Vol 9 - Operations Manual

Prepared for:

Sociedad Minera Cerro Verde S.A.A. Asiento Minero Cerro Verde - Uchumayo Casilla Postal 299 Arequipa, Peru

CERRO VERDE TAILING STORAGE FACILITY FINAL DESIGN Volume 9 – Operations Manual

September 2006

Prepared by:

MWH 1801 California Street Suite 2900 Denver, Colorado 80202 (303) 291-2222

MWH Project No. 1010211.012514

Cerro Verde TSF * Operations Manual  TOC-i TOC-i

September2006

TABLE OF CONTENTS Section No. 1.0

INTRODUCTION................. INTRODUCTION............................... ............................ ............................ ........................... ........................... ............................ ............................ ....................... ......... 1

1.1 1.2 1.3 1.4 2.0

DOCUMENT PURPOSE AND OBJECTIVES ........................... ......................................... ............................ ............................ ............................ .................... ...... 1 EGISTERED DOCUMENT HOLDERS ............................ R EGISTERED .......................................... ............................ ............................ ............................ ......................... ........... 2 EVIEW AND UPDATE .......................... OPERATIONS MANUAL R EVIEW ........................................ ............................ ............................ ......................... ........... 2 PROJECT HISTORY AND SCHEDULE ........................... ......................................... ............................ ............................ ............................ ...........................3 .............3 ROLES, RESPONSIBILITIES, RESPONSIBILITIES, AND TRAINING REQUIREMENTS.................................. REQUIREMENTS.................................... .. 4

2.1 2.2 2.3 2.4 3.0

Page No.

GENERAL .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ............................ ......................... ........... 4 ORGANIZATIONAL CHART ............................ .......................................... ............................ ............................ ............................ ............................ ......................... ........... 4 OLES AND R ESPONSIBILITIES ESPONSIBILITIES ........................... R OLES ......................................... ............................ ............................ ............................ ............................ .................... ...... 4 EQUIREMENTS............................ TRAINING R EQUIREMENTS .......................................... ............................ ............................ ............................ ............................ ......................... ........... 6 FACILITY FACILITY DESCRIPTION DESCRIPTION .......................... ........................................ ........................... ........................... ............................ ............................ ......................... ........... 7

3.1 BACKGROUND I NFORMATION ............................ .......................................... ............................ ............................ ............................ ............................ .................... ...... 7 3.2 FACILITY LOCATION AND BRIEF DESCRIPTION ............................ .......................................... ............................ ........................... ...................... ......... 7 3.3 SITE CONDITIONS ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ......................... ........... 8 3.3.1 Landscape and Topography ............................ .......................................... ............................. ............................. ............................ ............................ ................ .. 8 3.3.2 Climate and Hydrology .......................... ........................................ ............................ ............................ ........................... ........................... ...........................8 .............8 3.3.3 Seismicity........................... Seismicity......................................... ............................ ............................ ........................... ........................... ............................ ............................ .................. .... 10 3.3.4 Geology ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ .................. .... 10 3.4 DESIGN BASIS AND CRITERIA ........................... ......................................... ............................ ............................ ............................ ........................... .................... ....... 11 3.4.1 Compliance of Standards and Regulations ............................ .......................................... ............................ ............................ .................... ...... 11 3.4.2 International Guidelines................ Guidelines.............................. ............................ ........................... ........................... ............................ ............................ .................... ...... 16 3.4.3 Design Basis and Criteria Criteria ............................ .......................................... ........................... ........................... ............................ ............................ ................... ..... 16 4.0

FACILITY FACILITY OPERATION..................... OPERATION................................... ........................... ........................... ............................ ............................ ........................... .................. ..... 19

4.1 OBJECTIVE........................... ......................................... ............................ ............................ ............................ ............................ ............................ ............................ .................... ...... 19 4.2 TAILING PRODUCTION AND TRANSPORT ............................ .......................................... ............................ ............................ ............................ ................ .. 19 4.2.1 Tailing Characteristics and Production Schedule.......................... Schedule........................................ ............................ ..........................19 ............19 4.2.2 Tailing Thickening............................. Thickening.......................................... ........................... ............................ ............................ ........................... .......................... ................. .... 20 4.2.3 Whole Tailing Pipeline............ Pipeline .......................... ............................ ............................ ........................... ........................... ............................ ......................... ........... 21 4.2.4 Tailing Cycloning ........................... ......................................... ............................ ............................ ........................... ........................... ............................ ................... ..... 21 4.2.5 Jacking Headers....................................... Headers..................................................... ........................... ........................... ............................ ............................ ....................... ......... 22 4.2.6 Other Delivery Lines ........................... ......................................... ............................ ............................ ........................... ........................... ............................22 ..............22 4.3 EMBANKMENT CONSTRUCTION ........................... ......................................... ............................ ............................ ............................ ............................ ................ .. 22 4.3.1 Description of the Embankment Embankment .......................... ........................................ ............................ ........................... ........................... ..........................23 ............23 4.3.2 Embankment Design Assumptions............. Assumptions........................... ............................ ............................ ............................ ............................ ..................... ....... 24 4.3.3 Start-up Construction ............................ .......................................... ........................... ........................... ............................ ............................ ..........................24 ............24 4.3.4 Contingency Measures and Problem/Solution Matrix .................................... ................................................. ....................... .......... 29 4.3.4.1 4.3.4.2 4.3.4.3 4.3.4.4

4.3.5 4.3.6 4.3.7 4.3.8 4.3.9 4.3.10 4.3.11 4.3.12 4.3.12

Insufficient Quantity of Underflow ....................................................... .................................................................................... ....................................... .......... 29 Flatter or Steeper Embankment Slope ..................................................... .................................................................................. ..................................... ........ 30 Excessive Seepage at Start-up .................................................... ................................................................................ .................................................. ...................... 31 Problem/Solution Matrix ....................................................... .................................................................................... ....................................................... .......................... 31

General Embankment Construction ........................... ........................................ ........................... ........................... ........................... .................... ...... 35 Deposition on the Embankment Embankment Crest ........................... ......................................... ........................... ........................... ............................ ................ .. 37 Placement of the the Underflow Sands over the Drains........................ Drains...................................... ........................... .........................39 ............39 Special Embankment Features .......................... ....................................... ........................... ........................... ........................... ........................... ............... .. 39 Deposition of Underflow Underflow Sands into the Eastern Quebrada .......................... ........................................ ........................ .......... 39 Embankment Instrumentation ........................... ........................................ ........................... ............................ ........................... ........................ ........... 41 Embankment Construction Schedule ......................... ....................................... ............................ ............................ ............................42 ..............42 QA/QC of Embankment Construction...................... Construction.................................... ........................... ........................... ............................ ................. ... 42

4.3.12.1

Lift Thickness................................................ Thickness............................................................................. .......................................................... .................................................. ..................... 43

MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222

Cerro Verde TSF * Operations Manual  TOC-i TOC-i

September2006

TABLE OF CONTENTS Section No. 1.0

INTRODUCTION................. INTRODUCTION............................... ............................ ............................ ........................... ........................... ............................ ............................ ....................... ......... 1

1.1 1.2 1.3 1.4 2.0

DOCUMENT PURPOSE AND OBJECTIVES ........................... ......................................... ............................ ............................ ............................ .................... ...... 1 EGISTERED DOCUMENT HOLDERS ............................ R EGISTERED .......................................... ............................ ............................ ............................ ......................... ........... 2 EVIEW AND UPDATE .......................... OPERATIONS MANUAL R EVIEW ........................................ ............................ ............................ ......................... ........... 2 PROJECT HISTORY AND SCHEDULE ........................... ......................................... ............................ ............................ ............................ ...........................3 .............3 ROLES, RESPONSIBILITIES, RESPONSIBILITIES, AND TRAINING REQUIREMENTS.................................. REQUIREMENTS.................................... .. 4

2.1 2.2 2.3 2.4 3.0

Page No.

GENERAL .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ............................ ......................... ........... 4 ORGANIZATIONAL CHART ............................ .......................................... ............................ ............................ ............................ ............................ ......................... ........... 4 OLES AND R ESPONSIBILITIES ESPONSIBILITIES ........................... R OLES ......................................... ............................ ............................ ............................ ............................ .................... ...... 4 EQUIREMENTS............................ TRAINING R EQUIREMENTS .......................................... ............................ ............................ ............................ ............................ ......................... ........... 6 FACILITY FACILITY DESCRIPTION DESCRIPTION .......................... ........................................ ........................... ........................... ............................ ............................ ......................... ........... 7

3.1 BACKGROUND I NFORMATION ............................ .......................................... ............................ ............................ ............................ ............................ .................... ...... 7 3.2 FACILITY LOCATION AND BRIEF DESCRIPTION ............................ .......................................... ............................ ........................... ...................... ......... 7 3.3 SITE CONDITIONS ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ......................... ........... 8 3.3.1 Landscape and Topography ............................ .......................................... ............................. ............................. ............................ ............................ ................ .. 8 3.3.2 Climate and Hydrology .......................... ........................................ ............................ ............................ ........................... ........................... ...........................8 .............8 3.3.3 Seismicity........................... Seismicity......................................... ............................ ............................ ........................... ........................... ............................ ............................ .................. .... 10 3.3.4 Geology ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ .................. .... 10 3.4 DESIGN BASIS AND CRITERIA ........................... ......................................... ............................ ............................ ............................ ........................... .................... ....... 11 3.4.1 Compliance of Standards and Regulations ............................ .......................................... ............................ ............................ .................... ...... 11 3.4.2 International Guidelines................ Guidelines.............................. ............................ ........................... ........................... ............................ ............................ .................... ...... 16 3.4.3 Design Basis and Criteria Criteria ............................ .......................................... ........................... ........................... ............................ ............................ ................... ..... 16 4.0

FACILITY FACILITY OPERATION..................... OPERATION................................... ........................... ........................... ............................ ............................ ........................... .................. ..... 19

4.1 OBJECTIVE........................... ......................................... ............................ ............................ ............................ ............................ ............................ ............................ .................... ...... 19 4.2 TAILING PRODUCTION AND TRANSPORT ............................ .......................................... ............................ ............................ ............................ ................ .. 19 4.2.1 Tailing Characteristics and Production Schedule.......................... Schedule........................................ ............................ ..........................19 ............19 4.2.2 Tailing Thickening............................. Thickening.......................................... ........................... ............................ ............................ ........................... .......................... ................. .... 20 4.2.3 Whole Tailing Pipeline............ Pipeline .......................... ............................ ............................ ........................... ........................... ............................ ......................... ........... 21 4.2.4 Tailing Cycloning ........................... ......................................... ............................ ............................ ........................... ........................... ............................ ................... ..... 21 4.2.5 Jacking Headers....................................... Headers..................................................... ........................... ........................... ............................ ............................ ....................... ......... 22 4.2.6 Other Delivery Lines ........................... ......................................... ............................ ............................ ........................... ........................... ............................22 ..............22 4.3 EMBANKMENT CONSTRUCTION ........................... ......................................... ............................ ............................ ............................ ............................ ................ .. 22 4.3.1 Description of the Embankment Embankment .......................... ........................................ ............................ ........................... ........................... ..........................23 ............23 4.3.2 Embankment Design Assumptions............. Assumptions........................... ............................ ............................ ............................ ............................ ..................... ....... 24 4.3.3 Start-up Construction ............................ .......................................... ........................... ........................... ............................ ............................ ..........................24 ............24 4.3.4 Contingency Measures and Problem/Solution Matrix .................................... ................................................. ....................... .......... 29 4.3.4.1 4.3.4.2 4.3.4.3 4.3.4.4

4.3.5 4.3.6 4.3.7 4.3.8 4.3.9 4.3.10 4.3.11 4.3.12 4.3.12

Insufficient Quantity of Underflow ....................................................... .................................................................................... ....................................... .......... 29 Flatter or Steeper Embankment Slope ..................................................... .................................................................................. ..................................... ........ 30 Excessive Seepage at Start-up .................................................... ................................................................................ .................................................. ...................... 31 Problem/Solution Matrix ....................................................... .................................................................................... ....................................................... .......................... 31

General Embankment Construction ........................... ........................................ ........................... ........................... ........................... .................... ...... 35 Deposition on the Embankment Embankment Crest ........................... ......................................... ........................... ........................... ............................ ................ .. 37 Placement of the the Underflow Sands over the Drains........................ Drains...................................... ........................... .........................39 ............39 Special Embankment Features .......................... ....................................... ........................... ........................... ........................... ........................... ............... .. 39 Deposition of Underflow Underflow Sands into the Eastern Quebrada .......................... ........................................ ........................ .......... 39 Embankment Instrumentation ........................... ........................................ ........................... ............................ ........................... ........................ ........... 41 Embankment Construction Schedule ......................... ....................................... ............................ ............................ ............................42 ..............42 QA/QC of Embankment Construction...................... Construction.................................... ........................... ........................... ............................ ................. ... 42

4.3.12.1

Lift Thickness................................................ Thickness............................................................................. .......................................................... .................................................. ..................... 43


Cerro Verde TSF * Operations Manual  TOC-ii TOC-ii

September2006

4.3.12.2 4.3.12.3 4.3.12.4 4.3.12.5 4.3.12.6 4.3.12.7 4.3.12.8

In-place Density and Moisture Content ..................................................... ................................................................................. ................................... ....... 44 Gradation of In-p lace Underflow..................................................................... Underflow..................................................................................................4 .............................4 4 Compaction Characteristics of In-place Underflow...................................................................... Underflow...................................................................... 45 Slope................................................................................ Slope................................................... .......................................................... ............................................................ ................................. 45 Freeboard............................................................................... Freeboard.................................................. .......................................................... ....................................................... .......................... 45 Erosion............................................................ Erosion............................... .......................................................... .......................................................... ................................................. .................... 46 QA/QC Reporting............................................ Reporting......................................................................... .......................................................... ................................................ ................... 46

4.4 IMPOUNDMENT DEPOSITION PLAN............................ .......................................... ............................ ............................ ............................ ......................... ........... 47 4.4.1 Objectives ........................... ........................................ ........................... ............................ ............................ ........................... ........................... ............................ .................. .... 47 4.4.2 Description ........................... ......................................... ............................ ............................ ........................... ........................... ............................ ........................... ............... .. 47 4.4.3 Deposition Schedule...................................... Schedule.................................................... ............................ ........................... ........................... ............................ .................. .... 49 4.4.4 QA/QC................................... QA/QC................................................. ............................ ............................ ............................ ............................ ............................ ...........................50 .............50 4.5 SUSTAINING CAPITAL ITEMS............................ .......................................... ............................ ............................ ............................ ........................... .................... ....... 50 4.5.1 Drain Expansion ................. ............................... ............................ ............................ ............................ ............................ ............................ ........................... ............... .. 51 4.5.2 QA/QC of Sustaining Capital Drain Expansions ........................... ......................................... ............................ ..........................51 ............51 4.5.3 Header Extension ........................... ........................................ ........................... ............................ ........................... ........................... ............................ .................... ...... 53 4.5.4 Left Abutment Blanketing .......................... ........................................ ............................ ........................... ........................... ............................ ...................... ........ 54 4.5.5 4.5.5 Instrumentation Expansion................. Expansion............................... ........................... ........................... ............................ ............................ ........................... ............... .. 56 4.5.5.1

Details of Instrument and ADAS Installation and Maintenance................................................... Maintenance................................................... 57

4.5.6 Geotechnical Investigations .......................... ....................................... ........................... ........................... ........................... ........................... ................... ...... 57 4.6 WATER MANAGEMENT .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ................ .. 59 4.6.1 General.................................. General................................................ ............................ ............................ ............................ ............................ ............................ ...........................59 .............59 4.6.2 Reclaim Water Pond..................... Pond................................... ........................... ........................... ............................ ............................ ........................... ..................... ........ 59 4.6.3 Seepage Management................... Management................................. ............................ ............................ ........................... ........................... ............................ ..................... ....... 61 5.0

5.1 5.2 5.3 5.4 5.5 5.6 5.7 6.0

6.1 6.2 6.3 6.4 6.5 7.0

7.1 7.2 7.3 8.0

ENVIRONMENTAL ENVIRONMENTAL PROTECTION............. PROTECTION........................... ........................... ........................... ........................... ........................... ...................... ........ 62

GENERAL .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ............................ ....................... ......... 62 SOILS ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ ...........................62 .............62 AIR QUALITY........................... ......................................... ............................ ............................ ............................ ............................ ............................ ............................ ................ .. 62 VEGETATION AND WILDLIFE ........................... ......................................... ............................ ............................ ............................ ........................... .................... ....... 63 WATER QUALITY............................ .......................................... ............................ ............................ ............................ ............................ ............................ ....................... ......... 63 R ECLAMATION ......................................... ............................ ............................ ........................... .................... ....... 64 ECLAMATION AND R EHABILITATION EHABILITATION ........................... DOCUMENTATION ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ....................... ......... 64 SAFETY AND SECURITY................... SECURITY................................. ............................ ........................... ........................... ............................ ............................ .................. .... 65

GENERAL .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ............................ ....................... ......... 65 WORKER HEALTH AND SAFETY ........................... ......................................... ............................ ............................ ............................ ............................ ................ .. 65 SITE SECURITY ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ...........................66 .............66 EMPLOYEE TRAINING ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ................ .. 67 DOCUMENTATION ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ....................... ......... 67 MAINTENANCE MAINTENANCE ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ......................... ........... 68

R OUTINE .......................................... ............................ ............................ ............................ ............................ ......................... ........... 68 OUTINE MAINTENANCE ............................ EVENT- DRIVEN MAINTENANCE ........................... ......................................... ............................ ............................ ............................ ............................ ................ .. 68 DOCUMENTATION ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ....................... ......... 69 FACILITY SURVEILLANCE SURVEILLANCE ............................ .......................................... ........................... ........................... ............................ ............................ ................. ... 70

8.1 GENERAL .......................... ........................................ ............................ ............................ ............................ ............................ ............................ ............................ ....................... ......... 70 8.2 MONITORING EQUIPMENT ........................... ......................................... ............................ ............................ ............................ ............................ ......................... ........... 70 8.2.1 Piezometers ........................... ......................................... ............................ ........................... ........................... ............................ ............................ ........................ .......... 71 8.2.2 Staff Gauges ........................... ........................................ ........................... ............................ ............................ ........................... ........................... ........................ .......... 71 8.2.3 Seepage Monitoring Wells ........................... ......................................... ........................... ........................... ........................... ........................... ................ .. 71 8.2.4 Accelerometers............................ Accelerometers.............. ............................ ............................ ........................... ........................... ............................ ............................ .................. .... 72 8.2.5 Flow Meter................................ Meter.............................................. ........................... ........................... ............................ ............................ ........................... .................... ....... 72 8.3 MONITORING FREQUENCY ............................ .......................................... ............................ ............................ ............................ ............................ ....................... ......... 72 8.4 I NSPECTIONS............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ ................ .. 73 8.4.1 Regular Inspections .................. ................................ ............................ ........................... ........................... ............................ ............................ .................... ...... 74 8.4.1.1

Routine Daily Inspections - Instrumentation ....................................................... ................................................................................ ......................... 74


Cerro Verde TSF * Operations Manual  TOC-iii

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8.4.1.2 8.4.1.3 8.4.1.4

8.4.2

Inspection after Extreme Events.........................................................................................77

8.4.2.1 8.4.2.2 8.4.2.3

9.0

9.1 9.2 9.3 9.4 9.5 9.6 10.0

Earthquake.................................................................................................................................... 77 Flood............................................................................................................................................. 77 Landslide ...................................................................................................................................... 78

DOCUMENTATION AND REPORTING................................................................................. 79

DATABASE................................................................................................................................... 79 FILING WRITTEN R EPORTS .......................................................................................................... 79 STORING ELECTRONIC DATA ........................................................................................................ 79 R ETRIEVING ELECTRONIC DATA.................................................................................................. 80 FILING R EPORTS BY OTHERS ....................................................................................................... 80 A NNUAL OPERATIONS MANUAL UPDATE .................................................................................... 80 EMERGENCY RESPONSE PLAN ............................................................................................ 82

10.1 10.2 10.3 10.4 10.4.1 10.4.2 10.5 10.5.1 10.5.2 10.5.3 10.6 10.6.1 10.6.2 10.6.3 10.6.4 10.6.5 10.6.6 10.6.7 10.7 11.0

Routine Daily Inspections - Visual ............................................................................................... 74 Comprehensive Inspections .......................................................................................................... 76 Intermediate Inspections............................................................................................................... 76

OVERVIEW .............................................................................................................................. 82 R ESPONSIBILITIES.................................................................................................................... 82 EMERGENCY SUPPLIES AND R ESOURCES .................................................................................84 EMERGENCY CONDITIONS ....................................................................................................... 84 Earthquake.........................................................................................................................84 Flooding............................................................................................................................. 85 FAILURE CONDITIONS .............................................................................................................86 Failure is in Progress ........................................................................................................86 Failure is Imminent............................................................................................................87 Failure is Developing......................................................................................................... 87 R ESPONSE ACTIONS IF THERE IS ..............................................................................................87 Slide on the Downstream Slope of the Embankment.......................................................... 87 Loss of Freeboard..............................................................................................................88 Excessive Seepage..............................................................................................................88 Excessive Embankment Settlement..................................................................................... 88 High Phreatic Surface in Embankment.............................................................................. 88 Embankment Cracking....................................................................................................... 88 Seeps, Sandboils, and Sinkhole Development.................................................................... 89 POST-FAILURE ACTIONS ......................................................................................................... 89

SCHEDULE................................................................................................................................... 90

LIST OF TABLES Table No.

Description

1-1 2-1 2-2 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 4-2-1 4-3-1 4-3-2

Operations Manual Distribution List Roles & Responsibilities Recommended Training Requirements Meteorological Stations Coordinates and Years of Record Maximum Rainfalls at Different Return Periods Probable Maximum Precipitation Waste Water Discharge and Water Quality Standards Summary Air Quality Standards Summary Air Emissions Standards Cerro Verde TSF-Design Basis Cerro Verde TSF-Design Criteria Ramp-up Production Rates Daily Water Volume and Flow Rate for Start-up Water Filling Plan Problem-Solution Matrix for TSF Construction MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222

Cerro Verde TSF * Operations Manual  TOC-iv

September2006

4-3-3 4-3-4 4-4-1 4-5-1 4-5-2 4-5-3 7-1 8-1 8-2 8-3

Embankment Crest and Slope Areas Summary of QC/QA Observation Parameters Impoundment Deposition Points Estimated Jacking Header Line Extensions and Raise Rates Left Abutment Limestone Protective Blanket Planned Instrumentation Expansion Schedule Maintenance Program Filing System Seepage Flow Rates at V – Notch Weir Monitoring Instruments TSF Inspection Program

LIST OF FIGURES Figure No.

Description

2-1 2-2 2-3 3-1 3-2 3-3 4-2-1 4-2-2

Concentrator Management Organisational Chart General TSF Organizational Chart Detailed TSF Organizational Chart Site Location Map Primary Sulfide Project Facility Layout Plan Engineering Geology Map Tailing Particle Size Distributions Average Daily Tailing Production Rate and Minimum Required Cycloned Sand for that Production Rate Starter Dam Configuration and Material Zones Ultimate Embankment Cross-Section Schematic of Startup Embankment Construction Sequence Estimated Impoundment and Embankment Elevations with Time Estimated Time for Construction of a Complete Embankment Lift vs. Time Embankment Rate of Rise (m/week) Embankment Crest Deposition Initial and Final Underflow and Overflow Header Alignments (East Abutment) Profiles along the Initial Underflow and Overflow Header Alignments (East Abutment) February 1, 2008 3D Embankment Model El. 2500 m October 1, 2008 3D Embankment Model El. 2514 m December 1, 2008 3D Embankment Model El. 2518 m February 1, 2009 3D Embankment Model El. 2520 m June 1, 2009 3D Embankment Model El. 2525 m October 1, 2009 3D Embankment Model El. 2530 m Embankment Instrumentation Plan – Capital Construction Embankment Instrumentation Sections – Capital Construction Embankment Instrumentation Plan – Operations Embankment Instrumentation Sections – Operations Impoundment Filling Plan - Year 1 Impoundment Filling Plan - Year 2 Impoundment Filling Plan - Year 4 Impoundment Filling Plan - Year 10 Impoundment Filling Plan Year - 15 Impoundment Filling Plan Year - 22 (End of Operations) Plan of Blanket and Finger Drains Typical Embankment Underdrains Sections and Details Left Abutment Limestone Area Protective Measures Cross-Sections A-A’ and B-B’ Limestone Area Protective Measures

4-3-1 4-3-2 4-3-3 4-3-4 4-3-5 4-3-6 4-3-7 4-3-8 4-3-9 4-3-10 4-3-11 4-3-12 4-3-13 4-3-14 4-3-15 4-3-16 4-3-17 4-3-18 4-3-19 4-4-1 4-4-2 4-4-3 4-4-4 4-4-5 4-4-6 4-5-1 4-5-2 4-5-3 4-5-4


Cerro Verde TSF * Operations Manual  TOC-v

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11-1

TSF Construction and Operations Schedule

LIST OF APPENDICES Appendix A Appendix B Appendix C Appendix D

OM Revision and Holders Record Environmental Management Plan for the Tailing Storage Facility Operations Forms Sustaining Capital and Operations Cost


Cerro Verde TSF* Operations Manual  1

September 2006

1.0 1.1

INTRODUCTION

DOCUMENT PURPOSE AND OBJECTIVES

The purpose of this document is to serve as a reference manual for personnel involved in the construction and operation of the Cerro Verde Tailing Storage Facility (TSF) during its life cycle. The document should be kept current and should be revised periodically. This manual was prepared by MWH in support of the detailed design of the Cerro Verde TSF that was performed during the period from January 2005 to April 2006. It forms part of the following multi-volume compendium supporting final design of the Cerro Verde TSF: Volume 1 – Summary Report Volume 2 – Geological and Geotechnical Site Investigations and Assessments Volume 3 – PMP and Rainfall Frequency Analysis Volume 4 – Seepage Analysis Volume 5 – Material Balance Analysis Volume 6 – Water Balance Analysis Volume 7 – Static and Seismic Stability Analyses Volume 8 – Seepage Collection System Design Volume 9 – Operations Manual

Volume 10 – Drawings The objectives of the operations manual are to define and describe the following: •

Roles and responsibilities of the personnel assigned to the facility

•

The key components of the facility

•

The procedures required to construct, operate, monitor and maintain the facility so that it functions in accordance to its design, and meets regulatory and corporate policy obligations

•

Emergency response procedures

•

Requirements for documentation and reporting

•

Requirements for Quality Assurance and Quality Control (QA/QC)

This document does not address the operation and maintenance of the following facility components: • • • •

Mechanical and electrical systems Cyclone station Pump stations Tailing delivery, water supply, and water return pipelines

The operation and maintenance of the mechanical and electrical systems are addressed in Area 3800 prepared by Flour/PSI/SMCV.



September 2006

1.2

REGISTERED DOCUMENT HOLDERS

This Operations Manual will be revised, maintained and distributed by the Tailing Superintendent. Each copy of the manual is assigned an identification number for tracking purposes. The initial distribution list for the Operations Manual is provided in Table 1-1. TABLE 1-1 OPERATIONS MANUAL DISTRIBUTION LIST Department/ Position Name Company General Manager Cerro Verde Jesus Figueroa Operations Manager Operations Jim Vanderbeek Concentrator Manager Concentrator Oxide Plant Superintendent Concentrator Tailing Superintendent Concentrator Angel Manchego Engineering Superintendent Engineering Health, Safety, and Health, Safety and Environmental Superintendent Environmental Maintenance Superintendent Maintenance Control Supervisor Concentrator Cyclone Station Operator Concentrator Tailing Deposition System Concentrator Operator Designer (Engineer of Record) MWH James Obermeyer Review Board ETRB ETRB

Copy No. 1 2 3 4 5,6 7 8 9 10 11 12 13 14

The Tailing Superintendent is responsible for maintaining an up-to-date list of registered holders of the Operations Manual (Table A-1 in Appendix A). Each registered holder of the Operations Manual, including the Tailing Superintendent, must acknowledge responsibility for learning the contents of this document by returning a signed copy of the transmittal letter to the Tailing Superintendent within two weeks of receipt of this document (Table A-2 in Appendix A). 1.3

OPERATIONS MANUAL REVIEW AND UPDATE

This Operations Manual will be reviewed by Sociedad Minera Cerro Verde S.A.A. (SMCV) on an annual basis to address continual improvement and changes in the conditions and operation of the TSF. A review of the Operations Manual will also be required after a significant accident related to the operations of the TSF. All registered users of the Operations Manual are encouraged to provide comments and suggestions for improvement of the manual and the procedures specified in it. The comments and suggestions should be forwarded to the Tailing Superintendent and to the Designer (MWH) for consideration in the annual review of the document. The Tailing Superintendent is responsible for reviewing, updating and improving the manual, but no changes to the design criteria, design details, or specifications shall me made without the review and approval of MWH. The Tailing Superintendent is also responsible for implementing changes to the design and operation of the TSF when required. Revisions to the design and operation of the TSF will be performed according to the following steps: Step 1: Define need for change in design or operation. Step 2: Coordinate with other mine operations to evaluate the impacts of the proposed change. Step 3: Coordinate with TSF designers to obtain authorization for the change.



September 2006

Step 4: Communicate and coordinate the change with regulatory authorities and external stakeholders. Step 5: Obtain necessary permits. Step 6: Modify the Operations Manual to address the change. Step 7: Implement the change.

Potential situations that may result in a manual review and update are evolution of the design through capacity change, operational efficiencies, closure requirements, performance feedback, management changes, regulatory changes, variations of performance from design, and suggestions for improvement. Table A-3 in Appendix A should be updated to record any revisions of this document. 1.4

PROJECT HISTORY AND SCHEDULE

SMCV is in the process of development of the Cerro Verde Primary Sulfide Project. Phelps Dodge Mining Company (PD) is the majority shareholder and operator of SMCV. In 2001 and 2002, PD initiated scoping level studies to evaluate alternative TSF sites and tailing embankment construction methods. The results of these studies were presented in reports entitled “Tailing Scoping Study,” dated December 2001, “Scoping Level Study for Tailing Deposition at A5 Site,” dated January 2002, and “Scoping Level Study for Tailing Deposition at the A9 Site,” dated March 2002, by URS. In 2003, Fluor completed the “Cerro Verde Primary Sulfide Project Feasibility Study Report.” Part of the report was the “Tailing Embankment Feasibility Design Report” by URS, dated June 2004. As a part of the final design, SMCV contracted Montgomery Watson Harza Americas, Inc. (MWH) to develop final designs for the civil and geotechnical elements of the TSF. The MWH work scope consisted of site investigations, engineering analyses, design drawings, and specifications for the Starter Dam and Seepage Collection System, and Standard Operating Procedures (SOPs) for elements of the TSF within MWH’s scope of work. Final engineering design for the TSF was performed by MWH during the period from January 2005 to April 2006. Other design components of the TSF, such as tailing delivery system, cyclone stations, reclaim water system, and pump-back water system from the seepage collection system were designed by Fluor Mining and Minerals (Fluor). Permit for construction of the TSF was obtained from the Ministry of Energy and Mining (MEM) in September 2004. Construction of the Starter Dam was initiated in April 2005 and is scheduled to be completed in August 2006. Concentrator start-up is scheduled for November 1, 2006. Construction and operation of the TSF is planned to take place over a period of approximately 22 years.



September 2006

2.0 2.1

ROLES, RESPONSIBILITIES, AND TRAINING REQUIREMENTS GENERAL

A Cerro Verde TSF Management Team has been assembled to oversee the design, construction and operation of the TSF. The management structure is based on the principles outlined in the Mining Association of Canada Guide to the Management of Tailing Facilities. The organizational chart of the Cerro Verde TSF Management Team is presented in Figure 2-1. The team will be supervised by the Concentrator Manager with support from maintenance, environmental and engineering departments at SMCV. 2.2

ORGANIZATIONAL CHART

Figures 2-2 and 2-3 illustrate the organizational structure that will be used to operate the TSF. The Organization Chart considers the following: •

There will be 5 Shift Supervisors during all periods of operation of the TSF.

•

There will be 4 Cyclone Station Operators during all periods of operation of the TSF.

•

There will be 1 Tailing Embankment Specialist during all periods of operation of the TSF.

•

There will be 2 QA/QC Supervisors during all periods of operation of the TSF.

•

There will be 1 Surveyor during all periods of operation of the TSF.

•

There will be 18 Tailing Deposition System Operators during all daily operations of the TSF, and 14 Tailing Deposition System Operators during all night operations of the TSF.

•

There will be an independent 3rd party engineering firm (Engineer of Record) with a full time presence to manage and implement the QA/QC program and to monitor and document compliance of the operations and construction with the design requirements for the TSF. The Designer is preferred for this role.

2.3

ROLES AND RESPONSIBILITIES

The roles and responsibilities for each position and the authority during the operational cycle of the TSF are presented in Table 2-1.


September 2006

Cerro Verde TSF* Operations Manual

 5

TABLE 2-1 ROLES & RESPONSIBILITIES Position

Role

Responsibility Senior TSF operations and construction oversight. Provide recommendations for improvement of the tailing operations. Coordinate with other areas of the mine that may impact the tailing operations. Coordinate with other departments of the mine that will provide support for the tailing operations. Maintain relationships with external stakeholders related to the TSF. Safety/HERA oversight

Operations Manager

Overall Coordination

-

Concentrator Manager

Overall Management

-

Senior TSF operations and construction oversight. Coordinate with other areas of the mine that impact the tailing operations. Coordinate with other departments of the mine that will provide support for the tailing operations. Provide recommendations for improvement of the tailing operations. Ensure development, implementation and application of Safety/HERA program

Concentrator Superintendent

Plant Manager

-

Coordinate tailing production with Tailing Superintendent

-

-

Participate in start-up and commissioning. Implement Operations Manual Develop, implement, and apply Safety/HERA program for tailing facility Prepare reports according to the Operations Manual. Update the Operations Manual. Provide recommendations for improvement of the tailing operations. Detect and communicate potential problems related to the tailing operation to upper level management. Schedule sustaining capital investments. Coordinate with other areas of the mine that may impact the tailing operations. Coordinate work of sub-contractors to operate and maintain the TSF. Coordinate with other departments of the mine that will provide support for the tailing operations. Monitor and update closure plan as required. Implement activities as required by the operational permits for the TSF. Perform monitoring according to operational requirements. Update the Operations and Maintenance Manuals Maintain spare parts and equipment inventory. Maintain the document control system for the TSF. Maintain TSF equipment maintenance records. Stay up to date on new laws and permit requirements that relate to tailing operations. Prepare operation and sustaining capital budgets. Implement adjustments to the tailing pipeline operation. Wear monitoring of the pipelines. Update the water balance according to this Operations Manual. Prepare and update training programs for TSF personnel. Provide input to development, implementation, and application of Safety/HERA program Provide recommendations for improvement of the tailing operations. Implement Project Execution Plans for sustaining capital investments. Manage sustaining capital investment projects until they are turned over to operations. Implement independent review and audits of the TSF. rd Implement appropriate QA/QC through an independent 3 party (preferably the Designer) Provide support for monitoring the construction of the cycloned underflow raises to the TSF embankment. Provide technical support. Provide resources for TSF repair and cleanup. Interpretation of operati onal monitoring results Provide input to development, implementation, and application of Safety/HERA program Provide recommendations for improvement of the tailing operations. Implement activities as required by the environmental permits for the TSF. Perform monitoring according to environmental requirements. Incorporate the TSF into the SMCV site environmental management program. Ensure that SMCV environmental policies, guidelines and procedures are followed. Provide environmental training and technical support for exclusive tailing facility personnel. Interpret environmental monitoring data. Report non-compliance to the Tailing Superintendent. Validate environmental laboratory test results. Download and process meteorological data collected at the project site. Provide input to development, implementation, and application of Safety/HERA program Provide recommendations for improvement of the tailing operations. Provide emergency maintenance assistance during night shifts. Provide training and technical support for exclusive tailing facility maintenance personnel. Ensure that maintenance for the TSF is performed according to SMCVBT guidelines and procedures. Provide support to update the Operations and Maintenance Manuals Provide support to maintain spare parts and equipment inventory. Provide input to development, implementation, and application of Safety/HERA program Proactively monitor ongoing Safety/HERA program for Tailing Facility Provide recommendations for improvement of the tailing operations. Detect and communicate potential Health and Safety problems related to the tailing operation to upper level management. Provide health and safety training for exclusive TSF personnel. Ensure that health and safety programs and policies for the TSF are performed according to SMCV guidelines and procedures. Incorporate the TSF into the overall SMCV site Health and Safety Plan. Inspect the TSF related to Health and Safety requirements Supervise and ensure day to day application of Safety/HERA program Supervise TSF operations. Provide recommendations for improvement of the tailing operations. Detect and communicate potential problems related to the tailing operation to upper level management. Supervise, control and operate the TSF, according to this Operations Manual and related Operations and Maintenance Manuals. Supervise, control and operate the TSF reclaim water station according to this Operations Manual and related Operations and Maintenance Manuals Supervise, control and operate the TSF tailing pump station according to this Operations Manual and related Operations and Maintenance Manual prepared by Fluor. Day to day application of Safety/HERA program Supervise tailing distribution line operators and cycloned sand placement. Provide recommendations for improvement of the tailing operations. Detect and communicate potential problems related to the tailing operation to upper level management. Supervise, control and operate the TSF cyclone station and scalping cyclone station according to this Operations Manual and related Operations and Maintenance Manuals. Provide local site support to operate the TSF reclaim water barges. Day to day application of Safety/HERA program Provide recommendations for improvement of the tailing operations. Detect and communicate potential problems related to the tailing operation to upper level management. Operate the tailing distribution lines from the cyclone station to the impoundment according to this Operations Manual and related Operations and Maintenance Manuals. Day to day application of Safety/HERA program Provide recommendations for improvement of the tailing operations. Detect and communicate potential problems related to the tailing operation to upper level management. Implement the Operations and Maintenance Manuals. Control and replace the spare parts on a continual basis Provide recommendations for improvement of the tailing operations. Perform quarterly reviews of the TSF for compliance with design considerations and specifications. Support monitoring and monthly Operations Manual reporting requirements. Review instrumentation data Update Water Balance and Material Balance Provide technical support through the Tailing Superintendent including QA/QC program support and implementation/documentation Ensure HERA and Safety principles are designed into the system

-

Provide recommendations for improvement of the tailing operations. Perform annual reviews of the TSF for compliance with SMCV and international standards of practice.

Tailing Superintendent

Manager of Tailing System

Engineering Superintendent

TSF Stability and repairs

Environmental Superintendent

TSF environmental compliance / MEM reporting

Maintenance Superintendent

TSF pumps, electrical and piping maintenance

Health and Safety Superintendent

Facility and personnel health and safety

Shift Supervisor

Primary operations responsibility (day to day)

-

Cyclone Station Operator

Operation of cyclone station

Tailing Deposition System Operator

Operation / rotation of spigots

Electrical/ Mechanical Technician

Performance of maintenance

Designer (Engineer of record)

TSF engineering design and modifications

Tailing Review Board

TSF compliance with SMCV, Peru and International Standards

-

Authority Authorize dam operation and sustaining capital budgets

-

Assign resources to Tailing Superintendent consistent with capital and operational budgets Hire/replace Tailing Superintendent Decision to divert flows to auxiliary system during emergencies Coordinate with other areas Decision to shutdown concentrator and TSF during emergencies

-

Decision to divert flows to auxiliary system during emergencies Decision to shutdown the Concentrator during emergencies

-

Decision to divert flows to auxiliary system during emergencies Hire/replace TSF operational staff Decision to shutdown the tailing operations during environmental problems.

-

Carryout assigned duties / responsibilities Recommend actions to Tailing Superintendent resulting from interpretation of instrumentation and monitoring data

Carryout assigned duties / responsibilities

Carry out assigned duties / responsibilities

-

-

Direct health and safety plan development. Oversee plan implementation. Ability to stop activities deemed imminently dangerous.

Recommend emergency tailing diversion or mill shutdown to Tailing Superintendent Carryout assigned duties / responsibilities




Actions through recommendations to Operations Manager

Actions through recommendations to Operations Manager


September 2006

2.4

TRAINING REQUIREMENTS

The recommended training requirements are summarized in Table 2-2. TABLE 2-2 RECOMMENDED TRAINING REQUIREMENTS Recommended Training

Position n o g i n t i c n u i d a r n T I

n s l a n P o i t l a w a e r u i e n v p a e O M R

t w u e o i e v s e o R l C t r A o p Q e C R

d w n i e a e v s c e n n R a o l i t n e a a r t n u e i n p a a O M M

g n d i n n i a a A r D T A S C C S D

g n i y i n c e a n s r e n T g r o s e p s n a m e l E R P

Operations Manager

X

X

Concentrator Manager

X

X

X

X

X

Concentrator Superintendent

X

X

X

X

X


X

X

X

X

X

Engineering Superintendent

X

X

X

X

X

X

X

X

X

X

X

Control Supervisor

X

X

Cyclone Station Operator

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Environmental Superintendent Maintenance Superintendent Health and Safety Superintendent

Tailing Deposition System Operator Electrical/ Mechanical Technician Designer (Engineer of record) Technical Review Board

X

g l n a i n n d i o n a i r t a T a p t h y u l t e c a f c e a O H S

X

l a t n e m g n n o r i i n v i n a r E T

X

X X

X

X

X

X X

X

X

X

X

X

X

X

X

X

X

X

X

X


X

September 2006 Cerro Verde TSF * Operations Manual

3.0 3.1

 7

FACILITY DESCRIPTION

BACKGROUND INFORMATION

The Cerro Verde Mine is located in the District of Uchumayo, Province of Arequipa, Department of Arequipa. The Cerro Verde Mine has been in operation since the early 1970s. The current operation consists of two open pits: Cerro Verde and Santa Rosa, a heap-leach operation, and an SX/EW plant to produce copper cathode. The ore is processed through primary, secondary and tertiary crushers and placed on a leach pad after agglomeration. The produced copper cathode is loaded into trucks and shipped to the Port of Matarani, some 90 km west from the mine. The general site location is shown in Figure 3-1. We understand that according to the current mine plans higher-grade leachable material would be depleted by year 2025. Run of mine (ROM) ore will continue to be stacked until 2035. Sulfide mineralized ore was identified as a result of the exploration programs at the mine. Processing the sulfide ore requires the construction of a concentrating plant and a TSF to store the tailing materials produced as a part of the concentration operations. 3.2

FACILITY LOCATION AND BRIEF DESCRIPTION

The TSF site is located approximately 16 km southeast of the town of Arequipa in southern Peru. The TSF will be built in the Quebrada Enlozada immediately north of the processing plant, as is shown on Figure 3-2. The facility will consist of an 85 m high zoned rockfill starter dam, a 260 m high embankment constructed of cycloned tailing sand by the centerline method, and a tailing impoundment that will cover an area of approximately 453 Ha. The latitude and longitude of the Quebrada Enlozada at the location of the Starter Dam are S16 ° 29’ 34” and W71° 36’ 20”, respectively. The base of the Quebrada Enlozada at the location of the Starter Dam is at an approximate elevation of 2400 m above mean sea level (amsl). The elevation of the processing plant is about 2,700 m amsl. The Starter Dam crest elevation will be at 2485 m amsl and the ultimate embankment crest elevation will be 2660 m amsl. Tailing generated in the flotation process will be sent to two high capacity thickeners that will thicken the tailing slurry from about 27% solids to about 55% solids by weight. The thickened slurry will be conveyed by gravity through a 48-inch diameter HDPE SDR 21 pipeline to a cyclone station located on the right (East) abutment of the tailing embankment. At the cyclone station, the slurry will undergo two-stage cycloning to separate the sand fraction from the fine fraction. Silty sand (the underflow) will be used for embankment construction, and the fines (the overflow) will be discharged into the impoundment. A reclaim water pond will be maintained at the rear (upstream) end of the impoundment. Water from the reclaim water pond will be recycled to the processing plant for reuse and to the cyclone station for dilution. Seepage from the embankment will be collected by a network of finger and blanket drains and conveyed to a seepage collection sump located immediately downstream of the ultimate embankment toe. The water will then be pumped from the sump to the cyclone station and reused as dilution water. A scalping cyclone station located at the processing plant site will come in operation after the 1 st year. The purpose of the scalping station is to provide tailing overflow materials for deposition in locations where trapped water (i.e. water that would be inaccessible for recovery by the reclaim water return system) could accumulate. The scalping cyclone station is designed (by Fluor) to process up to 20% of the whole tailing feed from the plant. The separated sand will be combined with the remainder of the tailing feed from the concentrator and sent to the central cyclone station for subsequent cycloning at the main cyclone station. The overflow from the scalping cyclone station will be used for deposition from the upstream end of the facility as required for pond management. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 8

Make-up water to the plant to compensate for the losses at the TSF will be conveyed from Rio Chili via an 11.5 km long freshwater delivery pipeline. Prior to the start-up of the operations, water from Rio Chili will be pumped upstream of the Starter dam to form a start-up water pond. The required start-up water volume estimated by Fluor is 1,000,000 m 3. 3.3

SITE CONDITIONS

The following information describes the local landscape, topography, climatological conditions, seismicity, and site geology. 3.3.1

Landscape and Topography

The Cerro Verde Mine is located on the west slope of the Andes Mountains, in the south segment of what is referred to as the Coastal Batholith. The mine is situated on a plateau that has been eroded and dissected by numerous dry stream valleys to form locally steep and rugged. Elevations in the region range from about 2,300 to almost 3,000 m amsl. 3.3.2

Climate and Hydrology

The climate of the area is mild and arid with temperatures fluctuating between 10 ° and 24°C and average annual precipitation of approximately 36 mm. The rainstorms occur seasonally and are typically of short duration and high intensity. Over 90% of the annual rainfall is recorded during the months of January, February and March. The recorded evaporation exceeds the precipitation over 60 times. The estimated average annual evaporation rate is about 6.1 mm/day. The humidity ranges from about 30% in July to about 70% in February. The prevailing winds in the area are from the northeast. The region is characterized by distinct microclimate areas. Although located only a few kilometers away from the mine site, the Rio Chili valley receives significantly more rain than the area of the Cerro Verde mine. Based on general observations, the rainstorms are usually isolated in small areas, rather than covering a larger region. The rainstorms are typically of short duration and high intensity. These storms can cause unexpected floods with large peak flow rates in streambeds that are usually dry. The floods may entrain large amounts of sediment and debris and may cause damage to the local roads and infrastructure There are several meteorological stations located within about 15 km of the mine site. The coordinates and years of record of the meteorological stations that are closest to the project site are presented in Table 3-1.



 9 9

TABLE 3-1 METEOROLOGICAL STATIONS COORDINATES AND YEARS OF RECORD COORDINATES Meteorological Station Cerro Verde South Zone

La Pampilla

Latitude

Longitude

Elevation

16° 32' 23"

71° 35' 47"

2688 m

Data Description and Years of Record 1995 – 2004 daily data 1964-1977 max annual 24-hr data (from KP)

16° 24' 13"

71° 31' 6"

2360 m

Socabaya

16° 28'

71° 32'

2339 m

1966-1996 daily data (purchased from Senamhi)

Huasacache*

16° 28'

71° 33"

2242



*The Huasacache station replaced the Socabaya station in 1997. It was assumed that the Huasacache Station data is part of the Socabaya Station data.

The closest meteorological station is situated immediately south of the Cerro Verde pit and the collected data is considered to be the most representative of the climate of the area. However, data is available only since 1995 and is considered insufficient for hydrological studies. Other meteorological stations in the vicinity of the mine include the La Pampilla, Huasacache, and Socabaya stations, which are regional stations managed by Peru’s National Weather Service (Senamhi). The Huasacache and Socabaya stations located in the Río Chili valley are closest to the mine site and have the longest period of record (since 1966). The Huasacache and Socabaya stations were used to conduct rainfall frequency analyses and estimate the probable maximum precipitation (PMP) event for incorporation into the design and engineering of the TSF. Average precipitation at the Huasacache and Socabaya stations over the period of record is approximately 68 mm per year, which is substantially higher than that recorded at the Cerro Verde South station and therefore more conservative for the purpose of facility design and management. A summary of the results of the rainfall frequency analysis performed using the data from the Huasacache Huasacache and Socabaya stations is presented in Table Table 3-2. Detailed descriptions of the analyses are available in Volume 3 – PMP and Rainfall Frequency Analyses. TABLE 3-2 MAXIMUM RAINFALLS AT DIFFERENT RETURN PERIODS Return Period (Year) 24-Hour (mm) 48-Hour (mm) 2 13.3 17.0 5 23.7 29.4 10 30.6 37.7 25 39.2 48.1 50 45.7 55.8 100 52.1 63.5 500 66.9 81.2

72-Hour (mm) 20.1 36.1 46.7 60.1 70.0 79.8 102.5

The estimated Probable Maximum Maximum Precipitation (PMP) (PMP) for the project site for a range of durations is presented in Table 3-3.



Duration (hour) 1 2 3 4 5 6 12 18 24

TABLE 3-3 PROBABLE MAXIMUM PRECIPITATION PMP (mm) Duration (hour) 50 30 80 36 100 42 116 48 128 54 138 60 179 66 215 72 242

 10 10

PMP (mm) 265 286 307 307 324 324 343 343 360 360 376 391

The estimated drainage area contributing to the tailing impoundment site is 8.1 km2. The estimated total flood volume of the 72-hour PMP is 2,693,530 m3. The estimated peak Probable Maximum Flood inflow is 95.6 m3/sec. These values will be updated when a longer period of record of the Cerro Verde South Zone Station becomes available. available. 3.3.3

Seismicity

The TSF site is located in the “Big Bend” of the Peru-Chile subduction zone. Since 1471 some 20 earthquakes larger than MM (Modified Mercalli) Intensity IX have been recorded in this region. Deterministic and probabilistic seismic hazard evaluations were performed as part o f feasibility studies conducted by URS URS (URS, 2004). The results of these studies indicated that the design basis earthquake (DBE) would be the maximum credible earthquake (MCE) occurring along the Southern portion of the Peru-Chile subduction zone at a source-to-site distance of about 65 km from the TSF site. The DBE was specified as a moment magnitude magnitude 9.0 (Mw) megathrust earthquake producing producing a peak horizontal acceleration at the top of bedrock of 0.47g at the TSF site. The selected MCE is associated with return periods of about 2,000 to 3,000 years. The seismic hazard evaluations performed by URS were included in Volume 7 – Static and Seismic Stability Analyses. 3.3.4

Geology

Rocks that outcrop in the region include Precambrian gneiss that is overlain by a sequence of Jurassic to Tertiary age sedimentary units, extrusive volcanic units, and intrusive volcanic and igneous units. The region has a number of strong structural trends, including a predominant northwest no rthwest to southeast trends, as well as east to west and northeast to southwest trends. The northwest trending structures are predominant at the Cerro Verde Mine, with joint, fault, and geologic contact trends having this general orientation. The geology of the TSF site consists of a metamorphic metamorphic basement unit that has been overlain by a sequence of volcanic and sedimentary units that have been subsequently intruded. intruded. The valley bottom beneath the Tailing Embankment site is underlain by coarse dense alluvial outwash containing occasional pockets of volcanic ash. A thin veneer of colluvium covers the abutment slopes though rock outcrops are frequent. A large faulted block Middle Jurassic Jurassic Limestone referred to as the Socosani Formation bounds the upper Left Abutment. This unit lies unconformably unconformably on top of a Lower Jurassic Volcanic unit referred to as the Chocolate Formation. The lower Left Abutment consists of Cretaceous Gabbro, Diorite, and Andesite that has intruded the Chocolate and Socasani Formations. Subsequent intrusion intrusion by the Cretaceous Yarabamba Granodiorite has resulted in in the presence of numerous dikes throughout the Left Abutment and a later intrusion of the Tiabaya Granodiorite has resulted in a massive granodiorite outcrop adjacent to the crest of the Right Abutment. Subsequent intrusions of Microgranite are evident in the upper southeast portion of the impoundment. A geologic map of the project site is presented in Figure 3-3. Detailed descriptions and results of the geotechnical investigations are presented in Volume 2 – Geological and Geotechnical Site Investigations and Assessments.



3.4

 11 11

DESIGN BASIS AND CRITERIA

The general objective of the final design of the TSF was to provide storage for the planned tailing materials in a safe and environmentally responsible manner. Specific project objectives for the embankment design are to: •

Satisfy internationally accepted stability criteria for embankment construction in areas of high seismicity.

•

Minimize risk of seepage into the environment; aim at achieving zero discharge facility. A zero discharge facility in this case refers to a TSF and its ancillary facilities designed where necessary with liners to prevent seepage or with pump back systems to collect potential seepage, so that no contaminated seepage that can harm the environment is released.

•

Cost effectively incorporate locally available materials for construction without compromising safety.

•

Satisfy all Peruvian regulatory requirements associated with construction of TSF.

3.4.1

Compliance of Standards and Regulations

The operation o peration of the Cerro Verde TSF should comply with the regulations, standards and guidelines issued by the Peruvian Ministry of Energy and Mines (MEM), Ministry of Agriculture (MA), Ministry of Health (MH), and the National National Environmental Council (CONAM). (CONAM). To assure these standards are satisfied, an Environmental and Social Management Plan (ESMP) was developed. The PSP ESMP will be updated periodically throughout the life of the project in order to reflect operational and regulatory changes, to respond to monitoring results and incorporate improvements in environmental mitigation procedures. The ESMP will be the mandating document document for all environmental and social management, mitigation and monitoring, and should be consulted in conjunction with this TSF Operations manual. The regulations described in this section are those specifically related to the operation of the TSF, including general regulations applicable to all mining facilities and also specific regulations established in the Cerro Verde PSP EIA and ESMP; it is important to note that the environmental monitoring programs (such as meteorological, biological and geotechnical monitoring), included in the PSP EIA become legal obligations applicable to the TSF upon approval of the EIA, in accordance with the Peruvian legal framework. Water Quality Regulations Regulations

The MEM has developed water monitoring guidelines and requirements for monitoring frequency, locations and maximum permissible levels of parameters for designated mine effluent discharge presented in Ministerial Ministerial Resolution No. 011-96-EM/VMM (MEM, 1996a). 1996a). In addition, the MA, MA, in conjunction with the MH have developed water quality guidelines for receiving beneficial use waters presented in Supreme Decree No. 007-83-SA (MH/MA, 1983); some parameters were modified later in 2003 (Supreme Decree No. 003-2003-SA). These norms establish water water quality standards for the the protection of receiving water bodies in accordance with the level of treatment and their use. Receiving water bodies are categorized as Classes I to VI, as follows: • •

Class I: Domestic water supply with simple disinfection Class II: Treatment water supply equivalent to combined mixing and coagulation processes, settling, filtration and chlorination, approved by the Department of Health



• • • •

 12

Class III: Water used to irrigate raw-eaten vegetables and water consumed by animals Class IV: Water in recreational areas with primary contact (public toilets and similar uses) Class V: Water for fishing bivalve shellfishes Class VI: Water in aquatic or native preservation areas and for commercial fishing

The only receiving water body near the project area is the Río Chili, which is classified as Class III. A summary of the updated water quality standards for mine effluents and Class III waters are presented in Table 3-4.



 13

TABLE 3-4 WASTE WATER DISCHARGE AND WATER QUALITY STANDARDS SUMMARY

(1)

Parameters

Units

MEM - Regulatory Maximum Permissible Levels (MPL) for Mine Effluents

General Water Law - Perú Water

(2)

World Bank (3) Guidelines

Class III ANIONS, NUTRIENTS AND GENERAL CHARACTERISTICS (a)

Dissolved oxygen

mg/l

3

(BOD)

mg/l

15

(b)

Nitrate as N

mg/l

Sulfide

mg/l

pH

s.u.

6.0 - 9.0

6.0 – 9.0

TSS

mg/l

50

50

Cyanide, total

mg/l

1

1

Cyanide, free

mg/l

0.1

0.1

Cyanide, WAD

mg/l

0.2

Hexane extractable oil and grease

mg/l

Fenols

mg/l

METALS

100

-

0.1

0.5

0.5

10 -

(c)

Arsenic

mg/l

1

0.2

0.1

Cadmium

mg/l

0.05

0.1

Chromium

mg/l

1

0.1

Copper

mg/l

1

0.5

0.5

Iron

mg/l

2

Lead

mg/l

0.4

Mercury

mg/l

Nickel

mg/l

Selenium

mg/l

Zinc BACTERIAS

mg/l

Coliforms, total

(d)

Coliforms, fecal

(d)

3.5 0.1

0.2

0.01

0.01 0.5

3

0.05

-

25

2

MPN/100ml

5,000

MPN/100ml

1,000

-

Notes: (a)

Minimum required.

(b)

The Maximum Permissible Level (MPL) for Nitrate specified in the General Water Law of Peru is 100 mg/m , which is about 1,000 times lower than international standards. It is believed that the MPL should be 100 mg/l (for Class III), and the specified in the Law units are incorrect.

3

(c) The General Law of Waters of Peru and the WB refer to the total metals content; The MEM values refer to the dissolved fraction. (d) Considered as the maximum value in 80% of 5 or more monthly samples (e) The cells with no values indicate that no standards nor guidelines have been set up for this parameter Information Sources: MEM – Ministry of Mining and Energy (1996 and 1997). 1 MS – Ministry of Health, Class II, Class III and Class VI (2003); MS/MA – Ministry of Health and Ministry of Agriculture, Class II, Class III and Class VI 2 (1983). World Bank Pollution Prevention and Abatement Handbook, Base Metal and Iron Ore Mining, 1998. 3



 14

Air Quality Regulations

Air quality monitoring procedures, maximum permissible limits for emissions from miningmetallurgical activities and air quality standards were regulated by the MEM under Ministerial Resolution No. 315-96-EM/VMM (MEM, 1996b). Later, national air quality standards for residential areas have been established by CONAM under Supreme Decree No. 074-2001-PCM (CONAM, 2001) and Supreme Decree Nº 069-2003-PCM (2003), replacing the MEM MPL’s, except for the arsenic, for which the MEM’s MPL is still applicable. A summary of the ambient air quality standards is presented in Table 3-5. Table 3-5 AIR QUALITY STANDARDS SUMMARY PM-10 Reference

Period

Sulfur Carbon Dioxide Monoxide

Nitrogen Dioxide

Ozone Arsenic

Lead

3

(µg/m )

National Standards for Air (1) Quality

(5)

1 hour

-

-

30,000

8 hours

-

-

10,000

-

24-hours

Monthly Average Annual Average World Bank Annual (8) Guidelines Average 24-hours

(2)

(5)

200

-

(4)

120

-

(6)

150

365

-

-

-

6

-

-

-

-

-

-

-

1.5

50

80

-

100

-

-

0.5

100

100

-

100

-

-

-

500

500

-

200

-

-

-

(3)

(7)

Notes: 1 Supreme Decrees No 074-2001-PCM (2001) and Nº 069-2003-PCM (2003). 2 Not to be exceeded more than 3 times a year 3 Not to be exceeded more than 4 times a year 4 Not to be exceeded more than 24 times a year. 5 Not to be exceeded more than1 time a year. 6 Resolution No. 315-96-EM/VMM (MEM, 1996b) 7 Average of monthly values 8 WB Environmental Health and Safety Guidelines, Mining and Milling Open Pit, 1995

Air Emissions Regulations

The maximum permissible limits for emissions from mining-metallurgical activities are regulated by the MEM under Ministerial Resolution No. 315-96-EM/VMM (MEM, 1996b). These limits were established for PM-10, lead, arsenic and sulfur dioxide. In case of sulfur dioxide, the maximum permissible limits for emissions are linked to total sulfur input to the process, which is applicable to smelters. A summary of the air emissions standards is presented in Table 3-6.



 15

Table 3-6 AIR EMISSIONS STANDARDS

Reference

PM-10

Sulfur Dioxide

Lead

Arsenic

25

25

3

(mg/m ) MEM (1) Standards (2)

WB

100 (3)

50

According to sulfur input 2,000

Notes: (1) MEM, Ministerial Resolution No. 315-96-EM/VMM, 1996 (2) WB PPAH, General Environmental Guidelines, 1998 (3) Particulate Matter (PM)

Groundwater

No maximum allowable standards or limits for groundwater quality have been established in Peru. According to the commitment made by SMCV in the EIA, the established baseline values for groundwater quality will be statistically compared with the results of the groundwater monitoring. The methodology and criteria for groundwater monitoring established in the EMP (Appendix A) should be followed. Vegetation and Fauna

The Supreme Decree Nº 034-2004-AG “Categorization of Peruvian endangered species of fauna” establishes the list of protected species of fauna, but regulations and guidelines have not been established in Peru for biological monitoring. Therefore, the program for biological monitoring presented in the EMP (Appendix B) should be followed. The monitoring parameters are focused on both a qualitative and quantitative analysis of fauna and vegetation. A qualitative analysis of reptiles and mammals will be performed to establish a confirmed presence of these species. A quantitative analysis of birds will be performed to establish the overall abundance (estimated total numbers) of these species. A quantitative and qualitative evaluation of the guanaco and their use of the local habitat in and around the TSF will be performed. The list of protected species of flora has been established by INRENA (National Institute of Natural resources), but this regulation does not established monitoring procedures. Therefore, the program for vegetation monitoring presented in the EMP (Appendix B) should be followed. Soils

Regulations and guidelines have not been established in Peru for soil quality. The methodology and criteria to this respect presented in the Cerro Verde PSP ESMP should be followed. The proposed monitoring measures represent a qualitative procedure for ensuring that the tailing disposal system is functioning properly and that there are no unexpected equipment breakdowns. Visual inspections of the TSF will be systematically conducted including tailing delivery piping, cyclone station, reclaim water pond pump-back system, tailing delivery spigots, embankment seepage collection, and embankment crest (beach) area. The purpose of the inspections will be to detect evidence of tailing spillage that could occur outside of the established tailing deposition area.



 16

Geotechnical Conditions

Regulations and guidelines have not been established in Peru for the control of physical stability and geotechnical conditions. The monitoring activities to assess the geotechnical conditions of the embankment include piezometer monitoring, seepage monitoring, regular inspections, and planned geotechnical investigations. The results of the monitoring will be compared to the assumptions made in evaluating the stability of the embankment (Volume 7 – Static and Seismic Stability Analyses), and mitigation measures will be adopted as appropriate (see Section 10 Emergency Response Plan). 3.4.2

International Guidelines

The current international guidelines for environmental management were considered in the preparation of the environmental monitoring program for the Cerro Verde TSF. In 2004, the World Bank (the Bank) and the International Finance Corporation (IFC) which is an operating unit of the World Bank developed and issued what are known as the Equator Principles (IFC, Equator Principles, June 2003). The Equator Principles are implemented through the use of the Bank’s and IFC’s environmental guidelines related to environmental, socioeconomic, and cultural issues developed for the international financial entities. Many mining companies and international lenders have adopted the Equator Principles as a binding prerequisite for project financing. The Equator Principles were developed by the Bank and IFC to provide a framework for minimizing potential environmental and socioeconomic problems that may affect the lender’s investment risk in international mining projects. The Equator Principles require mining projects to develop an Environmental Management Plan that draws from information contained in a project’s Environmental Impact Assessment document. The EMP is required to address several topics including mitigation measures, monitoring programs, risk management, and environmental management scheduling. In addition, mining projects must adhere to applicable “Safeguard” policies and sector-specific environmental, health and safety (EHS) guidelines. The specific World Bank and IFC guidelines and standards that apply to the Cerro Verde mine include: World Bank Pollution Prevention and Abatement Handbook (PPAH), Base Metal and Iron Ore Mining, July 1998 • World Bank Mining and Milling – Open Pit Guidelines (1995) • IFC Operational Policy 4.01, Environmental Assessment • IFC Operational Policy 4.37, Safety of Dams •

3.4.3

Design Basis and Criteria

The design basis and design criteria adopted for the design of the Cerro Verde TSF are presented in Table 3-7 and Table 3-8, respectively.



 17

TABLE 3-7 CERRO VERDE TSF – DESIGN BASIS Site Characteristics Location Elevation Design Max Temperature Design Min Temperature Wind (max gust) Prevailing Wind Direction Average Annual Precipitation Average Daily Evaporation Catchment Area PMP MCE

16 km ESE of Arequipa 2400-2700 m 30 deg. C 0 deg. C 100 km/hr SW 36 mm 6.1 mm 810 Ha 391 mm M 9.0

Short occurrences only

South Zone Station No diversion channels 72-hr

Operating Requirements/Assumptions Ore type

Porphyry Copper

Ore Reserve

1.015 billion metric tons

Production Rate Total Years of Production Slurry Percent Solids from Plant Slurry Flow Rate Percent Solids from Tailing Thickeners Percent Fines in Tailing Slurry Slurry Solids SG Underflow Solids SG Overflow Solids SG Slurry pH

108,000 t/d > 25 27% 3 14,500 m /h 55% 67.5% 2.73 2.7 2.73 10

Average Dry Density of Overflow Average Compacted Underflow

Dry

Start-up Water Requirement

Varies Density

of

1.58 t/m

About 870 million tons will be accommodated in the designed tailing facility. Additional storage would be required for the remaining ore reserve. Ramp-up schedule for 1st 6 months 365 d/yr, 24 h/d Range 26-30% Range 50-60% Weighted Average Tailing Sample From Flour Lab test Lab test Range 9.0 – 10.5 based on consolidation testing and analysis

3

3

1,000,000 m

98% of max dry density (ASTM D 698); 3 the 1.58 t/m value will vary for different tailing materials over the life of the mine. From Fluor



 18

TABLE 3-8 CERRO VERDE TSF – DESIGN CRITERIA North America/ Peru

Regulations Flood Storage Requirement

PMF

Seismicity/Earthquake Load

MCE

Meet more stringent regulations when there is no conflict with Peruvian regulation. Contain within impoundment, min 100 m from embankment crest during flood conditions. Canadian Dam Association, Dam Safety Guidelines, 1999

Min Freeboard (Vertical distance between embankment crest and max impoundment elevation)

3m

Min Static Factor of Safety (FOS)

1.5

Post-earthquake FOS Max Embankment Deformation

1.2 3m

Canadian Dam Association, Dam Safety Guidelines, 1999; USBR, Chapter 4, 1987 ANCOLD Guidelines, 1998; USBR, Chapter 13, 2001 To preclude release of fluid from the impoundment.

Zero Discharge Concept

Embankment drains, sump, cut-off wall, grout curtain, monitoring/pumpback wells, limestone area treatment

Seepage/Solution Discharge Requirements Starter Dam Characteristics: Type Upstream Slope Downstream Slope (Upper Portion and between benches) Downstream Slope (Lower Portion) Starter Dam Crest Width Starter Dam Crest Elevation

To provide sufficient flood storage and accommodate anticipated settlements.

Zoned rockfill 2H:1V 2H:1V

Benches will be utilized for access and sand distribution.

3.5H:1V 15 m 2485 m

Embankment Characteristics: Construction Type Construction Material Maximum Percent Fines in Underflow Required Recovery of Underflow Cyclone System Operating Time (min) Maximum Lift Thickness (loose layer) Compaction Effort/Density Maximum Embankment Elevation Centerline Downstream Slope Crest Width

Centerline Compacted Underflow 15% 34% 90% 0.3 m 98% 2660 m 3.5H:1V 50 m

(Passing No. 200 sieve size) Of total tailing stream. Thickness prior to compaction 98% of maximum dry density (ASTM D 698) Private property restriction

Impoundment: Impoundment Beach Slope Pond Size Pond Location relative to Embankment

0.50% 20 Ha

Assumed beach slope From Fluor Pond located at upstream end of impoundment, possibly As far as possible two ponds. Pond will be against the starter dam for approximately 3 months during startup.

Seepage Collection System Characteristics: Power Outage

12 hrs

Flood Storage Requirement Drain Design Flow Factor of Safety

1 in 100 yr, 24 h storm 10

Seepage during this period to be contained within sump Contain runoff from design event within sump, and assume event coincides with power outage. Drain Capacity/Demand = 10 (no reliance on pipe conductors).



4.0 4.1

 19

FACILITY OPERATION

OBJECTIVE

The objective of this chapter is to describe the significant components of the tailing facility and to define operating standards and procedures in accordance with the design criteria, regulatory requirements, company policies and sound operating practices. The described procedures aim to provide guidance for safe, economical and environmentally responsible disposal and storage of tailing materials. 4.2 4.2.1

TAILING PRODUCTION AND TRANSPORT Tailing Characteristics and Production Schedule

Run of mine (ROM) ore is hauled from the open pits by trucks and dumped into the primary gyratory crushers. This crusher reduces the ROM ore from rocks up to 1-2 m in size down to all less than 280 mm. Crushed ore is transported by conveyors to an open stockpile adjacent to the concentrator. The 50,000 t live capacity of the stockpile allows the secondary and tertiary crushing stages to continue operating while the primary crusher is being serviced. The crushed product from the secondary crusher is returned to the coarse ore surge bin so it can be re-screened. Secondary screen undersize is 100% less than 50 mm. The tertiary crushing has four “lines” which operate independently of each other, although sharing common feed distribution and product conveyors. Each line includes a feed surge bin, a feeder and a high pressure grinding roll crusher (HPGR). These crushers exert a very high pressure on the ore passing through them. HPGR product is transferred to a row of ball mill feed bins. The HPGRs are in closed circuit, with the downstream ball mill feed screens providing a positive control on maximum particle size to the grinding circuit. Oversize from these screens returns to the HPGR surge bin for re-crushing. There are four independent grinding lines, each consisting of a feed surge bin, two reclaim feeders, two double deck screens, a sump and cyclone feed pump, a cyclone cluster and a ball mill. Each feeder discharges to a wet screen where the finely crushed ore is slurried and washed, with the fine underflow slurry discharging to the cyclone feed sump. The partly dewatered screen oversize is conveyed back to the HPGR surge bin. Screen undersize slurry is pumped to the cyclone cluster, which separates the finished product size material from the oversize. Oversize flows to the ball mill for grinding to finished size. The ball mill has a variable speed drive to control grind size to a narrow range. The particles need to be fine enough for mineral liberation, but coarse enough, so that sufficient sand is available to build the tailing embankment. The ball mill product discharges to the same cyclone feed sump as the screen undersize and is pumped to the cyclones for size classification. Cyclone overflow is sampled and analyzed for size and metal content as it flows to the rougher scavenger flotation row. Each grinding line has a dedicated row of flotation cells to make the initial recovery of mineral from the ground ore. Rougher concentrate from the first one or two cells in the row is higher grade than concentrate from the later scavenger cells and is handled differently. The rougher concentrate is given a short regrind in a stirred media detritor (“polish mill”) to clean the mineral surfaces and is then sent to the final stage of cleaner flotation. Scavenger concentrate from the remaining cells in the row is lower grade and needs more grinding and upgrading than the rougher concentrate. The combined scavenger concentrates from all four rows go to the regrind mills where size is reduced to about 80% passing 35 µm. These mills are vertical stirred mills, which are in closed circuit with cyclones to ensure a controlled product size. The reground scavenger concentrate feeds to the first cleaner cells for upgrading. These cells are the same size and type as the rougher scavenger cells and are in a parallel row immediately adjacent to the rougher-scavengers. Concentrate from the first half of the cleaner row joins the “polished” rougher concentrate as feed to the final stage cleaners. The lower grade concentrate from the second half of MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 20

the cleaner row, referred to as cleaner scavengers, returns to the regrind circuit for further grinding. The residual tailing from the cleaner scavengers is a final reject product and joins the scavenger tailing. Tailing from flotation represents 98% of the total plant feed weight and must be safely stored in perpetuity. The tailing is initially thickened in two high capacity thickeners to recover approximately 60% of the contained water for recycle to the process water system. The remaining thickened solids at 50-55% density are pumped to a pipe launder for transport to the tailing storage facility (TSF). This launder is at a shallow slope and flows by gravity at atmospheric pressure – the pipe is never more than half full. The realistic and aggressive start-up production schedules, provided by SMCV that were used as a basis for the material balance and water balance modeling for the TSF (Volume 5 and Volume 6, respectively), are presented in Table 4-2-1. TABLE 4-2-1 RAMP-UP PRODUCTION RATES Date

Realistic Ramp-Up Schedule

Aggressive Ramp-Up Schedule

11/01/2006 11/08/2006 11/15/2006 11/22/2006 11/29/2006 12/06/2006 12/13/2006 12/20/2006 12/27/2006 01/03/2007 01/10/2007 01/17/2007 01/24/2007 01/31/2007 02/07/2007 02/14/2007

t/d 27,000 29,500 32,500 36,500 40,500 44,500 48,500 52,500 81,000 84,000 88,000 92,500 97,000 101,500 106,000 108,000

t/d 54,000 54,000 54,000 54,000 54,000 54,000 54,000 108,000 108,000 108,000 108,000 108,000 108,000 108,000 108,000 108,000

Pilot testing on representative ore samples from the Cerro Verde mine was performed by Hazen during the project feasibility study. The results of the pilot testing included a range of gradations corresponding to the processing of the different ore samples. SMCV estimated the weighted average of the gradations of the whole tailing materials planned to be produced by the processing plant, which was used as a basis for the design. Krebs Engineers (Krebs) performed simulation analyses for the “weighted average whole tailing gradation” to estimate the quantity and quality of underflow materials that can be produced by a range of cyclone arrangements. The estimated weighted average whole tailing particle size distribution and the gradations of the tailing cyclone underflow and overflow estimated by Krebs, are presented in Figure 4-2-1. The presented gradations have been used as a basis for the design of the tailing facility. If a variation in the characteristics of the produced whole tailing is observed, its effect on the current design should be evaluated. SMCV is confident that an appropriate grind can be provided to satisfy the project requirements because of the fact that the HPGR technology and variable speed gearless drive ball mills will significantly reduce the amount of fines generated by milling and allow for production of a coarser grind. 4.2.2

Tailing Thickening

Tailing from flotation represents 98 percent of the total plant feed weight and must be safely stored in perpetuity. The tailing is initially thickened in two 75 meter diameter high capacity thickeners to recover approximately 60 percent of the contained water for recycle to the process water system. The remaining thickened solids are pumped to a pipe launder for transport to the TSF. Thickener MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 21

underflow density can range from 50 to 60 percent solids depending on feed rate and ore characteristics. Higher feed rate will typically result in reduced density. If more that one grinding line is out of operation, only one thickener would normally be operated for that period. Refer to the operations manual for Area 3700 for details of tailing thickener operation. 4.2.3

Whole Tailing Pipeline

Following thickening, the tailing slurry will be gravity-fed through a 48-inch HDPE pipe launder to a cyclone station located on the east abutment of the tailing embankment. This launder is at a shallow slope and flows by gravity at atmospheric pressure – the pipe is never more than half full. There are inspection manholes installed at 500 meter intervals along the length of the launder to allow inspection of the pipe for wear. If required, vents can also be installed at these manholes. Provision has been made for offtakes from the fresh water line adjacent to the tailing launder for potential local flushing of the line. Refer to the operations manual for Area 3700 for details of tailing launder operation. 4.2.4

Tailing Cycloning

Two cyclone stations will be constructed for the operation of the TSF. The purpose of the first cyclone station (the Central Cyclone Station) located on the east abutment of the tailing embankment is to produce tailing sand for the construction of the tailing embankment. The second cyclone station (the Scalping Cyclone Station) will be located at the Concentrator plant site and will come in operation after the first year of operation of the facility. The purpose of the scalping station is to separate the sand from a portion of the whole tailing stream. The sand would then be combined with the remainder of the tailing feed from the Concentrator and sent to the central cyclone station for subsequent cycloning. The tailing overflow produced at the scalping station will be used for deposition from the upstream ends of the impoundment to facilitate pond management. The slurry coming through the tailing launder (Section 4.2.3) to the Central Cyclone Station is rediluted to 39 percent solids prior to gravity feeding to two clusters of first stage cyclones. The first stage cyclones are equipped with an internal wash stage (cyclowash), which helps reduce the amount of fines reporting to the underflow stream. The sand underflow from this first stage is re-diluted and fed by gravity to a single cluster of second stage cyclones. The underflow from this final stage is rigorously controlled by the use of an on-stream particle size analyzer to ensure that the content of very fine particles remains within limits (<15 percent -75µm) while at the same time achieving maximum sand recovery. The sand balance is critical in that there is very little extra sand in the tailing beyond what is required for construction of the embankment. High operating time and production of on-specification sand are very important to the success of the operation. The sand is piped by gravity and distributed along the crest and downstream face of the embankment in 30 cm thick loose layers, which are drained and compacted before the next layer is placed. The compaction is critical to the structural integrity of the embankment. A separate sand line is provided to direct on-specification sand to the Eastern Quebrada during periods when the main on-dam distribution system cannot accept sand (first few months of operation). If the sand does not meet specifications it is diverted to a single point discharge that empties into the upstream impoundment area along with the cyclone overflow stream. As the embankment rises with ongoing sand deposition, the initial cyclone installation will have to be relocated to (or replaced with) a higher cyclone location. The location is a compromise between maintaining gravity flow of thickened tailing while minimizing pumping requirements for dilution water. The cyclone station will be moved twice over the life of the tailing impoundment facility, with the cost of relocation being more than offset by the savings in energy costs for pumping reclaim water MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 22

to cyclone system. Each move will have to be carefully orchestrated to minimize cyclone downtime and loss of sand production. It may be expeditious to replace much of the equipment and structure rather than moving the existing, just to maintain as much sand production as possible. During relocations, whole tailing will be discharged to the upstream impoundment area. During such periods, some of the whole tailing could be discharged to other fill areas in p lace of scalping cyclone overflow. The minimum required cycloned underflow sand for embankment construction versus time for a production rate of 108,000 t/d is illustrated in Figure 4-2-2. The sand requirement and whole tailing production were adjusted to reflect the realistic start-up production schedule (see Table 4-2-1) provided by SMCV. Refer to the operations manual for Area 3800 for details of cyclone and solids placement operation. 4.2.5

Jacking Headers

The coarse fraction (underflow) produced at the cyclone station will be used to construct the embankment and the fine fraction (overflow) will be discharged into the impoundment. The underflow will be transported from the cyclone station to the embankment via one of two pipelines. Initial operation will be with a 14-inch pipeline to the dam crest connected to a 12-inch pipeline across the starter embankment crest. Once production approaches normal design rates flow will be through an 18-inch line to the crest connected to 16-inch steel line along the crest. Both lines will initially be connected to downcomers fitted with spray bars, to distribute the sand across the face at a lower elevation. These downcomers will be retracted as the discharge level rises until ultimately each line will have its own spray bars mounted at the pipe. These two pipelines will be placed on a jacking header along the downstream side of the embankment bench on elevation 2475 m. The overflow will be transported via two 32-inch pipelines placed on another jacking header along the upstream side of the embankment crest (elevation 2485 m). The configuration and location of the jacking headers in cross section is illustrated in Fluor/PSI drawings PSP108-C-3830-50T-022, 023 and 025. Refer to the operating manual for Area 3800 for design and operating details of the jacking headers. 4.2.6

Other Delivery Lines

The feed launder to the first stage cyclones overflow lines is arranged to allow whole tailing to bypass the cyclones on an emergency basis and discharge to one of the overflow lines. The other overflow line extends beyond the initial deposition area to the western extremity of the embankment. This will be used intermittently to deposit overflow solids in the western valley to preclude the development of a pond in the limestone area. Second stage cyclone overflow contains a relatively small amount of solids and is discharged through a single point discharge pipe into the upstream side of the embankment, not far from the cyclone station. This line also picks up intermittent overflows from all the various tanks, launders, and vessels. If second stage cyclone underflow does not meet sand specifications, it is diverted to this single point discharge line. The future scalping cyclone station overflow will flow by gravity pipeline to the central and eastern valleys, where it will be discharged to manage where the reclaim water ponds can form. The overflow line will follow the tailing thickener underflow line to the area of the launder at the head of the 48-inch tailing pipe but will then diverge towards the west from that elevation. Scalping cyclone underflow rejoins the rest of the thickened tailing to flow to the tailing cyclone area. Refer to the operations manual for Area 3800 for details of the tailing delivery pipelines. 4.3 EMBANKMENT CONSTRUCTION MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 23

This section presents a description of the TSF embankment and provides guidelines for its construction. The following items are discussed: • • • • • • • • • • • •

Description of TSF embankment Embankment design assumptions Start-up Embankment Construction Contingency measures for embankment construction General embankment construction Deposition on the embankment crest Placement of underflow sands over the drains Description of special embankment features Deposition of underflow sands into the Eastern Quebrada Description of embankment instrumentation Embankment construction schedule Quality control and assurance of embankment construction

4.3.1

Description of the Embankment

The tailing embankment will consist of an approximately 260 m high (at maximum height) embankment constructed of cycloned tailing sand by the centerline method over an 85 m high zoned rockfill Starter Dam. The embankment is underlain by an extensive drain system to promote rapid drainage of the cycloned tailing sands. The Starter Dam, and the drain system within the estimated embankment limits for the first two years of operation are being built prior to the start of the operation of the concentrator plant. The embankment will be raised in lifts of cycloned tailing sands concurrent with filling the impoundment. A minimum of 3 m of freeboard between the embankment crest elevation and the elevation of the impounded tailing will be maintained at all times. As the embankment is raised in height, its footprint will expand downstream. Accordingly, the embankment underdrain system will be expanded. A brief description of the Starter Dam and the tailing embankment follows. •

Starter Dam: The purpose of the Starter Dam is to provide storage for the tailing overflow and whole tailing materials to be impounded during approximately the first year of operation as the embankment is being constructed of cycloned tailing underflow sand. The required height of the Starter Dam was established in an iterative process during the feasibility design of the tailing facility (URS, Tailing Embankment Feasibility Design, 2004). The suggested Starter Dam crest elevation of 2485 m was verified during the final design of the facility (Volume 5 – Material Balance Analysis).

The configuration and brief descriptions of the various zones of the Starter Dam are presented in Figure 4-3-1. The upstream slope of the Starter Dam is 2H:1V, and the downstream slope varies from 2H:1V to 3.5H:1V. There will be an 8 m and a 15 m wide bench at elevation 2455 m and 2475 m, respectively, along the downstream slope. The purpose of the benches and the flatter slope at the lower portion of the Starter Dam is to assist in the tailing underflow deposition during the first year of embankment construction. The detailed design drawings of the Starter Dam are included in Volume 10 – Drawings, Package 2 – Starter Dam Construction. •

Embankment: The tailing embankment will be constructed of compacted cycloned tailing underflow and raised by the centerline construction method. The embankment will have a crest width of 50 m and a 3.5H:1V downstream slope. The maximum ultimate embankment height will be approximately 260 m (crest elevation 2660 m). The ultimate embankment length will be approximately 2.5 km. Figure 4-3-2 shows a cross-section through the maximum height of the embankment in the center of the Quebrada Enlozada. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 24

The construction of the Starter Dam is scheduled to be completed in August 2006. The construction of the tailing underflow embankment is scheduled to begin on November 1, 2006 immediately following the commissioning of the processing plant. 4.3.2

Embankment Design Assumptions

The design of the embankment was performed following the design basis and design criteria presented in Table 3-6 and Table 3-7, respectively. Details on the assumptions and data used for the embankment design are presented in Volume 5 – Material Balance Analysis. A summary of the main assumptions for the embankment design is given below: •

Whole Tailing Production Rate (dry metric tons)= 108,000 t/d

•

Underflow Production (dry metric tons)= 33,048 t/d (34% recovery at 90% cyclone station availability)

•

Minimum Freeboard = 3 m *Freeboard is defined as the vertical distance between the embankment crest and the maximum level of the impounded tailing.

•

Embankment Slope = 3.5H:1V

•

Embankment Crest Width = 50 m

•

Underflow Percent Solids(by weight) = 70%

•

Maximum Percent Fines of the Underflow(particles smaller than 75 micron)= 15%

•

Compacted Dry Density = 98% of maximum dry density per ASTM D 698 (estimated 1.58 t/m 3 based on testing during design)

•

Maximum Lift Thickness (for compaction of embankment sands) = 30 cm (loose prior to compaction)

4.3.3

Start-up Construction

Embankment construction during start-up is critical to TSF performance from a material balance and stability standpoint. The start-up construction covers the period of time until the sand embankment reaches elevation 2485 m at 3.5H:1V downstream slope. Embankment Construction during Start-Up

The tailing embankment will be constructed of compacted underflow tailing materials and raised by the centerline construction method. The embankment construction will involve the following basic steps: Step 1: Deposit underflow tailing materials in a loose 0.3 m thick layer. Step 2: Allow the deposited underflow to drain. Step 3: Compact the drained underflow materials to 98% of the maximum dry density (ASTM D 698). Note: Part of the early deposition process will be to establish the number o f passes required to achieve 98% of the maximum dry density and use this as a general guidance for the compaction of the underflow. • • •



 25

To allow for the three steps to occur at the same time, the embankment will be divided into a minimum of three approximately 200 m long sections. The longitudinal length of the Starter Dam at elevation 2435 m is approximately 600 m and will allow the division into three zones. The downstream slope of the Starter Dam from the toe to elevation 2435 m was intentionally selected as 3.5H:1V to facilitate the initial placement of the underflow materials to the desired slope. The proposed sequence for the start-up embankment construction is as follows: •

A 12-inch HDPE underflow delivery line will be placed on a jacking header system on the Starter Dam bench at elevation 2475 m. This delivery line will be needed for the first two months when the mill production rate is about 54,000 tons/day. Subsequent to that time, the production rate will increase to 108,000 tons/day and a 16-inch underflow delivery line will be used.

•

Pipe extensions (6”) with a spray bar (4”) will be attached to the delivery line and extended to about elevation 2435 m along the slope (Figure 4-3-3a).

•

Underflow tailing deposition will take place along a segment of about 200 m length. After a layer of approximately 0.3 m loose thickness has been placed, deposition will progress to the next 200 m long segment. If deposition progresses from East to West, the most eastern open valve will be closed and the subsequent new valve following the last open valve (on the west) will be opened. This procedure will be repeated until all previously operated valves are closed and the valves on the next section for deposition are opened.

•

It was assumed that each of the three steps of the embankment construction would take about 24 hours. Thus, while depositing into the second segment, the first segment will drain, and while depositing in the third segment, the first segment will be compacted and the second segment will drain. Construction of two layers to elevation 2435 m is planned to take approximately 6 days (Figure 4-3-3a).

•

Over the following 2 to 3 months the spray bar extensions off the delivery pipe will be gradually withdrawn towards the bench at elevation 2455 m as the embankment elevation rises (Figure 4-33b).

•

Pipe extensions with spray bars from the delivery line on the header will be used until the embankment elevation approaches elevation 2475 m and an uniform 3.5H:1V slope has been established (Figure 4-3-3c).

•

The underflow deposition will continue by discharging from spigots in the delivery line on the jacking header at 2 m intervals (Figure 4-3-3d). Deposition will take place over about 200 m length along the crest at a time.

•

The header will be raised as required to provide sufficient space (underneath) for compaction of the deposited underflow along the crest of the embankment. A minimum of 4.5 m clearance beneath the header is required.

•

The downstream edge of the bench at elevation 2475 m coincides with the downstream edge of the 50-meter wide embankment crest. Upon reaching the bench at elevation 2475 m, deposition of horizontal lifts along the bench will be initiated. The width of the bench will vary from 15 m at elevation 2475 m to 35 m at elevation 2485 m (not including the 15 m starter dam crest width). Above elevation 2485 m the crest width will be kept constant at 50 m. The estimated embankment rate of rise between elevation 2475 m and 2485 m is about 1.2 m/week, which would require placement and compaction of about 4 lifts per week, assuming 30 cm (loose) lift thickness. The possibility of placement and compaction of thicker lifts (up to 45 cm) on the benches may be investigated at this time. The decision on the use of thicker lifts will depend on MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 26

the achieved lift compaction (homogeneous throughout the lift thickness at a minimum of 98% of the maximum dry density per ASTM D 698). •

Due to the limited initial bench width, and the fast embankment and header raise rate, hydraulic deposition of the underflow on the bench is expected to be difficult, so careful planning will be essential. The embankment crest between elevation 2475 and 2485 m should be raised by depositing underflow from the upstream spray bars and by dozing previously drained underflow upstream from piles that may form immediately downstream of the jacking header (along the edge of the embankment slope). Dozing and compacting the drained underflow is expected to increase the rate of lift construction. Beyond elevation 2485 m, the embankment crest will be raised following the procedure described in Section 4.3.5.

Underflow Stockpiling during Start-up

At the beginning of the embankment construction, the area available for deposition of underflow will be limited to the area of the downstream slope of the Starter Dam. This limited area will restrict the amount of underflow that can be deposited. The start-up embankment construction sequence and the area limitations during the first several months of the embankment construction are discussed in Volume 5 – Material Balance Analysis. It is estimated that during the first 4 to 6 months of operation, the amount of underflow that can be placed and compacted on the embankment is equivalent to 70 to 80 percent cyclone operating time. Two alternatives are available: 1) adjust the cyclone operating time to produce only the underflow quantities required for embankment construction and discharge the remainder of the tailing flow into the impoundment, and 2) produce as much underflow as possible and stockpile it downstream of the embankment toe. Alternative 2 above should be adopted to the extent feasible. Implementing this approach will have a positive effect on the material balance during this critical part of the embankment construction. Some quantities of underflow will be required for mechanical placement over the drains (Section 4.3.7) and the stockpiled underflow quantities could be used for this purpose. Stockpiled underflow can also be used as contingency for embankment construction during periods when the cyclone station is not in operation. All stockpiled material should be utilized for construction by hauling it to the place of final use, spreading it in 30-cm lifts and compacting it to 98% of maximum dry density (ASTM D 698). Stockpiled underflow material should not remain in uncompacted state in the stockpile area or elsewhere, as this would create a potentially liquefaction susceptible zone in the embankment. It is planned to stockpile the “extra” underflow from a ridge downstream of the Starter Dam toe on the east side of the valley (Figure 4-3-8). The underflow will be discharged via a 12” HDPE pipe off the main header. The underflow slurry would discharge into a pit excavated in bedrock for energy dissipation. The stockpiled underflow would be allowed to drain and would be mechanically transported and placed where required. By the time the underflow elevation reaches the elevation of the Starter Dam, it is anticipated that there will be no restriction on the amount of underflow that can be deposited (at 108,000 t/d production rate, 34% underflow recovery and allowing sufficient time for deposition, drainage and compaction). Start-up Water Pond

The purpose of the start-up water pond is to provide sufficient water in the beginning of the mill operations to compensate for the initial water losses and the expected delay in water recovery from the embankment and from the impoundment reclaim water pond. The design of the Starter Dam incorporates features that allow water storage to elevation 2430 m. Due to the achieved low permeability of the upstream embankment veneer (Zone 7), water could be stored to a higher elevation. The current start-up water filling plan, developed by MWH, Fluor, PSI and SMCV is MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 27

presented in Table 4-3-1. According to the plan, the start-up water pond elevation will be approximately 2431.34 m and will store approximately 1.9 million cubic meters of water.

Date

TABLE 4-3-1 PROYECTO CERRO VERDE - PRESA DE RELAVES DAILY WATER VOLUME AND FLOW RATE FOR START-UP WATER FILL PLAN Daily Water Water Daily Water Water Total Daily Daily Water Total Daily Total Average Volume Elev. East Volume Elev. West Water Water Elev. Water Cumulative Daily Water East Drainage West Drainage Volume Volume One Volume Water Flow Rate 3 Drainage Drainage East + one pond Pond (m ) Volume (Liter/sec) (m) (2) (m) (4) 3 3 3 3 West (m ) (m ) (1) (m ) (3) (m ) (6) (m) (7) (1)+(3)+(6) Drainage 3 (m ) (1)+(3)

7-Jul

1,926.01

2,412.0

1,926.01

1,926.01

1,926.01

22.29

8-Jul

2,487.04

2,413.0

2,487.04

2,487.04

4,413.04

28.79

9-Jul

4,145.18

2,414.0

4,145.18

4,145.18

8,558.22

47.98

10-Jul

6,215.12

2,415.0

6,215.12

6,215.12

14,773.35

71.93

11-Jul

2,609.93

2,415.3

2,609.93

2,609.93

17,383.28

30.21

12-Jul

2,609.93

2,415.6

2,609.93

2,609.93

19,993.21

30.21

13-Jul

2,609.93

2,415.9

2,609.93

2,609.93

22,603.14

30.21

14-Jul

3,251.58

2,416.2

8,259.37

2,410.0

11,510.95

11,510.95

34,114.08

133.23

15-Jul

3,572.41

2,416.5

10,344.20

2,411.0

13,916.61

13,916.61

48,030.69

161.07

16-Jul

3,572.41

2,416.8

18,105.56

2,412.0

21,677.97

21,677.97

69,708.66

250.90

17-Jul

6,587.19

2,417.1

21,629.69

2,413.0

28,216.88

28,216.88

97,925.55

326.58

18-Jul

12,616.76

2,417.4

25,090.43

2,414.0

37,707.20

37,707.20

135,632.74

436.43

19-Jul

12,616.76

2,417.7

28,806.28

2,415.0

41,423.05

41,423.05

177,055.79

479.43

20-Jul

12,616.76

2,418.0

9,515.50

2,415.3

22,132.26

22,132.26

199,188.05

256.16

21-Jul

14,245.66

2,418.3

9,515.50

2,415.6

23,761.16

23,761.16

222,949.21

275.01

22-Jul

14,245.66

2,418.6

9,515.50

2,415.9

23,761.16

23,761.16

246,710.38

275.01

23-Jul

14,245.66

2,418.9

10,255.73

2,416.2

24,501.39

24,501.39

271,211.76

283.58

24-Jul

4,748.55

2,419.0

10,625.84

2,416.5

15,374.39

15,374.39

286,586.15

177.94

25-Jul

2,419.0

10,625.84

2,416.8

10,625.84

10,625.84

2 97,211.99

122.98

26-Jul

2,419.0

11,036.42

2,417.1

11,036.42

11,036.42

308,248.41

127.74

27-Jul

2,419.0

11,857.58

2,417.4

11,857.58

11,857.58

320,105.99

137.24

28-Jul

2,419.0

11,857.58

2,417.7

11,857.58

11,857.58

331,963.58

137.24

29-Jul

2,419.0

11,857.58

2,418.0

11,857.58

11,857.58

343,821.16

137.24

30-Jul

2,419.0

13,473.02

2,418.3

13,473.02

13,473.02

357,294.18

155.94

31-Jul

2,419.0

13,473.02

2,418.6

13,473.02

13,473.02

370,767.20

155.94

1-Aug

2,419.0

13,473.02

2,418.9

13,473.02

4,491.01

2,419.0

4,491.01

2,419.0

13,473.02

3 84,240.22

155.94

14,930.55

2,419.2

19,421.55

4 03,661.77

224.79

3-Aug

22,395.82

2,419.5

22,395.82

4 26,057.59

259.21

4-Aug

22,395.82

2,419.8

22,395.82

4 48,453.41

259.21

5-Aug

23,324.01

2,420.1

23,324.01

4 71,777.41

269.95

6-Aug

25,180.39

2,420.4

25,180.39

4 96,957.80

291.44

7-Aug

25,180.39

2,420.7

25,180.39

5 22,138.19

291.44

8-Aug

25,180.39

2,421.0

25,180.39

5 47,318.58

291.44

2-Aug

9-Aug

27,970.38

2,421.3

27,970.38

5 75,288.96

323.73

10-Aug

27,970.38

2,421.6

27,970.38

6 03,259.34

323.73

11-Aug

27,970.38

2,421.9

27,970.38

6 31,229.72

323.73

12-Aug

29,748.52

2,422.2

29,748.52

6 60,978.23

344.31

13-Aug

30,637.58

2,422.5

30,637.58

6 91,615.82

354.60

14-Aug

30,637.58

2,422.8

30,637.58

7 22,253.40

354.60

15-Aug

31,559.49

2,423.1

31,559.49

7 53,812.89

365.27

16-Aug

33,403.29

2,423.4

33,403.29

7 87,216.18

386.61

17-Aug

33,403.29

2,423.7

33,403.29

8 20,619.47

386.61

18-Aug

33,403.29

2,424.0

33,403.29

8 54,022.76

386.61

19-Aug

36,090.60

2,424.3

36,090.60

8 90,113.36

417.72

20-Aug

36,090.60

2,424.6

36,090.60

9 26,203.96

417.72



Date

 28

TABLE 4-3-1 PROYECTO CERRO VERDE - PRESA DE RELAVES DAILY WATER VOLUME AND FLOW RATE FOR START-UP WATER FILL PLAN Daily Water Water Daily Water Water Total Daily Daily Water Total Daily Total Average Volume Elev. East Volume Elev. West Water Water Elev. Water Cumulative Daily Water East Drainage West Drainage Volume Volume One Volume Water Flow Rate 3 Drainage Drainage East + one pond Pond (m ) Volume (Liter/sec) (m) (2) (m) (4) 3 3 3 3 West (m ) (m ) (1) (m ) (3) (m ) (6) (m) (7) (1)+(3)+(6) Drainage 3 (m ) (1)+(3)

21-Aug

36,090.60

2,424.9

36,090.60

9 62,294.57

417.72

22-Aug

37,723.04

2,425.2

37, 723.04

1, 000, 017.60

436. 61

23-Aug

38,539.25

2,425.5

38, 539.25

1, 038, 556.86

446. 06

24-Aug

38,539.25

2,425.8

38, 539.25

1, 077, 096.11

446. 06

25-Aug

39,347.54

2,426.1

39, 347.54

1, 116, 443.65

455. 41

26-Aug

40,964.12

2,426.4

40, 964.12

1, 157, 407.77

474. 12

27-Aug

40,964.12

2,426.7

40, 964.12

1, 198, 371.89

474. 12

28-Aug

40,964.12

2,427.0

40, 964.12

1, 239, 336.00

474. 12

29-Aug

43,363.01

2,427.3

43, 363.01

1, 282, 699.02

501. 89

30-Aug

43,363.01

2,427.6

43, 363.01

1, 326, 062.03

501. 89

31-Aug

43,363.01

2,427.9

43, 363.01

1, 369, 425.05

501. 89

1-Sep

44,973.04

2,428.2

44, 973.04

1, 414, 398.09

520. 52

2-Sep

45,778.06

2,428.5

45, 778.06

1, 460, 176.15

529. 84

3-Sep

45,778.06

2,428.8

45, 778.06

1, 505, 954.21

529. 84

4-Sep

46,598.09

2,429.1

46, 598.09

1, 552, 552.30

539. 33

5-Sep

48,238.16

2,429.4

48, 238.16

1, 600, 790.46

558. 31

6-Sep

48,238.16

2,429.7

48, 238.16

1, 649, 028.62

558. 31

7-Sep

48,238.16

2,430.0

48, 238.16

1, 697, 266.78

558. 31

8-Sep

50,798.47

2,430.3

50, 798.47

1, 748, 065.25

587. 95

9-Sep

50,798.47

2,430.6

50, 798.47

1, 798, 863.72

587. 95

10-Sep

50,798.47

2,430.9

50, 798.47

1, 849, 662.20

587. 95

11-Sep

52,515.82

2,431.2

52, 515.82

1, 902, 178.02

607. 82

12-Sep

2 4, 90 8. 10

2 ,4 31 .3 4

24, 908.10

1, 927, 086.11

288. 29

NOTES 1. The water volumes and flow rates do not include water losses due to bank storage to saturate soils and bedrock in the reservoir area, seepage losses and evaporation losses. The total 3 3 volume of these water losses is anticipated to be in the range of 500,000 m to 600,000 m . 2. Eleven days of water transfer from the East Drainage to the West Drainage will be required (July 14 through July 24) until the two ponds become one. The water can be transferred by siphon lines or by pumping. 3. Average water flow rates assume pumping during a 24 hr period. T he actual flow rate can be increased and the pumping time reduced, as appropriate, to provide the total daily water filling volume.

Water losses are expected to occur while filling the start-up water pond. The losses are expected to be about 500,000 m3 to 600,000 m3 and include losses due to wetting the foundation, underseepage and evaporation losses. Filling the start-up water pond with water from the fresh water line from Rio Chili or other sources should consider the supply rate of available water including the rate at which water from the Rio Chili may be pumped, the required total start-up water volume and the potential water losses. The filling plan in Table 4-3-1 limits the fill rate to 0.3 m per day above elevation 2415 m to allow observation of the performance of the dam and mitigation of potential seepage. It is recommended that filling of the start-up water pond begins at least three months prior to the start of tailing deposition and that the filling be done at a controlled rate. It is estimated that the water within the start-up water pond will be used up by the end of the third month of the operation of the TSF. By this time, the development of a tailing beach should be in progress. With the tailing beach development two reclaim water ponds (East and Central) would form (Figure 4-4-1). A delay in the removal of the start-up water pond would potentially result in a lower density of the deposited tailing and a delay in the formation of a tailing beach. A lower density of the deposited tailing would result in a smaller capacity of the impoundment and a higher than estimated impoundment level, i.e. smaller freeboard. A delayed formation of a beach would potentially lead to MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


 29

the formation of a pond at or close to the embankment, which may compromise the embankment stability due to the formation of a higher phreatic surface or an increased risk of overtopping. For these reasons, it will be important to pump down the start-up water pond and to facilitate development of a tailing beach. 4.3.4

Contingency Measures and Problem/Solution Matrix

Producing insufficient quantity of underflow sand, development of a flatter or steeper than the design embankment slope, and occurrence of excessive seepage through the Starter Dam, have been identified as potential problems during the start-up of the embankment construction. Proposed contingency measures to mitigate the effects of such problems during start-up and beyond are discussed below. 1.1.1.1

Insufficient Quantity of Underflow

Problems at the cyclone station or at the Concentrator may result in insufficient production of underflow suitable for embankment construction. Potential problems could be originated by a change in the whole tailing grind, insufficient dilution water, failure of the equipment at the cyclone station, etc. Not being able to produce the minimum required underflow material would adversely affect the embankment construction schedule. As was discussed in Section 4.3.2 above, the rate of underflow placement during the start-up period will be constrained due to the limited initial embankment surface area. If underflow material is not available for a period of time during the start-up, the embankment construction will be delayed. Catching up would not be possible because of the relatively fixed disposal, drying and compacting cycle times. Exceeding the “allowed” underflow amount may compromise the quality of embankment construction. Only small variations in the production of underflow material required for construction could be acceptable due to the constrained underflow placement area and stringent compaction requirements. Potential delays in embankment construction during start-up may be avoided or mitigated by adopting the following measures: •

Cycloning as much tailing as possible while the station is in operation, and stockpiling the excess underflow. The stockpiled underflow could be used for embankment advancement during periods when the cyclone station is not in operation.

•

Supplement the underflow with borrow materials. This borrow material would need to be approved by the Engineer before placement.

Use of borrow material should be considered after evaluating the availability of previously stockpiled underflow materials. A decision to place borrow material should be made in the following circumstances: •

If the minimum available freeboard is less than 3 m, placement of suitable borrow material should begin immediately.

•

If there is a problem at the cyclone station that will take the station out of operation for more than three days, the existing condition of the facility should be carefully assessed.

•

In case, there is extra freeboard and production of sufficient underflow is expected to begin within a reasonable time period that will not compromise the freeboard requirements, the measures would include monitoring the progress at the cyclone station and the change in the freeboard. Preference should be given to a deposition from the upstream reaches of the impoundment, if such a deposition would not adversely affect the desired impoundment configuration and the reclaim pond location. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


•

 30

If there is extra freeboard, but a change in the tailing production or in the operation of the cyclone station that will result in a production of insufficient quantity of underflow is foreseen, planning for the use of borrow material should begin.

Suitable borrow material would be a mixture of clay, silt, sand, gravel and cobbles with a maximum particle size of 20 cm, and a maximum of 15 percent passing the No. 200 sieve. The borrow materials would be compacted to 98% of the maximum dry density (ASTM D 698) of the material at optimum moisture content. The Futuros Finos stockpile is an example of a borrow source that might be suitable. 4.3.4.2

Flatter or Steeper Embankment Slope

The main factors that influence the slope of the deposited underflow are its particle size distribution and the slurry percent solids. Coarser underflow sand produces a steeper slope, while finer underflow results in a flatter slope. A thin underflow tends to run down and produce a flat slope, while a thick slurry travels shorter distances and stacks at steeper slopes. Other factors that influence the slope of the deposited material are flow rate and potential energy of the flow (i.e. size and height of the spigots above the ground). Based on benchmarking studies and previous experience with similar materials it is expected that the slope of the underflow will deposit at about 3.5H:1V, which was selected as the basis for the embankment design. The developed material balance is based on the selected 3.5H:1V embankment slope. A flatter slope will potentially lead to insufficient material for embankment construction and will result in an inability to provide the required freeboard. A steeper embankment slope would result in an embankment that would be less stable than if it were constructed to the design 3.5H:1V slope. Flatter Embankment Slope

The slope of the underflow should be monitored during the start-up of the embankment construction. If a tendency to form a flatter than the design 3.5H:1V slope is established, measures to amend the situation should be immediately taken. The recommended approach is as follows: 1. Check the percent solids of the underflow slurry from the cyclone station. If the percent solids are lower than 70%, make adjustments at the cyclone station to increase the solids content and thicken the slurry. Monitor the effect of thickening. 2. If the percent solids is at least 70% and the slope of the deposited underflow is flatter than 3.5H:1V, check the gradation of the whole tailing feed to the cyclone station, the underflow recovery rate and the gradation of the produced underflow sand. Compare these gradations with those assumed in the design and proceed as follows: 

If the whole tailing gradation is finer than assumed for the design, make appropriate changes in the plant to produce coarser tailing materials.



If the gradation of the whole tailing matches the design, a variation in the recovery rate and/or in the gradation of the underflow material would most likely occur due to problems at the cyclone station. In this case, check the settings at the cyclone station and make the appropriate changes.

3. If the gradations of the whole tailing and underflow, and the percent solids of the underflow slurry are as per the design, and the slope of the deposited underflow is flatter than 3.5H:1V, report to the Tailing Superintendent, who should advise the Engineer on Record. Potential measures that should be evaluated at this stage include:  Further thickening of the underflow slurry (the maximum allowed percent solids should be established by the Shift Supervisor) MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222

September 2006 Cerro Verde TSF * Operations Manual   

 31

Production of coarser tailing (the economics of this action should be evaluated by the Concentrator Manager) Introducing changes to the deposition system Using approved borrow materials to supplement the underflow for embankment construction.

Using mine waste materials approved by the Engineer as borrow to be placed in the vicinity of the Starter Dam crest is an alternative for compensating for the additional embankment material that may be required in case the slope of the underflow is flatter than 3.5H:1V. Steeper Embankment Slope

If a tendency to form a steeper embankment slope is established, the recommended action plan is as follows: •

Reduce the percent solids by weight of the underflow from the cyclone station. Record the initial and reduced percent solids and the achieved embankment slope for both conditions.

•

If the reduced percent solids results in erosion of the embankment slope, the possibility of adopting a steeper than the design embankment slope should be investigated. The Engineer of Record should be immediately notified and assessments of the effect of the steeper slope on the embankment stability should be evaluated.

4.3.4.3

Excessive Seepage at Start-up

A start-up water pond will be impounded against the Starter Dam prior to the beginning of the operations of the TSF to compensate for initial water losses and potential delays in the water recovery from the impoundment and the embankment (Section 4.3.2). The design of the Starter Dam incorporates features intended to reduce the potential for seepage from the start-up water pond and from the deposited overflow tailing prior to the development of a tailing beach. The lower permeability veneer on the upstream face of the Starter Dam and the significant thickness of the body of the Starter Dam are expected to impede seepage from the impoundment to the downstream face of the Starter Dam. Seepage at the downstream face of the Starter Dam would generate difficulties for the construction of the tailing embankment. In the unlikely event of excessive seepage during the start-up period, the following measures are recommended: •

Install prefabricated seepage collection concrete sumps at locations where seepage is observed.

•

Install pumps in the sumps and direct the collected seepage away from the embankment face. Collected seepage may be discharged into the drains downstream of the active embankment toe. Care should be taken to protect the drains or the natural ground materials from erosion.

•

The number and size of the sumps would depend on the amount and distribution of the observed seepage.

4.3.4.4 Problem/Solution Matrix

An effort has been made to identify potential operational problems that could develop during operation of the TSF and corresponding solutions to the problems. Table 4-3-2 presents a summary of potential problems, possible solutions, and individuals that would be responsible for addressing the problems, should they occur. The table should be considered to be a “living document” and it should be expanded and updated to reflect lessons learned during operations. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


Table 4-3-2 Problem-Solution Matrix for TSF Construction.


 32


Problem 1. Insufficient u/f quantity in distribution to maintain velocity 2. Insufficient u/f quality (>15% minus #200 sieve) - not meeting target u/f gradation

3. Sanding of u/f line occurs

4. O/f line breaks or downcommer breaks or begins to significantly erode face of starter dam 5. Clear water pond develops in west drainage u/s of dam 6. Plugging of u/f discharge port (partial) Plugging of entire downcommer and spray bar 7. Insufficient u/f split/production

8. Pond management prior to beach formation 9. Pond management after beach formation

10. Erosion of embankment face 11. Flatter than 3.5H:1V embankment slope 12. Steeper than 3.5H:1V embankment slope 13. U/f drainage time longer than expected

14. Difficulty achieving specified u/f density

TABLE 4-3-2 TSF Operations Manual Problem-Solution Matrix Response

Symptom of Problem a. Sanding occurs b. Headers don’t operate properly c. Low line pressure Particle size analyzer alarm goes on

a. Divert u/f to Eastern Quebrada b. Divert to 12” header if 16” header is in use c. Once sufficient flow returns, return u/f feed to header on dam As trend of <#200 increases take action: st • Adjust dilution into 1 stage cyclones • Adjust cyclone pressure • Adjust cyclowash pressure

 33

Responsible Person The Tailing Operator or Tailing Control Room Operator identifies the problem and notifies Tailing Shift Supervisor to implement solution. The Control Room Operator notifies the Tailing Operator to checks the parameters and to correct the situation.

a. Distribution box overflows b. High pressure going onto dam. No pressure along dam crest (200 m away) Erosion observed

a. Switch to Eastern Quebrada or other u/f header b. Clear u/f line of sand (reestablish flow with water; flush entire u/f line at end of cleaning process) Switch to another u/f discharge line and repair cause of problem

The Tailing Operator or Helper informs Control Room Operator to implement response, or Control Room Operator implements response. The Tailing Operator informs theTailing Shift Supervisor. The Tailing Operator or Helper implements response.

Clear water pond observed

Deposit u/f into west drainage at end of u/f line.

The Tailing Operator or Helper observes problem and implements response, notifies Tailing Shift Supervisor

Plugging of individual ports occurs and is observed

Beat on it with mallet

The Tailing Operator or Helper implements response and notifies the Tailing Shift Supervisor.

Discharge flow from all ports stops a. Survey indicates that placed quantity is lower than theoretically predicted based on tonnage processed. b. Theoretical calculation of split based on concurrent samples of whole, o/f and u/f samples. Continued water pond located against starter dam

Move flow to another downcommer and clear blockage with water • Review grind gradations • Adjust cyclones • Adjust dilution water • Adjust cyclowash pressure • Reset grind target to coarser grind

a. Lack of uniform beach along u/s face of embankment b. Formation of trapped water ponds c. North limit of pond too close to dam face Erosion observed

Use less makeup water from fresh water system and more from the Tailing impoundment Adjust o/f discharge locations to result in uniform beach and eliminate trapped water ponds. Reduce pond size/depth

Repair eroded areas with dozers and compactors. Increase concentration of underflow

a. Flatter embankment slope b. Reduced freeboard Steeper slope

Increase u/f concentration. Check u/f gradation.

a. Inability to achieve the specified compaction according to the adopted schedule b. Wet surface observed. c. Water surfaces when heavy equipment passes.

Take a recently deposited underflow sample and check gradation. Report the results to the Engineer of Record. • Adjust cyclones to produce fewer fines. • Coarsen the tailing grind. • Reduce placement layer thickness. • Remove and mix the wet sand and recompact. • Conduct Standard Proctor Test on the area with difficulties for control. Measure “in-situ densities and moisture. • Adjust moisture of layer by spreading to a lower thickness if wet of optimum or by spreading to lower thickness and adding water if dry of optimum. • Spread sand layer to a lower thickness and then compact. • Increase number of compactor passes. • Identify source of erosion and divert or implement barriers. • Repair eroded areas by replacing eroded filter material. • Protect the filter material by mechanical placement and compaction of tailing underflow material to cover the filter material. Change tailing distribution locations in the impoundment to wet areas generating dust. Move sand distribution location to place over area generating dust. Check the availability of sufficient freeboard and adjust the overflow deposition location if necessary.

Measured “in-situ” densities do not meet specifications.

15. Erosion of the filter material over the drains

Erosion observed

16. Heavy dust problems

Dust observed on tailing impoundment Dust observed on downstream face of dam

Reduce u/f concentration •

The Tailing Shift Supervisor notifies the Tailing Superintendent. The Tailing Superintendent and Concentrator Manager implement solution.

Tailing Shift Supervisor The Tailing Superintendent and Concentrator Manager will coordinate The Tailing Shift Supervisor The Tailing Superintendent in coordination with Concentrator Superintendent

The Tailing Shift Supervisor The Control Room Operator as advised by the Tailing Operator. The Tailing Shift Supervisor to notify the Control Room Operator to implement solution. The Tailing Superintendent to notify the Control Room Operator to implement solution. The Tailing Dam QA/QC Supervisor

The Control Room Operator as advised by the Tailing Superintendent The Concentrator Manager The Tailing Superintendent Tailing Shift Supervisor


Tailing Shift Supervisor

Tailing Operator Tailing Shift Supervisor

Apply water with sprinklers.

17. Compaction equipment availability

18. Earthquake

Compaction takes longer than scheduled. Insufficient number of compactors available to replace faulty equipment. Earthquake felt by the personnel

Buy more compactors.


Rent or contract another compactor for temporary use. Access if there is imminent danger of failure. If a failure is imminent or in progress follow the emergency response procedures. If there is no imminent danger of failure, perform an immediate visual inspection of dam installations, download records from accelerometers, analyze piezometer data, and repair damage.

The Tailing Superintendent or qualified person, trained in safety and emergency response procedures

Tailing Superintendent Tailing Superintendent should advise Engineer of Record if signs of distress are identified.


Problem barge channel

23. More water reports to central drainage than accommodated by central barge 24. Lower than expected settling density of overflow

TABLE 4-3-2 TSF Operations Manual Problem-Solution Matrix Response

Symptom of Problem excess silt. Silty water appears at discharge of reclaim water. Increased size of pond in central drainage. Lack of sufficient water at Concentrator or Cyclone station Decrease of freeboard

• •

• •

•

25. Phreatic surface higher than the established limit.

High phreatic levels measured in piezometers

• • •

 34

Responsible Person

the downstream side of the reclaim water barge channel. Check bathymetry of the reclaim water pond Limit tailing deposition from the eastern side of the TSF. Change tailing distribution within impoundment as appropriate to encourage water flow into the east canyon. Install additional pump on the central barge. Increase sand production by increasing cyclone availability and/or increasing amount of sands produced (coarser grind). Investigate the possibility of using waste rock or quarry material to supplement the required sand to maintain freeboard.

Tailing Operator

Inspect the embankment for signs of distress (slides, cracks, seepage, etc.) Review the monitoring results to establish trends. Beach and Reclaim pond management if pond is too close to upstream embankment face.

The Tailing Superintendent notifies the Engineer of Record Engineer of Record and Tailing Superintendent


Concentrator Manager and Tailing Superintendent Tailing Shift Supervisor Concentrator Manager and Tailing Superintendent Engineer of Record and Concentrator Manager

Tailing Shift Supervisor

Cerro Verde TSF * Operations Manual  35

September 2006

4.3.5

General Embankment Construction

Raising the embankment will be ongoing throughout the operational life of the tailing storage facility. The embankment will be raised ahead of the impoundment by at least 3 m, at all times, except for the start-up period, as described in the previous Subsections 4.3.3 and 4.3.4. The estimated impoundment and embankment elevations with time are presented in Figure 4-3-5. Details on the development of the impoundment and embankment raise, depicted in Figure 4-3-5, are presented in Volume 5 – Material Balance Analysis. This Subsection describes the operation of embankment construction and how to implement key embankment features to facilitate performance according to design. Embankment Construction Process

The process of embankment construction will involve three basic steps: • • •

Step 1: Deposit underflow tailing materials in a loose 0.3 m thick layer. Step 2: Allow the deposited underflow to drain. Step 3: Compact the drained underflow materials to 98% of the maximum dry density per ASTM D 698.

The number of passes required to achieve 98% of the maximum dry density will be established during the start-up process and will be used as a general guidance for the compaction of the underflow. The underflow sands will be discharged in a consistent manner along the embankment crest beginning at either the East or the West end of the embankment and progressing towards the other end. The tailing underflow deposition along the downstream slope is intended to promote a “sheet-flow” and prevent erosion of the previously placed and compacted underflow tailing materials. If erosion of the previously deposited tailing materials is observed, the reasons for the erosion should be established and modifications to the operations implemented. Potential changes to the operations could be an increase in the percent solids of the underflow, a change in the gradation of the whole tailing materials (coarser grind), or an adjustment at the cyclone station to modify the gradation of the produced underflow, among others. The underflow will be discharged through spigots at about 2 m intervals off the underflow delivery line mounted on a steel structure with a jacking header. The spigots along an approximately 200 m length of the delivery line will be in operation at any one time. The deposition will continue until a 0.3 m thick loose layer parallel to the slope is created. The deposition will then progressively move to the next 200 m length along the embankment crest. Raising the jacking header should be coordinated with the embankment rate of rise and the deposition sequence. Clearance of a minimum of 4.5 m is required at any one time beneath the jacking header structure to allow compaction equipment to move beneath it. The newly deposited sands will then be allowed to drain until access of the compaction equipment on the sands is possible. The moisture content of the underflow should be near optimum prior to compaction. It is expected that it will take up to one day for the newly deposited underflow layer to drain. The drained underflow layer will be compacted using Caterpillar D6 dozers towing tandem 6 t vibratory compactors and self propelled 8 ton vibratory smooth drum compactors until 98% of the maximum density (ASTM D 698) is achieved. Typically 3 compaction units will be operating at the same time on the slope and one will be operating on the crest. A fifth unit will be on standby for use during maintenance. Embankment Lift Rate of Raise

The time to construct a complete 0.3 m lift along the entire embankment length will vary from a few days in the beginning of the operations to a few weeks at the end of the operations. The time depends MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

on the length of the embankment, the area of the embankment downstream slope, and the underflow production rate. The estimated crest and slope areas for various embankment elevations are shown in Table 4-3-3 below. Figure 4-3-6 presents the estimated time for construction of one lift at various points in time.

Approx. Year 1 3 5 8 11 14 17 22

TABLE 4-3-3 EMBANKMENT CREST AND SLOPE AREAS Embankment Crest Area Slope Area Crest Elevation 2 2 m m m 2485 40,000 208,000 2530 57,750 495,850 2550 83,500 660,250 2580 101,500 832,550 2600 109,000 955,100 2620 113,150 1,177,600 2640 118,800 1,445,200 2660 122,000 1,600,000

Raise Rate

The estimated embankment rate of rise in meters per week (monthly average) from the time the embankment reaches elevation 2485 m till the end of the operations, is presented in Figure 4-3-7. Accordingly, during the last 2 to 3 months of the first year of operation, the embankment raise rate would require the construction of two lifts per week as the embankment is raised above the starter dam crest. After approximately 2.5 years from the beginning of the operations, the construction of one lift per week will be sufficient. Freeboard

Freeboard is the vertical distance between the embankment crest elevation and the impoundment elevation against the embankment. The crest of the tailing embankment should be maintained at a minimum of 3 m above the impounded tailing slimes located upstream of the embankment crest. Considering the high rate of rise of the impoundment, it is recommended that underflow production and embankment construction continue even though 3 m or more of freeboard are available at any one time. This will be important to be able to maintain sufficient freeboard for events such as planned moves of the cyclone station and unplanned events. Beach Length

A start up water pond will be developed within the impoundment prior to the start of the operations. The volume of the water in the start-up water pond is intended to be consumed within the first few months of the operations. The deposition of tailing within the impoundment from the Starter Dam crest will push the pond away from the embankment and create a tailing beach. By the time the tailing impoundment reaches the crest of the Starter Dam, the length of the tailing beach should be at least 400 m. Due to the small size of the impoundment at this time, the estimated depth of a pond developed due to the PMF could be about 2 m at the upstream face of the embankment. For this reason, it will be preferable to maintain at least 5 m of freeboard within the first couple of years of operation. After the end of the second year of operation, 3 m of freeboard should be sufficient to store the runoff from the PMF. The location of the reclaim water pond and the length of the tailing beach throughout the operation of the TSF are illustrated in Figures 4-4-1 through 4-4-6. The expected beach length at the end of the 2nd year of operation is approximately 600 m. After about 10 years of operation, the reclaim water pond is expected to be at least 1000 m away from the embankment. These beach lengths will be sufficient to store the runoff volume from the PMF without encroaching on the embankment. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

In summary, the TSF should be operated and managed so that a minimum reclaim water pond is maintained, and a maximum beach length is achieved at any one time. The beach length should be at least 400 m when the impoundment reaches the crest of the Starter Dam and should increase continuously over time to 1000 m or more from the embankment by year 10 and beyond. Flow Length along the Slope

Based on experience at similar tailing facilities and benchmarking studies performed by MWH, PSI and SMCV/PD, it is expected that the underflow will deposit by gravity flow from the spray bars down the slope to a certain distance, generally between 400 and 600 m, before significant “mounding” of the downstream slope occurs. That distance cannot be determined with certainty at this time. The length of the downstream embankment slope is expected to reach 600 m within the fourth year of operation. The movement of the underflow along the slope will be monitored and when the length of the slope exceeds the underflow flow distance, additional measures will be needed to distribute the underflow along the slope. It is envisioned that spraybars fed from the header on the crest will be extended to deposit the material in the lower portions of the slope. A similar method is currently being used at the Quillayes TSF at Los Pelambres mine in northern Chile. Another option for facilitating the deposition of underflow along the embankment slope is by creating a separate bench on the embankment slope and placing an additional jacking header line on the bench for deposition of underflow to the lower portion of the slope. 4.3.6

Deposition on the Embankment Crest

This section describes the procedure for raising the embankment crest after it reaches elevation 2485 m (approximately 10 months after the start of the operations). The estimated embankment rate of rise at this time is about 0.6 m/week (Figure 4-3-7). The embankment crest is 50 m wide. While the embankment is raised, access along the crest should be provided for the purposes of operating the discharge spigots, jacking the underflow and overflow headers, and for underflow placement, spreading and compaction equipment. Raising the crest will follow the 3-step procedure for raising the embankment slope: deposit, drain, and compact. Underflow will be deposited on the crest using spray bars mounted inboard (i.e. facing upstream) on the underflow header line to produce windrows of sand. The configuration of the windrows is illustrated on Figure 4-3-7. The windrows will be spread and compacted mechanically. The following assumptions were made for the development of a procedure for raising the embankment crest: •

The embankment length at elevation 2485 m is 800 m. The embankment length was divided into 8 x 100 m segments.

•

The embankment width is divided into two approximately 25 m wide segments (upstream and downstream).

•

Deposition takes place over about 200 m embankment length at any time. Sufficient material for a 30 cm loose lift across the embankment crest (over 200 m length) is deposited. Deposition on the embankment crest will be concurrent with deposition on the embankment slope.

•

•

Sixteen hours are required for deposition along any 200 m segment.

•

Twenty-four hours are allowed for draining the deposited material.

•

Eight hours are allowed for spreading and compaction of a 30 cm lift. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

•

Access to the crest is from the east end of the embankment.

•

There is no vehicular access to the area where deposition or draining takes place.

The following sequence and procedure to raise the 50-m wide crest is proposed: EMBANKMENT CREST CONSTRUCTION East

Hours 0-8 U/S D/S SLOPE

P P

P P

C

C

West

C C C

D D

D D

D D

C

C C C

D D

D D

C

C C C

D D

8-16 U/S D/S SLOPE

D D

P P

P P

C

U/S D/S SLOPE

D D

D D

P P

P P

C

U/S D/S SLOPE

D D

D D

D D

P P

P P

C

C

C C C

U/S D/S SLOPE

C C C

D D

D D

D D

P P

P P

C

C

C

C C C

D D

D D

D D

P P

P P

C

C

C C C

D D

D D

D D

P P

P P

D D

D D

D D

P

C

C C C

16-24

24-32

32-40

40-48 U/S D/S SLOPE 48-56 U/S D/S SLOPE

C

56-64 U/S D/S SLOPE

C

Legend:

No Shading Notes: P= Place (deposit) D= Drain C = Compact

=No vehicular access from East =Limited vehicular access from East =Free access from East U/S= Upstream half of crest D/S = Downstream half of crest Slope = Downstream embankment slope



September 2006

4.3.7

Placement of the Underflow Sands over the Drains

A network of underdrains will be placed within the footprint of the ultimate embankment to assist in draining the embankment underflow materials. The underdrain system will consist of a blanket drain covering the alluvium at the valley bottom and finger drains in all main drainages. The drains will consist of three layers from the bottom up: a drain layer, a transition layer and a filter layer. The purpose of the transition and filter layers is to provide filter compatibility between the drain material and the underflow tailing material. The drains will be constructed in increments as the embankment is raised. Details about the drain design are provided in Volume 8 – Seepage Collection System Design. The drain construction schedule during the operating life of the TSF is presented in Section 4.5.1. Deposition over these drains should be done carefully to prevent damage to or contamination of the drains. After construction of the drains, the drain surface will be covered temporarily with geotextile to protect it from erosion, contamination, or equipment traffic. As the embankment rises and its footprint is extended, the geotextile will be removed progressively. At this time, to protect the top (filter) layer of the embankment underdrains from possible erosion and contamination by the hydraulically deposited underflow tailing, the drain surface will be covered with a protection layer. The protection layer will consist of an approximately 1 m thick layer of mechanically placed, drained underflow tailing materials. Three to four 30 cm thick loose layers will be placed and compacted to 98% of maximum dry density (ASTM D 698) to create the one-meter thick protective layer. The underflow material to be used for the drain protection layer will be stockpiled at pre-selected locations downstream of the embankment toe prior to placement. The underflow will be discharged via a 16” steel pipe off the main header down to the selected stockpile area. The underflow slurry will discharge into a pit excavated in bedrock for energy dissipation. The stockpiled underflow material will be allowed to drain and then will be hauled to the underdrains for placement and compaction. Prior to placement of the underflow material, the drain surface should be carefully inspected and any damage or contamination should be repaired before proceeding. 4.3.8

Special Embankment Features

The current design of the embankment has a few bends along its alignment. The reason for the bend on the left (west) abutment is the proximity of a private property. The purpose of the bends on the right side of the embankment is to avoid sections of the embankment crest being located over the upstream slope of hills where drainage of the embankment material will be difficult. The embankment alignment was optimized during the design of the pipeline corridor from the cyclone station to the Starter Dam. Figures 4-3-8 and 4-3-9 show a plan and a profile along the pipeline alignment, respectively. The original and optimized embankment alignments are also shown in Figure 4-3-8. Potential future changes to the embankment alignment should be consulted with the Design Engineer prior to implementation. 4.3.9

Deposition of Underflow Sands into the Eastern Quebrada

The steep (steeper than 3.5H:1V) and relatively high hills on the east side of the embankment were identified as representing a challenge to the embankment construction within the first few years of the operation. The identified potential issues include the following: •

Underflow placed on steep slopes will flow rapidly to the tributary valley bottom and down the plunge of the valley over the drain, thus potentially eroding them.


September 2006


•

It would be difficult to establish the required 3.5H:1V embankment slope, due to the steeper “starting” slope of the hills.

•

Filling the relatively large Eastern Quebrada (the second drainage on the east side of the valley downstream of the Starter Dam) represents a challenge.

Deposition over the steep hills is envisioned to take place with spray bars extended from the main header, similar to the start-up arrangement that will be used prior to the underflow reaching the Starter Dam crest. Some mechanical redistribution of the material beyond the edges of the spray bars using a dozer will be necessary as well. In addition, dozer pushing of material from the downstream face of the embankment is envisioned as the embankment spreads laterally up the drainages. To visualize the process of filling the Eastern Quebrada (EQ) a series of 3-dimensional (3D) “snap-shots” of the embankment construction spanning between month 16 and month 36 after the start of the operation were developed. The 3D snap-shots prepared are presented in Figure 4-3-10 through Figure 4-3-15 and described below. •

Figure 4-3-10 illustrates the estimated embankment configuration approximately 16 months after the beginning of the operations (February 1, 2008). The estimated embankment crest elevation is 2500 m. The portion of the finger drain in the EQ completed as a part of the capital construction (approximately 100 m into the drainage) is shown in the figure. The remainder of the finger drain will not yet be constructed at this point in time. Placement of the remaining portion of the finger drain in the EQ should begin in month 16. Production of the drain material should start several months prior to the finger drain construction.

•

Figure 4-3-11 illustrates the estimated embankment configuration at the end of year 2 (24 months; October 1, 2008). The embankment crest elevation is 2514 m. The first 100 m of the finger drain is covered with previously stockpiled material spread in 30 cm (loose) lifts with a dozer and compacted. The remaining part of the finger drain has been constructed in the EQ. Placement of 2 to 4 lifts of compacted underflow for drain protection is initiated. The underflow is deposited at 4 locations using spray bars. Boulders are placed at the discharge points to dissipate the energy of the slurry, if necessary.

•

Figure 4-3-12 presents the embankment configuration after 26 months (December 1, 2008). The crest elevation is 2518 m. It was assumed that one lift is placed along the quebrada every 2 days. The underflow is deposited using the spray bars, pushed and spread with dozers and compacted. It is assumed that the slope will be approximately 4H:1V at this time and will progressively steepen to 3.5H:1V. About 30 lifts have been placed during the 2-month period. The time required for placement and compaction will be only partial days because of the low volumes of underflow that will be placed. Therefore, placement of this number of lifts in the two-month period is considered feasible.

•

Figure 4-3-13 shows the embankment configuration after about 28 months (February 1, 2009). The embankment crest elevation is 2520 m. At this time a 3.5H:1V slope has been established. Deposition continues from the four locations using the spray bars. The material is pushed and spread between the deposition points to the required slope with dozers and compacted.

•

Figure 4-3-14 illustrates the embankment configuration after about 32 months from the start of the operations (June 1, 2009). The estimated embankment crest elevation at this time is 2525 m.

•

Figure 4-3-15 shows the embankment configuration at the end of the 3 rd year (36 months; October 1, 2009). The embankment crest elevation is 2530 m. At this time most of the EQ has been filled in and a slope of 3.5H:1V has been established from the crest of the embankment.



September 2006

Deposition in the EQ will begin from its downstream end by pushing previously stockpiled material over the initially installed drain. The “stockpile” line will be installed prior to the beginning of the operations. After the construction of the finger drains is completed, deposition from three or four spray bars off the main header line and from one spray bar off the “stockpile” line will begin. The spray bars will be located at about 100 to 150 m spacing. Initially the material will be discharged into a pile of boulders, if necessary, to prevent erosion of the drains. The first 2 to 4 lifts (0.6 to 1.2 meters) over the drain will be hauled and spread over the drains and compacted. Subsequently, the material will be hydraulically deposited via spray bars and spread in such a way so that a slope is established, and the slope is steepened with every consecutive lift until a 3.5H:1V slope is achieved. The pipes with the spray bars will be withdrawn/shortened as filling the valley progresses, similar to underflow placement concept planned for start-up. The locations of the spray bars shown in the attached figures are approximate and for illustration purposes only. The design of the spray bars is presented in drawings PSP108-C-3830-50T-026, 027 and 028 by Fluor/PSI. Filling the first (smaller) valley on the east side of the embankment is envisioned to take place by pushing and spreading underflow material from the embankment face into the valley as the embankment is raised. Another alternative is using a spray bar off the stockpiling line. The material will be spread in 30 cm lifts and compacted. 4.3.10

Embankment Instrumentation

Embankment instrumentation will consist of piezometers installed in the Starter Dam, in the foundation, in the drains, and in the embankment underflow. The purpose of these piezometers is to monitor pore water pressures and phreatic surface within the embankment. Maintaining pore water pressures and the phreatic surface within the design limits is critical to the performance and stability of the TSF. In addition, two accelerometers will be placed on bedrock outcrops close to the embankment to monitor ground accelerations during seismic events. The data registered in these accelerometers will be used to verify the seismic parameters utilized in the design of the TSF. Piezometers will be installed in the embankment throughout the operating life of the TSF according to the design and construction permit approved by the Ministry of Energy of Mines of Peru. A plan view of the piezometers that are being installed as part of capital construction are shown in Figure 4-3-16. The locations of the piezometers in cross sections are shown in Figure 4-3-17. Detailed design drawings for these piezometers are included as Package 6A in Volume 10. The locations of the piezometers planned to be installed during operations are shown in plan view on Figure 4-3-18 and on sections on Figure 4-3-19. A description of the system and layout of the piezometers is summarized below: •

Pore water pressures will be monitored within the embankment foundation, embankment drainage system, and Starter Dam and underflow embankment. Piezometers have been located accordingly.

•

The piezometer network is comprised mainly of electric Vibrating Wire Piezometers (VWPs). Some open-standpipe piezometers are installed to allow direct measurement of the phreatic surface or pore pressure without the need of electronic devices such as the VWPs.

•

Cables from the VWPs are extended to the surface to boxes named I/O XPAK. Data from the I/O XPAKs are transmitted through a wireless network to a host computer located at the cyclone station. The wireless network requires direct line of site between antennas and transmitters. The objective of the wireless network is to minimize cable runs prone to failure due to heavy equipment activity or lightning. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

Piezometers that will be installed during operations should be designed and implemented according to the following guidelines and criteria: •

Use piezometer locations indicated in Figures 4-3-19 as a basis. Move slightly or relocate piezometers to address specific issues that may be detected during operation of the TSF. These issues will likely be identified from the periodic monitoring of pore water pressures in previously installed piezometers and seepage monitoring data, among others.

•

Decide which locations would be implemented as stand-pipe piezometers.

•

Design Engineer will approve final location of piezometers before installation and supervise the installations.

•

Minimize cable runs and use existing support structures to the extent possible.

•

Drill and embed piezometers using as a basis the Drawings and Specifications utilized for capital construction.

•

Coordinate with the Tailing Superintendent to ensure that the data from the VWPs to be installed will be recorded, synthesized and interpreted in the plant SCADA system.

Electric and stand-pipe piezometers may fail. These piezometers may need to be replaced. Consult with the Design Engineer to define replacement or potential relocation of failed piezometers. 4.3.11

Embankment Construction Schedule

Construction of the embankment is envisioned to continue throughout the operational life of the TSF, currently estimated at approximately 22 years. Embankment construction is planned to take place 24 hours/day and 7 days/week. Details on the embankment construction schedule are presented in Section 11.0 and illustrated in Figure 11-1. 4.3.12

QA/QC of Embankment Construction

Quality Assurance and Quality Control (QA/QC) activities are critical to the proper construction of a stable and serviceable embankment. This section describes the QA/QC requirements for the construction of the embankment and the monitoring of tailing underflow sand placed as part of the embankment construction. This operation manual does not cover the operation of the tailing stream prior to it exiting the tailing distribution system, all processes prior to this limit shall be controlled by the Flour and PSI manuals governing these facilities. Table 4-3-3 contains a summary of the parameters, test methodologies, test frequency, and test location required under this manual. These requirements augment the general requirements for facility surveillance presented in a later section.



September 2006

Parameter Gradation* % Solids* % Fines* Lift Thickness

In Place Density and Moisture Content In Place Density and Moisture Content Gradation of In Place Underflow Compaction Characteristics

Slope

Freeboard

Erosion

TABLE 4-3-4 SUMMARY OF QC/QA OBSERVATION PARAMETERS Method Frequency Location Defined by Defined by PSI/Fluor, Cyclone Station PSI/Fluor continuous if possible Defined by Defined by PSI/Fluor, Cyclone Station PSI/Fluor continuous if possible Defined by Defined by PSI/Fluor, Cyclone Station PSI/Fluor continuous if possible Visual-Lathe Continuous as Throughout the active placement with 30 cm mark underflow is placed area. Lathe to be placed in a grid at 50m spacing. 2 ASTM D2922 1 test per 4800 m per Randomly within each 50x50m grid. ASTM D3017 lift ASTM D1556 1 test for every 10 One confirmation test using ASTM ASTM D2216 or measurements with D1556 for every ten measurements ASTM D4643 ASTM D2922 made using the ASTM2922. ASTM D422 2 tests per 24 hours Samples should be taken from points close to and far away from discharge points. ASTM D698 1 test per 24 hours Underflow Placement Area, alternate when underflow is being between three locations: (1) close to placed underflow discharge point, (2) center of slope downstream of discharge points, and (3) lower part along slope downstream of discharge points. Visual and Visual: daily The downstream slope of the survey Survey: weekly or as embankment. required based on visual inspections Visual and Visual: daily Along the entire crest survey Survey: weekly or as required based on visual inspections Visual Daily Observations should be made for the entire face and recorded daily.

*Refer to Operations Manual for Area 3800 for details.

It is planned that the QA/QC services will be performed by the facility Design Engineer during at least the first 3 years of operation. QA/QC responsibility beyond the first 3 years will be determined at that time. 4.3.12.1

Lift Thickness

Loose lift thickness (prior to compaction) shall be monitored for each lift in all active underflow placement areas on the embankment face and crest. Loose lift thickness shall not exceed 30 cm. Visual control of lift thickness should be maintained using survey lathe (or similar) marked at 30 cm and set in a grid at 50 meter spacing. Multiple lifts can be marked on a single lathe after the previous lift has been compacted. The change in lift thickness after compaction should be recorded. Lathe marking loose lift horizons will be buried as compaction equipment progresses across the working face and should be reestablished whenever a new lift is initiated within an area. Control of the lathe grid should be established with survey equipment. The grid points can be periodically reestablished using a survey tape to measure spacing and subsequent lift thickness between surveys of the embankment face in a working area. The density of the lathe grid may be adjusted if tighter spacing is needed to control lift thickness. Observations of lift thickness shall be recorded in the Daily Report (Appendix C) to document that the described loose lift thickness is not exceeded.



September 2006

4.3.12.2

In-place Density and Moisture Content

In place density and moisture content measurements shall be monitored to confirm that the underflow material is compacted to 98% of Standard Proctor maximum dry density (unit weight) at or close to optimum moisture content (estimated at 15% to 20% based on compaction tests performed during the final design of the TSF). The nuclear moisture density gauge shall be the primary method of measuring density and moisture content. Measurements with the nuclear moisture density gauge shall conform to the requirements of ASTM D2922 for density measurements and ASTM D3017 for moisture content measurement. Density and moisture content measurements should be taken at an interval of one test per 4800 m 2 of material placed for each lift. Additionally, one density and moisture content measurement conforming with the requirements of ASTM D1556 and ASTM D2216 or ASTM D4643, respectively, shall be made for every ten measurements using the nuclear gauge. The results of density and moisture content measurements and the compaction curve utilized to calculate percent completion shall be recorded on numbered Form A (included in Appendix C1) in order to document that the specified compaction requirements are being met in the field. In case compaction requirements are not met, this should also be documented in Form A, and measures shall be taken to meet the compaction requirements. These measures (e.g. number of additional passes of compaction) should be indicated in Form B (included in Appendix C1). Form B should be attached to Form A, and should show that compaction requirements are met after implementing the corrective measures. Density and moisture measurements will be submitted as part of the Weekly Tailing Facility Operations Report (Appendix C2). The frequency of measurements may be reduced with the approval of the Design Engineer once methodology and number of passes for compaction and management of moisture content have been developed and proven to be reliable. The Design Engineer shall be consulted prior to making any adjustment to the frequency of any testing described in this manual. Additional requirements for documenting the number of equipment passes shall be imposed as part of any quality assurance/control program adjustment that allows for the reduction in the frequency of direct density measurements. 4.3.12.3

Gradation of In-place Underflow

Gradation of in place underflow materials shall be characterized twice per 24-hour day. One sample for testing shall be collected from an area near the location of initial deposition from the discharge point. The second sample shall be collected from the portion of the active placement area farthest from the initial deposition point. The locations of sample collection should be varied between extremes vertically and horizontally across placement areas to provide data from which occurrence of segregation can be evaluated. Gradations shall be performed in accordance with ASTM D422 “Particle-Size Analysis of Soils”. The data generated from this testing shall be documented in Form C (included in Appendix C1) and included as part of the Weekly Tailing Facility Operations Report. The Design Engineer and the Tailing Superintendent will evaluate how closely the gradation matches the material considered in the design. If gradations deviate from the range provided in Figure 4-2-1, the operation of the cyclone station and plant will be checked. In no event will underflow material with a fines content (percent passing the No. 200 sieve) exceeding 15% be placed on the embankment.



September 2006

4.3.12.4

Compaction Characteristics of In-place Underflow

The compaction characteristics of the tailing underflow sands being deposited on the embankment shall be tested once every day when underflow is placed. Compaction characteristics shall be tested in accordance with ASTM D698. This data will be used in conjunction with the density measurements performed that day so that the proper compaction curve is used to calculate the percent compaction. The results of the testing shall be documented in Form D (included in Appendix C1) and reported as part of the Weekly Tailing Facility Operations Report. The project engineer may approve the use of ASTM D4253 to provide a maximum dry density if ASTM D698 fails to provide a well-defined compaction curve. If this adjustment becomes necessary, a new specification for in place density may be developed. 4.3.12.5

Slope

The slope of the embankment should be monitored on a daily basis within the active placement area to provide for construction in accordance with the 3.5H:1V design downstream slope of the embankment. Monitoring should be performed continually through visual observation. However, the control of the embankment slope should be surveyed on a weekly basis as a minimum. At least once a month the face of the embankment should be surveyed to provide data to measure the slope and progress of embankment construction. This survey should also be used to reestablish the grid of survey lathe used to control loose lift thickness as indicated in section 4.3.12.1. If the slope of the embankment is flatter or steeper than 3.5H:1V, the Design Engineer should be informed and the need to implement the contingency measures described in Section 4.3.2 should be considered. 4.3.12.6

Freeboard

Freeboard between the impounded tailing material and the crest of the embankment should be maintained at 3 meters or more throughout the operational life of the facility. The freeboard should be confirmed through visual observations on a daily basis. This daily observation should focus on the areas where tailing overflow is being deposited and where there is crest construction activity. Staff gauges will be installed on the tailing impoundment beach (up to about 100 m from the upstream edge of the embankment crest) at about 200 m distance along the perimeter, to facilitate weekly estimate of the available freeboard. The freeboard along the entire crest of the embankment should be surveyed at least once every month. In addition, survey equipment should be employed to confirm freeboard whenever a question arises as to the freeboard meeting the minimum requirements. Daily observations should be reported as part of the Daily Operations Report, and summarized in the Weekly Operations Report (Appendix C2). The elevation of the reclaim water pond in relation to the crest level should be recorded daily. If the measured freeboard is less than 3 m, crest deposition should immediately begin in the area of insufficient freeboard. If underflow is not available due to problems at the cyclone station, the use of borrow materials should be immediately investigated and implemented. Deposition in the impoundment should take place from an upstream deposition point and not from the embankment crest. The beach length and slope along the perimeter of the impoundment should also be surveyed at least monthly. Daily visual observations of the beach length should be made to verify that the minimum beach length criterion has been met (see Section 4.3.5).



September 2006

4.3.12.7

Erosion

The embankment face and crest shall be inspected for erosion upon occurrence of any construction, precipitation, or unplanned event that may induce erosion. Additionally, the Shift Supervisors should inspect areas around the underflow discharge points for signs of excessive erosion on a daily basis. Observations shall be documented in the daily reports. The reasons for the erosion should be investigated and appropriate measures taken to mitigate the problem. The most common reason for erosion of the embankment slope is expected to be a lower than desired underflow density. In such case, the density of the underflow should be immediately increased. 4.3.12.8

QA/QC Reporting

QA/QC activities and results should be reported on daily, weekly and monthly basis. Daily Reports

Daily reports should be prepared by each of the TSF QA/QC Inspectors and the Laboratory Manager responsible for daily testing. As a minimum, these reports will contain the following information: • • • • • • • • •

The name of the Inspector, date and rows and columns to record activities and events on an hourly basis. Description of health, safety and environmental events. Description of weather conditions. Description of location where inspections were conducted. Deposition locations by station for overflow and underflow. Description of construction activities observed and inspected. Description of special events observed (i.e. significant dust generation, unplanned discharge of water, etc.). Results of inspections and testing. Digital photographs of relevant issues and activities.

Copies of forms and laboratory test certificates should be submitted during the day. Complete and signed daily reports will be submitted to the TSF Shift Supervisor for review and filing at the end of each shift. Weekly Reports

Weekly Reports shall be prepared by the Shift Supervisors, consolidated into one Weekly Report, and submitted to the TSF Superintendent on a weekly basis. Weekly reports shall present a summary of the Daily Reports and tabulated results of tests performed. Laboratory certificates and copies of Daily Reports shall be included as Appendices to the Weekly Report. Monthly Report

Monthly Reports shall be prepared by the Tailing Superintendent. These reports will summarize the QA/QC information collected during the month, presenting the data in plots and tables. This report should also include a brief analysis of the data and trends. This report shall be submitted to the Plant Manager and a copy will be sent to the Design Engineer. The Design Engineer will interpret the data in the report and compare it with the TSF design basis. Results, conclusions and potential alerts will be drawn from this interpretation and recommendations for improvement will be provided to the Tailing Superintendent and the Concentrator Manager by the Design Engineer.



September 2006

4.4

IMPOUNDMENT DEPOSITION PLAN

4.4.1

Objectives

After separation of the sands (underflow) at the cyclone station, the remaining overflow will be deposited into the impoundment. Occasionally, when the cyclone station is not in operation (e.g. for maintenance), the whole tailing stream will bypass the cyclone station and will be discharged into the impoundment via the overflow pipelines. The objectives of the impoundment deposition plan and a brief summary of the methods to achieve the objectives are as follows: 1. Develop a beach from the embankment towards the reclaim water pond(s), thus keeping the pond(s) as far from the embankment as possible at all times. The deposition of the overflow and occasionally whole tailing will take place predominantly from the embankment crest. The number of deposition points along the crest will gradually increase with the increase of the embankment crest length. The overflow deposition points along the crest will be spaced at about one per every 100 meters. 2. Preclude development of a clear water pond adjacent to the potentially more permeable limestone that comprises the left (west) abutment of the TSF. Overflow quantities sufficient to accomplish this objective will be deposited in the western drainage of the tailing impoundment. With the exception of the first few months of the operation of the TSF, when the reclaim water pond will be located against the Starter Dam, the pond(s) will be located within the Central and/or the East Valley (Figure 4-4-1). No ponding should be allowed within the West Valley subsequent to the first few months of deposition. 3. Avoid the development of trapped water ponds (i.e., water that would be inaccessible for recovery by the reclaim water return system) in some of the side valleys on the upstream end of the impoundment. Overflow from the scalping station (see Section 4.2.4) will be deposited in these drainages after year one to accomplish this objective. 4. Manage the reclaim pond(s). According to the current reclaim water pond management plan there will be two ponds for the first 3 to 4 years of operation of the TSF, followed by 1 pond located in the East Canyon for the remainder of the operations. The number and location of the reclaim water ponds will be managed by appropriately selecting the location and amount of tailing to be deposited from each deposition point. The presented impoundment deposition plan is based on the current understanding of the project. The implementation of the plan should be carefully monitored and updates to the plan should be made as required to achieve the above objectives. The deposition plan should be updated by the Tailing Superintendent and the Design Engineer annually, or more often if considered necessary. 4.4.2

Description

The impoundment deposition plan was developed to address the objectives presented in Section 4.4.1 above. The location of the deposition points and the reclaim water pond during selected years of the operational life of the TSF are illustrated in Figures 4-4-1 through 4-4-6 and discussed below. The assumptions made for the development of the deposition plan as depicted in Figures 4-4-1 through Figure 4-4-6, are as follows: •

The elevation of the impounded tailing immediately upstream of the embankment at the end of the 1st, 2nd, 4th, 10th, 15th year and at the completion of the operations, are as estimated in the material balance model (see Volume 5 – Material Balance Analysis).

•

A uniform 0.5% beach slope develops from each deposition point.



September 2006

•

The underwater tailing slope (beneath the reclaim water pond) was assumed to be 0.5%. In reality, the slope is expected to be somewhat steeper.

Year 1 and Year 2

During the first year of operation, the focus of the deposition plan will be to develop a “beach” from the embankment towards the reclaim water ponds and to preclude ponding of water against the limestone area at the west drainage. There will be two reclaim water ponds for the first two years of operation – one in the Central Valley and one in the East Valley. During the first few months of operation the water from the Central pond will be pumped to the East pond over a saddle on the East Ridge. As the ponds move upstream the Central and East valleys during the second year of operation, the ponds will be connected through an excavation across the second saddle on the East Ridge (see Figure 4-4-2). Further details on the operation of the reclaim water system are presented in Operations Manual Area 3800 (Tailing Handling and Reclaim Water). By the end of the first year, the pond in the East Valley is expected to reach the largest side drainage to the East Valley – the East Canyon, where the reclaim water pond will be located for the remainder of the operations. To preclude the development of a large reclaim pond spanning across the East Valley and East Canyon, deposition from the upstream end of the East Valley (deposition point D1 on Figure 4-4-2) should start towards the end of the second year of the operation. The estimated extent of the impoundment, the locations of the deposition points and the location of the reclaim water ponds towards the end of the first and second years of operation are illustrated in Figure 4-4-1 and Figure 4-4-2, respectively. Year 3 to Year 10

As the embankment rises and its length increases, the underflow and overflow header lines will be extended and additional deposition points will be added along the crest (Figure 4-4-3). In year 3, the excavation across the East Ridge saddle is expected to be mostly covered with tailing and the connection between the East and Central ponds will be lost. To preclude the development of an isolated pond in the Central Valley, deposition into the Central Valley from the upstream side of the impoundment will be required. Deposition from points C1 and C2 is planned to begin in the 3 rd year of operation. The purpose of the C1 and C2 deposition points is to push the water towards the East Canyon and form one pond only. Deposition from points B1 and D1 will continue by relocating the line further upstream as the impoundment rises. As before, the purpose of deposition point B1 will be to preclude the development of standing water against the limestone area on the left abutment, and the purpose of deposition point D1 will be to push the water from the East Valley towards the East Canyon. The estimated extent of the impoundment, the locations of the deposition points and the location of the reclaim water pond towards the end the fourth and tenth years of operation are illustrated in Figures 4-4-3 and 4-4-4, respectively. Year 11 to Year 22

During the period from the 11 th year to the final year of operation of the facility, as the embankment and impoundment rise, the header line will be extended progressively and the remaining deposition points along the header will come into operation (Figure 4-4-5 and Figure 4-4-6). Deposition from points B1, C1, C2 and D1 will continue by relocating the line further upstream as the impoundment rises. Additional deposition points may be required (e.g. D2 and D3) if isolated ponds develop at the head of some side valleys (Figure 4-4-5 and Figure 4-4-6). MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

The estimated extent of the impoundment, the locations of the deposition points and the location of the reclaim water pond towards the end of the 15th year and at the completion of the operations, are illustrated in Figures 4-4-5 and Figure 4-4-6, respectively. 4.4.3

Deposition Schedule

The objectives of the impoundment deposition plan will be achieved by properly managing the location of the deposition points and the amount discharged from each point at any one time. Due to the difficulties in accurately predicting the behavior of the deposited tailing materials, the presented deposition schedule should be used with caution and modified as considered necessary by the Tailing Superintendent and the Design Engineer throughout the operating life of the facility. The impoundment deposition schedule presented in Table 4-4-1 has been developed based on the descriptions above and the material balance presented in Volume 5 – Material Balance Analysis. Table 4-4-1 contains a list of deposition points, time when each point needs to be commissioned, type of material to be discharged and other relevant information. TABLE 4-4-1 IMPOUNDMENT DEPOSITION POINTS Approximate Percentage of Total Tailing Solids (1) Discharged into the Impoundment

Year

1

2

Deposition Points

Central Station Overflow/Whole (2) Tailing %

A9-A16

80%

B1

N/A

A9-A16

65-70%

B1 D1 A6-A17

Central Station (3) Overflow %

20%

Scalping Station (4) Overflow %

N/A

20% 10-15% 50-70%

A-18

5%

B1

15-20%

3-5 C1

0-5%

C2

0-5%

D1 A3-A17

10-15% 50-63%

A18-A22

15-20%

B1

5-15%

5-10 C1

2-5%

C2

5%

D1

5-10%


Comments

The deposition points should be in place prior to the start of the operations


September 2006

TABLE 4-4-1 IMPOUNDMENT DEPOSITION POINTS Approximate Percentage of Total Tailing Solids (1) Discharged into the Impoundment

Year

Deposition Points

Central Station Overflow/Whole (2) Tailing %

A1-A17

55-60%

A18-A24

25%

B1

5%

10-22

Notes: (1) (2) (3) (4)

Central Station (3) Overflow %

Scalping Station (4) Overflow %

C1-C2

5%

D1-D3

5-10%

Comments

The percentages indicated refer to total amount of impounded tailing in dry weight. Overflow from the cyclone station or whole tailing that is not processed through the cyclone station may be distributed from these points. Only overflow from the cyclone station may be distributed from these points. Only overflow from the scalping station is distributed from these points.

The percentages of the total tailing solids to be discharged from each deposition point throughout the operational life of the impoundment are approximate and are based on proportions of the area of each drainage from the total impoundment area. The percentages in terms of volume of the tailing required to fill each of the valleys may differ from the percentages presented in Table 4-4-1. Careful monitoring of the entire tailing impoundment surface and the location of the reclaim water pond(s) should be performed on a daily basis and the required quantity to be discharged from each point should be determined at that time. The information provided in Table 4-4-1 should be used as guidance only. 4.4.4

QA/QC

The objectives of QA/QC of the deposition of tailing material within the impoundment are to facilitate proper pond location, and provide monitoring of impounded tailing and water levels. The pond should be maintained at the location delineated on the deposition figures presented in earlier section and as far away as practical from the left abutment and the embankment. Freeboard between the crest of the embankment and the impounded tailing material should be maintained at 3 meters or more. Observation requirements for embankment freeboard are detailed in Section 4.3.12.6. Daily observations of pond locations should be included in the daily log with an estimate of minimum beach length. Pond locations should be formally recorded on a drawing of the impoundment facility on a monthly basis. The basis of this drawing should be a combination of observations of the pond from various angles using landmarks to verify the pond extents. The information should be supported by inclusion of photographs of the impoundment. Further monitoring of the pond and extent of impounded tailing material is described in Section 6 of this manual. 4.5

SUSTAINING CAPITAL ITEMS

The TSF will be constructed and operated over a period of approximately 22 years. Within these 22 years, the finger and blanket drains, and the double filter blanket drain over the left abutment limestone will be built in phases. The underflow and overflow header lines will be expanded as the embankment crest expands over time. Geotechnical instrumentation will be added to the embankment over time as the embankment rises. The schedule for the planned expansion of the drains, the headers, the left abutment blanket, the geotechnical monitoring instrumentation, and the planned geotechnical investigations is discussed in the following sections. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

4.5.1

Drain Expansion

A network of finger drains and a blanket drain will be constructed within the footprint of the embankment. The finger drains will be located within the natural drainages beneath the embankment and the blanket drain will cover the alluvium at the base of the valley. The seepage flow collected by the drain system will discharge into a seepage collection sump located immediately downstream of the ultimate embankment toe. The seepage collection sump and a portion of the drains will be constructed as a part of initial capital construction (see Volume 10 Drawings, Package 3 – Construction of a Seepage Collection System). Details on the methodology for the design of the Seepage Collection System and the embankment underdrains, which are part of the capital construction, are presented in Volume 8 - Seepage Collection System Design. The drains to be constructed as part of capital construction are envisioned to be within the estimated embankment footprint by the end of the 3rd year of operation. The remaining drains will be constructed in three subsequent stages (Figure 4-5-1). The configuration and extent of the drains for the three subsequent stages may need to be adjusted based on observed performance of the initial drains constructed as part of initial capital construction. Figure 4-5-2 presents typical sections and details of the blanket drain, and for the 1st and 2nd order finger drains. Detailed designs will be required for each expansion. The proposed schedule for drain construction is described below. Schedule

Construction of the drains, which are part of the initial capital construction, is planned to be completed by October 2006. Considering the fast rate of rise of the embankment and the high cost for decommissioning and commissioning of the material processing plant used during capital construction, it is recommended to continue production of drain material after completion of the capital construction drains. This will speed up the drain construction process and save the cost for mobilizing and demobilizing of the material processing plant. Accordingly, it is recommended that production of drain and filter material required for the drains located within the 5 th year embankment footprint (see Figure 4-5-1) should begin as soon as production of filter and drain materials for capital construction is completed. The produced material for the blanket drain within the 5 th year embankment footprint will be stockpiled and will be placed after the road to Arequipa is relocated in about 2009. The finger drains within the 5th year embankment footprint (A1 to A11) will be constructed in late 2006 as the material is being produced. The remaining finger drains and blanket drains within the embankment footprint of the 10th year (B1 to B9) will be constructed within the 4 th year of operation. The remaining finger and blanket drains within the ultimate embankment footprint (C1 to C17) will be constructed within the 9th year of operation. The proposed drain construction schedule is shown in Figure 11-1. 4.5.2

QA/QC of Sustaining Capital Drain Expansions

The materials used in the construction of the drains should be crushed, processed, and screened, and should conform with the following gradation requirements:



September 2006

•

Zone 5–Filter Material –

Sieve No. or Size ¾”: ½”: 3/8”: #4: #8: #16: #30: #40: #50: #60: #200: •

Zone 6–Drain Material –

Sieve No. or Size 3”: 1 ½”: 1”: ¾”: 3/8”: #4: #8: #200: •

Percent Passing (By Weight) 100 87 – 100 79 – 100 59 – 100 42 – 82 24 – 58 8 –37 0 – 26 0 – 15 0 – 10 0–3

Percent Passing (By Weight) 100 90 – 100 60 – 91 40 – 83 14 – 57 0 – 28 0 – 10 0–3

Zone 6A–Coarse Drain Material –

Sieve No. or Size 3”: 1 ½”: 1”: ¾”: 3/8”: #4: #8: #200:

Percent Passing (By Weight) 100 60 – 100 40 – 80 20 – 60 0 – 25 0 – 15 0 – 10 0–3

The gradation of the materials used in the construction of the drains should meet the requirements of the construction specifications developed for and provided to the contractor for each sustaining capital construction phase and may vary from those stated above with approval from the Design Engineer. The Design Engineer will establish detailed specifications and drawings for each sustaining capital construction phase including requirements for the following: • • • • • •

Gradations of filter and drain materials Durability characteristics of filter and drain materials In-place densities and moisture contents Permeability of placed materials Provisions to avoid segregation of materials when placed Provisions to avoid contamination of materials with excess fines

A geotextile will be placed over the constructed drains to avoid contamination of the surface. This protective geotextile will be removed immediately prior to placement of underflow sands and as the MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

embankment footprint extends over the drains. The geotextile removal process and the placement of the initial layers of underflow material were discussed in Section 4.3.7. 4.5.3

Header Extension

Tailing underflow for embankment construction will be conveyed from the cyclone station via two pipelines placed on a jacking header (see Section 4.2.5). Tailing overflow or occasionally whole tailing will be conveyed via two 32” pipelines on another jacking header located close to the upstream edge of the embankment crest. The configuration of the headers is shown in Figure 4-3-7 (Fluor/PSI drawing PSP108-C-3830-50T-022, 023 and 025). Details on the jacking header designs and operational instructions are included in the Operating Manual for Area 3800. As the embankment is raised, its crest increases in length from about 800 m at the Starter Dam level (crest elevation 2485 m) to about 2,500 m at its ultimate height (crest elevation 2660 m). To facilitate an even tailing deposition, both the underflow and the overflow headers will be extended as required. Table 4-5-1 presents the estimated embankment elevations at the end of each operational year, approximate embankment length and required extension length of the jacking header line. The average estimated weekly raise of the header is also shown in Table 4-5-1.

Yr (end) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

TABLE 4-5-1 ESTIMATED JACKING HEADER LINE EXTENSIONS AND RAISE RATES Approximate Approximate Jacking Header Average Header Embankment Embankment Extension Raise Elevation Length m m/week m m 2485 800 (1) 2491 900 100 0.65 2514 1020 120 0.25 2530 1150 130 0.30 2542 1350 200 0.23 2553 1680 330 0.21 2562 1920 240 0.17 2571 1980 60 0.17 2580 2030 50 0.17 2587 2130 100 0.13 2595 2160 30 0.23 2602 2180 20 0.13 2608 2210 30 0.12 2614 2240 30 0.12 2620 2260 20 0.12 2626 2290 30 0.12 2632 2320 30 0.12 2637 2370 50 0.1 2642 2380 10 0.1 2647 2400 20 0.1 2652 2410 10 0.1 2657 2430 20 0.1 2660 2440 10

Notes: (1) st Applicable to the last 25 Weeks of the 1 year only (from El. 2475 m to El. 2490 m)



September 2006

Experience at similar facilities indicates that the underflow tends to flow by gravity approximately 400 to 600 m along the embankment slope (see Section 4-3-5). The maximum length of the embankment slope at the ultimate embankment height is about 1100 m. Therefore, it is likely that additional measures would need to be implemented to distribute the underflow along the entire slope length after about 5 years of operation. Potential ways to distribute the underflow along the lower ends of the downstream face of the embankment are: •

Provide pipe extensions with tees to take the underflow beyond 400 m to 600 m from the embankment crest.

•

Mechanically distribute the deposited underflow from the higher end of the slope to the lower end (remove the “hump”).

•

Install an additional header line at a selected location (mid-length) across the downstream slope.

The gravity flow characteristics of the underflow along the embankment downstream slope should be monitored and a decision be made regarding the need for additional measures after about 4 to 5 years of operation, to facilitate the distribution of the underflow down to the toe of the embankment between Years 5 and 22. 4.5.4

Left Abutment Blanketing

Geology and Potential Issues

The left abutment of the Cerro Verde Tailing Embankment and a portion of the ridge confining the west side of the TSF are underlain by the Middle Jurassic Socosani Limestone Formation (Figure 3-3). This unit has been identified as an area of higher permeability compared to the bedrock formations underlying the remainder of the TSF, and as an area at a higher risk of containing potential preferential flow pathways. Detailed discussion on the geology and the potential issues associated with this area are presented in Volume 2 – Geological and Geotechnical Site Investigations and Assessments. Based on the investigations in the area, two potential issues have been identified: 1) possible seepage flow, and 2) possible tailing flow through the potential preferential pathways. An observational approach has been proposed to address the potential seepage issue. The recommended monitoring and inspections program is discussed in Section 8. The concerns with regards to a potential tailing flow are related to the possibility of loose, unconsolidated overflow tailing materials entering the potential preferential flow system, and if unimpeded, piping of tailing through the system may occur. There is uncertainty with regards to the nature of the limestone, the extent and size of the karstic solution channels, and the existence of an interconnected solution channel systems that would transmit tailing flow. Although the likelihood of occurrence of a tailing flow is considered low, due to the potentially significant consequences of such a tailing flow, protective measures will be implemented. These measures are detailed below. Protective Measures

The protective measures will consist of the following components: •

A granular protective blanket placed on the surface of the limestone where impounded tailing materials will be in contact with the south facing slope of the limestone

•

A “double filter” blanket drain over the portion of the abutment/embankment footprint underlain by the limestone.



September 2006

Left Abutment Impoundment Protective Blanket

The purpose of the blanket over the limestone within the impoundment is to create a filter layer to impede the potential flow of tailing materials into the limestone bedrock. The existing haul road from the mine to the starter dam will be utilized as a starting surface for the construction of the blanket (Figure 4-5-3 and Figures 4-5-4). The blanket will be constructed in lifts of about 1 m thickness and a minimum of 8 m width (selected based on constructability). The lifts will be placed against the existing slope. Mine waste (North Dump 30 or similar) material will be used as a borrow source. The blanket will be constructed ahead of the placement of the overflow in the west drainage. Based on the deposition and filling plans, the lowest limestone outcrop may become flooded with tailing at the end of the first year of operation. Construction of the blanket should be planned to begin 6 months after the beginning of operations. The blanket will be extended up the slope periodically and will always be maintained at elevations at least 5 meters above the level of the impounded tailing materials. The proposed blanket construction schedule and volume estimates are presented in Table 4-5-2 and further discussed in Section 11.

Yr 1 3 5 7 9 14 17 (1)

Note:

Table 4-5-2 Left Abutment Limestone Protective Blanket Estimated Surface Area Maximum Blanket (1) Volume 2 m Elevation 3 m 18,000 144,000 2524 36,800 294,400 2550 32,000 256,000 2570 33,000 264,000 2590 47,700 381,000 2622 23,000 184,000 2640 29,500 236,000 2660

Comments rd

3 yr footprint th 5 yr footprint th 7 yr footprint th 10 yr footprint th 15 yr footprint th 18 yr footprint Ultimate

The volume is estimated assuming 8m width of the protective blanket

The ultimate extent of the blanket in plan view is shown in Figure 4-5-3 (hatched area). Figure 4-5-4 shows the configuration of the blanket in selected representative sections. Left Abutment “Double Filter” Abutment Blanket Drain

The purpose of the “double filter” blanket drain within the embankment footprint is to filter tailing fines that could potentially pipe through limestone karst channels, from plugging the embankment underdrains and to provide a drain layer to conduct potential seepage flows. Although the probability of piping of tailing fines in this area is considered remote, due to the magnitude of the potential consequences, the implementation of this measure is considered necessary. The double filter abutment drain will consist of a lower layer that will satisfy filter compatibility criteria between the impounded tailing materials and the drain material (probably cyclone underflow tailing sand), and an upper layer that will satisfy the filter compatibility criteria between the tailing underflow and the drain material. Details on the design of the “double filter” blanket drain on the left abutment will be developed in the future, sometime prior to the construction. The double filter blanket drain is planned to be constructed in two phases: • •

1st phase in year 4 (within the 10 year embankment footprint) 2nd phase in year 9 (within the ultimate embankment footprint)

It is recommended to have the construction phases concurrent with the construction phases of the finger and blanket drains.



September 2006

4.5.5

Instrumentation Expansion

The routine instrumentation maintenance will require periodic extension of the signal cables of existing instrumentation, routine extension of standpipes, and the movement of ADAS equipment upward along standpipe extensions. In addition, it will be necessary to install additional monitoring instruments as the embankment raises. The instrumentation plan for the embankment at its ultimate height is shown on Figure 4-3-19. The extent of the instrumentation including the number and locations of the equipment may change over time, based on results of the surveillance of the phreatic surface and pore pressures using previously installed instrumentation or other factors. The Design Engineer will review the data obtained from the embankment instrumentation and the inspection records and will make modifications to the current instrumentations plan, as appropriate. According to the current schedule (Section 11), the installation of the instrumentation would be performed in phases. The first two instrumentation expansion campaigns will take place within the 2 nd and 5th year of operation of the TSF. Subsequent instrumentation expansion campaigns are scheduled to coincide with the geotechnical investigations in the 7 th, 12th, and 17th year of operations. Depending on the conditions of the embankment, the results of the monitoring program and the regular inspections, expansion of the instrumentation system may be required earlier, more often, and/or to a greater extent than planned. The planned instrument expansions are presented in Table 4-5-3. Instrumentation and automated data acquisition (ADAS) equipment identifications used in this table correspond to those used in the figures showing the instrumentation plan. TABLE 4-5-3 PLANNED INSTRUMENTATION EXPANSION SCHEDULE Expansion Campaign nd

2 year

Instrument or ADAS Equipment Type

Equipment ID

Location*

Vibrating Wire Piezometer

CVW-10

Section D-D’


CVW-11

Section D-D’

I/O XPAK-RXB (Radio Extended to CVO-01)

CVX-05

Section F-F’

Standpipe Piezometer Instrumented with Vibrating Wire Pressure Transducer

CVS-05

Section F-F’


CVW-12

Section F-F’


CVX-06

Section B-B’


CVS-06

Section B-B’


CVW-13

Section B-B’

I/O XPAK-CXB (Cable Extended to CVX-03)

CVXC-02

Section D-D’


CVW-14

Section D-D’


CVW-15

Section D-D


CVX-07

Section F-F’


CVS-07

Section F-F’


CVX-08

Section F-F’


CVS-08

Section F-F’



September 2006

TABLE 4-5-3 PLANNED INSTRUMENTATION EXPANSION SCHEDULE Expansion Campaign

Instrument or ADAS Equipment Type

Equipment ID

Location*


CVX-09

Section B-B’


CVW-16

Section B-B’


CVW-17

Section B-B’


CVX-10

Section G-G’


CVW-18

Section G-G’


CVW-19

Section G-G’


CVX-11

Section G-G’


CVS-09

Section G-G’


CVW-20

Section G-G’


CVW-21

Section F-F’


CVW-22

Section F-F’


CVX-13

Section D-D’


CVS-10

Section D-D’


CVX-12

Section A-A’


CVW-23

Section A-A’


CVW-24

Section A-A’


CVX-14

Section A-A’


CVS-11

Section A-A’


CVW-25

Section D-D’


CVW-26

Section A-A’


CVX-15

Section B-B’


CVS-12

Section B-B’


CVW-27

Section B-B’

Vibrating Wire Piezometer *For the instruments location see Figure 4-3-19.

CVW-28

Section D-D’

th

5 year

th

7 year

th

12 year

th

17 year

4.5.5.1

Details of Instrument and ADAS Installation and Maintenance

Designs for the expansion of the instrumentation system will be needed in advance of the expansion. It is envisioned that designs will be done in general conformance to the drawings and specifications included in Package 6A used in capital construction (see Volume 10 - Drawings). Maintenance of the instruments should conform to the Maintenance Manuals and instructions provided by the suppliers. 4.5.6

Geotechnical Investigations

Geotechnical investigations will be required during the operations of the TSF. The main objectives of the investigations are: To assess the geotechnical conditions of the sand embankment for conformance with design assumptions. • To evaluate the impoundment foundation conditions at the West Saddle (see Figure 3-2). • To identify borrow or quarry materials for the expansion of the drain system. •

More details on the proposed investigations are presented below. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

Tailing Embankment

Geotechnical investigations on the tailing embankment are planned to take place throughout the operation of the facility. The objectives of these geotechnical investigations are as follows: • • • • • • •

Evaluate the in-situ geotechnical properties of the embankment sand. Verify the geotechnical parameters assumed in the engineering analyses performed during the final design of the facility. Check for existence of weaker layers within the embankment. Confirm the position of the phreatic surface within the embankment. Re-assess the stability of the embankment. Re-evaluate the current construction methods. Evaluate opportunities to modify the embankment configuration (e.g. potentially reduce the crest width if conditions are sufficiently favorable).

The geotechnical investigations may include drilling test holes and collecting undisturbed and disturbed samples, Standard Penetration Tests (SPT), cone penetration testing, laboratory testing, geophysics, and excavation of test pits. A detailed geotechnical investigation program for the first geotechnical investigation campaign will be prepared by the Design Engineer during the first year of operation. According to the current schedule, the first geotechnical investigations will take place within the 2nd year of operation of the TSF. Subsequent geotechnical investigations are scheduled for the 7 th, 12th, 17th and 22nd years of operations. Depending on the conditions of the embankment, the results of the monitoring program and the regular inspections, geotechnical investigations may be required earlier or more often than planned. West Abutment Saddle

The upper left flank of the impoundment area consists of a narrow ridge and a low saddle through which a small, unnamed fault strikes at a high inclination angle. The narrow configuration of the ridge and the presence of faulted ground form a basis for concern that late during the operation of the impoundment, seepage could migrate through the ridge. Geotechnical investigations to characterize the area of the saddle are scheduled to take place within the 17th year of operation. At this stage, the elevation of the impoundment should be low enough to allow access to the area. Depending on the results of the investigations, the Design Engineer may propose specific construction and seepage control measures that would be required in the saddle area. Borrow Materials

Geotechnical investigations will be required to select suitable borrow material for production of drain materials. The investigations may include drilling test holes, excavating test pits, collection of representative samples, performing laboratory testing, and possibly test blasting. The alluvium material within the bottom of Quebrada Enlozada, was used for production of the drain materials during the capital construction, is essentially depleted and a new borrow source (e.g. the Poderosa Pit near Rio Chili or bedrock quarry) will need to be identified. The investigations are scheduled to take place within the first year of operation of the TSF. A selection of a borrow source and obtaining the required permits has to take place early during the start of the operations.



September 2006

4.6

WATER MANAGEMENT

4.6.1

General

TSF water management includes the following main components: •

Surface Water (runoff) Management. The dry climate and limited catchment area of the TSF were the main reasons for the decision not to construct diversion channels around the facility. The design of the TSF has a provision for storing the runoff generated by the PMP from the entire impoundment catchment area during the operational life of the facility and after closure. Therefore, no additional provisions are required during operations other than maintaining the design freeboard. The runoff from the embankment will be collected at the Seepage Collection Sump and the water will be used during the operations.

•

Management of the Reclaim Water Pond. Managing the reclaim water pond at a minimum size and away from the embankment is required to maintain embankment stability and minimize the water losses.

•

Seepage Management. Seepage from the TSF should be minimized for the following reasons: 1) maintain the TSF in compliance with the “zero discharge concept” facility, and 2) maximize reuse of the process water.

•

Water Balance Model Calibration. A water balance model was developed to provide an estimate of the potential water losses from the TSF and the required make-up water requirements for the operations. The water balance model is described in detail in Volume 6 – Water Balance Analysis. The model should be regularly updated with actual data and the make-up water requirements estimated to facilitate effective water supply planning.

Procedures for water management are described in the following sections. 4.6.2

Reclaim Water Pond

A start-up water pond will be developed within the impoundment prior to the start of the operations (Section 4.3.3). Start-up water will be required in the beginning of the operations to compensate for the initial water losses and the expected delay in water recovery from the embankment and from the impoundment. Two reclaim water ponds will be operated within the impoundment during the first 2 to 3 years of operation: one pond in the Central Valley, and one in the East Valley (Figure 4-4-1 and Figure 4-4-2). Water will be pumped from the Central to the East pond over a small saddle on the East Ridge during the first 3 to 4 months of operation. Subsequently, the water from the Central pond will be pumped to the East pond through an excavation in the East Ridge (Figure 4-4-2). The excavation is expected to be inundated with tailing within the 3rd year of operation. At this time, deposition of tailing overflow from the scalping station will begin from the upstream ends of the Central Valley of the impoundment. Deposition of overflow from the scalping station into the upstream reaches of the east valley will begin within the second year of operation. The purpose of this upstream deposition will be to push the pond from the Central Valley and from the East Valley towards the East Canyon, where the pond will be located during the remainder of the operations. One reclaim water pond located in the East Canyon (see Figures 4-4-3 through 4-4-6) will be operated after the 3rd year of operation. Variations in this schedule may be expected depending on the amount of tailing materials produced, impoundment filling procedures and characteristics of the tailing beaches that are created.


September 2006


The position of the reclaim water pond relative to the embankment is critical to TSF stability and overall performance. The pond is expected to be against the Starter dam during the first 3 to 5 months of operation prior to establishing a tailing beach and pushing the pond away from the embankment. Following this period, and especially when the crest of the Starter Dam has been reached (towards the end of the 1st year), the pond should be kept as far away from the embankment as possible. The minimum distance between the pond and the embankment is 300m at that time. As the impoundment increases in size, the pond should be maintained further from the embankment crest and the pond size should be limited to approximately 20 hectares. The size of the reclaim water pond affects a number of TSF components. A large pond will decrease the rate of consolidation of the impounded tailing materials. A small pond results in a larger area of the beach, increased drying of the impounded tailing, hence increased density. The higher density leads to a higher storage capacity of the impoundment, and generally improved stability of the facility. Some of the effects of a large pond are an increase in the water losses, and more importantly, to a reduction in the available flood storage capacity of the impoundment. A reduction in the flood storage capacity leads to an increased risk of embankment overtopping. Considering the requirement to maintain a small pond, and the depth requirements for the operation of the pumps at the barges, it was decided by Fluor to excavate a trench in the original ground and create a corridor for the barges. More details on the configuration of the trench, barges and pumps are provided in FLUOR/PSI drawings PSP 108-C-3800-10Z-406 and PSP108-C-3840-50Z-050. Given the importance of maintaining the reclaim water pond in the desired location, as far as possible from the embankment and at a small size, the following measures should be considered in operating this aspect of the facility: • •

Maintain the surface area of the reclaim water pond at 20 hectares or smaller. Conduct daily inspections of the size, location, and configuration of the reclaim water pond. Record findings together with the measured water level.

•

Based on the information obtained, review the location of the deposition points currently in use and decide if changes are required to alter the pond location and shape. If isolated ponds have formed in some of the side valleys, consider placing additional deposition points (overflow from the Scalping Cyclone Station) to displace these isolated ponds.

•

If the pond approaches the embankment without an increase in the pond size, increase the amount of tailing discharged from the embankment crest.

•

If the pond approaches the embankment due to an increase in its surface area, investigate if this is due to a reduced reclaim water pumping rate or problems at the barges. Some of the reasons leading to a large pond size could be excess water after a large storm, reduced tonnage at the mill and associated reduced water demand, reduced depth at the barge due to a flatter underwater slope or inadequate trenching at the barge.

•

If the reason for the large pond size is excess water that cannot be handled at the mill, the measures may include reduction in the make-up water flow rate, finding other water users, creating an alternative storage pond, or using sprinklers or other measures to increase evaporation.

•

A large pond size could also be caused by inability of the reclaim water pump system to convey sufficient flow. The reasons for this lack of sufficient pumping capacity will need to be investigated. Some of the reasons that may cause lack of reclaim water pumping capacity are undersized pump capacity, inadequate location of the pump barge, or excess tailing fines into the pump barge area. Corrective measures would be implemented accordingly. Potential measures could be placement of an additional pump, deepening the barge trench or construction of a small berm to restrict the flow of tailing fines into the po nd. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

The operation of the reclaim water system is not part of this document. Details on the design and operation of the barges (including the pumps), the excavation of the cut through the East Ridge, the excavation of a “barge trench”, the construction of a rockfill dike, power supply, maintenance and operation of the reclaim water system are provided in Operations Manual for Area 3800. 4.6.3

Seepage Management

Seepage from the TSF will be managed by means of the features described below. Seepage Collection Sump

Seepage collected by the network of finger drains and blanket drain within the footprint of the embankment will be conveyed to the seepage collection sump located immediately downstream of the ultimate embankment footprint (Figure 3-2). Seepage flow will be measured in a weir located immediately downstream of the ultimate embankment footprint and upstream of the seepage collection sump (Figure 4-3-17). The seepage collection sump provides a pond from which the collected seepage and tailing embankment stormwater runoff can be pumped to the cyclone station or to the reclaim water pond on the tailing impoundment for reuse. The seepage collection sump includes design components to minimize the risk of seepage from the TSF past the sump and into the environment and to satisfy the “zero discharge concept” criteria (Section 3.4.2). Main design components of the seepage collection sump are: •

An excavation through the alluvium across the valley down to fractured bedrock.

•

A geosynthetic liner on the downstream slope of the sump anchored into a concrete grout cap at the excavation bottom and side slopes.

•

A grout curtain at the bottom of the excavation extending through the fractured bedrock into low permeability bedrock.

Details of the seepage collection sump design can be found in Drawings 29 through 41 from Package 3 and in Volume 8 – Seepage Collection System Design (Volume 10 – Drawings). During the operation of the TSF, the seepage collection sump should be regularly inspected (Section 8) and maintained (Section 7). According to the project design criteria (Table 3-7), the seepage collection sump has been designed to provide storage for the 100-year 24-hour flood, plus operation flows during a 12-hour power outage and the expected seepage during normal operating conditions. Power supply, pumping systems and details on the operation of the seepage collection sump are provided in Operations Manual Area 3800. Left Abutment Seepage

Due to the relatively higher permeability of the limestone on the left abutment of the TSF, seepage through this rock may potentially exit downstream of the facility when sufficiently high head builds up in the impoundment. The identified most likely locations where seepage may appear are the two drainages along the northern extent of the limestone leading to the Quebrada Tinajones, and the drainage downstream of the narrow saddle on the left uppermost extreme of the impoundment (Figure 1-2 in Appendix B). These areas should be carefully monitored during the operations and if seepage is observed, measures to collect it should be immediately implemented. Potential measures may include construction of lined sumps in the area of the seeps. Depending on the quantity of the collected seepage, the water may be evaporated or pumped back for reuse.



September 2006

5.0 5.1

ENVIRONMENTAL PROTECTION

GENERAL

The TSF is designed to provide storage for the tailing materials in an environmentally acceptable manner consistent with Peruvian and international environmental standards. Operational personnel must have a clear understanding of the key environmental issues and compliance criteria associated with the TSF and environmental monitoring will be performed on a routine basis. Operators are required to report any instances where environmental protection may be lacking and take corrective action as appropriate to provide acceptable performance of the facility. These actions comprise the environmental management program that must be implemented during TSF operations. A detailed environmental management plan (EMP) that effectively implements the program is presented in Appendix B. The EMP describes the objectives and scope of environmental management with respect to the TSF. The EMP refers to and complements the site-wide Environmental Management System and the site-wide closure plan (MWH, 2006, Closure Plan for the Unidad de Produccion Cerro Verde). The EMP presents an overview of the monitoring program that will be implemented at the TSF. Routine field inspections and reporting requirements are also described so that inspection results are adequately documented and any deficiencies are promptly corrected. Specific inspection requirements are outlined below. 5.2

SOILS

Soil characterization studies performed at the site concluded that most of the soils in the TSF area are deficient and cannot support significant agriculture. Furthermore, soils that would be affected by TSF operations are those soils that would be buried by tailing and this represents the primary impact of TSF operations on the soils. Another potential effect of the TSF on the soils is soil erosion or contamination caused by a spill due to an unforeseen pipeline rupture or equipment failure. Because of their deficient agricultural characteristics, there are no environmental benefits for recovering soils prior to tailing deposition. Soils monitoring will be performed on an as-needed basis. 5.3

AIR QUALITY

Access roads, the beach area, and embankment face may emit airborne dust because of their material properties and exposure to local weather, particularly under high wind conditions or when equipment is working with dry materials. Air quality is a concern because it potentially impacts habitat immediately adjacent to the facility and potentially the community further afield. The finer (respirable) dust fraction also represents a human health hazard with respect principally to silica. This O&M manual describes measures to be taken to reduce dust emissions, including watering of the TSF embankment, and cyclical deposition of tailing materials. The operator is to use visual inspection of the work areas, beach area, and the embankment to verify that wind and vehicle activity is not raising dust. When conditions are dusty the operator is to irrigate the offending area with tailing deposition streams or process water, as appropriate, or cease movement of machinery (if that is raising dust) until weather conditions improve. Appendix B describes environmental monitoring that will be conducted to demonstrate that these measures are successful. Six air quality monitoring stations are utilized for monitoring air quality in the TSF area. The monitoring stations include: • • • •

Cerro Verde South Cerro Verde North TSF Jacobo Hunter MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

• •

PJ Cerro Verde Village Tiabaya

Details on the air quality sampling and analytical protocols are provided in the EMP (Appendix B). The locations of the air quality monitoring stations are presented in Figure 1-2 in Appendix B. When air quality analyses indicate that the air quality standards in Table 3.5 are not met, the operator is to implement alternative mitigation measures until air quality is again consistently in compliance. 5.4

VEGETATION AND WILDLIFE

The TSF footprint contains very sparse vegetation. The impact on vegetation is related to potential loss of vegetation as a result of the inundation of the ground surface caused by the gradual deposition of tailing in the TSF. Another potential effect of the TSF on the vegetation is related to tailing or process water spillages could occur outside of the TSF due to tailing delivery or return water systems breakdowns. In addition, high wind conditions could cause dry tailing to be mobilized from the TSF and deposited on downwind vegetation potentially causing vegetation damage. Mitigation measures have been implemented in the vicinity of the mine to offset any loss of vegetation due to normal operation of the TSF. Details of the implemented plant propagation program are presented in Section 3.6.3 of the ESMP (SMCV, Environmental and Social Management Program, 2005). The vegetation-monitoring program described in the ESMP will be performed. No additional monitoring is envisioned. The primary impacts on wildlife from the SMCV Project involve habitat loss and intervention, and potential injury to animals that enter the area. Mitigation measures involve avoiding close human contact with the local fauna in the TSF area and implementing a fauna management program. These measures will include the placement of warning signs, safe vehicle driving, implementation of dissuasive measures (i.e., fencing or crossing guards, etc.), and wildlife rescue. Specific mitigation measures have been developed for guanaco management that focus on minimizing direct contact with the TSF systems. Additional measures include TSF operator training in guanaco rescue in cases where guanaco become stranded in the TSF. TSF personnel will chase guanacos away from the TSF, as necessary. Future studies designed to propagate the guanaco species will be conducted. SMCV will continue to distribute water to the watering containers used by guanaco. The fauna monitoring procedures described in the ESMP will be followed. The monitoring will be performed using the identified in the ESMP (Section 3.7.3) viewpoints located south of the mine. The TSF operator will note in the daily diary any tracks, encounters, injury or takes (kills) and bring these to the attention of the environmental department. In the event that these incidents are more than rare, the operator will implement contingency measures to control access of wildlife to the site. 5.5

WATER QUALITY

The “zero discharge” concept has been adopted for the TSF. Seepage from the TSF is therefore to be contained on SMCV property to the extent practical. Embankment seepage exiting the facility is intended to be captured at the seepage collection sump located downstream of the ultimate embankment toe and used for dilution water at the cyclone station or recycled for reuse in the concentrator plant. The quality of this water is to be monitored to verify that the chemistry is as predicted. However, this monitoring is not regarded as environmental monitoring, rather the monitoring is required for process control purposes. There are no surface water monitoring stations that will require routine environmental monitoring. However, surface water monitoring stations could be added in the future if a specific data requirement has been identified. If this becomes the case, then this Operations Manual and supporting Appendix B can be updated at the appropriate time and SMCV personnel will be informed of the monitoring program changes in daily operations meetings or annual employee training. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

Five groundwater monitoring wells (MW-01, MW-02, MW-03, MW-04, and MW-05) are located immediately downstream of the seepage collection pond and three additional groundwater monitoring wells are located downstream in the Quebrada Enlozada (MAS-25, MAS-26, and MAS-31). Two monitoring wells are located downgradient of the TSF in the Quebrada Tinajones (MAS-27 and MAS30). Two to four future monitoring wells may be installed downgradient of the TSF in the Quebrada Tinajones to monitor potential effects of the TSF at the potentially karstic limestone contact. There are currently no groundwater monitoring wells in the La Quebradita. However, two future monitoring wells may be installed in the quebrada to monitor baseline groundwater conditions. The watersheds and groundwater monitoring wells are described in Appendix B. Samples will be collected monthly from each of the groundwater monitoring wells in accordance with the sampling and analysis protocols in Appendix B, Table 1. If water is not present in any of the wells, the lack of water will be recorded. In the Quebrada Enlozada, groundwater downgradient of the Seepage Collection Sump must meet the water quality criteria presented in Table 3-4. If the required water quality is not met, the environmental staff and the Tailing Superintendent and senior SMCV managers will be informed. Collectively, SMCV will design and implement a contingency measure to address the situation. This may include activating the well pumps that will already be in place in four of the five monitoring wells located downgradient of the Seepage Collection Sump. 5.6

RECLAMATION AND REHABILITATION

As the embankment of the TSF is constructed of cycloned sand using the centerline construction method, there is no opportunity for progressive reclamation or revegetation. The closure plan is for placement of an erosion resistant rock cover from a benign source once embankment construction is complete. This is addressed in the site-wide closure plan (MWH, 2006, Closure Plan for the Unidad de Produccion Cerro Verde). 5.7

DOCUMENTATION

The environmental staff will record air and water quality data as described in Appendix B. The Tailing Superintendent will receive the results and should note in daily reports that the information has been reviewed and that the TSF is in compliance. When a non-compliance has been identified, the Tailing Superintendent is required to note measures being implemented to achieve compliance with the target performance criteria. The daily report should also note: • • • • •

Incidence of blowing dust and what was done to mitigate it Encounters with wild or domestic animals on the property Seeps or standing water encountered beyond the limits of the TSF Spills or containment problems to be brought to the attention of the environmental department Sampling events



September 2006

6.0 6.1

SAFETY AND SECURITY

GENERAL

Safety of the workers and the public is of prime concern to SMCV. Correct operation of the TSF is important for the protection of public safety. For this reason, all elements of construction and operation at the TSF will be under the management and supervision of the Tailing Superintendent at all times. Only trained personnel will conduct the work. Authorized personnel will accompany visitors or maintenance personnel not usually working in the area. 6.2

WORKER HEALTH AND SAFETY

The tailing facility will be operated under the requirements of the SMCV Health & Safety program. All tailing department employees will be periodically updated regarding the requirements and expectations of the program. When department meetings are conducted for the tailing crew, the Tailing Superintendent will provide constructive reminders about the importance of following the program and SMCV’s commitment to provide a safe working environment. In particular, workers are to note the procedures for working adjacent to open water, on mobile equipment, on stacked activities (that is when one worker is potentially uphill or above another) and the lock-out tag-out procedures. SMCV believes that the tailing materials are not toxic, and will analyze them periodically to validate this. However, SMCV worker health and safety guidelines apply with respect to the use of respirators to protect against silicosis. The process water is caustic and workers must wear protective footwear (rubber boots) and rubber gloves when their work requires them to be in contact with the moist tailing materials or process water. Workplace Hazards

A number of workplace hazards are inherent in the operation and maintenance of the TSF. These workplace hazards are associated with tailing delivery, water reclaim, TSF embankment, TSF surface, and seepage collection areas. The tailing delivery system operations include a tailing department shop, heavy maintenance equipment, utility vehicles, delivery pipeline, cyclone station, and tailing distribution system. Workplace hazards that are inherent in the operation of these systems include pinch points, unstable ground, water hazards, pressurized pipelines, rotating machinery, electrical supply, overhead assembly, crane use, and confined spaces. Pinch points involve the handling of large equipment components such as pipeline sections, reclaim

barge and pumps, cyclone station components, and spigot system components. The pinch points become most hazardous during maintenance, modification, relocation and expansion of these components. Unstable ground may be encountered on the TSF embankment and impoundment surface.

The instability is caused by freshly deposited coarse tailing on the embankment or fine/coarse tailing that is deposited in the impoundment. Freshly deposited tailing cannot support the weight of a utility vehicle or personnel on foot. Water hazard refers to the Reclaim Water pond and Seepage Collection Sump. Significant water depths

can exist in the reclaim water pond and Seepage Collection Sump and the hazard is most significant when personnel are performing work adjacent to or over the ponds (while servicing the pumps, for example) or are inspecting the water ponds by watercraft.



September 2006

Pressurized pipelines include the tailing delivery/distribution pipelines and reclaim water pipelines. In

these cases, a pipeline breach during maintenance activities would result in rapidly escaping fluids and the SMCV maintenance crew would be at risk of personal injury. In addition, undetected release of flows in unplanned locations could cause hazardous conditions and instability of slopes and/or embankments. Rotating machinery is found at the reclaim water pumps located on the barge, at the seepage collection

sump, and at the cyclone station/tailing pumping station. The pumps at the reclaim water pond and at the seepage collection sump consist of high-capacity vertical turbine pumps. The exposed pump shaft will be rotating at a speed of about 1,500 revolutions per minute. Other rotating machinery would include hand-held power tools that are used during both operations and maintenance. High-voltage (1,440 VAC primary voltages and 480 VAC secondary voltages) electrical hazards exist near pumping facilities including the reclaim barge and the seepage collection sump. The electrical hazard is compounded by the close proximity of grounding sources such as metal decking, structural steel, and water. Several confined spaces exist within the TSF facilities. Confined spaces are defined as tanks, sumps, conduits, etc. where access and egress is limited. These include the tailing delivery and reclaim pipelines, tailing delivery system vaults, and seepage collection sump. The hazard that is inherent in confined space situations includes poor air quality. Safe Operating Procedures (SOPs)

During startup, SMCV is to develop specific SOPs for each of the tasks to be routinely conducted. The SOPs are to be appended to this Operations manual and the SMCV Health and Safety Manual. At a minimum, the SOPs will address: Confined Space Entry, Hot Work, Lock out-Tag out, Work on the barge-mounted pumps, Maintenance of the cyclones, Relocating the cyclone station, Shut down, Start-up, Relocation and raising of tailing distribution pipelines, Draining and inspection of pipes and vessels, Driving at the site, Operation of heavy equipment while placing and compacting embankment fill, night shift work, overhead assembly, crane use, etc. 6.3

SITE SECURITY

The performance of the TSF depends upon consistent application of rigorous procedures to monitor and control the quality of the tailing underflow material produced for embankment fill, and for the maintenance of equipment used to place, and compact the tailing materials, pump and convey fresh water, and process water. While the scale of the operation will attract the interest of workers from other areas and the public, only operators trained to safely operate the facility are authorized to be present at the site. Restricted Access

The TSF facilities are not secured from unauthorized access. As a result the following pieces of equipment should be gated or otherwise managed to restrict access: • • • •

The walkway to the reclaim barge, with water and electrical hazards The entry stairway to the cyclone station with elevated equipment at high pressure The seepage collection pond pump station with electrical and water hazards The secondary electrical power supplies that power the barge and the seepage collection sump with electrical hazards

Access to these components is restricted both for safety and security reasons. The SMCV Security Department will conduct random patrols of the TSF during each day of operations including both MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

daylight and nighttime hours. The patrols will also be conducted during periods of temporary suspensions of operations. If the security department observes any security concerns (unlocked or damaged gates and locks, unauthorized visitors, or damaged equipment), the department will notify the Tailing Superintendent. The Tailing Superintendent will verify the status of the TSF facilities and will give instructions for appropriate follow-up actions. Communications

Because elements of the work are hazardous and the TSF site is somewhat remote from the rest of the operations, the Tailing Superintendent is responsible for facilitating the communication between the TSF labor force and the control room at all times. As for confined space work, work adjacent to open water is not to be conducted alone and without prior authorization from the control room. The Seepage Collection Sump and the Reclaim Water Pond are examples of open water. The Tailing Impoundment surface is also considered in this category due to the soft nature of the deposited tailing. Any breaches of the security measures are to be brought to the attention of the Tailing Superintendent, Security Department, and the Health and Safety department immediately. 6.4

EMPLOYEE TRAINING

Each member of the Tailing Department will receive formal TSF operations training and at least once per year and upon starting a new assignment. The training will be planned and conducted by the Tailing Superintendent or his designee. Informal crew meetings and briefings will be conducted daily to discuss specific operations issues. The annual and new employee training will instruct the tailing technicians how to operate the tailing delivery system including equipment operations and tailing deposition strategy. The training will also describe how the cyclone station is to be operated and how construction of the embankment will be conducted to satisfy design requirements. Operation of the reclaim barge and the seepage collection pond and pumps, monitoring of TSF instrumentation as well as piezometer monitoring training will also be included. The Preventive Maintenance Program for these systems will be covered in detail. This TSF-specific training will consist of a combination of video presentations, verbal discussions, review of this Operations Manual and demonstrations in the field. Field training and facility tours will be conducted to provide hands-on review of operating procedures. The training will take approximately 8 hours to complete. Training in workplace safety, hazard recognition, accident prevention, and the proper use of Personal Protective Equipment (PPE) will be provided by the Safety Department. Environmental Monitoring training will also be provided by the Environmental Superintendent. Regarding the proper use of PPE, personnel who use PPE while performing a job function will be trained to recognize the limitations of the equipment and to properly select, fit, use, inspect, maintain, and store the PPE. Such PPE training will occur and be documented before the user enters the TSF area where the use of the PPE may be required. 6.5

DOCUMENTATION

Safety and security records are kept by the Safety Department. All incidents are to be recorded by the Tailing Superintendent on the daily report as well.



September 2006

7.0

MAINTENANCE

The objective of the maintenance program for the TSF is to provide protocols and processes to facilitate maintenance of the individual components of the facilities in accordance with sound operating practices, company standards, performance criteria, and legislative requirements. Detailed maintenance plans tailored to the unique characteristics of the facility and the site conditions should be prepared. Presented below are examples of routine and event-driven maintenance requirements. The presented lists cover some of the main items and are not intended to cover all maintenance requirements. Also presented below is a maintenance documentation system that the Tailing Department should implement. Following initial TSF operations, additional maintenance data requirements may be identified or revisions to specific existing requirements may be needed. The documentation system will be updated by the Tailing Superintendent in collaboration with senior SMCV managers, if necessary, to reflect the new requirements. 7.1

ROUTINE MAINTENANCE

The routine maintenance includes scheduled maintenance for the construction equipment as per the manufacturer’s recommendations, road maintenance, maintenance of the tailing delivery and reclaim water pipelines, seepage collection sump, gates, fences, signs, lighting systems, dust control irrigation systems, and protective equipment. It is anticipated that routine maintenance on the dozers and compactor used to spread and compact underflow materials on the TSF embankment will be significant. In particular, replacement of under carriages for the dozers should be planned and spare parts for this and other parts recommended by the manufacturers should be maintained in sufficient supply at the Cerro Verde Mine Site. Maintenance plans for the tailing and water pipelines, jacking header, pumping systems, electrical supply, roads, and cyclone station are provided in the appropriate vendor manuals. There is no routine maintenance for the embankment of the TSF or the liner, embankment and spillway of the Seepage Collection Sump, the drains, or monitoring instrumentation. The Tailing Superintendent will identify persons responsible for the maintenance of the various components of the TSF. All routine maintenance will be documented and reported to the Tailing Superintendent. 7.2

EVENT- DRIVEN MAINTENANCE

Some components not requiring routine maintenance could require event-driven maintenance. For example, precipitation, wind, or leaking embankment drains. An adverse reduction in the percent solids of the underflow can cause erosion on the downstream face of the dam. The Tailing Superintendent should determine when maintenance is required based on the routine inspections and monitoring discussed in Section 8 – Surveillance. The Engineering Department will provide field engineering support, construction equipment, and construction management for the repair of major damage. Erosion repair should be documented in the Daily Operations Reports, Weekly Reports, and Monthly Operational Reports. Other examples of situations requiring event-driven maintenance are damage to the seepage collection sump liner, replacement of ropes and sandbags on the upstream face of the seepage collection sump, reclaim barge pump failure, blocked or restricted tailing delivery line(s), spigot or leadoff, cyclone system blockage, or inoperative monitoring instrument. All event-driven maintenance should be documented and reported to the Tailing Superintendent. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

7.3

DOCUMENTATION

Each routine or event-driven maintenance event should be recorded in a maintenance record for the particular TSF component. The maintenance record should reflect the condition of the component prior to the maintenance, the maintenance action taken, the maintenance standard met, a recommendation for follow-up action, date, time and name of the person performing the maintenance. The record may include photos, videos, memorandums, reports, communication records and other relevant information. All maintenance activities described above will be documented and kept on file within categories as listed below in Table 7-1. TABLE 7-1 MAINTENANCE PROGRAM FILING SYSTEM Equipment Maintenance Logs

Photographs and Videos

Work History

Spares, Materials, Tools, and Equipment Inventories

Equipment Breakdown and Reliability Analysis

Critical Spares List Maintenance Schedules

Quality Control Records

Change Orders

Daily Diary Entries

Memorandums

Communications and Activity Records

Reports



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8.0 8.1

FACILITY SURVEILLANCE

GENERAL

Surveillance includes inspection and monitoring of the facility operation, structural integrity and safety. It consists of both qualitative and quantitative comparisons of actual facility performance to expected or planned performance. Regular review of surveillance information can provide an early indication of performance trends that warrant further evaluation and/or action. All personnel working at the TSF should be involved in surveillance as a routine part of daily activities. They should maintain visual awareness of the facility and have knowledge o f warning factors and procedures to follow in the event that a deviation from the planned facility performance is observed. Facility monitoring guidelines from the following two publications were used in the preparation of this surveillance plan: •

A Guide to the Management of Tailings Facilities, prepared by The Mining Association of Canada, September 1998.

•

Dam Safety Guidelines, prepared by the Canadian Dam Association, January 1999.

The purpose of this TSF Operations Manual is to show how environmental and operational surveillance and inspections are to be conducted. The reader will note that this Operations Manual is self-contained regarding both types of monitoring. All of the Operational Monitoring procedures are presented in the main body of this document. Environmental monitoring procedures are discussed in Section 5 and in the Environmental Monitoring Plan included as Appendix B to this document. This was done to better distinguish between the environmental requirements (environmental protection) and the operational requirements (system integrity) discussed in Section 4. The following sections provide a description of the proposed monitoring and inspections that will be a responsibility of the operator. 8.2

MONITORING EQUIPMENT

TSF instrumentation includes piezometers, survey monuments, flow meters, staff gauges, and accellerometers. The instruments will be installed in stages as the embankment is constructed. The first stage of the instrumentation will be installed during the capital construction phase (see Package 6A Geotechnical Instrumentation). The plan for installation of instrumentation throughout the operation of the TSF is discussed in Section 4.3.10. Information and data obtained from this system will be reviewed and compared with design assumptions. Periodic observation and documentation of conditions that develop will also be accomplished. This observational method will help in recognizing conditions that vary from those assumed for the design in a timely manner. Modifications to construction and operation can then be made to address these conditions. Survey monuments will be established by the SMCV surveyors to facilitate topographic survey of the TSF. The locations of these monuments will be established based on the limitations of the equipment to be used, and are not prescribed here. A brief description of the other monitoring instrumentation is given in the sections below.



September 2006

8.2.1

Piezometers

Three study sections normal to the tailing embankment alignment have been established, with piezometers installed in the alluvium foundation, the blanket drain, and the Starter Dam as illustrated in Figures 4-3-16 and 4-3-17. These instruments will monitor pore pressure and phreatic surface development in the embankment and its foundation. The information obtained will be used in assessing the stability of the embankment and the performance of the drain system. Additional instruments will be installed as the embankment is raised. The proposed instrumentation is listed in Table 4-5-3 and illustrated in Figures 4-3-18 and 4-3-19. The vibrating wire piezometers are tied into an Automated Data Acquisition System (ADAS) network connected through radio links and cable links to a central remote terminal unit (RTU) on the tailing distribution header. Data can be read directly at the RTU, which also transmits readings to the site SCADA system through a radio link to the cyclone station. Signal cable is laid in trenches extending to the radio i/o points where required. Some of the piezometer sensors are installed in open standpipes that allow confirmatory sounding with a water level indicator and allow different instrumentation to be lowered into the embankment and foundation, if needed. The standpipe casings support the radios and i/o assemblies of the ADAS system. Provision should be made for extending the instruments casing, extension of the signal cables and raising the ADAS equipment as the embankment raises. Technical specifications and installation details are presented in Package 6A, and illustrated in drawings included in Volume 10. As-built and calibration information is to be recorded in Table C3-1 in Appendix C3. The table is to be updated whenever new instruments are added, or instruments are replaced. The piezometers are installed at strategic locations to monitor the water level inside the embankment and the drains. The water levels will be monitored on site and reported to the Engineer of Record periodically as discussed in Section 9. 8.2.2

Staff Gauges

Staff gauges will be installed within the impoundment to monitor the elevation and rate of rise of the tailing surface to aid the operator in pond management. These gauges will consist of a vertical pole about 5 m in height founded in the natural ground near the perimeter of the impoundment. The staff gauges will be graduated to allow for reading of the elevation of the tailing surface. When a staff gauge is inundated (buried) it is to be replaced with a new gauge installed on native ground adjacent to the impounded tailing. Approximately 6 to 8 gauges will be operated around the perimeter of the impoundment. Staff gauges may also be used to monitor freeboard as discussed in Section 4.3.12.6. Those gauges will be placed on the tailing beach. Monitoring of freeboard will begin once the beach elevation approaches the elevation of the Starter Dam. 8.2.3

Seepage Monitoring Wells

The five seepage monitoring wells (MW-01 to MW-05) located immediately downstream of the seepage collection sump are intended to monitor groundwater quality and provide means of early detection of seepage past the grout curtain. In the event that seepage is detected in these wells, pumps will be activated to extract impacted water and return it to the seepage collection sump. The location of the wells is shown on Figure 2 in Appendix B. Water quality in these wells is to be monitored monthly to demonstrate that the seepage cutoff is functioning as intended. The operator is to check the pH, Conductivity, and Sulfate in the field. If these are elevated above the baseline established at startup, the environmental department is to be informed and the pump-back system activated. Construction details and specifications are part of Package 6B. The drawings are included in Volume 10. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

Environmental Monitoring wells have previously been installed in the Quebrada Enlozada and Quebrada Tinajones to provide baseline data and to monitor the water quality and the ground water levels in the valleys on an ongoing basis. Figure 2 from the Environmental Management Plan (EMP) in Appendix B shows the locations of the environmental monitoring wells. The EMP provides detailed information on the environmental monitoring procedures, frequency and reporting and these are not discussed further in this operating manual. 8.2.4

Accelerometers

Two accelerometers are planned to be installed: one on the right abutment at a location to be selected in the field, and one on bedrock adjacent to the spillway of the seepage collection sump. The purpose of the accelerometers is to record strong ground motions in bedrock near the final toe and crest of the embankment. These units have internal memory, from which local acceleration data will be retrieved after each seismic event. For reference, a copy of the Modified Mercalli Intensity scale is included in Appendix C3 (Table C3-2). 8.2.5

Flow Meter

A continuous flow-measuring weir is installed immediately upstream of the seepage collection sump as shown on Figure 4-3-16. Construction details of the V-notch weir are provided in Package 6A. The weir is housed in a concrete flume where the water level is measured by a pressure transducer submerged upstream of the weir and recorded in the SCADA system. The flow can also be read at the RTU. In the event that the pressure transducer fails, the operator will measure the depth of flow upstream of the weir directly and estimate the flow based on Table 8-1 below: TABLE 8-1 SEEPAGE FLOW RATES AT V–NOTCH WEIR Measured Depth (cm)

(1)

70

80

90

92

94

96

98

100

20

30

40

42

44

46

48

50

Q (m3/hr)

93

255

522

590

662

740

823

911

Q (l/s)

26

71

145

164

184

205

229

253

Flow depth (cm)

(2)

(1) From bottom of weir pool to water surface upstream of weir (2) Depth above invert of weir

8.3

MONITORING FREQUENCY

Table 8-2 presents a summary of the monitoring frequency for the various instruments.



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TABLE 8-2 MONITORING INSTRUMENTS Instrument

Number of (1) Instruments

Monitoring Frequency


13

Weekly

Stand-pipe Piezometer

4

Monthly

Accelerometer

Staff gauges Seepage Monitoring Wells (2) Tailing and reclaim water instruments (slurry density, tailing cyclone split and volume, water recovery )

(3)

Event Triggered

2

Weir – Pressure Transducer

(4)

1

Continuous

6 to 8

Weekly

5

Monthly

Various

Responsible Person

(5)

(5)

Continuous

Notes: (1) Number of instruments at the beginning of the operation of the TSF. More will be added as embankment is raised. (2) Wells immediately downstream of the seepage collection sump only. Environmental monitoring wells are not included. (3) ADAS system will record levels each approximately 8 hours. Instruments can be read continuously and ADAS can read and record data at a higher or lower frequency (for example after an unplanned incident or during critical activities), as determined by the Engineer. (4)

Collect data from accelerometers after seismic events with MMI IV or greater, for review by Engineer. The accelerometers are not tied into the SCADA system and must be read manually.

(5)

Monitoring of tailing and water monitoring systems is described in Area 3800.

Monitoring documentation and reporting procedures are discussed in Section 9. In addition to the standard monitoring frequency, the Tailing Superintendent will request piezometer readings be taken as soon as practical after any sort of significant unplanned event such as a seismic event, storm event, appearance of cracks or seepage. For details on emergency procedures see Section 10. 8.4

INSPECTIONS

The purpose of conducting field inspections is to observe system characteristics and visually detect system malfunctions. Table 8-3 below summarizes the inspection program including regular (routine, intermediate, and comprehensive) inspections and inspections after extreme natural events (major storms, earthquakes, or landslides, etc.).



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TABLE 8-3 TSF INSPECTION PROGRAM Inspection Type Daily Routine (instrumentation) by Operating Staff Routine (visual) by Operating Staff Routine (visual) by TSF Superintendent Intermediate (visual and data review) Comprehensive (visual, data, and engineering review) Post-Extreme Event

Weekly

Frequency Monthly

Semiannual

AsNeeded

*

X X

X **

X

X X

* Monitoring frequencies are variable, see Table 8-2. ** To be reduced to semi-annual after Year 3 of operations, if the TSF’s operational performance is acceptable.

8.4.1

Regular Inspections

Regular inspections of the TSF should include routine, intermediate, and comprehensive inspections. The routine inspection should be made as part of the daily and weekly responsibilities of the Tailing Superintendent and should be performed to cover the items described below in Routine Inspections . Intermediate and comprehensive inspections of the TSF are also required as part of this operations manual. The Intermediate Inspections , discussed below, are semi-annual reviews of the TSF performance and condition. The Comprehensive Inspections section below describes a complete review of the TSF performance, conditions and safety by the design engineer and other experts. The requirements of and frequency of comprehensive inspections are described under Comprehensive Inspections . 8.4.1.1

Routine Daily Inspections - Instrumentation

Inspection of facility instrumentation should be performed on a daily basis so that the entire instrumentation package is checked for visual indications of improper operation or the development of unplanned conditions. The personnel responsible for the instrumentation surveillance activities should be trained in identifying potential or developing problems through visual inspections. At a minimum the routine inspection should include the following: •

Vibrating Wire Piezometers are delivering reasonable readings, wires are not damaged.

•

Stand-pipe Piezometers have not been damaged, data transmitters are intact and not buried, batteries are charged.

•

Accelerometers are intact and power supply is adequate.

•

Flow-Measuring Weir Transducer is delivering reasonable reading, and the weir is not obstructed.

The inspection results will be presented in the Daily Operations Report. A form template (C2-1) is included in Appendix C2. 8.4.1.2

Routine Daily Inspections - Visual

Routine inspections of the facility should be performed on a daily basis by operating staff and on a weekly basis by the Tailing Superintendent. These inspections should focus on embankment construction activities, pond location and embankment performance. The personnel responsible for the visual surveillance activities should be trained in identifying potential or developing problems through visual inspections. At a minimum the routine inspection should include the following: 1. Description of weather conditions including temperature, precipitation, wind direction, and wind speed. The data should be quickly accessed when operational problems due to weather are MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

observed. This monitoring will be conducted using the South Meteorological Station. The station is operated by the Environmental Department and the Tailing Department will have real-time access to the weather data as it is being collected. 2. A review of the entire TSF embankment for: • • • • • • • • •

Cracks Wind scour Sloughs Settlement, Sinkholes Sandboils Seeps Erosion Other unusual conditions based on the operators experience

3. A visual survey of the impoundment including: • • • • •

Adequate freeboard from the crest to maximum impounded tailing level Clarity of water in the reclaim pond Reclaim pond level and distance from embankment crest Pond perimeter – wildlife activity, safety hazards Beach perimeter

4. A visual survey of the condition of the seepage collection sump and flow measurement weir. The general condition of the HDPE liner on the downstream face of the sump should be noted. Any damage, theft, blockage, or excessive wear on the seepage measurement weir and appurtenant facilities (ADAS and instrumentation) should also be recorded. 5. Review ADAS system signals for proper operation and storage of data 6. Monitoring data for high phreatic levels, unusual seepage flow amounts, or other nonconforming conditions Any unusual or nonconforming conditions should be recorded. Notifications should be made for any observation that requires maintenance activities to reestablish proper operating conditions, limit damage, limit excessive wear, or correct potential noncompliance with the EMP. Documentation requirements for the TSF inspections are detailed in Section 9, these include the completion of a “TSF routine inspection checklists”. Unusual or non-conforming conditions requiring immediate implementation of emergency response protocols include, but may not be limited to: • • • • • • • • • •

Slide on the downstream slope of the embankment Slide on the upstream slope of the embankment Loss of freeboard Excessive seepage Excessive erosion Excessive embankment settlement High phreatic surface in embankment Embankment cracking Sinkhole development New seep, spring, sandboil MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

The inspection results will be reported using the Routine Inspection Report (forms C2-1 and C2-2) included in Appendix C2. Emergency response procedures are addressed in Section 10.0. 8.4.1.3

Comprehensive Inspections

The comprehensive inspections of the TSF are a more formal review of the condition of the TSF by a representative of the Engineer of Record and SMCV managers. These inspections will be performed monthly for approximately the first three years of operation while the Engineer has a representative on-site. The frequency of these inspections may be reduced to semi-annual or annual after the first three years of operation or as approved by SMCV and following the recommendations of SMCV’s External Technical Review Board. The comprehensive inspection will be performed by an inspection team with representatives of the Engineer of Record, operations staff, and owners representative, and will include: •

Review of TSF performance versus design

•

Review documentation of construction QC/QA activities and embankment gradation and density test results

•

Review data from monitoring

•

Detailed field inspection of all TSF facilities (may be limited to fewer review team members and operational staff)

•

Review of survey data (beach profile, pond location, embankment profile)

•

Review embankment construction progress and impoundment filling rates

•

Review water balance data

•

Inspect condition of instrumentation installations for remaining battery charge (more than one month), movement of instrument relative to datum (pressure transducers in standpipes and at flow measurement weir), and damage

The inspection results will be reported using the Comprehensive Inspection Report form (Form C2-3) included in Appendix C2. 8.4.1.4

Intermediate Inspections

The intermediate inspections should precede detailed design of sustaining capital expansions, modifications to the design or other issues. The inspection should focus on the identified issue. The purpose and scope of the inspection should be described in a report template generated by the design engineer prior to the inspection. The scoping memo should take into account the results of previous inspections and note operational concerns that may require the attention of the inspection team. At a minimum the comprehensive inspection should include: •

Review team including representatives of operators, owner, design engineer, external review board, and specialty experts as needs are identified.

•

Review items critical to detail design of the next sustaining capital expansion phase.

•

Review of TSF performance. MWH * 1801 California Street, Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

•

Establish the condition of the seepage measurement weir, instrumentation installations, and ADAS system equipment.

•

Review of cyclone underflow quality and quantity.

•

Review of cyclone operating time and material balance.

•

Review of embankment density test results.

•

Review of actual water balance, including flow rates to the seepage collection sump.

•

Review the performance and condition of the seepage collection system. Primarily this would include of review of piezometric data, and inspection of the seepage collection sump, the sump embankment, liner, and spillway.

8.4.2 8.4.2.1

Inspection after Extreme Events Earthquake

Following a significant earthquake, the TSF should be inspected by the operator and Engineer for any indications of damage or instability. A significant earthquake is defined, for purposes of inspection, as V (five) or greater on the Modified Mercalli Intensity Scale (Table C3-2 in Appendix C3). The inspection should include the following: • • • • • •

Embankment inspection: cracks, sloughs, seeps Header line inspection Collect data from accelerometers (per unit instruction manual) Review of monitoring results (piezometers, accelerometers,) Seepage collection system – flows, sump structural integrity Survey of the embankment profiles and beach elevations

Extreme event results will be reported using the Extreme Event Report described in Section 9.2 and included in Appendix C2. 8.4.2.2

Flood

Following a flood or precipitation event causing significant run-off, the TSF should be inspected by the operator and the Engineer for indications of damage or instability. The inspection should include at a minimum: •

Embankment inspection: erosion, seeps, sloughs

•

Review of erosion adjacent to structures or at the seepage collection sump spillway

•

Inspection of seepage measurement weir and seepage collection sump for sediment accumulation, and liner or structure damage

•

Deposition lines for movement or damage due to inundation

•

Review of erosion or sedimentation of the channel downstream of the seepage collection sump

All findings should be immediately reported verbally and in writing to the design engineer of record.



September 2006

8.4.2.3

Landslide

Following a landslide, the inspection of the TSF by the Engineer and o perator should include: • • • • • • •

Embankment inspection: movement, sloughs, excessive settlement Impoundment inspection: displacement of tailing material, creation of potential release pathway Review structure, instrumentation, and ADAS equipment for damage from debris Inspection of seepage measurement weir and seepage collection sump for accumulation of slide material Deposition lines for movement or damage due to debris Seepage collection sump spillway for blockage Header line inspection

All findings should be immediately reported verbally and in writing to the design engineer of record.


Cerro Verde TSF * Operations Manual  79 79

September 2006

9.0

DOCUMENTATION DOCUMENTATIO N AND REPORTING

All inspection reports and monitoring data must be archived in an orderly manner so that they can be retrieved and reviewed at any time. This section presents the archiving system and formats for retrieval of data. Environmental data is to be archived in existing SMCV environmental archive from which SMCV extracts reports for submittal to the regulators. The various field forms used for recording the environmental monitoring data relating to the TSF are contained in Appendix B. 9.1

DATABASE

The monitoring and inspection results described in in Section 8 will be distributed using using the report forms included in Appendix C2. C2. The content of these reports is also to be recorded by type of data data and by monitoring point in order to provide a record of the changes at each monitoring point over the life of the TSF and, in some cases, post-closure. The SCADA system will record in an electronic database all all measurements taken at the various points. The database is searchable by type of measurement, location and date range. Various standard reports are available to present information regularly reviewed by the Operator or the Engineer of Record. Examples of typical report formats are included in Appendix C2, similar to the reports to be programmed into the SCADA system. The Engineer of Record may from time to time establish criteria and acceptable ranges to guide the operator, and these should be programmed into the reports for easy monitoring of performance. Unfavorable trends or measurements outside the acceptable ranges will trigger review by the Engineer or a review of the operator’s procedures. 9.2

FILING WRITTEN REPORTS

The Daily and Weekly reports described in Section 8 are to be scanned and archived electronically by date after they have been reviewed and approved by the Tailing Superintendent. That review includes ensuring that all required information is recorded – no blanks. While in some cases this represents represents a duplication of data that is recorded automatically, it permits the reconstruction of portions of the record in the event that an automatic data logger were to fail. One paper copy is to be filed by the Operator on site by date for use by the review team or the Engineer of Record during during the periodic review. Once the annual review is complete complete and the completeness of the electronic copy is validated, the paper copies may be destroyed. 9.3

STORING ELECTRONIC DATA

All electronic instrumentation instrumentation is monitored remotely and readings readings are stored in the SCADA database. database. Data stored on SCADA is available to the Operator through a graphical interface and a series of reports customized for easy easy interpretation of the data. Upon startup, the zero readings readings and calibration coefficients will be established for each instrument and used to convert the raw data into the values reported. After any subsequent recalibration (due to replacement or repair of an instrument) the algorithms used to prepare the reports will be updated. Certain information must be recorded recorded manually. This includes water quality quality data, production rates (embankment fill placed each each shift), density test results, results, etc. This information is to be entered entered into a database and archived in the same SCADA system, subject to the same access and backup protocols. Access to the data will be through customized customized reports as described above.

MWH * 1801 California Street, Suite Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

The following data will be recorded in SCADA: Daily total tailing production from the Concentrator (dry tons) Slurry density from the Concentrator, after the thickeners, at the Cyclone station Tailing stream to the Scalping station station (dry tons, percent solids by weight) pH of slurry Whole Tailing Gradation Pressure monitoring at pumps and cyclones Corrosion monitoring (cathodic protection and corrosion instrumentation) Daily total reclaim water quantity (to mill) Total make-up (fresh) water Daily total seepage water quantity (to cyclone or reclaim pond) Daily total dilution water to cyclone station Cyclone operating time each day Daily total cyclone underflow (for embankment construction) Underflow slurry density Tailing flow parameters Results of quality control and quality assurance testing Daily Precipitation Piezometer readings Seepage water quality, pH, Conductivity, Sulfate Reclaim water quality, turbidity, pH Elevations of embankment and beach along critical sections (estimated weekly, updated with survey monthly) • List of upset or unusual conditions encountered • • • • • • • • • • • • • • • • • • • • •

9.4

RETRIEVING ELECTRONIC DATA

The SCADA system will have a reporting interface through which the operator can access raw data or a variety of reports comparing data from a selected range with the control parameters established by the Engineer. 9.5

FILING REPORTS BY OTHERS

The operator will file a paper copy and scan into the SCADA system for archiving each of the monthly, periodic and annual reports by the Engineer and the External Technical Review Board for use by the staff. This library will include include also the design report, as-built reports, any reports on remedial work by the Engineer, and reports on investigations and responses to seismic or flood events. Copies of equipment specifications, specifications, catalogues and manuals manuals are also to be kept on site for the the operators use and updated as equipment is replaced or upgraded. The bibliography is to be kept up to date and appended to this manual. 9.6

ANNUAL OPERATIONS MANUAL UPDATE

This Operations Manual will be updated once per year. The purpose of the updates will be to reflect operation improvements that may be identified by tailing department department personnel. The updates will also also respond to changes in reporting requirements and the environmental monitoring program that is being conducted. The Tailing Superintendent will be responsible for updating the Operations Manual. The purpose of updating the manual is to incorporate operational improvements that have been identified, including opportunities to reduce operating operating costs. Another objective will be to update update the emergency reporting procedures and the personnel who will be notified notified in the event of an emergency. Finalization of the MWH * 1801 California Street, Suite Suite 2900 * Denver, Colorado 80202 * (303) 291-2222

September 2006


manual will be supported by the SMCV General Manager, Manager, Mill Manager, and the Mine Manager. The Environmental Manager will provide support with respect to the environmental monitoring program information.

MWH * 1801 California Street, Suite Suite 2900 * Denver, Colorado 80202 * (303) 291-2222


September 2006

10.0 EMERGENCY RESPONSE PLAN 10.1

OVERVIEW

This Emergency Response Plan (ERP) is a comprehensive plan developed to guide the operators of the Cerro Verde TSF in the event the facility is faced with upset or extreme operating conditions. The objective of the ERP is to define responsibilities and provide procedures designed to identify unusual and unlikely conditions, which could endanger the TSF, in time to take remedial action and to notify the appropriate entities and agencies if possible, regarding an impending or actual failure of the TSF. The ERP contains notification procedures that are intended to safeguard the environment and lives of citizens in downstream areas in the event of a failure or damage to the TSF. The emergency response procedures should be compatible and integrated with the disaster, fire and/or emergency response plans of local governmental agencies. The personnel at the TSF should be trained and should rehearse the procedures regularly as part of the training program for site operations. An employee alarm system will be used to notify employees of an on-site emergency, to stop work activities if necessary, to lower background noise (i.e. turn machinery off) in order to speed communication, and to begin emergency procedures. This ERP covers the emergency procedures related to a potential significant problem that may lead to a failure at the tailing embankment, tailing impoundment or the Seepage Collection Sump. The ERP does not include emergency actions related to the tailing delivery or the reclaim water systems since emergency actions for these facilities are to be prepared by their designers and will be present in the appropriate Operations Manual. This ERP does not replace or supplement the routine inspections and monitoring of the TSF as described in Section 8. Rather, the intent of the ERP is to provide a relatively brief summary of what actions to take in case of a real or impending emergency. The ERP should be updated annually and/or when major changes have occurred. Information to update should include: • • • • • • •

New emergency numbers Changes in personnel assignments A record of new dwellings or buildings in the downstream area Supplies and their locations Changes made to the TSF design, construction and operation Changes to the mine infrastructure that could impact appropriate emergency response Changes in the local agencies and authorities

10.2

RESPONSIBILITIES

The Concentrator Manager should designate a corporate health and safety officer who will have overall responsibility for the emergency response procedures identified. This health and safety officer is:



September 2006

The person with responsibility for day-to-day operation and maintenance of the TSF is: Angel Manchego, Tailings Superintendent, phone number 951-6310. Implementation of this ERP is the responsibility of: Angel Manchego, Tailings Superintendent, phone number 951-6310, or his designated local representative. Determining and identifying conditions or events that require emergency action will be the responsibility of: Angel Manchego, Tailings Superintendent, or his designated local representative. Angel Manchego, or his designated local representative, is also responsible for: a.

Conducting training of key personnel in emergency response procedures

b. Obtaining and maintaining emergency response supplies and equipment c.

Maintaining on and offsite communications during an emergency

d. Establishing emergency escape routes and training onsite personnel in emergency response procedures e.

Evacuating and preventing company personnel from accessing areas downstream from the TSF during an emergency

f.

Contacting emergency response officials in downstream communities (in order progressing downstream):

The lack of road access and telephone inaccessibility should be taken into consideration when evaluating how to contact the officials and residents of at any remote locations that could be affected by a failure of the TSF in the event of an emergency condition at the TSF. g.

Contacting downstream water users: 1. _____________________________________________________ 2. _____________________________________________________ 3. _____________________________________________________ 4. _____________________________________________________

h. Contacting the Local Authorities and Agencies (SMCV to list them) i.

Contacting the MEM

j.

Contacting the Engineer of Record, MWH, tel. 1 303 291-2222

k. Taking emergency measures at the TSF to prevent failure l.

Documenting emergency response actions and measures taken



September 2006

10.3

EMERGENCY SUPPLIES AND RESOURCES

In an emergency situation, equipment and supplies might be needed on short notice, such as sandbags, rip rap, fill materials, equipment, and laborers. These items and personnel are available from: Angel Manchego_______________________________________________________ Tailings Superintendent________________________________________________________________
____________________________________________________________________ 381515 ext. 4347_(office)_951-6310 (Cell phone)_________________________________________________ [email protected]___________________________________________________________ _______ 10.4

EMERGENCY CONDITIONS

Listed below are some, not necessarily all, of the events that could lead directly to an instability of the TSF. Included after each one is a brief outline of steps that should be considered in order to stabilize the situation. 10.4.1

Earthquake

If an earthquake has been felt, or an earthquake of magnitude 6 or greater has been reported in the vicinity, the following procedures should be followed: 1. The Tailing Superintendent should identify a qualified person, trained in the safety and emergency response procedures to immediately conduct a general overall visual inspection of the tailing embankment. 2. If the embankment is failing, immediately implement the instructions in the section entitled FAILURE IS IN PROGRESS (Section 10.5.1). 3. If the embankment is damaged to the extent that there is flow passing downstream, immediately implement the procedures outlined in the section entitled FAILURE IS IMMINENT (Section 10.5.2). 4. If damage has occurred, but is not judged to be serious enough to cause failure of the embankment, observe the nature, location, and extent of the damage, as well as the potential for failure. Then follow the procedure outlined in Section 10.5.3 FAILURE IS DEVELOPING. 5. If there is no imminent danger of dam failure then The Tailing Superintendent, or a qualified person trained in the safety and emergency response procedures, should thoroughly inspect the following: a. The entire crest and face of the embankment for cracks, settlement, slumping or seepage b. The pipe conveyance systems on the TSF for ruptures, displacements, or other damage c. The abutments for possible displacement



September 2006

d. e. f. g. h.

The Seepage Collection Sump embankment for cracks, settlement, slumping or seepage The liner of the Seepage Collection Sump for tears or other damage The spillway of the Seepage Collection Sump to confirm that it’s free of debris and damage The drains or seeps for cloudy or muddy water, or increased flow The impoundment perimeter for signs of landslides

Readings from all instrumentation (piezometers and seepage monitoring weir) should be obtained and compared to previous readings. Readings from the two accelerometers located at the TSF should also be reviewed. All findings should be immediately reported to the Design Engineer (Engineer of Record) and the agencies that had been contacted earlier during the emergency. The facility should be closely observed for two to four weeks following the earthquake as some damage might not show up immediately. 10.4.2

Flooding

Routing of the inflow design flood indicates that the probable maximum flood (PMF) will be stored on the impoundment under normal operating conditions, unless the Reclaim Water Pond is unusually large and is located too close to the embankment. The Seepage Collection Sump is designed to store the inflow from the 100 year, 24 hour flood in addition to normal seepage flows during a 12-hour power outage. The spillway is designed to pass the 500 year, 24 hour flood with a freeboard of 0.5 m. In the unlikely event that the water within the impoundment reaches within less than 50 m of the embankment crest (with the exception of the start-up period before reaching the Starter Dam crest), immediately implement the following procedures: A. Check the downstream toe and abutments for any unusual seepage and the drain flows to the Seepage Collection Sump. If there is any indication of cloudy or muddy flow, or the flow is increasing, implement FAILURE IS IMMINENT process (Section 10.5.2) immediately. B. Check for increased/decreased seepage. C. Check for cracks, slumping, sloughing, sliding, or other distress signals near the embankment abutments or crest. D. Contact the Design Engineer (Engineer of Record). The ability to access the dam for inspection may be restricted due to safety concerns during flooding. Vehicle access to the embankment under such a scenario may not be advisable. If access is considered imperative, other means of access should be considered. Under imminent failure conditions, access to the embankment crest, downstream face and toe areas should be prohibited.



September 2006

10.5

FAILURE CONDITIONS

10.5.1

Failure is in Progress

If a failure is in progress, evacuation of the downstream floodplain must be initiated immediately and the local emergency response agencies must be notified. The roads within the downstream floodplains and the tunnel should be immediately closed and any people at the road immediately evacuated from the area. In an event of a failure, immediate notification of the parties listed in the following flow chart should be undertaken:

NOTIFICATION CHART Observer of Emergency Situation:

Name: Title: Phone: Health and Safety Officer or his Designated Representative:

Name: Title: Phone: Cerro Verde Mine Contact:

Name: Title: Local Police Contact:

Name: Title: Phone: Department of Emergency Management Duty Officer:

Name: Title: Phone: Mining Department:

Name: Title: Phone:

Following these notification procedures, the post-failure actions indicated in Section 10.7 should be initiated.



September 2006

10.5.2

Failure is Imminent

If a failure is imminent, but has not yet begun, the following steps should be initiated immediately: A. Advise all personnel working downstream of the TSF of the situation and have them evacuate the flood plain area of any personnel or equipment. B. Advise local agencies to notify persons downstream from the TSF to evacuate due to the potential failure of the embankment. C. Implement the notification flow chart in section 10.5.1. D. Take preventive actions described in Section 10.6. 10.5.3

Failure is Developing

If there is a slowly developing failure or unusual situation, where failure is not imminent, but could occur if no action is taken, the TSF operational personnel should: A. Notify all people working on or downstream of the tailing embankment. B. Contact a local experienced geotechnical engineer for an immediate inspection of the dam. C. Contact and inform the Design Engineer (Engineer of Record), MWH (telephone: 1 303-2912222) of the situation. D. Notify the local authorities of the potential problem and keep them advised of the situation. E. During these contacts, find out if there are any immediate actions that can be taken to reduce the risk of failure. F. If necessary, implement preventative actions described in Section 10.6. 10.6 10.6.1

RESPONSE ACTIONS IF THERE IS Slide on the Downstream Slope of the Embankment

Communicate the situation to the Design Engineer who should provide direction or appropriate response measures. Measures such as those summarized below may b e appropriate. If the slide affected the freeboard, immediately restore the lost freeboard by placing sandbags or compacted fill on the embankment crest. If the slide is on the downstream slope of the embankment, establish the potential reasons for the slide. If a reason for the slide is an excessive seepage in the area, install a temporary sump to remove the water from the embankment. If the seepage is cloudy, place a filter blanket to stop removal of particles. Then stabilize the slide area by placing suitable additional soil, rock, or gravel in the area. If the slide is at the toe of the embankment, install a drain blanket and then stabilize the area by weighting the toe area with additional suitable soil.



September 2006

Special care and safety measures should be taken when working in a slide area. The possibility of a progressive failure should be considered. 10.6.2

Loss of Freeboard

Communicate the situation to the Design Engineer (Engineer of Record) who should provide direction or appropriate response measures. Measures such as those summarized below may be appropriate. Restore the lost freeboard by placing sandbags or compacted fill along the embankment crest. Then, investigate the reasons for the loss of freeboard and take appropriate remediation measures. 10.6.3

Excessive Seepage

Communicate the situation to the Design Engineer (Engineer of Record) who should provide direction or appropriate response measures. Measures such as those summarized below may be appropriate. Frequently monitor the embankment for signs of slides, cracking, or signs of instability. Monitor concentrated seepage for changes in the flow quantity, extent, cloudiness of the flow. Consider possible remedial actions, such as filter blankets and/or a stabilizing buttress. 10.6.4

Excessive Embankment Settlement

Communicate the situation to the Design Engineer (Engineer of Record) who should provide direction or appropriate response measures. Measures such as those summarized below may be appropriate. Restore lost freeboard by placing sand bags or compacted fill on the embankment crest. Continue monitoring the area for more settlement or any signs of instability. Immediately investigate the reasons for the settlement and implement remedial measures. 10.6.5

High Phreatic Surface in Embankment

Communicate the situation to the Design Engineer (Engineer of Record) who should provide direction or appropriate response measures. Measures such as those summarized below may be appropriate. Frequently monitor the embankment for signs of slides, cracking, or concentrated seepage. Take frequent readings of the monitoring instruments and analyze the results to establish trends or changes in the expected embankment behavior. If the observations indicate that the phreatic surface is higher than the maximum allowable limit established by the Design Engineer (Engineer of Record), measures to reduce the water level and/or to stabilize the embankment should be immediately taken. These may include a temporary termination of the embankment construction, installation of additional drains, construction of a buttress, or other measures. 10.6.6

Embankment Cracking

Communicate the situation to the Design Engineer who should provide direction or appropriate response measures. Measures such as those summarized below may b e appropriate.



September 2006

If cracking is observed on the embankment crest or slope, the affected area should be clearly marked and surveyed. The area should be carefully monitored for any changes in the crack width and length. The downstream slope of the embankment should be inspected for any signs of instability. Piezometer and other monitoring instrumentation readings should be taken and the results should be reviewed. All results of the inspection, survey and monitoring should be forwarded to the Design Engineer (Engineer of Record) for review and assessment. 10.6.7

Seeps, Sandboils, and Sinkhole Development

Communicate the situation to the Design Engineer (Engineer of Record) who should provide direction or appropriate response measures. Measures such as those summarized below may be appropriate. If there is a rapid increase in flow from previously existing seeps, an increase in under-drain flow, or if new springs, seeps, or boils appear that are associated with the TSF, establish the location, size of the affected area, estimated discharge, and nature of the discharge (clear or cloudy). If a sinkhole is observed, secure the area with appropriate signs and fencing, so access of people or wild life is restricted. Continue monitoring the affected area. If failure appears likely, implement the procedures outlined in the section entitled FAILURE IS IMMINENT (Section 10.5.2); otherwise, report all findings to the Design Engineer and the local agencies. 10.7

POST-FAILURE ACTIONS

If a failure of the embankment or a release has occurred, Angel Manchego, Tailing Superintendent, or the designated local representative, should notify the local authorities and downstream water users to: A. B. C. D.

Issue a notification for a drinking water ban until the impacts can be assessed Initiate import of drinking water to affected communities Initiate downstream impact assessments Develop and implement cleanup plans



September 2006

11.0 SCHEDULE Based on the planned mining rate, an average of 108,000 tons of tailing will be deposited in the TSF each day for the next 22 years. Construction of the embankment and filling of the impoundment will be a continuous process. However, as it is not practical or cost effective to conduct some activities at a slow rate continuously, several construction campaigns will be undertaken to expand the drainage blanket, drains, instrumentation and blanket over the limestone on the left (West) abutment. In addition, management of the tailing surface through deposition in specific areas is required to maintain the reclaim water pond in the correct location. To do this a scalping station will be constructed near the mill in about 2007. The most significant activities are described below and indicated in the TSF Construction and Operations Schedule presented in Figure 11-1. It should be noted that the time and duration of all activities presented in the schedule might change, depending on the actual production rates and on conditions encountered during the operation of the facility. The intent of this overall schedule is to provide general guidance for planning purposes, and detailed schedules will be required for each campaign. The schedule should be updated at least annually to address changes to the design, construction and operation of the TSF. •

Embankment Raise. The embankment raise will be a continuous process throughout the operation of the facility. The only specific event during embankment construction is a change in the crest alignment when the elevation reaches 2525 m (in year 3). At that time a bend is to be introduced in the alignment on the left abutment in order to avoid encroaching on the neighboring private property.

•

Underflow Header Extension. The crest length will increase with elevation and the underflow header will need to be extended accordingly. The header must be extended each year as indicated in Table 4-5-1.

•

Underflow Header Relocation. Approximately 250 meters of underflow header alignment will be relocated to the downstream side of the embankment crest where it contours around the bedrock knob on the East abutment. This relocation will occur between about years 5 and 6 when the embankment elevation reaches about 2560 m.

•

Overflow Extension. The pipeline extending from the left abutment to the discharge point in the West valley will be extended and relocated each year as the impoundment level rises. This pipeline will be placed on an access road, or on top of the West abutment protective blanket over the limestone.

•

Embankment Drains. The toe of the embankment will expand downstream as the crest is raised. The drain under the embankment will be expanded in stages as discussed in Section 4.5.1. The estimated timing and durations for drain expansions are shown in Figure 11-1. The first drain expansion will extend the drain system to the five-year embankment footprint, the second to the ten-year footprint and the third to the ultimate footprint. The drain design will be developed prior to each expansion. The duration of drain construction activities will depend on the production rate of the material processing plant and the required drain quantities, which will be estimated after completion of the design. Production of materials for the drain may start earlier so that suitable materials can be produced and stockpiled on site in advance of placement. The drain construction durations shown on Figure 11-1 are therefore not definitive.


September 2006


•

Left Abutment Protective Blanketing. Limestone that is exposed in the left abutment will be covered with a blanket of waste rock and compacted in 1-meter lifts. This blanket is to be placed ahead of tailing deposition, but not so far ahead that it is exposed to the risk of damage by storm runoff or other means. The purpose of the left abutment blanket is to avoid flow of the tailing fines into the potentially karstic limestone. It is not expected to provide a barrier to water flow. The estimated construction times and durations depend on the actual rate of rise of the impoundment, the availability of borrow materials and the material placement rate and method. Deferral of sustaining capital cost will also be a consideration in the timing of construction.

•

Instrumentation. Additional instrumentation will be installed in the embankment at the end of year one, and again in approximately years 5, 7, 12 and 17 as the embankment footprint is developed. It is possible that instrumentation in addition to that currently planned may be required, or some instruments may need to be replaced.

•

Geotechnical Investigations. Several geotechnical investigations are planned to be conducted as the embankment is raised. The main objectives of the investigations will be to identify suitable materials for construction, to evaluate the stability of the TSF through characterizing the properties of the embankment materials, and to review the overall performance of the facility. The embankment will be investigated at the end of year one, then again in years 5, 7, 12, 17 and 22. The embankment investigation may be coordinated with the installation of additional piezometers where practical and cost effective.

•

Tailing Deposition. Generally tailing will be deposited into the impoundment from the embankment. However at some stages tailing overflow will be deposited from other areas to force the supernatant pond into the desired position. Deposition in the West, Central and East drainages will be required to avoid the formation of additional ponds from which supernatant water cannot be reclaimed for use in the process. To do this and not waste valuable embankment building material, a scalping station will be put into service near the mill, from which only fine-grained tailing will be deposited to the drainages. The scalping station will be required after the 1st year of operation.

•

Cyclone Station Relocation. When the embankment reaches 2550 m approximately in year 5, the cyclone station will be relocated to a higher location on the right abutment. At least one additional cyclone station relocation will be required to bring the TSF to its ultimate configuration.

A sustaining capital and operations cost estimate based on the presented TSF schedule is included in Appendix D to this report. The cost estimate does not include provisions for the relocation of the road, construction of the scalping station, relocation of the central scalping station, tailing delivery and reclaim water system costs.


September 2006

Cerro Verde TSF * Operations Manual  Appendices

APPENDIX A OM Revision and Holders Record


September 2006


APPENDIX B Environmental Management Plan for the Tailing Storage Facility Operations



September 2006

APPENDIX C Forms


Vol 9 - Operations Manual

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