasing over time Hg Decreasing over time Ni No change over time Pb <LOR <LOR No change over time Se Decreasing over time Zn Decreasing over time Table 3-26 Performance criteria of metals in fish liver at lower river reference site determined by Spearman Rank correlation against time Fish liver Site Element rho P-Value (P=.5) Reference Site Performance Lower Riv Ref (Trend of Annual Median) As No change over time Cd No change over time Cr Decreasing over time Cu No change over time Hg No change over time Ni Decreasing over time Pb Decreasing over time Se No change over time Zn No change over time 72

100 Table 3-27 Performance criteria of metals in prawn abdomen at lower river reference sites determined by Spearman Rank correlation against time Prawn Abdomen Site Lower Riv Ref (Trend of Annual Median) Element LOR = Analytical limit of reporting Spearman s rho P-Value (P=.5) Reference Site Performance As No change over time Cd <LOR <LOR No change over time Cr No change over time Cu No change over time Hg <LOR <LOR No change over time Ni <LOR <LOR No change over time Pb <LOR <LOR No change over time Se No change over time Zn No change over time Table 3-28 Performance criteria of metals in prawn cephalothorax at lower river reference sites determined by Spearman Rank correlation against time Prawn Cephalothorax Site Lower Riv Ref (Trend of Annual Median) Element Spearman s rho P-Value (P=.5) Reference Site Performance As No change over time Cd No change over time Cr No change over time Cu No change over time Hg No change over time Ni No change over time Pb No change over time Se No change over time Zn No change over time Lake Murray and ORWBs Background Tissue Metal Tissue metal risk assessment TVs for the Lake Murray and ORWBs could not be developed due to a lack of tissue metal data from the North Lake Murray reference site locations within the past 24 months. A lack of community support for the monitoring program has prevented access to the sites for the purposes of fish and prawn sampling. As an interim measure, the full historical database for North Lake Murray ( ) was used to derive tissue metal performance assessment criteria for Lake Murray and ORWBs and these are presented in Table 3-29 and Table 3-3. Note that only fish flesh and liver data have ever been recorded at this site, no sampling of prawn has been conducted. The data show an increasing trend of copper and selenium in fish flesh and mercury and zinc in fish liver over time. All other metals at the Lake Murray and ORWBs reference site locations showed either no change or a decreasing trend for fish flesh and fish liver. 73

101 Table 3-29 Performance criteria of metals in fish flesh at Lake Murray and ORWB reference sites determined by Spearman Rank correlation against time Fish Flesh Site LMY Ref Site (Maka) (Trend of Annual Median) Element Spearman s rho P-Value (P=.5) Reference Site Performance As No change over time Cd <LOR <LOR No change over time Cr Decreasing over time Cu Increasing over time Hg No change over time Ni No change over time Pb ND ND No change over time Se Increasing over time Zn No change over time LOR = Analytical limit of reporting; ND All results within the data set are equal, in which case the Spearman Rank test returns an error result, however the results indicate no change over time. Table 3-3 Performance criteria of metals in fish liver at Lake Murray and ORWB reference sites determined by Spearman Rank correlation against time Fish Liver Site LMY Ref Site (Maka) (Trend of Annual Median) Element Spearman s rho P-Value (P=.5) Reference Site Performance As Decreasing over time Cd No change over time Cr Decreasing over time Cu No change over time Hg Increasing over time Ni No change over time Pb <LOR <LOR No change over time Se No change over time Zn Increasing over time LOR = Analytical limit of reporting 3.6 Background Aquatic Biology Throughout the development of the revised AER methodology for the 213 AER, it became apparent that the data set for biological indicators was not capable of supporting the development of impact assessment criteria in accordance with the method being applied to water, sediment and tissue metals data. The following issues have contributed to this situation: Inconsistent sampling methodology has been applied between sampling events and between sites over the history of the program making it difficult to compare data spatially and temporally. The assumption that equal sampling effort was being applied within and between sites could not be substantiated. Therefore the results could not continue to be assessed accurately on a catch per unit of effort bases. Some of the sampling methods have resulted in fatality of animals which may have been adversely affecting population sizes. Low numbers of the target species exist at both the reference and test sites, particularly within the upper catchment. The ineffectiveness of the sampling methods, combined with the small spatial scale of sampling relative to the low density/high dispersion of the target animals 74

102 results in a highly variable data set that is dominated by low or zero value results, which in turn reduces the statistical power of the data set and ultimately limits the ability of the monitoring program to statistically detect change within the ecosystem. Application of the proposed methodology to these data would result in very low or zero values for impact criteria TVs at reference sites, which are not an appropriate benchmark for comparison with test site data as it does not provide a basis upon which to assess change at the test site. To address this issue, Porgera began a revision of the biological monitoring program in 214. The process included a review of current fish and prawn sampling methods with a view to achieving better standardisation between sampling events and between sites. At the time of writing the department is in the process of finalizing updated standard operating procedures for sampling, data management and reporting. It is expected to take two to three years of sampling to determine whether the revised methods for assessing fish and prawn communities has been effective in improving the dataset for fish and prawn biology. Additionally, in 214, Barrick engaged Wetland Research and Management (WRM) to undertake a scoping study to investigate whether monitoring benthic macroinvertebrate populations within the receiving environment could provide a robust basis for impact assessment. Macroinvertebrates (i.e. fauna visible to the eye and retained by a 25 µm aperture mesh) typically constitute the largest and most conspicuous component of aquatic invertebrate fauna in both lentic (still) and lotic (flowing) waters. Macroinvertebrates are used as a key indicator group for bioassessment of the health of Australia s streams and rivers under the National River Health Program (NRHP) (Schofield and Davies 1996), and have inherent value for biological monitoring of water quality (ANZECC/ARMCANZ 2) (WRM 215). Macroinvertebrates are more easily sampled, function at a lower spatial scale than prawns and fish, are less mobile, likely more sensitive to changes in water quality, and would not be so susceptible to the challenges that are faced by fish and prawn sampling (WRM 215). The initial sampling program for the study was carried out in August and September 214, the results show there are rich macroinvertebrate fauna populations within the local and receiving water ways making them suitable as the basis of a sensitive ecological health monitoring program. However, being the first monitoring event, the data are temporally limited and at least three years of data from reference sites are required to characterise temporal variability, confirm consistency in responses observed, and form an adequate baseline for developing robust TVs (WRM 215). As noted above, it is expected to take two-three years for the revised biological monitoring program to yield a dataset to which the revised method for impact assessment can be applied. In the meantime however, Porgera will continue with the amalgamation of the entire historical data set in an effort to develop interim performance criteria which will provide an indication of potential impact, as was performed for the 213 AER. The 214 data were added to the historical record which includes baseline data where available The data were then grouped by combining the results from all sampling methods and all indicator subspecies of fish and prawns throughout the historical data set to establish an annual median with which an historical trend could be established. It should be noted that the grouping process is by no means ideal and carries over a high level of inherent uncertainty to the results. Therefore where possible, the presence or absence of potential impact is inferred, rather than the preferred and more robust, statistically-based conclusion of the presence or absence of actual impact. The results presented in this section provide an indication of the trend of the biological indicators at the reference sites, which then act as a basis for inferring whether potential impact is occurring at test sites in Section 6. 75

103 3.6.1 Upper and Lower River Background Aquatic Ecosystem Condition Biological performance assessment criteria for the upper and lower river reference sites are presented in Table 3-31 to Table The results show that all indicators are either stable or increasing over time at the reference sites. Table 3-31 Performance criteria for fish at upper river reference sites determined by Spearman Rank correlation against time Indicator Spearman s rho P-Value Upper River Reference Condition Fish Abundance Increasing over time Fish Richness No change over time Fish Biomass.723 <.1 Increasing over time Fish Condition No change over time Table 3-32 Performance criteria for prawns at upper river reference sites determined by Spearman Rank correlation against time Indicator Spearman s rho P-Value Upper River Reference Condition Prawn Abundance Increasing over time Prawn Richness.779 <.1 Increasing over time Prawn Biomass No change over time Prawn Condition No change over time Table 3-33 Performance criteria for fish at lower river reference sites determined by Spearman Rank correlation against time Indicator Spearman s rho P-Value Lower River Reference Condition Fish Abundance No change over time Fish Richness No change over time Fish Biomass No change over time Fish Condition No change over time Table 3-34 Performance criteria for prawns at lower river reference sites determined by Spearman Rank correlation against time Indicator Spearman s rho P-Value Lower River Reference Condition Prawn Abundance No change over time Prawn Richness No change over time Prawn Biomass No change over time Prawn Condition Increasing over time 76

104 3.6.2 Lake Murray Biological performance assessment criteria for Lake Murray are presented in Table The results show no change in any of the indicators over time. Monitoring has not been conducted within Lake Murray since 29 due to a lack of community support for the monitoring program. Table 3-35 Performance criteria for fish at Lake Murray reference site determined by Spearman Rank correlation against time Indicator Spearman s rho P-Value Lake Murray and ORWB Reference Condition Fish Abundance No change over time Fish Richness No change over time Fish Biomass No change over time Fish Condition No change over time 3.7 Summary of Background Environmental Conditions Climate and Hydrology Rainfall in 214 was approximately 1% above average in the upper reach. In the middle and lower reaches, rainfall data were incomplete due to equipment vandalism. River flows were about 3 4% below average in the upper reach, about 15 2% above average in the middle reach, and 5 1% above average in the lower regions, which is commensurate with rainfall being slightly above average Background Water Quality Water quality in local site runoff was typical of an undeveloped catchment with limestone geology, exhibiting elevated ph and alkalinity, generally low TSS and low dissolved metal concentrations. However detectable concentrations of mercury and selenium throughout the historical record are noted. The 8%ile values at the reference sites show dissolved silver, copper and zinc in the upper river, silver in the lower river and silver and cadmium at Lake Murray, exceeded the ANZECC/ARMCANZ (2) guideline for 95% species protection. This indicates that concentrations of these parameters are naturally elevated at these sites compared with the ANZECC/ARMCANZ (2) default guidelines. The 8%ile concentrations of all other dissolved metals at these sites fell below the ANZECC/ARMCANZ (2) TV for 95% species protection. Analysis of long-term water quality trends at the upper and lower river and Lake Murray reference sites show no statistically significant change in any of the indicator parameters Background Sediment Quality The 8%ile concentrations of all indicator WAE metals in benthic sediment from the upper river, lower river and Lake Murray reference sites fell below the ISQG-Low values, indicating that WAE concentrations of those metals at upper and lower river reference sites are naturally low compared to the ANZECC/ARMCANZ (2) sediment quality data set. The analysis of long-term trends of metals in benthic sediment is based on total digestible metals concentrations in whole sediment. Analysis of WAE metals in whole sediment began in 213 and so the data set is insufficient for the analysis of long-term trends. The data show an increasing trend in total digestible concentrations of chromium, copper and nickel at the upper river reference sites. An increasing trend of nickel and selenium concentrations and 77

105 decreasing trends for cadmium and zinc were observed for the lower river reference sites. An increasing trend in chromium was observed in the Lake Murray reference sites Background Tissue Metal Concentrations Risk assessment TVs for metal concentrations in the tissue of fish and prawns were established by comparing the 8%ile value from the baseline data set, the 8%ile value from the combined reference site data over the most recent 24-month period and US EPA guidelines values where applicable, and selecting the highest value. Analysis of long-term trends shows an increasing trend of copper in prawn abdomen at the upper river reference sites. All other metals at the upper and lower river reference sites for all tissue types either decreased or remained stable over time. Tissue metal concentrations in Lake Murray reference site showed increasing trends for copper and selenium in fish flesh and for mercury and zinc in fish liver. All other metals at the Lake Murray reference site for all tissue types either decreased or remained stable over time Background Aquatic Biology The current biological monitoring data set does not support the development of impact assessment TVs in the same fashion as water, sediment quality and tissue metals. Barrick Porgera is working to improve the biological data set to support these methods through a review of fish and prawn sampling procedures and the use of benthic macroinvertebrates as additional indicators of ecosystem health, however these changes are expected to take two to three years to yield a reliable data set. In the meantime, the method established for the 213 AER will continue to be applied whereby the impact assessment is based on a comparison of the long-term trends of biological indicators between reference and test sites. The long-term trends for the upper river, lower river and Lake Murray reference sites show either an increase or no change for all biological indicators. 78

106 Barrick Porgera Annual Environment Report MINE OPERATIONS AND ENVIRONMENTAL ASPECTS This section provides a summary of key operational parameters and environmental aspects for 214 and throughout the history of the operation. A summary of results is presented in Table 4-1. Table 4-1 Mine production and environmental aspects summary Production / Discharge 214 Life of Mine total Comments Ore processed (Mt) Consistent with recent years. Gold production (oz) 527,535 18,664,435 Exceeded 214 guidance. Competent waste rock produced (Mt) Incompetent waste rock produced Anawe (Mt) Incompetent waste rock produced Anjolek (Mt) Tailings to underground paste (% total tailings volume) Majority to Kogai dump Lower than 213 due to reduced mud movement from open cut mine. LoM total differs from 213 AER as a result of a data reconciliation exercise Low due to mining schedule. LoM total differs from 213 AER as a result of a data reconciliation exercise Record diversion of tailings to paste. Tailings production (Mt) Consistent with previous years. Total sediment discharged to river (Mt) (from tailings and erodible dumps) Consistent with historical trend. Calculated from incompetent waste rock and tailings production. Sewage discharge (m 3 ) 37,468 NA Discharge volume from Tawisakale exceeded permit limit. Total volume discharged from all plants compliant with permit limit. Some incidents of exceeding TSS discharge criteria. Mine contact rainfall runoff (Mm 3 ) Greenhouse gas and energy efficiency (kg CO2-e / t processed ore) 25.3 NA 76.6 NA 6.5% improvement from 213 Water use and efficiency (Ltr / t processed ore) 5,66 NA 2% improvement from 213 Land Disturbance 214 Comments Area land disturbed Area of disturbed land under rehab Not surveyed ha (1%) Total disturbance to date ha. From 213 survey 79

107 Annual (Mt) Cumulative (Mt) Monthly (t) Cumulative (t) 4.1 Production Mining and Processing Operations Total Ore Processed The total quantity of ore processed in 214 was 5.86 million tonnes (Mt), which is the highest since 28. Figure 4-1 shows the monthly and cumulative quantities of ore processed in 214. The cumulative quantity of ore processed from 199 to 214 was 114 Mt, Figure 4-2 shows annual and cumulative quantities of processed ore since production began in 199. Ore Processed 214 6, 7,, 5, 4, 3, 2, 1, 6,, 5,, 4,, 3,, 2,, 1,, Monthly (LHS) Cumulative (RHS) Figure 4-1 Monthly and cumulative ore processed in 214 Ore Processed Annual (LHS) Cumulative (RHS) Figure 4-2 Yearly and cumulative ore processed

108 Annual (Oz) Cumulative (Oz) Monthly (oz) Cumulative (oz) Gold Production Total gold production in 214 was 527koz. Figure 4-3 shows monthly and cumulative gold production during 214. Total gold production from 199 to 214 was 18.6 million ounces. Figure 4-4 shows annual and cumulative gold production since operations began in 199. Gold Produced 214 6, 5, 6, 5, 4, 3, 2, 1, 4, 3, 2, 1, Monthly (LHS) Cumulative (RHS) Figure 4-3 Monthly and cumulative gold production in 214 Gold Produced ,, 1,8, 1,6, 1,4, 1,2, 1,, 8, 6, 4, 2, ,, 18,, 16,, 14,, 12,, 1,, 8,, 6,, 4,, 2,, Annual (LHS) Cumulative (RHS) Figure 4-4 Yearly and cumulative gold production

109 Water Consumption (Ltr / tonne processed ore) GHG Emission (kg CO2e / tonne ore processed) 4.2 Greenhouse Gas and Energy Figure 4-5 presents information on the average annual rate of carbon dioxide equivalents (CO 2 -e) emissions per tonne of ore processed. The Porgera annual emission rate (76.6 kg CO 2 -e/t processed ore) is considerably higher than at other gold mining operations because of the high energy requirement for the pressure oxidation processing of ore in autoclaves. Porgera has implemented energy conservation measures, such as capacitor banks which have reduced the need to operate diesel gensets to balance transmission line losses. The reduction in fuel usage, together with slightly increased mill throughput has resulted in decreased emission rate Greenhouse Gas Emissions Figure 4-5 Energy efficiency Water Use Figure 4-6 shows the annual average water use rate per tonne of ore processed. The pressure oxidation of pyrite ore in autoclaves produces sulfuric acid liquor as a by-product. Porgera uses significant quantities of water for washing the acidic liquor from the oxidised solids. Water Consumption 6,6 6,4 6,382 6,2 6, 5,8 5,6 5,4 5,985 5,496 5,818 5,781 5,66 5,2 5, Figure 4-6 Water use efficiency

110 4.4 Land Disturbance Land Disturbance Porgera mine holds eight leases under the PNG Mining Act (1992) which are shown in Figure 4-7 and listed in Table 4-2, with a total area of 3, ha of land held under lease. The Special Mining Lease (SML) encompasses 2,16.85 hectares and includes the mine and the project infrastructure. The other Leases for Mining Purposes (LMP) correspond to land use associated with the mining operation such as waste rock dumps, Suyan accommodation camp, limestone quarry and water supply, which cover a total of 1, hectares. The company also maintains Exploration Leases (EL) which surrounds the SML and some key LMPs for ongoing exploration. Mining Easements (ME) are held for utilities such as power transmission lines and water supply pipelines. The EL and ME land areas are not covered in the scope of this report. The total area disturbed by mining and other related activities since the start of the project in 1989 for all leases, was 2,31.4 hectares. Approximately 64% of the SML has been disturbed by mining activities. A survey of disturbed areas was not conducted in 214 because there was no significant expansion of mining operations and figures reported have not changed from the 213 AER. Table 4-2 Areas of cumulative land disturbance and reclamation to December 214 Lease Total Lease Area (ha) Total Disturbed (ha) Undisturbed area (ha) Total Under Progressive Reclamation (ha) SML Kogai LMP Kaiya LMP Anawe North LMP 72 Anawe South LMP Anawe LMP Suyan LMP Pangalita LMP Waile LMP TOTAL

111 Figure 4-7 Special mining lease and leases for mining purposes boundaries 84

112 Month (Mt) Cumulative (Mt) 4.5 Waste Rock Production The mine generates two types of waste rock with very different physical properties. Competent or hard rock is durable, is not prone to weathering and therefore does not break down into smaller particles after mining. Incompetent waste comprising colluvium and mudstones breaks down rapidly into sand and silt-sized particles on exposure to air and water. Competent rock is selectively mined and stored in engineered waste rock dumps constructed as a series of terraces into the hillside. Incompetent waste rock is placed in erodible dumps that behave similar to and resemble natural landslides in the area. Waste rock production between 1989 and 214 is presented in Table 4-3. The data show that to date, the quantity of competent waste rock placed at Kogai dump is approx twice the total amount placed at Anawe North competent dump since dumping commenced at Anawe in 21, while similar quantities of incompetent waste rock have been placed in the Anjolek and Anawe erodible dumps. Table 4-3 Total quantities of waste rock placed in each dump Waste dump Total dumped (t) Anawe North Competent 132,634,14 Kogai Competent 282,181,57 Competent Sub-total 414,815,71 Anjolek Erodible 212,274,324 Anawe Erodible 22,491,253 Erodible Sub-Total 432,765,577 TOTAL 847,58, Kogai Competent Dump The total quantity of competent waste rock placed at the Kogai dump in 214 was 4.25 million tonnes, Figure 4-8 shows the monthly and cumulative quantities sent to Kogai during 214. The dump received the competent waste rock mined from Stages 5B and 5C of the Open Pit during the year Competent Waste Rock to Kogai Dump 214 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Monthly Cumulative (RHS) Figure 4-8 Monthly tonnages of competent waste rock placed at Kogai Dump in

113 Month (Mt) Cumulative (Mt) Annual (Mt) Cumulative (Mt) The total quantity of competent waste rock placed at Kogai since 1989 was million tonnes, Figure 4-9 shows the annual and cumulative quantities placed at Kogai since construction of the dump began in As can be seen from the graph, most of the waste was placed between 1989 and 21 when mining was being carried out at the upper sections of the open pit. Placement of waste rock at Anawe North competent dump commenced in 21, and Anawe North has been the recipient of the majority of competent rock since then due its closer proximity to active mining areas at the bottom of the open pit Competent Waste Rock to Kogai Dump Annual Cumulative (RHS) Figure 4-9 Yearly tonnages of competent waste rock placed at Kogai Dump Anawe North Competent Dump Anawe North received 1.6 Mt of competent waste rock in 214. Figure 4-1 shows the monthly and cumulative quantities of competent rock placed at Anawe North during 214. The total quantity of competent waste rock placed at Anawe North dump since construction began in 21 was Mt. Figure 4-11 shows annual and cumulative quantities of competent waste rock placed at Anawe North Competent Waste Rock to Anawe Nth Dump 214 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Monthly Cumulative (RHS) Figure 4-1 Monthly tonnages of competent waste rock placed at Anawe North Dump in

114 Annual (Mt) Cumulative (Mt) Competent Waste Rock to Anawe Nth Dump Annual Cumulative (RHS) Figure 4-11 Yearly tonnages of competent waste rock placed at Anawe North Dump Incompetent Waste Rock Disposal Incompetent waste rock, comprising brown mudstone and colluvium stripped from the open pit, is disposed in the Anawe and Anjolek erodible dumps. Fluvial processes from rainfall runoff erode unconsolidated waste from the dumps and this is discharged as sediment to the receiving river system. The total quantities of incompetent waste rock placed during 214 were slightly less than those for 212 and 213, due to decreased mining of incompetent material from the bottom of the open pit, however rates of dumping during 214 are significantly lower than has been the case in the past Anawe Erodible Dump Monthly spoil placement volumes at Anawe erodible dump for 214 are shown in Figure A total of 4.85 Mt of incompetent waste was placed in Anawe during 214, the majority of which was mudstone material excavated from the bottom of the open pit. The volume placed was 32% of the annual permit limit of 15.7 Mt. Figure 4-13 shows the annual volumes of spoil placed in the Anawe dump since dumping began there in 1989; Figure 4-14 shows the cumulative surface area of the dump since

115 Annual (Mt) Cumulative (Mt) Month (Mt) Cumulative (Mt) Erodible Waste Rock to Anawe Erodible Dump 214 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Month Cumulative (RHS) Permit Limit (RHS) Figure 4-12 Monthly tonnages of spoil placed at Anawe Erodible Dump in Erodible Waste Rock to Anawe Erodible Dump Annual Cumulative (RHS) Figure 4-13 Yearly tonnages of spoil placed at Anawe Erodible Dump July

116 Month (mt) Cumulative (Mt) Surfac Area (ha) Volume (million m3) Jan-1 Jan-2 Jan-3 Jan-4 Jan-5 Jan-6 Jan-7 Jan-8 Jan-9 Jan-1 Jan-11 Jan-12 Jan-13 Jan-14 Jan-15 Jan-16 Area Dump Volume Waste Placement Figure 4-14 Area and volume of Anawe Erodible Dump based on LiDAR survey Anjolek Erodible Dump Figure 4-15 shows monthly spoil placement volumes at Anjolek dump during 214. A total of.26 Mt was placed during 214, the majority of which was mudstone from a cut-back of the west wall of the open pit. This was equivalent to 2% of the annual permit limit of million tonne. There was no significant waste rock dumping during the year because of the limited mining at Stage 5C at the top of the open pit. Figure 4-16 shows the volume of spoil placed in the Anjolek dump since dumping began there in 1992, Figure 4-17 shows the cumulative surface area of the dump since 21 and Table 4-7 provides a summary of 214 and historical data Erodible Waste Rock to Anjolek Erodible Dump 214 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Month Cumulative (RHS) Permit Limit (RHS) Figure 4-15 Monthly tonnages of spoil placed at Anjolek Erodible Dump in

117 Surface Area (ha) Volume (million m3) Annual (Mt) Cumulative (Mt) 3 Erodible Waste Rock to Anjolek Erodible Dump Annual Cumulative (RHS) Figure 4-16 Yearly tonnages of spoil placed at Anjolek Erodible Dump Jan-1Jan-2Jan-3Jan-4Jan-5Jan-6Jan-7Jan-8Jan-9Jan-1Jan-11Jan-12Jan-13Jan-14Jan-15Jan-16 Area Dump Volume Waste Placement Figure 4-17 Area and volume of Anjolek Erodible Dump based on LiDAR survey

118 Status of the Erodible Dumps in 214 Anawe Erodible Dump Visual observations and photographs taken from an aerial inspection by helicopter on 2 April 215, showed that the morphology of Anawe Dump has remained relatively stable since 214 with the exception of some material accumulation and valley wall erosion in the lower dump tract. The tailings continue to discharge from the outfall to a point adjacent to the Pongema River fan. The flow then splits, with some tailings directed to the north boundary below Anawe Stable Dump and the remainder to the south boundary where it combines with the Pongema River flow along the margin of the dump and the Paiam Colluvium. The lower part of the dump is on a flatter longitudinal slope and appears less active due to increased vegetation cover compared with the upper tract. In the middle part of the dump tract where there is a change in the longitudinal gradient, deposition of tailings has occurred. Elsewhere, there was no notable change to the morphology of the historic overspill area to Maiapam creek, and no notable increased erosion of the Maiapam slide toe, while the lower half of the dump below the Pongema Fan appeared relatively stable and well-vegetated. Figure 4-18 and Figure 4-19 show downstream and upstream view of the central dump tract. LiDAR mounted in an unmanned aerial vehicle was used in late 214 for detailed survey of the dump surface. Overall, survey data indicated that there had been an increase in surface area of approximate 1% (2.83 ha) and a reduction in volume of approximately 1% (596,387 m 3 ) since 213. These changes are relatively small in an historical context. Figure 4-14 shows that, while dump volume has remained relatively constant since 28, surface area has continued to increase. Close inspection of the survey plans indicates that erosion of the natural hillslopes at both the northern and southern margins of the lower dump tract has occurred, shown in Figure 4-2. This has apparently been caused by dump material flowing laterally towards the Pongema River on the southern margin, and tailings flow on the northern margin, thus pushing these streams towards the hillslopes. Therefore the increase in surface area may be due to this lateral expansion. Figure 4-18 View downstream along the Anawe Erodible Dump 91

119 Figure 4-19 View upstream along Anawe Erodible Dump Figure 4-2 Extract from survey plan showing erosion of the Anawe dump at the south boundary adjacent to Paiam Slopes and the north boundary between the Anawe Stable Dump and the toe 92

120 Anjolek Erodible Dump Anjolek has received minimal amounts of waste in recent years and continues to be in a phase of erosion, with the majority of the material loss occurring from the toe of the dump, while the head and the body of the dump remaining largely static. Much of the dump is covered with vegetation, and the creeks and drainage paths are deeply-incised into the dump surface, shown in Figure The Kaiya River continues to maintain a course through the centre of the dump tract where it is confined by high banks of waste material. The Kaiya alluvial fan shown in Figure 4-21 is well vegetated and appears stable indicating that there has been little recent mass movement in this area. There also appears to have been little recent morphologic change in the lower tract, including the slopes adjacent to Timorope, Apalaka and Lepalama. The toe of the dump continues to erode, but the morphology of the toe and the immediate downstream reaches of the Kaiya River appear relatively unchanged. The upper tract of the dump between the tiphead and the Kaiya River confluence is an erosional surface, characterised by deep gullies. Survey data indicated that while the Anjolek Dump volume reduced between 21 and 213, there was a minor (.5%) increase of 176, m 3 between 213 and 214, shown in Figure Despite the overall reduction of volume, the surface area has increased by 4% (11 ha) since 21, but the increase has only been 1 ha since 211. For surface area to increase while overall volume is decreasing it appears that the dump may have widened in certain locations. A close inspection of the survey plans shows apparent erosion of the valley walls in the Lepalama and Nikelama areas, shown in Figure In March 213 the toe reached it most downstream location. Since then there has been a steady retreat of about 8 m to its current position. Figure 4-21 Kaiya Alluvial Fan well-vegetated and stable 93

121 Figure 4-22 Central Tract of Anjolek showing a dissected and relatively stable landform Figure 4-23 Extract from survey plan showing toe location and changes to the northern boundary adjacent to Nikelama and Lepalama 94

122 Annual (Mt) Cumulative (Mt) Discharge Volume (Mm3) Cumulative (Mm3) 4.7 Tailings Disposal Riverine Tailings Disposal The monthly and cumulative volumes of tailings discharged in 214 are shown in Figure 4-24 and are compliant with the environmental permit discharge limits. The yearly and cumulative tonnages discharged over the life of the mine are shown in Figure 4-25, and the discharge in 214 was consistent with recent years. Tailings Discharge to Anawe Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Monthly Cuml Discharge (RHS) Permit Limit (RHS) Figure 4-24 Monthly discharge of tailings in 214 (m3) Tailings Discharge Annual Cumulative (RHS) Figure 4-25 Annual and cumulative tailings discharge (dry solids) ( ) 95

123 Volume to Paste Monthly (%) Volume to Paste Cumulative (m3) Tailings used as Underground Mine Backfill The paste plant operated consistently throughout 214. The monthly and cumulative volumes diverted to the underground mine are shown in Figure A total of 252,329 m 3 of the coarse fraction of tailings were diverted to paste in 214, which is approximately 8.2% of the total tailings produced. The volume of tailings diverted in 214 was the highest in the sites history and is attributed to the increased availability of the paste plant through improvements in the maintenance system. 3, Tailings to Paste (monthly average = 8.2%) 6,, 25, 2, 15, 1, 5, Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 5,, 4,, 3,, 2,, 1,, Monthly % tails to paste Cumulative Vol (RHS) Monthly target % tails to paste Permit Limit Vol (RHS) Figure 4-26 Tailings diverted monthly to underground backfill in Tailings Quality Contaminants of concern within the tailings discharge are cyanide (CN), total suspended solids (TSS) and metals. The quality of the discharge is influenced by the rate of tailings production, geochemistry of the ore being processed, the gold extraction process and the operational effectiveness of the tailings treatment circuit. Tailings treatment is managed to ensure compliance with internal sitedeveloped requirements at the discharge point, permit requirements at the SG3 compliance monitoring station, and to mitigate the risk of environmental impact within the receiving environment downstream from the point of discharge. The rate of discharge and the slurry density, which influence TSS concentration of the tailings, have remained relatively consistent throughout the history of the operation. Discharge volumes and TSS concentration in 214 were consistent with historical levels. Cyanide concentrations within the tailings discharge are dictated by the effectiveness of the tailings treatment circuit. Cyanide concentrations in the discharge during 214 were lower than historical levels and exhibited less variability, achieving 1% compliance with the internal site-developed end of pipe criterion. The performance achieved during 214 has continued the trend of low CN concentrations demonstrated since the commissioning of the CN destruction plant in 29. The improved consistency achieved in 213 and 214 is attributable to the implementation of greater process control in the form of a Trigger Action Response Plan (TARP) for managing the operation of the treatment circuit. 96

124 The ph of the tailings discharge is dictated by the geochemistry of the ore, the gold extraction process and by the addition of lime during the tailings treatment stage. Controlling ph is critical for limiting the concentration of dissolved metals in the discharge. A range of metals within the discharge have the potential to impact the downstream environment if the treatment process is not managed appropriately. The metals are found naturally within the ore body and pass through the process plant with the tailings. Tailings discharge ph is managed primarily through the addition of hydrated lime during the tailings treatment stage to achieve the internal site-developed ph discharge target. The ph target for discharge has varied throughout the history of the operation, however after reviewing historical data and expert advice the criteria established in 212 are set between ph 6.3 and ph 7. to optimize the precipitation of dissolved metals. Discharge during 214 achieved 1% compliance with the internal site-developed end of pipe criteria for ph. Similar to management of CN in the discharge, the consistency achieved in 213 and 214 is attributable to the implementation of greater process control in the form of a TARP for managing operation of the treatment circuit. The median concentrations of metals in tailings water and solids are shown in Table 4-4 and Table 4-5 respectively. The concentrations of dissolved arsenic, silver, chromium, mercury, lead and selenium in 214 were low and equal or close to the analytical limit of reporting, which is consistent with recent years. The concentrations of TSS, dissolved cadmium, copper, nickel and zinc are significantly greater than the upper river reference values. The concentrations of total digest (TD) silver, arsenic, lead and zinc in tailings solids are significantly greater than the upper river reference values. The concentrations of dissolved silver, arsenic, chromium, copper, iron, mercury, nickel and lead have either significantly decreased or remained unchanged over the history of the operation. The concentrations of dissolved cadmium and zinc have increased significantly over the history of the operation. The increasing trend for dissolved cadmium concentration is in contrast to a reduction in total cadmium concentrations over the same period, and does not correlate well with tailings discharge ph. This result will be the subject of further investigation. Concentrations of total silver, arsenic, cadmium, copper, iron, mercury, nickel, lead and zinc in 214 were consistent with or less than those during recent years and all have significantly decreased throughout the history of the operation. Concentrations of total chromium have increased over the history of the operation. The concentrations of contaminants of concern within the tailings are shown in Figure 4-27 to Figure 4-54 for 214 and throughout the history of the operation. Long-term trends throughout the history of the operation are shown in Table 4-6. The details of the statistical analysis are shown in Appendix C. Table Median dissolved metal concentrations in tailings discharge 214 (µg/l) Site ph* TSS # Ag- D As- D Cd- D Cr- D Cu- D Fe- D Hg-D Ni-D Pb- D Se- D Zn-D Tailings , , , * = Standard ph units; # = mg/l Table 4-5 Median total digest metal concentrations in tailings solids 214 (mg/kg) Site n Ag- TD As- TD Cd- TD Cr- TD Cu- TD Hg- TD Ni- TD Pb- TD Se- TD Zn- TD Tailings ^ 19 97

125 Barrick Porgera Annual Environment Report ph (standard units) January High TARP (ph 7.) Low TARP (ph 6.3) February March April May Trigger Value TARP - Trigger Action Response Plan June July MONTHS August September October November December Figure 4-27 Monthly ph in tailings discharge in 214 Figure 4-28 Annual ph in tailings discharge ph (standard units) Low TARP (ph 6.3) Trigger Value High TARP (ph 7.) TARP - Trigger Action Response Plan 25 YEARS TSS (%w/v) January February March April May June MONTHS July August September October November December Figure 4-29 Monthly TSS in tailings discharge in 214 (mg/l) TSS (%w/v) YEARS Figure 4-3 Annual TSS in tailings discharge (mg/l) 98

126 WAD-CN (mg/l) High TARP (.5mg/L) January February March April May Trigger Value TARP - Trigger Action Response Plan June July MONTHS August September October November December Figure 4-31 Monthly WAD-CN concentration in tailings discharge in 214 (mg/l) Figure 4-32 Annual WAD CN concentration in tailings discharge (mg/l) WAD-CN (mg/l) High TARP (.5mg/L) Trigger Value TARP - Trigger Action Response Plan YEARS.25 Dissolved silver (Ag) 2.5 Total silver (Ag).5 Dissolved silver (Ag) 3.5 Total silver (Ag) Ag (mg/l) Ag (mg/l) January February March April May June July August September October November December 1..5 MONTHS January February March April May June Jul y August September October November December Figure 4-33 Monthly dissolved and total silver concentrations in tailings 214 (mg/l) YEARS Figure 4-34 Annual dissolved and total silver concentrations in tailings (mg/l) 99

127 .44 Dissolved arsenic (As) 7 Total arsenic (As).2 Dissolved arsenic (As) 2 Total arsenic (As) As (mg/l) As (mg/l) January February March April May June July August September October November December 2 1 MONTHS January February March April May June July August September October November December Figure 4-35 Monthly dissolved and total arsenic concentrations in tailings 214 (mg/l) YEARS Figure 4-36 Annual dissolved and total arsenic concentrations in tailings (mg/l).3 Dissolved cadmium (Cd) Total cadmium (Cd).4 Dissolved cadmium (Cd) Total cadmium (Cd) Cd (mg/l) January February March April May June July August September October November December MONTHS January February March April May June July August September October November December Figure 4-37 Monthly dissolved and total cadmium concentrations in tailings 214 (mg/l) Cd (mg/l) YEARS Figure 4-38 Annual dissolved and total cadmium concentrations in tailings (mg/l) 1

128 Cr (mg/l) January February March Dissolved chromium (Cr) April May June July August September October November December MONTHS January February Total chromium (Cr) March April May June July August September October November December Figure 4-39 Monthly dissolved and total chromium concentrations in tailings 214 (mg/l) Cr (mg/l) Dissolved chromium (Cr) YEARS Total chromium (Cr) Figure 4-4 Annual dissolved and total chromium concentrations in tailings (mg/l).5 Dissolved copper (Cu) Total copper (Cu) 1 Dissolved copper (Cu) 5 Total copper (Cu) Cu (mg/l) Cu (mg/l) January February March April May June July August September October November December 1 MONTHS January February March April May June July August September October November December Figure 4-41 Monthly dissolved and total copper concentrations in tailings 214 (mg/l) YEARS Figure 4-42 Annual dissolved and total copper concentrations in tailings (mg/l) 11

129 Fe (mg/l) January February March Dissolved iron (Fe) April May June Jul y August September October November December MONTHS January February Total iron (Fe) March April May June July August September October November December Figure 4-43 Monthly dissolved and total iron concentrations in tailings 214 (mg/l) Fe (mg/l) Dissolved iron (Fe) YEARS 1994 Total iron (Fe) Figure 4-44 Annual dissolved and total iron concentrations in tailings (mg/l).14 Dissolved mercury (Hg).4 Total mercury (Hg).25 Dissolved mercury (Hg) 1.4 Total mercury (Hg) Hg (mg/l) January February March April May June July August September October November December MONTHS January February March April May June July August September October November December Figure 4-45 Monthly dissolved and total mercury concentrations in tailings 214 (mg/l) Hg (mg/l) YEARS Figure 4-46 Annual dissolved and total mercury concentrations in tailings (mg/l) 12

130 2.5 Dissolved nickel (Ni) 12 Total nickel (Ni) 5 Dissolved nickel (Ni) 25 Total nickel (Ni) Ni (mg/l) January February March April May June July August September October November December MONTHS January February March April May June July August September October November December Figure 4-47 Monthly dissolved and total nickel concentrations in tailings 214 (mg/l) Ni (mg/l) YEARS Figure 4-48 Annual dissolved and total nickel concentrations in tailings (mg/l).5 Dissolved lead (Pb) 3 Total lead (Pb).14 Dissolved lead (Pb) 3 Total lead (Pb) Pb (mg/l) January February March April May June July August September October November December MONTHS January February March April May June July August September October November December Figure 4-49 Monthly dissolved and total lead concentrations in tailings 214 (mg/l) Pb (mg/l) YEARS Figure 4-5 Annual dissolved and total lead concentrations in tailings (mg/l) 13

131 .8 Dissolved selenium (Se).55 Total selenium (Se).2 Dissolved selenium (Se) 6 Total selenium (Se) Se (mg/l) January February March April May June July August September October November December MONTHS January February March April May June July August September October November December Figure 4-51 Monthly dissolved and total selenium concentration in tailings 214 (mg/l) Se (mg/l) YEARS Figure 4-52 Annual dissolved and total selenium concentrations in tailings discharge (mg/l) Zn (mg/l) January February March Dissolved zinc (Zn) April May June July August September October November December MONTHS Total zinc (Zn) January February March April May June July August September October November December Figure 4-53 Monthly dissolved and total zinc concentrations in tailings 214 (mg/l) Zn (mg/l) Dissolved zinc (Zn) YEARS Total zinc (Zn) Figure 4-54 Annual dissolved and total zinc concentrations in tailings (mg/l) 14

132 Barrick Porgera Annual Environment Report 214 Table 4-6 Tailings discharge quality trends Indicator Spearman s rho P-Value (P=.5) Trend ph No change over time TSS Decreasing over time WAD-CN Decreasing over time Dissolved silver (Ag-D) Decreasing over time Total silver (Ag) Decreasing over time Dissolved arsenic (As-D) Decreasing over time Total arsenic (As) Decreasing over time Dissolved cadmium (Cd-D).67.1 Increasing over time Total cadmium (Cd) Decreasing over time Dissolved chromium (Cr-D) Stable over time Total chromium (Cr) Increasing over time Dissolved copper (Cu-D) Stable over time Total copper (Cu) Stable over time Dissolved iron (Fe-D) Decreasing over time Total iron (Fe) Decreasing over time Dissolved mercury (Hg-D) Decreasing over time Total mercury (Hg) Decreasing over time Dissolved nickel (Ni-D) Decreasing over time Total nickel (Ni) Decreasing over time Dissolved lead (Pb-D) Stable over time Total lead (Pb) Stable over time Dissolved zinc (Zn-D) Increasing over time Total zinc (Zn) Decreasing over time 4.9 Sediment Contributions to the River System The quantity of incompetent waste rock placed in the erodible dumps over the period of mine operation and the quantity of tailings produced by the mine are summarised in Table 4-7. Figure 4-55 presents the yearly and cumulative quantity of incompetent waste rock and tailings produced by the mine. It should be noted that these figures do not reflect sediment contribution to the river system as the majority of the incompetent waste rock is stored in the erodible dumps and is eroded gradually into the river system. Table 4-7 Summary of incompetent waste rock and tailings disposal tonnages in 214 and Waste Disposal Total for 214 (Mt) Total (Mt) Anawe Erodible Dump Anjolek Erodible Dump Tailings Discharge TOTAL

133 Annual (Mt) Cumulative (Mt) Production of Tailings and Incompetent Waste Rock , Incompetent Waste Rock Tailings Cumulative Total (RHS) Figure 4-55 Production of incompetent rock and tailings In order to estimate the discharge of silt, sand and gravel from the erodible dumps into the downstream environment, it is necessary to estimate the particle size distribution for material at the toe of the dumps. A summary of the various estimates of particle size distribution for the combined Anawe and Anjolek dump toes is presented in Table 4-8 which also shows the adopted size distribution used for the purposes of sediment transport calculations. It was assumed that 5% of all tailings discharged are trapped and stored in the dump and that, of the tailings leaving the dump, a further 5% is lost to long term storage (bed, bars and overbank) between the dump toe and SG3. Table 4-8 also shows the adopted size distribution used for the purposes of sediment discharge calculations. Table 4-8 Estimates of particle size distribution of material sampled at erodible dump toe Reference Silt (%) Sand (%) Gravel (%) 1. CSIRO review PJV 1995 samples (average) Anawe toe 1997 samples (average) Black Sed. Accelerated Weathering Tests Davies et al Median (1, 2, 4 and 5) Long-term survey data (since 22) and mass-balance calculations for the dumps indicate that approximately 5-6% of material input has been lost downstream as a long-term average (these figures do not account for valley wall erosion), although Davies et al. (22) suggested that this figure was about 2-3%. More recent survey data indicate that the amount of material exported downstream since 21 expressed as a percentage of the amount of material dumped was higher at approximately 8% for Anawe and 29% for Anjolek. This partly reflects the lower rates of dumping in recent years whilst there has been consistent erosion of material from the dumps by river flows. The data also indicate that there has been a net reduction in dump volume for Anjolek as erosion exceeds 16

134 the low rates of dump input. These results are consistent with observations which suggest that the morphology of Anawe is relatively unchanged while Anjolek appears to be eroding. The estimates of dump sediment loss are summarised in Table 4-9, which also shows that the estimated tonnage of sediment that is mobilized from the erodible dumps and is transported downstream is 9.2 Mt/y (based on survey data since 21). This appears a reasonable estimate as the estimated suspended load at SG1 (based on historic measured flow and TSS data) works out to be approximately 1 Mt/y. Table 4-9 Summary of long-term dump mass balance from survey data Dump Proportion of total dumped material released based on long term survey data since 22 (%) Median downstream transport rate since 22 (Mt/y) (Total mass exported downstream from survey data divided by number of years between survey) Downstream transport rate since 21 (Mt/y) and percentage of dumped material released (%) Anjolek [29%] Anawe [8%] Total NA Based on the figures above, Table 4-1 presents estimates of suspended sediment discharge from the SML for both tailings and waste rock. It should be noted that a level of inherent uncertainty exists within the survey data on a year to year basis due to the large area of the dump, difficult terrain in which the survey is conducted and changes to survey equipment and personnel from year to year. Therefore to account for this uncertainty the sediment discharge rate from the erodible dumps is based on the average volume change recorded since 21. Table 4-1 Estimate of sediment discharge from erodible dumps and tailings during 214 Source Total Sediment Discharged from Dumps (Mt/y) Suspended Sediment Component (Mt/y) Comments Erodible Dumps Assumes 59% (silt fraction) travels as suspended load Tailings 5.1 (5.4 x.95) 4.9 (5.1 x.95) Assumes 95% of tailings is transported to the river system and 5% remains stored in Anawe dump TOTAL Other Discharges to Water Treated Sewage Effluent The total volume of treated sewage effluent discharged from the 5 treatment plants that service the mine site and accommodation camps is shown in Figure The volumes discharged were within the environment permit limits, except for Tawisakale STP. Barrick is proposing to amend the environmental permit to increase the permitted discharge volume from Tawisakale STP. 17

135 TSS (mg/l) Volume (m3) 12, Sewage Effluent Discharge 214 1, 8, 6, 4, 2, Alipis STP Suyan STP Plant Site STP Yoko STP Tawisakale STP Discharge Volume Permit Limit Figure 4-56 Total annual discharge volumes of treated sewage 214 Figure 4-57 to Figure 4-59 show the monitoring results for TSS, BOD 5 and faecal coliforms, respectively from the STPs. Operation of the sewage treatment plants did not consistently achieve compliance with the TSS criterion of 3 mg/l throughout the year. All plants were effective for achieving compliance with the BOD 5 criterion and chlorination of the treated effluent was effective for achieving compliance with the faecal coliform criterion throughout the year. Barrick has developed SOPs for each of the treatment plants and in September 214 improved the competence of the operators through training. At the same time, higher level supervision and leadership were improved, which resulted in more consistent operational performance of the treatment plants in the fourth quarter of the year. Barrick also has completed a specialist wastewater treatment audit of the operation of the sewage treatment plants and is implementing a project to upgrade the Alipis treatment plant, which was recommended by the audit report. TSS in Sewage Effluent Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Tawisakale Alipis Suyan Yoko Plant Site Limit Figure 4-57 Average monthly TSS concentration in treated sewage discharge

136 Faecal coliforms (CFUs/1mL) BOD5 (mg/l) 12 BOD 5 of Sewage Effluent Tawisakale Alipis Suyan Yoko Plant Site Limit Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Figure 4-58 Average monthly BOD 5 concentration in treated sewage discharge Faecal Coliforms in Sewage Effluent Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Tawisakale Alipis Suyan Yoko Plant Site Permit Limit Figure 4-59 Average monthly faecal coliform count in treated sewage discharge Oil/Water Separator Effluent The mine operates 19 oil-water separators at maintenance workshops and fuel storage and refuelling installations. Figure 4-6 shows the average monthly monitoring results for the discharge of total hydrocarbons from the oil-water separators to local streams, compared with the internal sitedeveloped target of 3 mg/l. Hydrocarbons were detected in contact water sampled at the mine site boundary in April, May and December. 19

137 Total Hydrocarbons (mg/l) Oil Water Separator Discharge Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Site Boundary Average OWS Discharge Site Target Figure 4-6 Average monthly total hydrocarbon concentrations in oil water separator discharges Mine Contact Runoff Mine contact runoff is rainfall runoff from land disturbed by the mining operation and therefore has the potential to contribute contaminants to the receiving environment. The volume and quality of mine contact runoff are described in the following sections Runoff Volumes Table 4-11 shows the estimated volume of contact runoff from land disturbed by mining. It is impractical to measure runoff volumes and these have been estimated from rainfall and catchment areas. Table 4-11 Estimated volumes of contact runoff from mine lease areas 214 Location Total Rainfall run off 214 (Mm 3 ) Permit Limit (million m 3 /y) Starter Dump A (DP3) Wastewater from civil crusher to Kogai Creek (DP4).2.57 Kogai Waste Dump to Kogai Creek (DP5) , Open Pit and UG Mine via drainage tunnel into Kogai Creek (DP6) Anawe stable dump to Wendoko Creek (DP7) Rainfall runoff from Hides to a tributary of the Tagari River (DP16) <.1.9 TOTAL

138 Contact Runoff Quality This section presents the results of water quality monitoring from creeks within the mine lease area that are potentially contaminated by drainage from the mining operation, also known as mine contact runoff. The monitoring sites and length of record are shown Table The locations of local sampling sites are presented in Figure Table 4-12 Mine contact runoff monitoring sites Site Type Site Name Contact Runoff 28 Level (underground water discharge at adit) ( ) Anjolek starter dump A (SDA) toe ( ) Kaiya River at Yuyan Bridge ( ) Kaiya River downstream of Anjolek erodible dump ( ) Kogai Culvert (24 214) Kogai stable dump toe area ( ) Lime Plant discharge ( ) Wendoko Creek downstream of Anawe North stable dump (2 214) Yakatabari Creek downstream of 28 Level discharge ( ) Yunarilama at portal for drainage tunnel (21 212, 214)* * Yunarilama Portal was not sampled during 213 because of security issues The box plots show that the quality of mine contact runoff in 214 was within the range of results sampled over the past 2 years of mine operation, the median 214 concentrations are shown in Table Water quality is generally related to the catchment characteristics, with drainage from the waste rock dumps (Kogai Toe and Wendoko), the open pit and the underground mine (Yakatabari and Yunarilama) typical of neutral metalliferous mine drainage and exhibiting elevated concentrations of sulfate, TSS, cadmium, copper and zinc compared to undisturbed catchments. In addition to drainage from Anawe North competent waste rock dump, Wendoko Creek also receives tailings discharged from the mine. Discharge from the lime plant exhibits elevated ph and chromium. Details of the statistical analysis are presented in Appendix C. Long-term trends are summarised in Table 4-14 and the details of the long-term trend analysis are also shown Appendix C. 111

139 Table 4-13 Contact Water Quality- 214 median values (µg/l) Site ph* TSS # Ag- D As- D Cd- D Cr- D Cu- D Fe- D Hg-D Ni- D Pb- D Se- D Zn- D 28 Level Anjolek SDA Kaiya River at Yuyan Bridge Kaiya River d/s Anjolek erodible Kogai Culvert , , Kogai stable dump toe Lime Plant discharge Wendoko Creek d/s Anawe Nth Yakatabari Creek d/s 28 Lvl portal , , * = Standard ph units; # = mg/l; = µg/l 112

140 Figure 4-61 Mine area runoff sampling locations 113

141 Barrick Porgera Annual Environment Report 214 Table 4-14 Summary of water quality trends in mine area runoff (as tested using Spearman Rank Correlation) SITE ph Sulfate ALK - T TSS SDA Toe Kaiya D/S Anjolek Yuyan 28 Level Yakatabari Yunarilama Wendoko Kogai Toe Culvert Stn Lime plant D = Dissolved T = Total Decreasing or no change over time Ag As Cd Cr Cu Fe Hg Ni Pb Se Zn D T D T D T D T D T D T D T D T D T D T D T Increasing over time 114

142 Barrick Porgera Annual Environment Report Point Source Emissions to Air Barrick Porgera carried out monitoring of concentrations of metals in the emissions from stationary sources at the mine site, the Lime Plant and at Hides Power Station. Papua New Guinea does not have legislation for controlling emissions to air and Barrick Porgera has voluntarily set a target of complying with the relevant Australian Standards, which are the NSW Protection of the Environment Operations (Clean Air) Regulation 21 and the Victoria State Environment Protection Policy (Air Quality Management) 21. Stack emission sampling is carried out two-yearly and was not conducted in 214, but is scheduled in 215. Data from 213 sampling are presented in Table 4-15 and compared with the relevant Australian emission criteria. Table 4-15 Point source emission metal concentrations 213 (mg/m 3 ) Source As Cd Hg Pb Anawe Autoclaves Hides Gas Turbine Anawe Diesel Generator Assay Laboratory Kiln Carbon Regeneration Cyanide Destruction Lime Kiln No Primary Crusher Criterion No Criterion 3.* 3.* 1.** * NSW Protection of the Environment Operations (Clean Air) Regulation 21 ** Victoria State Environment Protection Policy (Air Quality Management) 21 Compliant Non-Compliant In late 214, a new scrubber was installed on the carbon regeneration kiln and emission testing of all stacks is planned to be carried out in 215. Barrick Porgera operates four autoclaves for oxidation of the sulfides present in the ore. The discharge of oxidized ore slurry from the autoclaves is quenched using water and wet scrubbers are used to prevent the potential carry-over of sulfuric acid mist. Porgera monitors sulfuric acid mist concentrations from the four autoclaves on a monthly basis, following SOPs for sampling and analysis. The results were compared with the NSW Protection of the Environment Operations (Clean Air) Regulation 21 standard of.1 g/m 3 sulfuric acid mist (as sulfur trioxide SO 3 ) for non-sulfuric acid producing plants. The stacks were sampled during the year and average concentrations for sulfuric acid mist emissions from the four autoclaves are summarised in Table The stack emissions were within the relevant Australian standard during each of the months sampled in 214. Table 4-16 Mean monthly sulfuric acid mist (as SO 3 ) emissions from the autoclaves (g/m 3 ) Stack No N Mean Median Stdev Min Max NA Criterion.1.1 NA NA.1 NA Not Applicable Compliant Non-Compliant 115

143 4.12 Closure Planning and Reclamation Mine Closure Plan In 214 Porgera mine revised the draft Mine Closure Plan in line with the Barrick Closure Standard and Guidelines. This plan was based on the content from previous draft closure plans produced for the project in 27 and 211 and highlights closure considerations for the mine infrastructure, including safety and environmental aspects during the closure process. The plan also includes estimates of closure costs Life of Mine The Life of Mine (LOM) for Porgera mine was reviewed and revised in 214, following the revision of the geological model reserves. Ore production and processing are expected to cease in 225. The closure period will begin in 226 with decommissioning and dismantling of plant and infrastructure which is expected to take approximately three years. The establishment of a stable vegetation cover across the plant site and related infrastructure will take approximately two years while the post closure period including monitoring and maintenance will be eight years, inclusive of the time required for revegetation Mine Closure Vision and Objectives Porgera s vision for mine closure is leaving behind a better future. This vision will be achieved through Porgera s specific objectives for mine closure: Fully integrate mine closure planning with operational mine planning during the life of the project ensuring orderly, cost-effective and timely mine completion. Ensure the safety and health of workers during site closure activities (decommissioning and rehabilitation). Retain transport facilities considered of value to the local community in an operational condition for transfer to local and regional authorities. Ongoing maintenance and liability for such structures will be passed to the local authority. Monitor rehabilitation performance during all phases of the project and implement appropriate actions where observed trends do not reflect agreed closure criteria. Ensure that adequate financial provision is made to cover all agreed closure commitments until such time as final lease relinquishment. Comply with mine closure permitting and regulatory requirements and at all times obtain documented confirmation of compliance Key Closure Environmental and Social Issues Some of the key environmental issues identified affecting closure include waste rock dump stability, water quality and final void management, while social considerations at mine closure include loss of employment, livelihood, artisanal mining and facilities and social services. These issues and the associated risks will be looked at closely and measures highlighted in the plan will be implemented to mitigate closure liability Mine Closure Consultation and Stakeholder Identification The mine closure and stakeholder consultation will be critical in ensuring a safe and successful exit from the operation. Stakeholders views and expectations will be discussed during the consultation process to achieve balanced, realistic and achievable outcomes during closure. 116

144 Porgera closure stakeholders will include those listed in the closure plan. Key people will be nominated by respective stakeholder groups to represent the closure committee group. The closure committee group s primary role will be to identify issues of concern, look at ways to address those issues and to monitor their projected outcomes during the closure process Progressive Closure and Reclamation Since the start of mining at Porgera, the majority of the areas of land disturbance are still being actively used for mining operations, which has limited the land available for reclamation and revegetation. The total area reclaimed to date is approximately hectares and most of this area is on the Kogai competent waste rock dump, where the use for mining purposes was completed in 23. The area was reclaimed by placement of a soil cover of brown mudstone and colluvium, and then revegetated. The soil cover was stabilized to protect it from erosion by planting with a range of grasses and legumes. Following the establishment of the groundcover of grasses and legumes, local lower montane tree species were planted. Very limited areas of disturbed land became available for reclamation in 214 as mining and related activities were still progressing. The revegetation activities for the year included planting the reclaimed area with a grass and legume seed mix to stabilize soil as the first phase of vegetation establishment. The hydroseeder was used to seed failed areas within the open pit mining area during the year. As with previous years, planting of tree seedlings in 214 has been restricted to within the security fence to avoid seedlings being damaged by illegal miners trespassing through the area. A total of 1678 lower montane tree seedlings were planted on the Kogai dump at K62 and K65. Tree seedlings were purchased from local suppliers and raised at the nursery for hardening before transplanting. The numbers and species planted are shown in Table Table 4-17 Species of tree seedlings planted in 214 Scientific Name Local Name Total Number Planted Casurina oligodon Yarr 48 Podocarpus Neriifolius Kaipu 7 Daphniphllum sp Parap 2 Daphniphllum sp Yongena 2 Mixed softwoods - 16 Saurauia alitterra Royen Lank 4 Saurauia conferta Ward Malangera 2 Acalypha villosa Souk 5 Perrotteia aipestris Blume Emblome 7 Quintinia altigena Schltr Leok 1 TOTAL

145 4.13 Non-mineralised Waste Non-mineralised waste is all waste produced by the operation other than waste rock and tailings. Porgera has developed a Waste Management Plan that describes the methods for waste segregation, reuse, recycling or treatment for safe disposal. Figure 4-62 shows the proportion of each type of waste produced at the mine site. Waste oil made up 26% of the non-mineralised waste in 213, 1% of which is re-used as fuel for heating the lime kiln. Sewage Treatment Plant sludge is disposed by land application at a reclaimed area of Kogai Waste Rock Dump. Scrap paper is shredded and used as mulch for hydroseeding in land reclamation. Scrap steel and other metals are stored for sale to a recycling contractor. Combustible wastes are disposed by incineration at 11 o C and remaining materials are disposed to a landfill. Waste Volume by Category Raw Effluent Food Waste Oil Misc Plastic & PVC Cardboard Paper STP Sludge Pallets Oily Rags & Filters Cement Bags Incineration Ash Medical Waste 1ltr Pods Conveyors & Rubber Pipe Light Steel Plastic Drum (2ltr & 2ltr) Electronics Elec & Fibre Black Jack Optic Cables Waste Production Lead Acid Batteries Assay Figure 4-62 Non-mineralised waste production by type 118

146 5 COMPLIANCE This Section provides a summary of the operations compliance with environmental legal requirements. Table 5-1 is a summary of compliance with the operations environmental permit conditions, Table 5-2 outlines corrective actions being applied to non-compliance issues and Table 5-3 is a summary of water quality results at the SG3 compliance point and other monitoring stations between the discharge point and SG3. It should be noted that SG3 is the only compliance point and the results from other monitoring stations are reported for information purposes only. Table 5-1 Compliance Summary Permit % Compliance Comments Waste Discharge Permit WD L3 (121) 94% Non-compliant with three (3) of 48 conditions (6, 8, and 35) One (1) condition relates to bunding of fuel storage tanks in accordance with AS194. Two (2) Conditions relate to operation and maintenance of the sewage treatment plants to achieve the required discharge quality. Total suspended solids concentrations exceeded the discharge criteria on a number of occasions throughout 214. Water Extraction Permit 1% Compliant with all eight (8) conditions. WE L3 (91) TOTAL 94% Target is 1% compliance Table 5-2 Summary table Corrective Actions Non-Compliance Hydrocarbon Management Corrective Actions Completing upgrades of a number of bunds to comply with AS194 Implemented corrective and preventative action plan procedure in response to non-compliant results. Continue workplace inspection schedule to improve work and condition. Sewage Discharge Quality Elevated TSS Provided specialist training to sewage treatment plant supervisors and operators. Improved supervision and focus on compliance with standard operating procedures. Improved quality of investigations and corrective and preventative action plans in response to non-compliant results. 119

147 Table 5-3 Compliance Assessment at SG3 and Water Quality at Upper River Test Sites 214 (dissolved µg/l) Site Parameter n ph* Ag As Cd Cr Cu Ni Pb Zn SG1 Median SG2 Median Wasiba Median Wankipe Median SG3 Median CEPA SG3 Permit Criteria *Standard ph units Note: There are no permit criteria for mercury (Hg) and selenium (Se) Compliant Non-compliant 12

148 6 ENVIRONMENTAL RISK, PERFORMANCE AND IMPACT ASSESSMENT 6.1 Land Disturbance The total area of disturbed land in 214 for the mine infrastructure and related areas including the erodible dumps was hectares. Table 6-1 presents the areas of disturbed land for the open pit mining operations, the waste rock dumps and limestone quarry, which are the active areas of the operation. The total area of disturbance increased by 15.7 ha during 214, 3.4 ha was due to expansion of the erodible dumps, 1 ha due to expansion of the Kogai diversion drain,.6 ha was due to expansion at Anawe competent dump,.6 ha was due to mining expansion at Open pit and 1.1 ha due to expansion of the Pangalita limestone quarry, all areas remained within the SML and LMP boundaries. The area of disturbance is measured using standard survey techniques and LiDAR survey, which uses a combination of laser imaging and radar to measure distance. Note that the areas of disturbance for previous years have increased from those reported in the 213 AER due to a review of the survey methodology and data. Table 6-1 Land disturbance footprints from 21 to 214 (ha) Impact Sites Dec 21 Dec 211 Dec 212 Dec 213 Dec 214 Anjolek Erodible Dump Anawe Erodible Dump Anawe Stable Dump Kogai Waste Rock Dump Pangalita Limestone Quarry Open Pit Development Area TOTAL AREA Hydrology and Environmental Flows Waile Creek Figure 6-1 shows a flow duration curve for Waile Creek Dam in 214, the data are used for estimation of spillway flows to the creek downstream of the extraction point, and are generated from dam water level measurements. Outflows were relatively constant for the reporting period but occasional higher flow peaks occurred. The frequency and duration of zero-flow periods are important in terms of environmental flows and it is likely that zero-flow periods would have occurred in Waile Creek from time to time before construction of the dam, particularly during dry (El Nino) years. During 214, there were 27 zero-flow occurrences (of one or more days) with the longest zero-flow period being 12 days. Water leaks from the base of the dam, but the flow downstream of the dam has not been measured recently or assessed for adequacy as an environmental flow. 121

149 Figure 6-1 Daily flow duration curve (estimated) for Waile Creek Dam outflow Kogai Creek Figure 6-2 shows daily flow duration curves for Kogai Creek upstream (Kogai at SAG Mill) and downstream of the Mill extraction point. Water is extracted at a constant daily rate and the graph shows that water extraction resulted in minimal change to the flow duration curve downstream. Approximately 5 m downstream of the extraction point, Kulapi Creek joins with Kogai Creek. The water extraction results in a reduction of the Kogai flow but did not result in any zero flow events within Kogai Creek. Figure 6-2 Daily flow duration curves for Kogai Creek 122

150 6.3 Sediment Transport and Fate of Sediment Sediment exported from the toe of the dumps and that contributed by the tailings are transported downstream by the river flow. Erodible waste is deposited at the head of the dumps and is gradually eroded into the river system, and it is estimated that approx 5% of the tailings is retained along the Anawe erodible dump. Coarser particles may settle out on the bed, on bars or on the floodplain from time to time along the river valley. Estimating the volumes of sediment that actually reaches the river system each year, and the relative contribution of natural, waste rock and tailings are made using the product of the volumes of waste deposited to the erodible dumps and tailings discharge, the change in volume of the erodible dumps using survey, TSS in water downstream of the mine and river flow rate. This calculation is undertaken for SG3 as a much higher sampling intensity is performed at SG3 for compliance purposes which therefore provides a much larger TSS data set which can be combined with a continuous stream flow record. Only single monthly TSS samples are taken at the other river stations, meaning that reliable suspended sediment load estimates cannot be made for stations other than SG3. It should be noted that the river stage at the time of sampling has a significant effect on the TSS concentration, with higher TSS generally measured during high flows although the relationship between TSS and flow is complex because mine inputs are relatively constant while natural inputs are more variable. Sampling at SG3 is carried out over 4 successive days and the conditions at the time of sampling may not be representative of flows during the whole of the month. Despite this limitation, the data are considered to provide a reasonable estimate of monthly suspended sediment loads for SG3. Monthly mean TSS concentrations at SG3 in 214 are shown in Figure 6-3, 214 monthly TSS loads are shown in Figure 6-4 and historical annual TSS loads are shown in Figure 6-5. The annual suspended sediment load at SG3 is estimated from the TSS and flow records using a statistical analysis to correct the results for discrepancies arising from irregularly sampled record and continuous record of flow. The statistical analysis is contained in a computer program called Gumleaf (Generator for Uncertainty Measures and Load Estimates using Alternative Formulae). The program computes sediment load using 22 different formulae. The program authors are Dr. K. Tan, Professor David Fox (Environmetrics Australia P/L) and Dr. Teri Etchells. Permission for use of Gumleaf was kindly provided by Professor Fox. The median annual suspended sediment load at SG3 for 214 was estimated by Gumleaf to be 31 Mt, this compares to the long term median since 199 of approximately 45 Mt/a, and an annual load in 213 of 116Mt. The 213 AER showed that the elevated load in 213 was due to elevated contribution of natural sediment to the system upstream of SG3 throughout

151 Suspended Sediment Load (Mt) TSS (mg/l) Mean Monthly Flow (Cumecs) Figure 6-3 Mean monthly TSS and flow at SG3 for Figure 6-4 Estimated mean monthly suspended sediment loads for SG3 (Mt) 124

152 Monthly Suspended Sediment Load (Mt/a) TSS (mg/l) Figure 6-5 Estimated monthly suspended sediment load (black bars) with 3-month moving average at SG3 for full record (red solid line) To determine the relative contributions of mine-derived and natural sediment to the total sediment load at SG3, the results of the Gumleaf analysis were compared with estimates of mine-derived inputs, based on the survey analysis and tailings data. Figure 6-6 shows historical average TSS values at river monitoring stations upstream of SG3. All sites, reference and test, showed a reduction in TSS values compared with 214 values, with a minor increase in TSS values for SG1 being the exception, however this is not considered significant in the context of historical variability, meaning that there was a lower contribution of natural TSS to the system compared to SG1 SG2 SG3 1 Wankipe Ok Om* 5 Upper Lagaip* * Reference site Figure 6-6 Historical average TSS

153 Figure 6-7 shows the estimated relative contribution of tailings, waste rock and natural suspended sediment to the total suspended sediment load at SG3 since Figure 6-8 shows the same data set presented in terms of the percentage contribution of tailings, waste rock and natural suspended sediment to the overall suspended sediment load. The analysis shows that the estimated loads contributed by tailings and waste rock in 214 were consistent with historical volumes, and also that the natural sediment load was significantly less than 213 and historical volumes. As a result of consistent mine-derived load and a reduction in natural load, the proportion of total suspended sediment load that was mine-derived during 214 at SG3 was estimated to be approximately 3% which compares to 11% in 213 and is consistent with the long term median value of approximately 23%. By way of comparison, geochemical analyses on sediments conducted as part of the NSF (US National Science Foundation) sponsored Margins Source to Sink Research Program found that, by using silver and lead as tracers, the proportion of mine-derived sediment was 29% for SG3 and 12-13% for SG4 (Swanson et al. 28). 14. Suspended Sediment Load (Million Tonnes) Estimated Natural Suspended Sediment Load Estimated Suspended Load from Waste Rock Estimated Export of Tailings from Anawe Dump Figure 6-7 Suspended sediment budget at SG3 since

154 1% Percentage of Total Suspended Sediment Load 9% 8% 7% 6% 5% 4% 3% 2% 1% % Estimated Suspended Load from Tailings Estimated Natural Suspended Sediment Load Estimated Suspended Load from Waste Rock Figure 6-8 Estimated suspended sediment budget at SG3 expressed as % 6.4 River Profiles Surveying of river profiles (river-bed cross sections) is performed downstream of the mine at designated locations to evaluate changes in bed levels (aggradation or degradation). Unfortunately over the last few years, it has not been possible to undertake surveys at historical sites along the Porgera River (SG1 8km downstream of the mine) due to community access issues. Profiling was performed at the Kaiya River, SG2 and the lower riverine site Profile 1 (PF1) on the Strickland River, the monitoring locations are shown in Figure 2-1. Additionally, following the observation of changes in the Kaiya River below the Anjolek erodible waste dump, three profiles were established in 29. Observations from previous years indicate sediment moves along the Kaiya River in an episodic fashion (pulses) showing alternate phases of degradation and aggradation (cut-and-fill) of around.5 m to 2 m. These phases of cut-and-fill are caused by the interplay of a number of factors including sediment supply from the dump and river flow rates, which reflect rainfall. Figure 6-9, Figure 6-1 and Figure 6-11 illustrate the current situation within the Kaiya Valley, compared with past surveys. The profiles show that the 214 bed levels are relatively low compared to levels recorded since 21. Figure 6-12 presents a time series of the minimum surveyed point at each cross section which is a useful metric of aggradation or degradation trends given the difficulties associated with calculating a representative mean bed elevation. Data for 214 suggest that the Kaiya River between Anjolek Toe and the Porgera River is generally in a phase of erosion, with bed levels trending downwards. This is consistent with the interpretation of observations of Anjolek Dump which also indicate that landform is eroding and that the capacity of river flow to transport sediment currently exceeds supply. 127

155 Cross Section Plots Site Date Name 84634H 17/7/214Profile Kaiya River downstream Kogai Creek (PF9) 84634H 2/7/213Profile Kaiya River downstream Kogai Creek (PF9) 84634H 26/12/212Profile Kaiya River downstream Kogai Creek (PF9) 84634H 24/6/211Profile Kaiya River downstream Kogai Creek (PF9) 84634H 23/11/21Profile Kaiya River downstream Kogai Creek (PF9) 1 8 R L in metres Chainage in metres Figure 6-9 Profile comparison (29 214) at Kaiya River downstream of Kogai Confluence Cross Section Plots Site Date Type Name 84634G 28/11/214Profile Kaiya River upstream Yuyan Bridge (PF8) 84634G 18/12/213Profile Kaiya River upstream Yuyan Bridge (PF8) 84634G 26/12/212Profile Kaiya River upstream Yuyan Bridge (PF8) 84634G 29/12/211Profile Kaiya River upstream Yuyan Bridge (PF8) 84634G 18/6/29Profile Kaiya River upstream Yuyan Bridge (PF8) R L in metres Chainage in metres Figure 6-1 Profile comparison (29 214) for Kaiya River upstream of Yuyan Bridge 128

156 Assumed RL m Cross Section Plots Site Date Name 84634E 27/11/214Profile Kaiya River downstream Yuyan Bridge (PF6) 84634E 14/12/213Profile Kaiya River downstream Yuyan Bridge (PF6) 84634E 25/12/212Profile Kaiya River downstream Yuyan Bridge (PF6) 84634E 24/11/21Profile Kaiya River downstream Yuyan Bridge (PF6) 84634E 19/6/29Profile Kaiya River downstream Yuyan Bridge (PF6) R L in metres Chainage in metres Figure 6-11 Profile comparison (29 214) for Kaiya River downstream of Yuyan Bridge Minimum RL, Kaiya River Profiles Feb-8 Jul-9 Nov-1 Apr-12 Aug-13 Dec-14 May-16 K1 - Kaiya d/s Kogai Jnct K3 - Yuyan Bridge K2 - Kaiya us Yuyan Bridge K4 - Kaiya ds Yuyan Bridge Figure 6-12 Time series of minimum bed elevations along the Kaiya River 129

157 As discussed in previous Annual Reports, the bed of the Porgera River at SG1 aggraded during mine construction and initial disposal of sediment at Anawe between about 1988 and Since then the bed elevation has remained variable but more or less consistent. Although there have been no flow measurements or cross-section surveys along the Porgera River for some time, due to law and order issues preventing access, there is no evidence from qualitative observations alone that significant aggradation or erosion of valley walls is occurring along the Porgera River. Observations from a helicopter flyover in April 215 suggested some bed scour may have occurred in the vicinity of SG1. Figure 6-13 illustrates changes at SG2, approx. 42 river km downstream from the mine site. There is evidence of sediment aggradation since 211, though it is not possible at this stage to isolate this from sediment redistribution and cross section shape variability throughout the cross section that is common in mountain streams. Cross Section Plots Site Date /3/ /8/ /4/ /7/ /1/ R L in metres Chainage in metres Figure 6-13 Profile comparison (21 215) at Lagaip River at SG2 As the river descends to the lowlands (the Fly Platform) from the upland areas, the velocity slows and temporary sediment deposition starts to occur in the form of transient gravel and sand bars. Further downstream, floodplain connections become better established and the bed material becomes predominantly sands and silts. Figure 6-14 illustrates changes at Profile 1, approx. 4 km downstream from Tomu/Strickland confluence, and approx. 4 km from the mine. There is no discernible change or evidence of sediment aggradation aside from the isolated spatial redistribution throughout the cross section that is indicative of natural behaviour in a meandering lowland river. The right bank of the channel has been eroded progressively over the 13 years, resulting in widening of the channel by approximately 3 m, which is attributed to natural meandering processes. 13

158 Barrick Porgera - Environment Dept. Cross Section Plots Site Date Type Name 8485A 9/12/214Profile Strickland River at Profile A 16/7/213Profile Strickland River at Profile A 19/11/212Profile Strickland River at Profile A 17/12/211Profile Strickland River at Profile A 1/8/2Profile Strickland River at Profile R L in metres Chainage in metres Figure 6-14 Profile comparison (2 213) at Profile 1 The results of Swanson et al, 28 indicated that there is approximately a 13% long-term loss of total sediment load to the floodplain below this zone (of the order of 1 Mt per year based on estimates of sediment load in this zone). 6.5 Local Water Supplies Sampling and Analysis Participatory sampling of local village water supplies was carried out at four Special Mining Lease Villages (Yarik, Apalaka, Panadaka and Kulapi) in June 214 to assess suitability of water for domestic use. The sampling was arranged in consultation with the Porgera Land Owners Association (PLOA), who participated in the sampling of the water supplies. Samples were collected from drinking water sites which included tanks, a drum and two springs, as well as at creeks that are commonly used by local villagers for laundry, bathing, panning for gold or other recreational activities. Sampling at each village was conducted at the same sites as in 213 except for Panadaka Village where samples were collected from new tanks installed by Barrick Porgera. Sampling sites and details are given in Table 6-2 and Figure The samples were prepared at the onsite laboratory and shipped to two independent laboratories to carry out microbiological and trace metals analyses. Samples for microbiological tests for total and faecal coliforms were sent to SGS laboratory in Port Moresby, Papua New Guinea, while samples requiring trace metals tests were sent to National Measurement Institute (NMI) laboratory in Sydney, Australia. Physico-chemical analyses were conducted at the onsite laboratory. 131

159 Table 6-2 Sampling sites for Local Village Water Supplies Sites Name on map Easting Northing Kendo Spring Kendo Spring Apalaka H1 Tank AP_H Apalaka H2 Tank AP_H Yarik H1 Tank YR_H Yarik H2 Tank YR_H Yarik H3 Tank YR_H Yarik School Tank Yarik School Panadaka 1 Jack Inji Tank PA_V1H Panadaka 1 Catholic Church Tank PA_V1H Panadaka 1 Panda Ekepa Tank PA_V1H Panadaka 1 Bus David Yandapa Tank PA_V1H Panadaka 1 John Pokean Tank PA_V1H Panadaka 1 Bilip Aile Tank PA_V1H Panadaka 1 Roselyn Pokean Tank PA_V1H Panadaka 1 Joseph and Rueben Kiala PA_V1H Tank Panadaka 1 Joseph Kiala Tank PA_V1H Panadaka 1 United Church Tank PA_V1H Panadaka 1 Neslon Nai Tank PA_V1H Panadaka 2 Akena Pawa Tank PA_V2H Panadaka 2 Nickson Yambu Tank PA_V2H Panadaka 2 Tomson Kuna Tank PA_V2H Panadaka 2 Timothy Kerene Tank PA_V2H Wendako Spring Wendako Spring Kulapi V1 H1 drum KL_V1H Kulapi V2 H 1 tank KL_V2H Kulapi V4 H1 tank KL_V4H The water quality test results for raw drinking water sites are presented in Table 6-3 and Table 6-4. Two of the supplies, Apalaka H1 Tank and Panadaka 1 Bus David Yandapa Tank showed total coliform contamination, while ph was also non-compliant at Padadaka 1 Bus David Yandapa s Tank. The water quality results for other parameters complied with the PNG Raw Drinking Water Standard at all sites. Dissolved and total metal concentrations were very low in all water supplies, although zinc concentrations were typical of rainwater from galvanized roof catchments (i.e. slightly elevated but still within the standard). Barrick Porgera has implemented a pilot rain water supply project at Panadaka Village to improve the availability and reliability of safe drinking water for local communities. The project has received strong community support and is being expanded to Alipis and Apalaka local SML Villages. 132

160 Figure 6-15 Sampling Sites for Local Village Water Supplies 133