INTERNATIONAL EXPERTS’ REVIEW HYDRIC COMPONENT OF THE ENVIRONMENTAL IMPACT ASSESSMENT CONGA MINING...

7/31/2019 INTERNATIONAL EXPERTS REVIEW HYDRIC COMPONENT OF THE ENVIRONMENTAL IMPACT ASSESSMENT CONGA MI

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INTERNATIONAL EXPERTS REVIEW

HYDRIC COMPONENT OF THE ENVIRONMENTAL IMPACT

ASSESSMENT

CONGA MINING PROJECT

(CAJAMARCA PERU)

Lima, April 17, 2012

This Ruling cannot be reproduced without written consent of the

authors.

Prepared for: Presidencia del Consejo de Ministros Per (Peruvian

Premiers Bureau)

Jointly prepared by: Professor D. Rafael Fernndez Rubio, Mining

Engineering, Emeritus Professor of Hydrogeology. Universidad

Politcnica de Madrid (Spain)

D. Luis Lopez Garca, Road, Canals and Ports Engineer, Hydraulic

Resources Consultant

Professor in Geosciences, D. Jos Martins Carvalho, Professor of

Hydrogeology. Instituto Superior de Engenharia do Porto

(Portugal)


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International Experts Review Ruling. Hydric componentOf the Environmental Impact Assessment for the Conga Mining Project (Cajamarca Peru)

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Source file: Proyecto Conga_Dictamen Pericial

internacional_Componente Hidrico del EIA_17-04-2012.doc

INTERNATIONAL EXPERTS REVIEW

HYDRIC COMPONENT OF THE ENVIRONMENTAL IMPACT

ASSESSMENT

CONGA MINING PROJECT

(CAJAMARCA PERU)

Lima, April 17, 2012

Team:

Professor D. Rafael Fernndez Rubio, Mining Engineering

D. Luis Lopez Garca, Road, Canals and Ports Engineer

Professor in Geosciences, D. Jos Martins Carvalho

(Illegible signature) (Illegible signature) (Illegible signature)

Rafael Fernndez Rubio Luis Lpez Garca Jos Martins Carvalho


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Table of Contents

1. EXECUTIVE SUMMARY AND RECOMMENDATIONS ................................................................................................ 12

1.1 Summary ......................................................................................................................................................................... 12

1.1.1 Surface waters ........................................................................................................................................................ 12

1.1.2 Underground water ................................................................................................................................................. 17

1.1.3 Water quality ........................................................................................................................................................... 18

1.2 Recommendations .......................................................................................................................................................... 22

1.2.1 Infrastructure proposals pending for review .......................................................................................................... 22

1.2.2 Support Committee ................................................................................................................................................ 22

1.2.3 Creation of a Major in the University Mining and Environmental Hydrology Company ................................... 23

2 INTRODUCTION .................................................................................................................................................................... 24

2.1 Experts Review Ruling Framework............................................................................................................................... 24

2.2 Experts Review Ruling Authors .................................................................................................................................... 25

2.3 Location of the Conga Mining Project............................................................................................................................ 30

2.4 Conga Mining Project History ........................................................................................................................................ 32

2.5 Evaluation Procedure of the Environmental Impact Assessment ................................................................................ 34

2.6 International Experts Review ........................................................................................................................................ 36

3. INSTALLATIONS AND INFRASTRUCTURES OF THE CONGA PROJECT .................................................................... 38

3.1. General components ..................................................................................................................................................... 38

3.2. Mining installations and infrastructures ........................................................................................................................ 38

3.2.1 Perol and Chailhuagn pits .................................................................................................................................... 38

3.2.2 Topsoil deposits ...................................................................................................................................................... 40

3.2.3 Perol and Chailhuagn waste dumps .................................................................................................................... 40

3.3 Processing installations .................................................................................................................................................. 44

3.4. Tailings deposit .............................................................................................................................................................. 44

3.5 Auxiliary hydraulic installations ............................................................................................................................. 49

3.6 Water handling and management ......................................................................................................................... 50

3.7 Facilities and infrastructures alternatives analysis ........................................................................................................ 53

3.7.1 Proposal .................................................................................................................................................................. 53

3.7.2 Alternatives valuation ............................................................................................................................................. 53

4. CONGA PROJECT ENVIRONMENTAL IMPACT STUDY .................................................................................................. 56

4.1 Prior observations to the EIA ......................................................................................................................................... 56

4.2 General Framework ........................................................................................................................................................ 57

4.3 Hydroclimatology ............................................................................................................................................................ 59

4.4 Geology ........................................................................................................................................................................... 61


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4.5 Superficial Water ............................................................................................................................................................ 63

4.5.1 Studied Area ........................................................................................................................................................... 63

4.5.2 Quantity ................................................................................................................................................................... 68

4.5.3 Quality ..................................................................................................................................................................... 70

4.6 Ground Waters ............................................................................................................................................................... 74

4.6.1 Studied Area ........................................................................................................................................................... 74

4.6.2 Quantity ................................................................................................................................................................... 76

4.6.3 Quality ..................................................................................................................................................................... 80

5 HYDROLOGICAL/ENVIRONMENTAL IMPACTS ................................................................................................................ 83

5.1 Overall Framework ......................................................................................................................................................... 83

5.2 Impact Analysis............................................................................................................................................................... 84

5.2.1 Surface Water ......................................................................................................................................................... 84

5.2.2 Ground water .......................................................................................................................................................... 84

5.2.3 Aquatic Life ............................................................................................................................................................ 84

5.3 Prevention, Control and Mitigation Measures ............................................................................................................... 85

5.3.1 Approach ................................................................................................................................................................. 85

5.3.2 Impact Mitigation Surface Water ........................................................................................................................ 85

5.3.3 Impact Mitigation Ground Water ......................................................................................................................... 89

5.3.4 Impact Mitigation Wetlands ................................................................................................................................. 92

5.3.5 Impact Mitigation Revegetation .......................................................................................................................... 92

6. ENVIRONMENTAL MONITORING PROGRAM .................................................................................................................. 94

6.1 Approach ................................................................................................................................................................ 94

6.2 Objectives and scope ............................................................................................................................................ 94

6.3 Water components to be evaluated ...................................................................................................................... 95

7. Conceptual Closing Plan ................................................................................................................................................. 98

7.1 Starting Point .................................................................................................................................................................. 98

7.2 Progressive Closing........................................................................................................................................................ 98

7.3 Final Closing .......................................................................................................................................................... 99

7.3.1 Disassembling ........................................................................................................................................................ 99

7.3.2 Demolition, Salvage and Disposition ..................................................................................................................... 99

7.3.3 Physical Stability ........................................................................................................................................ 100

7.3.4 Chemical Stability ................................................................................................................................................. 101

7.4 Post-Closure Conditions............................................................................................................................................... 103

7.4.1 Surface waters ........................................................................................................................................... 104

7.4.2 Underground water ............................................................................................................................................... 105


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7.4.3 Hydrobiology ......................................................................................................................................................... 105

7.4.4 Wetlands ............................................................................................................................................................... 105

8. Surface Hydrology ............................................................................................................................................................... 106

8.1 Aspects to be analyzed in this chapter ........................................................................................................................ 106

8.2 Reviewed Chapters and appendixes from the EIA ..................................................................................................... 106

8.3 Summary of hydrology for the project area within the regional framework................................................................ 107

8.4 Technical analysis of surface water treatment in the EIA ........................................................................................... 109

8.4.1. Necessary Data ................................................................................................................................................... 109

8.4.2 Hydrological studies ............................................................................................................................................. 117

8.4.3 Hydric balance of reservoirs ................................................................................................................................ 136

8.4.4 Mitigation of impacts on surface water ................................................................................................................ 141

8.4.5 Direct and Indirect Areas of influence ................................................................................................................. 143

8.4.6 Feasibility Studies for the reservoirs.................................................................................................................... 145

8.5 Conclusion on effects of the surface water component .............................................................................................. 146

8.6 Recommendations ........................................................................................................................................................ 149

9 HYDROGEOLOGY ............................................................................................................................................................... 153

9.1 Regional Geomorphology and Geology ...................................................................................................................... 155

9.1.1 Quaternary sedimentary deposits ........................................................................................................................ 156

9.1.2. Volcanic rocks: Calipuy Group ............................................................................................................................ 157

9.1.3 Cretaceous sedimentary rocks ............................................................................................................................ 157

9.1.4 Intrusive Rocks ..................................................................................................................................................... 160

9.1.5 Structures .............................................................................................................................................................. 161

9.2 Hydrogeology at a regional scale ............................................................................................................................... 163

9.3 Recharge....................................................................................................................................................................... 167

9.4 Hydrogeology at local scale (pits, tailings and dumps) ............................................................................................... 169

9.4.1 Lithological units and geological structure .......................................................................................................... 170

9.4.2 Hydrodynamic Characterization........................................................................................................................... 174

9.4.3 Hydrology Inventory ............................................................................................................................................. 182

9.4.4 Hydrochemical description ................................................................................................................................... 184

9.4.5 Vulnerability and contamination risk .................................................................................................................... 192

9.5 Conceptual hydrogeological model ............................................................................................................................. 197

9.5.1 Type and structure of aquifers ............................................................................................................................. 197

9.5.2 Recharge, discharge areas, flow model and relationships groundwater surface water.................................... 198

9.6.1 Mitigation measures suggested in the EIA .......................................................................................................... 200

9.6.2 Additional mitigation measures ............................................................................................................................ 201


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9.6.3 Environmental control Network of groundwater monitoring in the ..................................................................... 201

9.7 Conclusions .................................................................................................................................................................. 204

10.1.2 Work Methodology ............................................................................................................................................. 207

10.1.3 Detailed Results ........................................................................................................................................ 212

10.1.4 Conclusions............................................................................................................................................... 229

10.2 Pre-mine stage: ground water quality ................................................................................................................. 231

10.2.1 Approach ................................................................................................................................................... 231

10.2.2 Work Methodology .................................................................................................................................... 232

10.2.3 Detailed results ......................................................................................................................................... 234

10.3 Mine and post-mine stage: contact waters ......................................................................................................... 237

10.3.5 Tailings ....................................................................................................................................................... 244

10.3.6 Ore treatment ............................................................................................................................................. 250

10.4 Deposition and storage of tailings ...................................................................................................................... 251

10.4.1 Disposal system ......................................................................................................................................... 252

10.5 Water discharge from the zone with mining-metallurgical activity ..................................................................... 253

11. PROPOSAL OF FACILITIES TO BE REVIEWED ........................................................................................................... 254

11.1 Approach ..................................................................................................................................................................... 254

11.2 Topsoil deposits .......................................................................................................................................................... 254

11.3 Wetland deposit .......................................................................................................................................................... 254

11.4 Perol waste dump ....................................................................................................................................................... 255

11.5 Rejection of Acid Water Treatment Plant ................................................................................................................ 256

11.6 Passive Treatment of Acid Waters ............................................................................................................................ 256

11.7 Capacity Increase of Reservoirs ................................................................................................................................ 257

12. BACKGROUND DOCUMENTATION ............................................................................................................................... 259

12.1 Reference Bibliography .............................................................................................................................................. 259

12.1 Other documentation considered............................................................................................................................... 262

12.3 Images (Photographs) ................................................................................................................................................ 262

13. ACKNOWLEDGEMENTS ................................................................................................................................................. 262

14. FINAL RULING .................................................................................................................................................................. 264


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LIST OF GRAPHICS

Graphic 1. Location of the Conga Project................................................................................................................................. 30

Graphic 2 Administrative boundaries of the Conga Project Mining Concession .................................................................... 31

Graphic 3. Arrangement of the main elements of the Conga Project...................................................................................... 32

Graphic 4: Main installations and infrastructures of the Conga Project .................................................................................. 38

Graphic 5. Location of mining main infrastructures .................................................................................................................. 39

Graphic 6. Concentrator plant feeding plan per pits during the mining operation stage. ....................................................... 39

Graphic 7. Scenario planned for the pit sector and Perol waste dump ................................................................................... 40

Graphic 8. Forecast distribution for the Chailhuagn pit sector .............................................................................................. 40

Graphic 9. Perol and Chailhuagn waste dumps ..................................................................................................................... 41

Graphic 10. Geological map of the sector where the Perol waste dump would be located. .................................................. 42

Graphic 11. Location of Perol waste dump .............................................................................................................................. 42

Graphic 12. Geological view of the Perol waste dump substrate ............................................................................................ 43

Graphic 13. Geological map of the sector where the Chailhuagn waste dump would be located. ...................................... 43

Graphic 14. Ore processing installation .................................................................................................................................... 44

Graphic 15 Forecast arrangement of the tailings deposit and adjacent infrastructure ........................................................... 45Graphic 16. Tailing deposits and enclosed installations .......................................................................................................... 45

Graphic 17. Collector system for possible filtrations at the foot of the Toromacho dam. ....................................................... 47

Graphic 18. Location of tailings deposit filtration collector well and acid water treatment plant. ........................................... 48

Graphic 19. Double dam to filter tailings and retain infiltrations. ............................................................................................. 48

Graphic 20. Acid water treatment plant drawing. ..................................................................................................................... 49

Graphic 21. Auxiliary hydraulic installations. ............................................................................................................................ 50

Graphic 22. Water balance in all the project area. ................................................................................................................... 52

Graphic 23. Conga project environment meteorological stations location. ............................................................................. 60

Graphic 24. Conga project environment geological map. ........................................................................................................ 62

Graphic 25. Conga project environment physiographic map. ................................................................................................. 63

Graphic 26. Project traces and micro basins in the regional departmental context. .............................................................. 64

Graphic 27. General hydrographic system in micro basins environment. .............................................................................. 65Graphic 28. Project footprint distribution among five micro basins. ...................................................................................... 66

Graphic 29. Project footprint distribution by micro basins. .................................................................................................... 67

Graphic 30. Selected years flows from 1964-2008 series, in Alto Jadibamba river, downstream of Lluspioc ravine (MC-

11). ............................................................................................................................................................................................. 69

Graphic 31. Evolution of Perol reservoir reserves in reservoirs during the closing operation in terms of probability. .......... 70

Graphic 32. Superficial waters quality control stations in Conga project environment. ......................................................... 73

Graphic 33. Phreatic levels hydrogeological map. ................................................................................................................... 75

Graphic 34. Cutaneous system estimated piezometry. ........................................................................................................... 76

Graphic 35. Location of the Regulation Reservoirs Planned ................................................................................................... 88

Graphic 36. Cover To Be Applied to the Perol Waste Dump................................................................................................... 90

Graphic 37. Lagoons and Cultivation Areas Broadly Surrounding the Conga Project ........................................................... 93

Graphic 38. Average monthly flow in storage stations close to the area of the project........................................................ 108

Graphic 39. Regional hydrographic network .......................................................................................................................... 110

Graphic 40. Media Isohyets..................................................................................................................................................... 110

Graphic 41. Location of meteorological stations used in the rainfall studies for the Conga project .................................... 111

Graphic 42. Example of annual and monthly distribution of rainfall in the station Old Minas Conga located in the zone of

the project................................................................................................................................................................................. 112

Graphic 43. Stations of flow control ........................................................................................................................................ 114

Graphic 44. Location of channels and near stations .............................................................................................................. 115


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Graphic 45. Rainfall Series estimated in Old Minas Conga 1965-2006 (annual rainfall and monthly rainfall) .................... 119

Graphic 46. Flows of each year of the series 1964-2008 estimated in MC 11 (Alto Jadibamba, downstream of Lluspioc

ravine)....................................................................................................................................................................................... 120

Graphic 47 Continuous control of flows at MCPCH and MCLCH stations ............................................................................ 121

Graphic 48 Results of models adjusted at MCPCH station ................................................................................................... 122

Graphic 49. Details of the adjusted model at the MCPCH station: flows adjustment during dry seasons and of volumes in

the complete series and during dry seasons. ......................................................................................................................... 124

Graphic 50. Lagoons impacted by the project ........................................................................................................................ 129

Graphic 51. Relationship of rainfall vs. altitude in 391 stations in the Amazonic basin of the Andean countries ............... 132

Graphic 52. Relationship between altitude and rainfall in 1970-2004 periods in Pacific, Titicaca and Amazonas basin ... 133

Graphic 53. Relationship rainfall vs altitude, zones 5 +6 ....................................................................................................... 133

Graphic 54. Relationships rainfall vs. Altitude, zones 1+2+3+4+5 (north 6 latitude South) ................................................. 134

Graphic 55. Media Isohyet in the region ................................................................................................................................. 136

Graphic 56. Flows of water in relationship with the project ................................................................................................... 137

Graphic 57. Results of the model adjusted in the MCPCH station with HFAM and Goldsim: flows .................................... 139

Graphic 58. Results of the model adjusted in the MCPCH station with HFAM and Goldsim: volume accumulated .......... 139

Graphic 59. Provisions of reserves in the reservoirs in terms of probability ......................................................................... 140Graphic 60. AID and AII of quantity and quality of surface water in stage of construction and extension relative to the area

of the project, in relationship with the downstream basin ...................................................................................................... 144

Graphic 61. Proposal of inclusion of beneficiaries of water regulated in the reservoirs in Alto Jadibamba, Chailhuagn and

Alto Chirimayo microbasins: detail .......................................................................................................................................... 145

Graphic 62. Proposal of inclusion of beneficiaries of water regulated in the reservoirs of Alto Jadibamba, Chailhuagn and

Alto Chirimayo microbasins: general plant. ............................................................................................................................ 148

Graphic 63. Geological sketch of the area of Conga. ............................................................................................................ 159

Graphic 64. Geological Plan of the area of Conga. .............................................................................................................. 162

Graphic 65. Structural section of Conga project area showing the Punre fault and, the anticline of El Galeno; as well as

the zones of El Perol and Chailhuagn .................................................................................................................................. 163

Graphic 66. Hydrogeological sketch of the area of Conga .................................................................................................... 164

Graphic 67. Regional and local Stratigraphic column of the Conga area and surroundings. ............................................. 165

Graphic 68. Piper diagram of water surveys in the Conga Project ....................................................................................... 187

Graphic 69. Stiff diagrams of survey waters located on alluviums / volcanic rocks ............................................................. 188

Graphic 70. Stiff diagrams of surveys waters located in limestone ....................................................................................... 188

Graphic 71. Stiff diagrams of surveys waters located on marbles/skarn .............................................................................. 189

Graphic 72. Stiff diagrams of surveys waters located on intrusive rocks .............................................................................. 190

Graphic 73. Stiff diagrams of surveys waters located on volcanic rocks .............................................................................. 191

Graphic 74. Stiff diagram of surveys waters located on volcanic/limestone rocks ............................................................... 191

Graphic 75. Sample stations for surface water quality (pre-mine stage) .............................................................................. 208

Graphic 76. Quality control stations for surface water in Toromacho ravine micro-basin. ................................................... 213

Graphic 77. Quality control points for surface water in Alto Jadibamba river micro-basin. .................................................. 215

Graphic 78. Surface water quality control points in Chugurmayo ravine micro basin .......................................................... 219Graphic 79. Surface water quality control stations in Alto Chirimayo ravine micro basin .................................................... 221

Graphic 80. Surface water quality control stations in Chailhuagn micro-basin................................................................... 226

Graphic 81. Location of ground water stations for quality control ......................................................................................... 232

Graphic 82. Humidity cell outline ............................................................................................................................................ 241

Graphic 83. Vertical cut view of Perol waste dump. ............................................................................................................... 255

Graphic 84. Relative position of the Perol and Chailhuagn open-pits................................................................................. 255


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LIST OF TABLES

Table 1. Distribution by micro basins impacted by the project ................................................................................................ 66

Table 2. Surface waters control stations in the project environment....................................................................................... 81

Table 3. Environmental Impacts Assessment Matrix Construction Stage, in regard to overall hydrological aspects ....... 83

Table 4. Environmental Impact Assessment Matrix Operations Stage, in regard to overall hydrological aspects. ........... 83

Table 5. Current and Future Storage Capacities of Lentic Water Bodies as a Result of the Inception of the Conga Project

.................................................................................................................................................................................................... 87

Table 6 Environmental Monitoring Program Summary ............................................................................................................ 97

Table 7. Average monthly flow registered in storage stations in the region. ....................................................................... 108

Table 8. Existing Stations in the region .................................................................................................................................. 113

Table 9 Capacity of proposed reservoirs ................................................................................................................................ 117

Table 10. Low flows in current situation (baseline) ................................................................................................................ 126

Table 11. Minimum flows of pre-mining and mining in key points. ........................................................................................ 127

Table 12 Mitigation flow of water balance model ................................................................................................................... 138

Table 13. Compensation of water volume after eliminating the lagoons .............................................................................. 141

Table 14. Lithostratigraphic regional units ............................................................................................................................. 160Table 15. Lithological and lithostratigraphic regional units and their hydrogeological aptitudes ......................................... 166

Table 16. Evaluation of recharge and recharge index in the area of project Conga ........................................................... 169

Table 17, Hydraulic conductivity of the main hydrogeological units. ..................................................................................... 176

Table 18. Hydraulic conductivity minimum, maximum, average and median of near80 surveys located at the area of

Conga project, .......................................................................................................................................................................... 176

Table 19 Chart of hydraulic conductivity obtained in EIA and SWS, 2012 ........................................................................... 179

Table 20- Comparison of the maximum and minimum hydraulics conductivities of the Lugeon and Lefranc trials by

lithologies (maximum range found) ......................................................................................................................................... 180

Table 21.- Comparison of the medians hydraulic conductivities by lithologies (maximum and minimum) ........................ 180

Table 22. Values of hydraulic conductivities expect in the different structures of the Conga project. ................................. 181

Table 23.- Hydraulics conductivities to consider in the new exploration of the numeric model. .......................................... 181

Table 24. Distribution of springs and volumes of water by microwatersheds. ...................................................................... 183Table 25.- Magnitude of springs volumes of water ................................................................................................................ 183

Table 26. General features of productive springs .................................................................................................................. 184

Table 27. Average results of the chemical analyses to main ions by lithologies (Na*, K*, Mg*, Ca2, HCO2, Cl, and SO4) 186

Table 28. Medium chemical features of waters by lithology .................................................................................................. 192

Table 29. Weighting factors for the parameters used in the DRASTIC method ................................................................... 193

Table 30. Vulnerability types of DRASTIC rate ...................................................................................................................... 193

Table 31. Vulnerability types of GOD rate .............................................................................................................................. 194

Table 32. DRASTIC Rate. Physical model, weighting rate and value for each parameter .................................................. 195

Table 33. Final calculation of DRASTIC Rate. ....................................................................................................................... 195

Table 34. Calculation of GOD Rate for the three locations. .................................................................................................. 196

Table 35. Results of vulnerability rates in tailing ponds ......................................................................................................... 196

Table 36. Parameters recorded on the control network of the EIA ....................................................................................... 201

Table 37. Cardinal points and location of control piezometers .............................................................................................. 202

Table 38. Creation of a control network of groundwater resources ...................................................................................... 204

Table 39. Hydrographic micro basin in the project environment ........................................................................................... 206

Table 40. Control stations for surface water quality upon micro-basin ................................................................................. 209

Table 41. Water characteristics at Mamacocha lagoon (LMAM)........................................................................................... 214

Table 42. Water characteristics at Toromacho ravine ........................................................................................................... 214

Table 43. Water characteristics at Azul lagoon ...................................................................................................................... 216


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Table 44. Water characteristics at Chica lagoon.................................................................................................................... 216

Table 45. Water characteristics at Jadibamba river ............................................................................................................... 217

Table 46. Water characteristics at Reynaldo Jambo canal ................................................................................................... 217

Table 47. Characteristics of water at El Perolito canal .......................................................................................................... 218

Table 48. Water characteristics at El Bado canal .................................................................................................................. 218

Table 49. Water characteristics at La Chilca canal ................................................................................................................ 219

Table 50. Water characteristics at Chugurmayo ravine ......................................................................................................... 220

Table 51. Water characteristics at Alto Chirimayo ravine ...................................................................................................... 221

Table 52. Water characteristics at Perol wetland ................................................................................................................... 222

Table 53. Water characteristics at Perol lagoon .................................................................................................................... 222

Table 54. Water characteristics at Huashwas lagoon ............................................................................................................ 223

Table 55. Water characteristics at El Perolito canal .............................................................................................................. 224

Table 56. Water characteristics at canals Villanueva ChvezIVillanueva Atalaya and Chugur ......................................... 224

Table 57. Water characteristics at canals Chirimayo and Lozano Izquierdo ........................................................................ 225

Table 58. Water characteristics at Mala lagoon ..................................................................................................................... 227

Table 59. Water characteristics at Chailhuagn river ............................................................................................................ 227

Table 60. Water characteristics at Chailhuagn lagoon ........................................................................................................ 229Table 61. Ground water characteristics at Toromacho ravine wells ..................................................................................... 234

Table 62. Evaluation criteria for acid-base balance tests ...................................................................................................... 240

Table 63. Concentration of metal of environmental significance upon SPLP analysis: Tailings from Perol pit. ................. 247

Table 64. Concentration of metal of environmental significance upon SPLP analysis: Tailings from Chailhuagn pit. ..... 248

Table 65. Concentration of metal of environmental significance upon humidity cell analysis: Tailings from Perol pit. ...... 249

Table 66. Concentration of metal of environmental significance upon humidity cell analysis: Tailings from Chailhuagn pit.

.................................................................................................................................................................................................. 250

Table 67. Consumption of reagents during ore processing ................................................................................................... 251

Table 68. Tailings production during mine life ........................................................................................................................ 252

Table 69. Approximate flows of regulated discharge for dry season coming from projected reservoirs ............................. 253


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LIST OF FIGURES

Figure 1. Satellite image of the Location of the Conga Project ............................................................................................... 30

Figure 2. Dense cloud covering the Conga project area. ........................................................................................................ 61

Figure 3 Mountainous landscape next to Conga project environment .................................................................................... 63

Figure 4 Fluvial-glacial plain landscape next to Conga project environment .......................................................................... 63

Figure 5. Micro reservoirs next to project area. ........................................................................................................................ 69

Figure 6. Detail of the micro-reservoirs of the area .................................................................................................................. 69

Figure 7. Cattle grazing around the Conga project area without housing ............................................................................... 71

Figure 8. Concentration of houses near Conga project areas. ................................................................................................ 71

Figure 9. pH control, conductivity and temperature in wetlands water. .................................................................................. 74

Figure 10. Humic soil, barely 20 to 30 cm on unaltered rock. ................................................................................................. 77

Figure 11. Locally permeable carbonated rocks outcrop in table-shaped suspended structure. .......................................... 77

Figure 12. Superficially marmored, folded, fissured and karstificated limestones outcrop .................................................... 78

Figure 13. Humic soil on low permeability lime clayish matrix morainic deposit. ................................................................... 78

Figure 14. Front glacial moraine cemented with impermeable matrix and dissected by fluvial erosion................................ 79

Figure 15. Chailhuagn permanent lagoon (with established fish farms). .............................................................................. 79Figure 16. Different permeability sediments interstratifications decreasing all materials permeability. ................................ 80

Figure 17. Fish farm in Mamacocha lagoon where non-native rainbow trout is bred............................................................. 82

Figure 18. Storage and initial section of Chaihuagn Yerbabuena channel ......................................................................... 115

Figure 19. Intermediate sections of Chailhuagn Yerbabuena channel. .............................................................................. 116

Figure 20. Lagoon Chailhaugn and discharge flow path ..................................................................................................... 129

Figure 21 Wetlands: view from a helicopter and in detail. ..................................................................................................... 130

Figure 22. Quaternary deposits in Alto Jadibamba River ...................................................................................................... 170

Figure 23. Volcanic rocks of Calipuy Group in Alto Jadibamba ........................................................................................... 171

Figure 24. Pulluicanas Limestone near the lake Chailhuagn (detail). ................................................................................ 171

Figure 25. Pulluicanas Limestone near Chailhuagn Lake ................................................................................................... 172

Figure 26. Intrusive Rocks (Chailhuagn pit) ......................................................................................................................... 172

Figure 27. Detail of the intrusive rocks (Chailhuagn pit) ..................................................................................................... 173


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1. EXECUTIVE SUMMARY AND RECOMMENDATIONS

1.1 Summary

1.1.1 Surface watersThe studies included within the Conga EIA analyze in enough detail, every aspect that may

impact surface hydric components. Details used are correct with some deficiencies that are normalat isolated and small areas such as the one of Conga. The methods employed are correct, althoughsome minor differences have been found with respect to procedures or results that will not modify inessence the conclusions but that must be considered within the systematical annual updates of thehydric components.

The impact to the surface hydric component has been well appraised and the proposedmitigation measures are correct. The considered actions are, mainly, the construction of three

reservoirs of exclusive use to replace impacted flows and a fourth reservoir of shared use with themine that after closure will be solely use for reposition. The reserves within these reservoirs, duringrainy seasons, ensure perfectly well that downstream flows during dry season will continue to be, atleast, as now. The impact during rainy season does not cause environmental damages or harm tothe users since there is not excess of water in the system.

The proposed reservoirs may improve water management at microbasins, further more thanjust replace the impacted flows. An inclusive management of the reservoirs will allow to beingdischarged the required flows, at any time, by the users, even with a target amount higher thantoday that will increase their agricultural production.

To have a suitable management of these reservoirs, we need to state, without any doubt,

the group of users that will benefit from the regulated water, as stated as follows. It is safe to assertthat those far away from the project area will not have an important impact from the available flowsand, on the other hand, reservoirs lack the capacity and do not receive enough contribution toregulate the required flows and serve wide basins.

The EIA does not discuss these aspects since the regulations only mandates to ensure themitigation flows of its surroundings. However, this review, proposes such enhancement.

The loss of four lagoons and 103 ha of wetlands, from the amount of surface waterperspective, reduce the flows generated within the project area proportionally to the subtractedsurface that is little. Therefore, the impact is not as meaningful and it has been properly accountedby the EIA. In no way they could be considered as singular water sources.

The impact to the amount of water produced at the basin headers is practically proportionalto the area impacted by the project. The main contribution of water from microbasins will not be lost,as it may be assumed from a literal interpretation of Article 75 of the Hydraulic Resources of Peru

Act. Basin headers are the water sources from a geographical perspective and not of the flowsproduced in them.

The EIA states as Direct and Indirect Areas of Influence (AID and AII, for their name inSpanish), regarding surface water quantity and quality, as the area occupied by the project facilities.


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It is a valid criterion from the legal standpoint since it complies with the specifications of theRegulations on Protection to the Environment (Minem, 2003.)

Nonetheless, it would be convenient, due to good neighbor reasons with the mine

surrounding population, to include among the future benefits of the water regulated within the

reservoirs the maximum amount as possible of users to improve the positive impacts of the project.This is why it is recommended that, in the future, reservoirs should supply users with water farbeyond from the AII limits as stated on the EIA, only if the studies ensure the necessary amount offlow. At Alto Jadibamba, it could be extend to Jerez Jadibamba canal that irrigates 697 ha with 280users. at Chailhuagn up to Dos Tingos and at Alto Chirimayo up to Lozano Izquierdo. What is notreasonable is trying to include basins as wide as Cajamarca surroundings or Sendamal, that willreceive an impact on their flows but, due to the vast basin surface, it would be meaningless,approximately the impact would be within 0,3% and 3,8% accordingly.

The EIA dos not make any reference to the possible impact on the climate change aboutfuture rains and flows. Currently, no accurate forecasts are available on the climate change impact,not enough to be applied to the detailed hydrological studies. It is worth to estimate the likely impactto the flows and the recharge of the hydrological systems of the area and to reflect a little bit, eventhough with speculations about the risk of natural diminution of future flows. Annual update of thehydrological studies must consider this possibility.

The recommendations regarding the amount of surface water propose the progressiveimprovement of the EIA flows estimates and the hydrological knowledge of the area, following theline of works proposed for this experts review that must be framed within the systematical updatesof the project that should be carried out by the mining company. Besides, the recommendationsstate the need to control and follow up in detail the actions proposed in the EIA, in particular, theactions to mitigate the impact on river flows.

The progressive improvement of the EIA estimates will contribute to improve the definitionof the low flows and the hydric balance. Regarding flows, it is recommended to adjust theprecipitation run-off model on the hydrogram recession sections, since it tends to overestimate thelow flows, which are the base of every following analysis. Although this overestimation will benefitthe downstream users since they will receive higher mitigation flows, it is convenient to adjust theresults. Upon adjustment of the model, the flows recorded at Chailhuagn must be verified. Thesehave been excluded from the EIA for having gaps during dry seasons. This verification is needed toprove the validity of the parameters adjusted at Alto Chirimayo when applying them to this basin,even if it is an estimate.

It is advisable to estimate again the low flows representative of each sub-basing, byclassifying them in percentile ranges usual method to estimate ecological flows. It is a methodmore transparent than the one used on the EIA that, in any case is an accepted procedure thatestimates the probability of having middle 7-day flows.

The hydric balance showed on the EIA is a first approximation, it was performed based on aprior estimate of the mitigation flows. This is why it applied different values from the finally adopted.However, even when the applied flows were smaller, the balance hypothesis is conservative since itholds them for 8 months and, when forced to discharge, are added to the flows discharged from thereservoirs. Hydric balance updates will consider the best information available at each time.


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Recommendations regarding the control and follow-up of the proposed actions, haveseveral objectives. The main objective is to allow Ministries, with decision-making on the process toensure that forecasts and proposals of the EIA are met, and thus apply the relevant correctivemeasures when suitable. The secondary, but not less important, provide transparent information tothe specially impacted population. The third would be to systematically record and from the first timeall the hydro meteorological data as possible in order to raise the awareness of the hydrology of thebasins.

The control and follow-up is basically supported by the establishment of a hydrometeorological data registry, more complete than the current one and the definition of protocols toanalyze data and edition of follow-up reports.

The meteorological data that are currently collected are enough to define the precipitation insuch a small area. The data deficit is on the flow information since the three continuous controlstations were destroyed in 2004 after vandal acts (2007 or sooner), and the vital data registry toimprove the hydrological knowledge of the area were lost.

Therefore, it is recommended to install, as soon as possible new continuous control pointsof flows at the discharge points of the project area, at the five microbasins which may allow to adjustprecipitation run -off models, independents for each and analyze if their hydrological behavior issimilar. It is critical to solve the security problem of these facilities.

As a supplement to these controls, it would be convenient to add an additional pointdownstream, especially at Alto Jadibamba (for example, before the Jerez Jadibamba collection tap)and at Chailhuagn (former Dos Tingos canal) since these basins are the most impacted by theproject, without eliminating the possibility of also controlling the Alto Chirimayo basin. In this way, anextremely valuable hydrological knowledge will be obtained on the functioning of wider basins.

Also, it would be interesting to record the flows at a non-impacted basin, such as

Chugurmayo. It would be used as control point of the natural changes of the hydrological regime,produced simultaneously but independent from the impact of the project.

It is critical to have these controls in a participative manner, through records verificationprotocols or through manual supplementary controls involving the communities of the area, in whichdesign sociologists (with a good knowledge of the problem) should participate. On the other hand,the trust from the communities in the control results will increase with the access to real time data.Thus, they will compare them with their (the communitys) informal observations of the current flowthrough the collection points of the canals.

In addition to the communities, Universities or well-known technical groups of Cajamarcashould intervene with a superior technical level participation. For example, they should

systematically evaluate the microbasins hydrology via studies based on the accumulatedinformation on the continuous control of hydrometereological variables that has been proposed.Thus, any anomaly with respect to the predictions or possible errors in reservoirs management maybe detected on time.

We should keep in mind that a simple data collection is not enough to meet the desiredobjectives. It needs to go along with systematic treatment protocols of the information received.

Analysis frequency and contents must be defined together with the corresponding reports, thewarning and emergency limits before the occurrence of anomalous situations (regarding data


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failure, unusual values or failure to comply with the EIAs expectations), the actions to take in caseof overcoming them and the information spread strategies and mechanisms with graphical solutionsto control and follow up in the most transparent manner.

An important recommendation is to define the management procedures of the three

reservoirs, exclusively devoted to the mitigation flows and, upon closure, also the Superiorreservoir. This action has two aspects: financial, to ensure the availability of enough funds to carryout a suitable management of the reservoirs that should be committed in the Final Closure Plan;and the operational, to define the water management and exploitation decision-making processflowchart.

Regarding the financial aspect, it is recommended that the ownership should continue beingof the Mining Company since in this manner the Company will continue accountable for itsmaintenance. Now the needed economical resources availability should be defined and ensured toimplement the suitable water management organizations.

The operative aspect must define the management organizations structure. The mostsuitable thing to do is to hold the Autoridad Nacional del Agua (Public Water Management

Authority) accountable. Below it, some sort of procedure should be implemented, or the onesfollowed by ANA that have been proved to work in prior cases or a similar model to the one of theComisiones de Desembalse de las Confederaciones Hidrogrficas de Espaa (Overflowcommissions of the Hydrographic Confederations of Spain). It is critical that, regardless themodality, the social stakeholders must participate in the water management and, in particular theirrigation water users that are the largest consumers of the area. Also, the hamlets and humansettlements that may consume water from these rivers in the future should participate. It is

recommended to build water collectors to supply the hamlets that are currently using water fromsprings flowing during the dry season, that in this manner they will benefit from the guarantee ofhaving water available produced by the reservoirs and will compensate the impact to their watersprings.

We should remember that the future management of the reservoirs must not be done tooverflow mitigation flows (that is the mandatory objective of the EIA) but to respond as possible tothe waterusers demands, by taking advantage of its good regulation capacity. This is why, themanagement organizations goal is to define the overflowing flows at each reservoir, in theimmediate term that may be one month, considering the users needs and the situation of theoverflowed reserves, as well as the restrictions imposed by ANA, for example regarding ecologicalflows.

A proper management will ensure that water users not only will be impacted by the projectbut also they will notoriously improve their situation, since the reservoirs may ensure low waterlevels higher than the current ones, increasing the available irrigation provision and the agriculturalproduction. This statement, very optimistic, apparently, is based on the universally proved fact ofthe important efficiency of the first regulation works built at any area, such as in Conga area sincethe regulation capacity/overflow volume ratio is very high.


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In any case, we should act as realistic as possible, and not to provide people with falseexpectations that may emanate from who think that a project shall reduce a water structural deficitduring low water level seasons, independent from the implantation of a mining operation.

The EIA proposals improvement regarding surface water amount is based on the

construction of bigger reservoirs that will facilitate more regulated flows.

The EIA estimates that the reservoirs will be almost always full during operation and closurestages of the mine. This indicates that are undersized in its regulation capacity of the natural flows,since this is not an EIA objective. Thus, any capacity increase technically or economically viable -will result in a notorious increase of the regulated flows and, in consequence, of the positive impactof the project. The proposals here are purely ideas, which feasibility should be confirmed withtopographic, geotechnical and economic data, not available at the time of preparing this Ruling.

The first possibility is the regrowth of the inferior reservoir, expanding as possible its volumeto maximize the flows regulation capacity for the micro basin of Alto Jadibamba within the technicaland economic feasibility of the Work.

It is unknown if Alto Chirimayo users, downstream from Perol reservoir, needsupplementary flows since the registered canals in this basin are small. If this is the case, it wouldbe necessary to consider the expansion of such reservoir capacity.

The Chailhuagn reservoir expansion seems difficult because the topographical conditionsthat constrain the regrowth possibility of this lagoon. Even though, if it would be possible, it willbenefit many downstream users, this is why it would be convenient to explore this possibility.

It would not be necessary to expand the Superior reservoir that is the only with difficulties tofill up due to its increased capacity. However, upon the mine closure (after more than 20 years),pumping facilities may be implemented to send the water to the inferior reservoir as a

supplementary or alternative solution to the possibili ty of expanding its capacity.

The reservoirs proposed on the EIA and their likely expansion are the first step todevelop a regulation system of the microbasins. The Autoridad Nacional del Agua will considerwithin its water management improvement plans in Peru if supply and irrigation demands areproperly served with these reservoirs or if the construction of other water sources under the projectis justified.


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1.1.2 Underground water

After the hydrogeological study submitted in March 2012, we consider there is ahydrogeological conceptual model and the subsequent numerical model. This model should berecalibrated and validated every four years, including the new hydraulic conductivity scenarios

suggested by this ruling, and the data provided by the hydrogeological control, allowing thereforethe adaptive management of underground water resources.

In this way, it would be possible to foresee the qualitative and quantitative project impactswith more rigidity in the microbasins involved, and redefine the dimensions of the impacted areas interms of quality and quantity.

An effort to summarize the hydrogeological inventory considering all campaign, improvingquality of field cards (and georeference) and considering this activity as an important part ofhydrogeological studies to be part of this future control network is recommended.

This control network would include the six expected surveys, downwater of the mainpotentially contaminant structures; the springs nearby selected to this effect; and, also, additional

surveys in points considered as critical. Two or three control points should be installed in knownbasins far away from areas potentially impacted by the project.

The analyzed data allow coming to the conclusion that the underground waters in the studyarea are present in non-confined cutaneous systems, alluvial and fluvioglaciar materials, and thattheir movement happen at shallow depth and in short periods after the rains.

The flow in eruptive substrate rocks and limestone is poor, due to its aquitard behavior. Nopresence of karstic or deep fissured aquifers has been seen.

In very restricted sectors it is possible there are semi-confined, confined or pseudo-confinedfissured hydrogeological systems or small magnitude, that may allow the spreading of influences,and the transport of masses for distances, in an influenced regime, as would be the case with thestopes during the closure stage.

The hydraulic connection between the several hydrogeological systems barely exists orpresents itself in a non-significant way.

Cutaneous underground waters are responsible to feed ravines and rivers and, along withsurface waters, they are in charge of temporarily feeding lagoons and wetlands characteristic ofecosystems in this Andean region. Underground water replenishes at about 34mm, which means3% of precipitation.

Aside from prevention, mitigation and compensation measures proposed by the EIA, wesuggest cartography of vulnerability to contamination in order to optimize the protection andmitigation acts provided under dump sites and tailings deposit.

Also, protection parameters for human use collection should be established in potentialimpact areas, in order to better apply the mitigation measures.

The numerical model should be used as management model, incorporating simulations ofwork for the main project infrastructures. In the extraction stage, Perol and Chailhuagn pits wouldextract water locally granted by the shallow cutaneous aquifer and may cause quantitative problemin nearby collections found in more fractured areas, which must be included in control programs.


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In order to avoid possible qualitative problems (during and after pit mining stage) in themain ravines and rivers, it is possible there is need to place waterproof curtains and/or pump pondsin the shallow hydrogeological subsystem.

Problems in eruptive volcanic substrate rocks and limestone discontinuous hydrogeological

systems are considered marginal, due to the aquitard behavior these geological formations have.

The intervention plan for each scenario must be established previously, based on the waterpoints inventory, which must be constantly updated.

Due to their being scarce, underground waters do not offer availability to generatesystematic alternatives; also, the main underground water resources are related to shallow aquifersand their management should be performed in the perspective of using superficial waters.

Aside from the small reservoirs provided, collection alternatives should be considered forprevention, mitigation and compensation measures , based in surveys or other sub-horizontalcollections, which would imitate current springs and be good socially accepted alternatives.

1.1.3 Water quality

Ample information appears on the EIA about water quality, provided by officially creditedlaboratories in Cajamarca, Lima and Ontario (Canada), using the usual control and qualityassurance processes.

1.1.3.1. Surface waters in pre-mine stage

The quality of surface waters during pre-mine stage, including lagoons, ravines, rivers andcanals, appears studied in the EIA for the five microbasins located in the project environment:Toromacho ravine, Alto Jadibamba river, Chugurmayo ravine, Alto Chirimayo ravine andChailhuagn river.

The investigation performed is based on the historical information obtained from severalstudies elaborated for the Conga project, as well as from the periodical controls performed byMYSRL. . In this sense, quality studies have been performed since 2003 for the project area waters,which have been reviewed for comparison against more recent data (period 2007-2009) consideredmore accurate since they include a higher volume of data and have homologated laboratoryreports.

This experts review considers the general characterization regarding the superficial watersin pre-mine stage as accurate, even though the number of control points must be extended beforestarting mine operations for a proper time-space quality follow-up to be performed during theoperation. Also, reference points must be sele4cted in areas not impacted by the proposed miningactivities.

In the EIA the analytical data appears compared to the National Environmental qualitystandards(ECA) established by the Ministry of Environment (MINAM) and, concretely, with those ofCategory 3, corresponding to the irrigation of long-stem and short-stem vegetables and water foranimals, since these are the main uses for surface waters.

The most significant aspects regarding quality of surface waters in pre-mine stage are thefollowing:


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Chemical facies of most waters analyzed is calcic bicarbonate, as corresponding to low-slatwaters; some of the samples are calcic bicarbonated-sulfated in Chailhuagn river; calcicsulfated in Laguna Azul and Alto Chirimayo surface run-offs, and clearly calcic sulfated inPerol wetlands.

The field-measured pH for most samples is over 7, reaching even 9. Ocasionally there aresamples that have low values between 6,5 and 7 (some Laguna Azul analyses and surfacerun-offs in Alto Jadibamba river, and Alto Chirimayo ravine). In Perol wetlands, pH is verylow (from 3,0 to 6,4, with average values of 3,1 to 4,2).

The total of dissolved solids shows values going from below 3 mg/L to 302 (the highestvalue determined corresponds to Mala Lagoon); low values, as corresponds topredominantly calcic bicarbonate waters, and that evidence the reduced solubility oflithological materials over which these waters flow.

The minimum alkalinity values have been registered I Perol wetlands (>1,0 to 12 CaCO3/L,with an average of 1,3), which manifests the bad quality of these waters. In the rest ofanalyses, very variable values are observed, going over 202 equivalents of CaCO3/L. All

Laguna Azul and Laguna chica samples have values lower than 20, which reflects theirinadequate quality for animal life development. Records below 20 were also found onToromacho ravine, Chirimayo ravine waters and in waters of some canals.

The sulfide content can be considered low (between


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Since these waters are used for human consumption, their quality has been assessed as areference, applying the National water quality environmental standards (ECA) established by theMinistry of Environment (MINAM, 2008) for Category 1 subcategory A1 (waters that may be madepotable with a simple disinfection).

The results have been processed using statistic techniques and graphic representations,also using the usual geochemical modeling programs. This is for the global behavior of eachparameter, as well as for their variations between maximum, minimum and average concentrations.

Even though some values obtained present discrepancies with the natural expectedconcentrations, results provide a good contribution to the knowledge of characteristics, compositionand general behavior of underground water quality.

The most outstanding aspects are:

Most chemical facies are calcic bicarbonate, even though there are calcic sodic-potassicone and others.

The pH in general ranges from neutral to alkaline, but there are very high values higherthan 11, possibly because of additives used in the drilling or due to the use of cement(these ponds would need a cleaning and development work, since their waters are not aptfor human consumption).

The total of dissolved solids is usually very low, but there are also valued higher than 4,000mg/l.

Most metals regulated by the ECA for Category 1 subcategory A1 have shownthemselves quite below the maximum established values; however, in a series of pondwater samples there has been excess content of Al, As, Fe, Hg, Pb and Mn during differentsampling campaigns, a situation that cannot be attributed to mining, since it has nothappened yet.

This may correspond to a regional mineralization bottom, a geological area that hasreceived analytical inconsistencies, such as the difference reported between concentrationsof dissolved metals and concentrations of total metals, which seems to indicate there aremany times the samples have not been correctly filtered, therefore higher values can bedetermined caused by suspended solids. For this reason, it is necessary to use adequatefiltering in situduring samplings, to eliminate the solid part.

On the other hand, there seems to be a co-relation in the balance of pH values registered instudy area underground waters (almost neutral or slightly alkaline pH, between 7,5 and 8,2)and the dissolved metals concentrations for Al, Cu, Pb and Fe, located in the range frommicrograms per liter to tens of micrograms per liter.

Total and fecal coliforms have usually been low; however, there has been frequent excessof fecal coliforms compared to ECA in some underground water points, which evidence thealready stated anthropogenic or animal influence also identified in surface waters.

Though dissolved oxygen, DBO and DQO present normal values for the most part,sometimes the sampled ponds do not comply with the ECA.


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1.1.3.3. Contact waters in mine and post-mine stages

Quality prevision on water that may be drained during a mining operation as the subjectmatter always has a high degree of uncertainty, especially for waters in contact with reagent rocks(presence of pyrite and oxygen).

To have an estimate a series of leaching hydrogeochemical studies and tests (including wetcells) has been carried out, to forecast the future quality of the waters that seem reflected on theEIA and its appendixes. On the safety section of EIA, it has been foreseen to treat all the potentiallyimpacted waters on their quality. It is predicted to have more impact on waters in contact with wastematerials from Perol pit that shown sulfur ores (pyrite and marcasite), which when exposed to theenvironment would be the main source of acidity generation leaving little material for naturalneutralization.

Calcic carbonate dissolution at Chailhuagn pit may contribute with a neutralization factor inthe case of acid water generation.

Regarding tailings reactivity, in presence of water and oxygen, and considering their small

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