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Note: This is a written explanation of the meeting and the materials included. All of these materials are in DRAFT form and have been made for the sole purpose of stimulating conversation and documenting any necessary information to be considered by the team.
Tailings Design Tech Transfer Meeting
May 12, 2009
The following people were invited to attend the meeting: Name
Company/Agency
The following people attended the meeting: Name Eli Curiel
Company/Agency Coronado National Forest
John Able Coronado National Forest Salek Shafiqullah Coronado National Forest Teresa Ann Ciapusci Coronado National Forest Bev Everson Coronado National Forest Walt Keyes Coronado National Forest Debby Kriegel Coronado National Forest Roger Congdon Coronado National Forest Tom Furgason SWCA Dale Ortman SWCA Melissa Reichard SWCA Mike Sieber SRK Clara Balasko SRK Orlanthia Henderson Town of Sahuarita Bob Casavant Arizona State Parks Bob Sejkora Arizona State Parks David Pfordt Town of Sahuarita Derek Wittwer AMEC John Lupo AMEC
Goal: This meeting was conducted in order to convey the technical information from the Dry Tailings design to the Forest Service and Cooperating Agencies and provide a venue for deliberation among the specialists.
Draft Work Product- Intended for Deliberative Use Only Page 2 of 2
Meeting Overview: John Lupo of AMEC presented general information about tailing types and necessary processes involved. Derek Wittwer of AMEC had a much more detailed explanation of the tailings process, design and new possibilities in the design. Cooperating Agencies sent representatives to the meeting. The Forest Service specialists along with the Cooperators were able to ask detailed questions and make comments based on the presentation. There was much discussion about the technicalities of the process and design of Dry Stack Tailings in general and the proposal. List of attached presentations: Dry Tailings Overview Dry Tailings Facility Design List of attached handouts: None
Proposed Rosemont Copper Project ID Team Meeting Guest Sign- In
Date I \\c Sf-e-Lc h
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First Name Last Name Company & Role
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Proposed Rosemont Copper Project ID Team Meeting Sign-In
Date 5\1210 Dr
First Name
Alan
Andrea
Bev
Bob
Camille
Cara
Chris
Dave
Deanne
Debby
Deborah
Eli
Geoff
George
Glenn
Harmony
Heidi
Heidi
Janet
Jeanine
Jeff
Jennifer
Jerome
Joe
John
John
Keith
Ken
Kendall
Kendra
Kristen
La ra
Larry
Marcie
Mary
Melissa
Ralph
Reta
Rion
Last Name Belauskas
Campbell
Everson Lefevre Ensle
Bellavia
LeBlanc
Morrow
Rietz
Kriegel
Sebesta
Curiel
Soroka
McKay
Dunno
Hall
Orcutt-Gachiri
Schewel
Jones
Derby
Connell
Ruyle
Hesse
Ezzo
Able
MacIvor
Graves
Kertell
Brown
Bourgart
Cox
Mitchell
Jones
Bidwell
Farrell
Reichard
Ellis
Laford
Bowers
Role
Noise
NEPA Cornpliance/FOIA Officer
ID Team Leader Air Resources, Clean Water Act
Presentation
Social & Economic Environments Heritage
Air Resources
Hazardous Waste
Light (Night Skies)
Vegetation, Reclamation, Wildlife
Hazardous Waste, Mining Vegetation, Reclamation, Wildlife Access/Lands/Realty
Data Management
External Communications
Tech Editing
Media
Admin Support
Forest Supervisor
Social & Economic Environments
Forest Planner Geology
Heritage
Communications Team
SWCA Project Leader
Recreation, Social & Economic Env.
Wildlife Resources
Range
Team Admin Asst Light (Night Skies)
Data Management
Wildlife Resources
Recreation
Heritage
Team Admin Asst
Transportation/Engineering
Deputy Forest Supervisor Clean Water Act Compliance
Initials
, 4e--5// 2/6 7
Roxane Raley Mailing Database Salek Shafiqullah Hydrologist, Hydrogeologist Shane Lyman Fire/Fuels Suzanne Griset Heritage Tami Emmett Access/Lands/Realty
Teresa Ann Ciapusci Ecosystem Management & Planning Tom Furgason SWCA Project Manager Tom Skinner Water Resources/Riparian Walt Keyes Transportation/Engineering William Gillespie Heritage
sf.--%0--c107414
Rosemont Copper Project May 12, 2009
Last Name First Name CompanyAble John USFSBalasko Clara SRKCasavant Bob AZ State ParksCiapusci Teresa Ann USFSCongdon Roger USFSCuriel Eli USFSEverson Bev USFSFurgason Tom SWCAHenderson Orlanthia Town of SahuaritaKeyes Walt USFSOrtman Dale SWCAPfordt David Town of SahuaritaSebesta Debra USFSSejkora Bob AZ State ParksShafiqullah Salek USFSSieber Mike SRK
2009 05 12 Transcribed Participant List.xls
1
Dry Stack Tailings OverviewDry Stack Tailings OverviewJohn F. Lupo, Ph.D., P.E.John F. Lupo, Ph.D., P.E.
Principal EngineerPrincipal Engineer
Introduction
Types of tailings materials Filtered (Dry Stack) tailings Benefits
2
Tailings Materials Typesg yp
Tailings Continuum
Tailings Slurry
Thickened Tailings BL
E
Thin milk shake
Water w/ sand
NT
EN
T
Tailings Type Consistency
g
Paste Tailings
Wet Filtered Tailings
PU
MP
AP
UM
PA
BL
E
Wet Sand
Sandy yoghurt
RE
AS
ING
WA
TE
R C
O
Fully Saturated
Unsaturated
Dry Filtered Tailings NO
N-P
Moist SandDE
CR
3
67 % Tailings Slurry: 30% solids by wt
Tailings Percent Water
42 %
27 %
Thickened Tailings: 60% solids by wt
Paste Tailings: 75% solids by wt27 %
19 %
Paste Tailings: 75% solids by wt
Filter Tailings: 18% moisture content
Tailings Slurry
4
Tailings Slurry
Least water conservative. Losses to: Evaporation Seepage Lock-up (in tailings pore space)
Seepage issues depending on water quality and impoundment design
Water management (reclaim pool) critical to facility operation
Most often lowest operating cost option
Tailings Slurry Design Considerations
Containment dam: Usually High Hazard Impoundment of water pool Piping concerns through dam
Seepage management: Underdrains Underdrains Cut-off walls Pump back systems
5
Tailings Slurry Closure Considerations
Closure challenges:g Concurrent reclamation difficult Long-term consolidation settlements Water management (seepage, consolidation,
etc) continue during post-closure Changing geochemical environment (saturated g g g (
to unsaturated)
Thickened Tailings
6
Thickened Tailings
Dewatered material but still a slurry. Better water conservative than slurry. Losses
to: Evaporation Seepage Lock-up (in tailings pore space)
Seepage issues depending on water quality Seepage issues depending on water quality and impoundment design
Moisture content control – deposition angle Non-segregating (suspended fines)
Thickened Tailings Design Considerations
Containment dam: Low, Medium, High Hazard Containment of process water and tailings Tailings “stacked” (.5 to 1 % slope) Stability of tailings stack (seismic, high rainfall,
etc)) Seepage management: Underdrains Pump back systems
7
Thickened Tailings Closure Considerations
Closure challenges:g Concurrent reclamation difficult, but can be
accomplished after surface drying Long-term consolidation settlements Water management (seepage, consolidation,
etc) continue during post-closure Changing geochemical environment (saturated
to unsaturated)
Paste Tailings
8
Paste Tailings
Dewatered, but still a slurry (100% saturated) Better water conservative than thickened.
Losses to: Evaporation Seepage Lock-up (in tailings pore space)
Seepage issues depending on water quality and impoundment design
Moisture content control - slope Non-segregating (suspended fines)
Paste Tailings Design Considerations
Containment dam: Low, Medium, High Hazard Containment of process water and tailings Tailings “stacked” (.5 to 3 % slope) Stability of tailings stack (seismic, high rainfall,
etc)) Seepage management: Underdrains Pump back systems
9
Paste Tailings Closure Considerations
Closure challenges:g Concurrent reclamation difficult, but can be
accomplished after surface drying Long-term consolidation settlements Water management (seepage, consolidation,
etc) continue during post-closure Changing geochemical environment (saturated
to unsaturated)
Filtered Tailings
10
What Are Filtered Tailings ?Crushing
CircuitMill
CircuitProcess Circuit
Recovered Metal
Tailings
ThickenerCommon to all tailings
Filter Press
Vacuum Belt/Plate
Filtered/Dry StackOR
Filtered Tailings
Most water conservative. Losses to: Evaporation Seepage Lock-up (in tailings pore space)
Seepage issues depending on water quality and impoundment design
Moisture content and dust control critical to facility operation
One of the highest operating cost option
11
Filtered Tailings Design Considerations
Containment dam: Low to Medium Hazard Tailings stacked (+10% slope). Tailings become construction material. Stability of tailings stack. No liquefaction
Seepage management: Seepage management: Underdrains Pump back systems
Filtered Tailings Closure Considerations
Closure challenges:g Amenable to concurrent reclamation No long-term consolidation settlements Minimal water management during post-closure No changing geochemical environment
12
Filtered Tailings Benefitsg
Filtered Tailings
Limited seepage compared to other tailings. Rate Rate Quantity
Material can be used as construction material Compacted fill with high shear strength.
Concurrent reclamationS f t t Surface water management No water pool to manage No chance of upset condition discharge
13
Filtered Tailings Seepage
Saturated ~ 25 % Moisture Content
Seepage occurs as draindown from as-
As-Placed ~ 18 % Moisture Content
Moisture Content
Draindown moisture
draindown from as-placed to field capacity moisture content.
No water pool providing constant
Field Capacity ~ 11 % Moisture Content
recharge (like slurry tailings)
LIMITED VOLUME OF SEEPAGE WATER
Seepage Rates
Slurry tailings: 6.4 gpm/ac Paste/Thickened tailings: 0.4 gpm/ac Filtered tailings: 0.007 gpm/ac
14
Construction
Dry Stack ExamplePogo - Alaska
15
Dry Stack ExamplePogo - Alaska
Dry Stack ExampleLa Coipa Mine – Chile
16
THANK YOU
5/12/2009
1
SSDry StackDry StackTailings Storage FacilityTailings Storage Facility
Advantages of Dry Stack TSF Over Conventional Advantages of Dry Stack TSF Over Conventional Slurry Tailings Slurry Tailings
Tailings are placed under unsaturated conditions resulting in minimal seepage
Dry Stack TSF not susceptible to breaching because there is no reclaim pond
Significant water conservation minimizes water usage and consumption requirements
Facilitates concurrent reclamation and revegetation during operation
Minimizes disturbance area
Minimizes visual impact from surrounding areas
5/12/2009
2
Dry Stack TSF Design CriteriaDry Stack TSF Design Criteria Production rate = 75,000 tpd (tons per day) or 27 MT per yearProduction rate = 75,000 tpd (tons per day) or 27 MT per year
Storage capacity estimated at 596 MT and mine life estimated at approximatelyStorage capacity estimated at 596 MT and mine life estimated at approximately Storage capacity estimated at 596 MT and mine life estimated at approximately Storage capacity estimated at 596 MT and mine life estimated at approximately 21 years21 years
Average tailings inAverage tailings in--place dry density = 109 pcf (pounds per cubic foot)place dry density = 109 pcf (pounds per cubic foot)
Compliance with all applicable regulations including the Arizona Best Available Compliance with all applicable regulations including the Arizona Best Available Demonstrated Control Technology (BADCT) standardsDemonstrated Control Technology (BADCT) standards
Rockfill Buttresses are placed around the perimeter of the facility in 50Rockfill Buttresses are placed around the perimeter of the facility in 50--foot high foot high lifts with 3H:1V side slopes and 25 foot bencheslifts with 3H:1V side slopes and 25 foot benches
3.5H:1V overall side slope3.5H:1V overall side slope
D St k TSF ill b t t d i t h (Ph I d II)D St k TSF ill b t t d i t h (Ph I d II) Dry Stack TSF will be constructed in two phases (Phases I and II)Dry Stack TSF will be constructed in two phases (Phases I and II)
Implement dust control suppression measures throughout the production periodImplement dust control suppression measures throughout the production period
Concurrent reclamation and revegetation during operationsConcurrent reclamation and revegetation during operations
Phase I Dry Stack TSF CharacteristicsPhase I Dry Stack TSF Characteristics Contains Approximately 12 years of productionContains Approximately 12 years of production
Maximum Buttress elevation = 5250 feetMaximum Buttress elevation = 5250 feet
Maximum Tailings surface elevation = 5237.5 feetMaximum Tailings surface elevation = 5237.5 feet
Total capacity = 343 million tons (MT)Total capacity = 343 million tons (MT)
Total footprint of 706 AcresTotal footprint of 706 Acres
Footprint outside of McCleary CanyonFootprint outside of McCleary Canyon
5/12/2009
3
Phase I Dry Stack TSF CharacteristicsPhase I Dry Stack TSF Characteristics Evaporation ponds will be incorporated into tailings lifts to capture Evaporation ponds will be incorporated into tailings lifts to capture
stormwater runoff from the tailings surfacestormwater runoff from the tailings surfacestormwater runoff from the tailings surfacestormwater runoff from the tailings surface
Temporary perimeter ditches will be constructed where necessary to route Temporary perimeter ditches will be constructed where necessary to route stormwater runoff to evaporation pondsstormwater runoff to evaporation ponds
A temporary diversion channel will be constructed at startA temporary diversion channel will be constructed at start--up to capture up to capture stormwater runoff upstream of the phase I Dry Stack TSF through stormwater runoff upstream of the phase I Dry Stack TSF through production year 4production year 4
A permanent Diversion Channel sized for the PMF and armored for the 200 A permanent Diversion Channel sized for the PMF and armored for the 200 year storm will be constructed at startyear storm will be constructed at start--up and will divert stormwater up and will divert stormwater yy ppupgradientupgradient of the plant site into of the plant site into McLearyMcLeary canyon north of Phase Icanyon north of Phase I
Phase I Dry Stack TSFPhase I Dry Stack TSF
5/12/2009
4
Phase I Dry Stack TSF Typical SectionsPhase I Dry Stack TSF Typical Sections
Phase I Dry Stack TSF Filling CurvePhase I Dry Stack TSF Filling Curve
5/12/2009
5
Phase II Dry Stack TSF CharacteristicsPhase II Dry Stack TSF Characteristics
Contains approximately 8 years of production Contains approximately 8 years of production pp y y ppp y y p
Maximum Buttress elevation = 5250 feetMaximum Buttress elevation = 5250 feet
Maximum Tailings surface elevation = 5237.5 feetMaximum Tailings surface elevation = 5237.5 feet
Total capacity = 253 million tons (MT)Total capacity = 253 million tons (MT)
Total footprint 400 AcresTotal footprint 400 Acres
Phase II Dry Stack TSF CharacteristicsPhase II Dry Stack TSF Characteristics Evaporation ponds will be incorporated into tailings lifts to capture runoff Evaporation ponds will be incorporated into tailings lifts to capture runoff
from the tailings surfacefrom the tailings surfacefrom the tailings surface from the tailings surface
Temporary perimeter ditches will be constructed where necessary to divert Temporary perimeter ditches will be constructed where necessary to divert stormwaterstormwater to evaporation pondsto evaporation ponds
An additional permanent diversion channel will be constructed in year 12 to An additional permanent diversion channel will be constructed in year 12 to divert divert stormwaterstormwater upstream of phase II as well as from the diversion channel upstream of phase II as well as from the diversion channel upgradientupgradient of the Plant siteof the Plant site
Dry Detention Basins will be constructed as part of Permanent Diversion Dry Detention Basins will be constructed as part of Permanent Diversion Channel system and will greatly reduce peak runoff produced by storm Channel system and will greatly reduce peak runoff produced by storm y g y p p yy g y p p yeventsevents
5/12/2009
6
Phase II Dry Stack TSFPhase II Dry Stack TSF
Phase II Dry Stack TSF Typical SectionsPhase II Dry Stack TSF Typical Sections
5/12/2009
7
Phase II Dry Stack TSF Filling CurvePhase II Dry Stack TSF Filling Curve
Ultimate Dry Stack TSFUltimate Dry Stack TSF
5/12/2009
8
Dry Stack TSFDry Stack TSFProduction ProgressionProduction Progression
Production Year 0 to Year 1Tailings capacity = 30 MT
5/12/2009
9
Production Year 2 to Year 5Tailings capacity = 153 MT
Production Year 6 to Year 10Tailings capacity = 288 MT
5/12/2009
10
Production Year 11 to Year 12Tailings capacity = 333 MT
End of Phase I-Start of Phase IIProduction Year 13
Tailings capacity = 357 MT
5/12/2009
11
Production Year 14 to Year 15Tailings capacity = 425 MT
Production Year 16 to Year 20Ultimate Dry Stack TSF
Tailings capacity = 586 MT
5/12/2009
12
Dry Stack TSF Site ConditionsDry Stack TSF Site Conditions
ClimateClimate Tetra Tech conducted the meteorological analysis as part of their Feb 2009 design Tetra Tech conducted the meteorological analysis as part of their Feb 2009 design
processprocessMonth Precipitation Pan Evaporation Projected Pan EvaporationMonth Precipitation Pan Evaporation Projected Pan EvaporationJanuary 1.10 3.59 4.13February 0.85 4.46 4.28
March 0.90 7.01 7.11April 0.39 9.35 8.50May 0.22 11.91 10.38June 0.47 13.31 10.75July 4.34 10.00 4.93
August 4.13 8.28 2.89September 1.55 8.06 4.40
October 1.33 7.17 6.15November 0.66 4.49 4.11December 1.43 3.57 3.89
Total 17.37 91.20 71.52
Event 1-Hour 3-Hour 6-Hour 24-Hour2-yr 1.42 1.60 1.83 2.215-yr 1.85 2.03 2.30 2.7510-yr 2.16 2.38 2.68 3.1825-yr 2.57 2.86 3.22 3.7750-yr 2.87 3.24 3.66 4.23100-yr 3.17 3.63 4.12 4.75500-yr 3.84 4.59 5.24 6.001000-yr 4.14 5.03 5.76 6.57
5/12/2009
13
Site Geology SummarySite Geology Summary
Project specific geology is discussed in the Tetra Tech report entitled “Geologic Project specific geology is discussed in the Tetra Tech report entitled “Geologic j p g gy p gj p g gy p gHazards Assessment” dated June 2007Hazards Assessment” dated June 2007
The geologic units underlying the Dry Stack TSF includeThe geologic units underlying the Dry Stack TSF include
•• Gila ConglomerateGila Conglomerate
•• Mount Fagan Mount Fagan RhyoliteRhyolite
•• Apache Canyon FormationApache Canyon Formation
•• Willow Creek FormationWillow Creek Formation
•• Alluvial materialsAlluvial materials
5/12/2009
14
Seismic Hazard Analysis SummarySeismic Hazard Analysis Summary
The Maximum Credible Earthquake (MCE) based on a deterministic The Maximum Credible Earthquake (MCE) based on a deterministic q ( )q ( )analysis was used for the design of the TSFanalysis was used for the design of the TSF
The deterministic analysis included:The deterministic analysis included:•• Identifying the largest potentially active fault close to the siteIdentifying the largest potentially active fault close to the site•• Determining earthquake magnitude that the fault is capable of producingDetermining earthquake magnitude that the fault is capable of producing•• Determining the Peak Ground Acceleration (PGA) that will be produced at the site from this Determining the Peak Ground Acceleration (PGA) that will be produced at the site from this
eventevent
The Santa Rita fault zone determined to be the controlling of 27 The Santa Rita fault zone determined to be the controlling of 27 contributing fault sources within a 200 kilometer radius of the project site contributing fault sources within a 200 kilometer radius of the project site with a distance from site of 11.2 kilometers and a length of with a distance from site of 11.2 kilometers and a length of
i t l 52 kil ti t l 52 kil tapproximately 52 kilometers.approximately 52 kilometers.
The Santa Rita fault zone capable of producing a PGA of 0.33g and a The Santa Rita fault zone capable of producing a PGA of 0.33g and a magnitude 7.1 eventmagnitude 7.1 event
Geotechnical InvestigationGeotechnical Investigation
Geotechnical field investigation were carried out in two phases by Tetra Geotechnical field investigation were carried out in two phases by Tetra g p yg p yTech, between November 2006 and March 2007 and between May and July Tech, between November 2006 and March 2007 and between May and July of 2008. The objective of the investigations included the following:of 2008. The objective of the investigations included the following:
•• To define general subsurface conditions for use in evaluation of the Dry Stack TSF stabilityTo define general subsurface conditions for use in evaluation of the Dry Stack TSF stability
•• To identify suspect zones that could affect the performance of the Dry Stack TSFTo identify suspect zones that could affect the performance of the Dry Stack TSF
•• To quantify engineering characteristics of the materials incorporated into the Dry Stack TSFTo quantify engineering characteristics of the materials incorporated into the Dry Stack TSF
A total of 10 test pits and 38 geotechnical borings in the vicinity of the Dry A total of 10 test pits and 38 geotechnical borings in the vicinity of the Dry Stack TSF allowed subsurface conditions to be definedStack TSF allowed subsurface conditions to be defined
A total of approximately 13,000 feet of seismic refraction survey was also A total of approximately 13,000 feet of seismic refraction survey was also completed near the vicinity of the Dry Stack TSF footprintcompleted near the vicinity of the Dry Stack TSF footprint
5/12/2009
15
Geotechnical InvestigationGeotechnical Investigation
Geotechnical Investigation SummaryGeotechnical Investigation Summary
Depth of Bedrock varied across the footprint from 0 to 100 feetDepth of Bedrock varied across the footprint from 0 to 100 feet
Average depth to bedrock approximately 40 feetAverage depth to bedrock approximately 40 feet
Soils included 1 to 3 feet of topsoil underlain by alluvial materialSoils included 1 to 3 feet of topsoil underlain by alluvial material
Groundwater elevations vary across the footprint from elevations 4,650 Groundwater elevations vary across the footprint from elevations 4,650 to 4,850 feetto 4,850 feet
5/12/2009
16
Geotechnical Investigation SummaryGeotechnical Investigation Summary
The foundation consists primarily of relatively shallow, dense to very dense The foundation consists primarily of relatively shallow, dense to very dense granular soils.granular soils.
Foundation preparation will require stripping loose Foundation preparation will require stripping loose surficialsurficial soils providing a soils providing a uniformly dense founding surface for the tailings.uniformly dense founding surface for the tailings.
A Laboratory testing program was completed on select disturbed samples and A Laboratory testing program was completed on select disturbed samples and bench scale tailing samples obtained from field investigations and pilot plant bench scale tailing samples obtained from field investigations and pilot plant studies.studies.
Two bench scale tailings samples, Colina and MSRDTwo bench scale tailings samples, Colina and MSRD--1 were tested. Both samples 1 were tested. Both samples were determined to be lowwere determined to be low--plastic silt (ML) with a plasticity index of 1.plastic silt (ML) with a plasticity index of 1.
Colina maximum dry density of 115.8 at 14.9%Colina maximum dry density of 115.8 at 14.9% MSRDMSRD--1 maximum dry 1 maximum dry denstiydenstiy of 118.9 at 14.8%of 118.9 at 14.8%
Geologic Hazard SummaryGeologic Hazard Summary
Landslides or rockfall hazard potential will be minimal within the Dry Stack Landslides or rockfall hazard potential will be minimal within the Dry Stack TSF project area.TSF project area.
Collapsible soils are not considered to be an issue within the footprint.Collapsible soils are not considered to be an issue within the footprint.
Historic mining activity will require further field reconnaissance to Historic mining activity will require further field reconnaissance to determine the extent of workings for remediation purposes.determine the extent of workings for remediation purposes.
Earthquake induced ground failure (liquefaction) is not anticipated to Earthquake induced ground failure (liquefaction) is not anticipated to occur within either the foundation or the Dry Stack TSF.occur within either the foundation or the Dry Stack TSF.yy
5/12/2009
17
Tailings Testing SummaryTailings Testing Summary
Other laboratory testing performed on the bench scale tailings samples included:Other laboratory testing performed on the bench scale tailings samples included:•• OneOne--Dimensional ConsolidationDimensional Consolidation•• TriaxialTriaxial ShearShear•• Flexible Wall PermeabilityFlexible Wall Permeability•• Rigid Wall PermeabilityRigid Wall Permeability•• Moisture Retention TestingMoisture Retention Testing•• Geochemical Tailings Characterization (Tetra Tech)Geochemical Tailings Characterization (Tetra Tech)
AcidAcid--Base AccountingBase Accounting Net Acid GenerationNet Acid Generation pH TestingpH Testing Humidity Cell Testing (Kinetic)Humidity Cell Testing (Kinetic) Synthetic Precipitation LeachingSynthetic Precipitation Leaching Meteoric Water MobilityMeteoric Water Mobility
•• Solids Liquid SeparationSolids Liquid Separation FlocculantFlocculant Screening and EvaluationScreening and Evaluation Static ThickeningStatic Thickening Dynamic High Rate ThickeningDynamic High Rate Thickening Pulp Pulp RheologyRheology Pressure Filtration StudiesPressure Filtration Studies Vacuum Filtration StudiesVacuum Filtration Studies
Geochemical Test ResultsGeochemical Test Results
Tailings generally contain less than 0.01 percent sulfideTailings generally contain less than 0.01 percent sulfide--sulfursulfur
Tailings possess high capacity for acid neutralizationTailings possess high capacity for acid neutralization
Tailings produce very low metal concentrations in the resulting leachateTailings produce very low metal concentrations in the resulting leachate
TotalTotal--sulfur concentrations less than 0.3 percent and a neutralization potential ratio sulfur concentrations less than 0.3 percent and a neutralization potential ratio greater than 3greater than 3
Testing indicate the tailings meet ADEQ criteria as inertTesting indicate the tailings meet ADEQ criteria as inert Testing indicate the tailings meet ADEQ criteria as inertTesting indicate the tailings meet ADEQ criteria as inert
5/12/2009
18
Engineering Properties of TailingsEngineering Properties of Tailings
Laboratory gradations of the tailings indicate an average of approximately 72.6 Laboratory gradations of the tailings indicate an average of approximately 72.6 percent by weight passing the No. 200 sievepercent by weight passing the No. 200 sieve
Atterberg limit testing indicates the tailings have:Atterberg limit testing indicates the tailings have:•• PI of 1PI of 1•• PL of 20PL of 20•• LL of 21LL of 21
The tailings classify as a lowThe tailings classify as a low--plastic silt (ML), as defined by the USCSplastic silt (ML), as defined by the USCS
A ff ti h t th i t l 36 5 dA ff ti h t th i t l 36 5 d Average effective shear strength approximately 36.5 degreesAverage effective shear strength approximately 36.5 degrees
Engineering Properties of Alluvium/FoundationEngineering Properties of Alluvium/Foundation
Average Average of approximately 26.8 percent by weight passing the No. 200 sieveof approximately 26.8 percent by weight passing the No. 200 sieve
Atterberg limits ranging between nonAtterberg limits ranging between non--plastic and 26plastic and 26
Average effective shear strengths ranging between 33 and 41 degrees with Average effective shear strengths ranging between 33 and 41 degrees with cohesions ranging between 1,600 and 2,500 psfcohesions ranging between 1,600 and 2,500 psf
5/12/2009
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Dry Stack TSFDry Stack TSFDesignDesign
Dry Stack TSF DesignDry Stack TSF Design
The Dry Stack TSF consists of two separate areas referred to as Phase I The Dry Stack TSF consists of two separate areas referred to as Phase I y py pand Phase IIand Phase II
Phase I is located between the McCleary Canyon wash and the Waste Phase I is located between the McCleary Canyon wash and the Waste Rock Storage Area (12 years, 343 MT)Rock Storage Area (12 years, 343 MT)
Phase II is an extension of the phase I facility and will be constructed Phase II is an extension of the phase I facility and will be constructed north of Phase I within McCleary Canyon (years 12north of Phase I within McCleary Canyon (years 12--21, 253 MT)21, 253 MT)
Tailings properties were determined through testing of bench scale Tailings properties were determined through testing of bench scale tailings samples.tailings samples.
The specified moisture range of placed tailings is 15% (by weight) plus or The specified moisture range of placed tailings is 15% (by weight) plus or minus 3%. minus 3%.
5/12/2009
20
Dry Stack TSF DesignDry Stack TSF Design
Foundation preparation will include clearing and grubbing, tree removal, Foundation preparation will include clearing and grubbing, tree removal, p p g g g, ,p p g g g, ,access road construction and topsoil salvaging and stockpiling.access road construction and topsoil salvaging and stockpiling.
In the TSF footprint, most of the existing natural drainages will be filled In the TSF footprint, most of the existing natural drainages will be filled with inert rock and function as flowwith inert rock and function as flow--through drains.through drains.
An initial starter buttress will be constructed in the lower Barrel Canyon An initial starter buttress will be constructed in the lower Barrel Canyon drainage to accommodate three months of tailings storage.drainage to accommodate three months of tailings storage.
Rockfill Buttresses will advance ahead of tailings in 50Rockfill Buttresses will advance ahead of tailings in 50--foot high lifts foot high lifts using upstream construction methods.using upstream construction methods.
Buttresses will have 150Buttresses will have 150--foot top widths to accommodate twofoot top widths to accommodate two--way haul way haul traffic and outer slopes of 3H:1V.traffic and outer slopes of 3H:1V.
Dry Stack TSF DesignDry Stack TSF Design
Dry tailings will be delivered from the filter plant by conveyor and placed Dry tailings will be delivered from the filter plant by conveyor and placed y g p y y py g p y y pin 25in 25--foot lifts using a radial stacker upgradient of the Rock Buttress.foot lifts using a radial stacker upgradient of the Rock Buttress.
Tailings will be spread with a dozer and compacted with a vibratory Tailings will be spread with a dozer and compacted with a vibratory smooth drum roller to provide compaction for trafficability of the smooth drum roller to provide compaction for trafficability of the conveyor and to minimize dust.conveyor and to minimize dust.
The outer perimeter of the tailings beneath the Rock Buttress will be The outer perimeter of the tailings beneath the Rock Buttress will be placed in 5placed in 5--foot lifts and compacted 90% of standard proctor density.foot lifts and compacted 90% of standard proctor density.
A bypass conveyor will be provided to allow temporary disposal of tailings A bypass conveyor will be provided to allow temporary disposal of tailings d i i t i t t ditid i i t i t t ditiduring primary conveyor movement, maintenance or upset conditions.during primary conveyor movement, maintenance or upset conditions.
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Dry Stack TSF DesignDry Stack TSF Design
FlowFlow--through drains will be constructed of 12through drains will be constructed of 12--inch minus rockfill and inch minus rockfill and ggseparated from the tailings above by a layer of 10 oz/ydseparated from the tailings above by a layer of 10 oz/yd22 geotextile.geotextile.
Seepage is anticipated to peak at year 18 at a rate of 8.4 gpm. Seepage is anticipated to peak at year 18 at a rate of 8.4 gpm.
Natural seepage and springs will be captured with collection drains Natural seepage and springs will be captured with collection drains consisting of shallow trenches filled with rockfill wrapped in 10 oz/ydconsisting of shallow trenches filled with rockfill wrapped in 10 oz/yd22
nonnon--woven geotextile.woven geotextile.
Existing water wells within the Dry Stack TSF footprint will be abandoned Existing water wells within the Dry Stack TSF footprint will be abandoned according to ADWR regulations.according to ADWR regulations.
Dry Stack TSFDry Stack TSFSurface Water ManagementSurface Water Management
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Dry Stack TSF Surface Water ManagementDry Stack TSF Surface Water Management
Water management will be addressed in the Water Management Plan to Water management will be addressed in the Water Management Plan to g gg gbe submitted in July 2009. General water management concepts specific be submitted in July 2009. General water management concepts specific to the Dry Stack TSF are listed below:to the Dry Stack TSF are listed below:
Perimeter ditches and evaporation ponds will collect stormwater runoff Perimeter ditches and evaporation ponds will collect stormwater runoff from the tailings surfacefrom the tailings surface
FlowFlow--through drains will allow stormwater that does not come into through drains will allow stormwater that does not come into contact with tailings to be routed beneath the Dry Stack TSFcontact with tailings to be routed beneath the Dry Stack TSF
Diversion channels will be constructed in two phases concurrent with the Diversion channels will be constructed in two phases concurrent with the D St k TSF h Th ill b i d t th PMF d dD St k TSF h Th ill b i d t th PMF d dDry Stack TSF phases. They will be sized to pass the PMF and armored Dry Stack TSF phases. They will be sized to pass the PMF and armored to protect against the 200 year/24 hour storm.to protect against the 200 year/24 hour storm.
A Temporary diversion channel will be constructed upstream of the initial A Temporary diversion channel will be constructed upstream of the initial lifts of phase I and will function through year 4lifts of phase I and will function through year 4
Dry Stack TSFDry Stack TSFSeepage AnalysisSeepage Analysis
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Dry Stack TSF Seepage AnalysisDry Stack TSF Seepage Analysis Seepage analysis conducted using the finite element method based Seepage analysis conducted using the finite element method based
computer program computer program SVFluxSVFlux Version 2.0.13Version 2.0.13
Tailings modeled at average moisture content of 18% (or less) by weightTailings modeled at average moisture content of 18% (or less) by weight
OneOne--dimensional tailings column models were incrementally evaluated dimensional tailings column models were incrementally evaluated using 50 foot lifts to the full height of 550 feetusing 50 foot lifts to the full height of 550 feet
Developed Developed isopachisopach maps representing average depths of tailings for each maps representing average depths of tailings for each lift and phaselift and phase
Each successive model incorporated the pore water distributions from the Each successive model incorporated the pore water distributions from the previous modelprevious modelprevious modelprevious model
Dry Stack TSF Seepage AnalysisDry Stack TSF Seepage Analysis Included climatic flux comprised of environmental factors including
precipitation, pan evaporation, relative humidity and temperature.precipitation, pan evaporation, relative humidity and temperature.
The greatest average annual precipitation of 22.2 inches was used, and the lowest average annual pan evaporation of 71.5 inches was used.
The dry stack tailings are considered to be relatively homogeneous in nature.
Laboratory testing was performed to determine hydraulic conductivity at various depths.
Hydraulic conductivity ranges between 4 x 10-3 cm/sec near the top of the Dry Stack TSF and 6 x 10-7 cm/sec at depths of 50 feet or greater.
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Saturated Hydraulic Conductivity With DepthSaturated Hydraulic Conductivity With Depth
Dry Stack TSF Seepage AnalysisDry Stack TSF Seepage Analysis
A series of moisture retention laboratory tests were completed on the y ptailings samples .
These tests were used to develop a soil water characteristic curve (SWCC) for the tailings materials.
The SWCC defines the soil’s ability to store and release moisture.
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Soil Water Characteristic CurveSoil Water Characteristic Curve
INSERT SWCC CurvesINSERT SWCC Curves
Relative Hydraulic Conductivity FunctionRelative Hydraulic Conductivity Function
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Dry Stack TSF Seepage Analysis ResultsDry Stack TSF Seepage Analysis Results
As the Dry Stack TSF expands over time, the estimated seepage rate y p , p gincreases to a peak value of approximately 8.4 gpm, at production year 18.
The upper 8 feet of the tailings performs as a storage-release unit, where moisture lost to evaporation is replenished by precipitation.
Based on the model, the seepage is due solely to drainage of pore water.
Meteoric influences will have a small recharging effect on the top several feet of tailings, but due to the large evaporation rate there will be an overall negative flux at the surface.
A two-dimensional model of the ultimate Dry Stack TSF was also developed to verify the results.
Seepage Over Life of MineSeepage Over Life of Mine
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Seepage After Life of MineSeepage After Life of Mine
Moisture Content with Depth Over TimeMoisture Content with Depth Over TimeNote:The data represents a typical 100-foot column. h lThe initial moisture
content was modeled at 18% by weight
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Dry Stack TSF Seepage Analysis ResultsDry Stack TSF Seepage Analysis Results
The estimated maximum seepage from the Dry Stack TSF is expected to p g y pbe 0.007 gpm/acre. For comparison, the following tailings disposal methods and associated expected seepage rates are as follows:
Slurry Tailings (no liner) 6.4 gpm/acre Slurry Tailings (with liner) 0.06 gpm/acre Paste and Thickened tailings 0.4 gpm/acre
Dry Stack TSFDry Stack TSFStability AnalysisStability Analysis
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Dry Stack TSF Stability AnalysisDry Stack TSF Stability Analysis
Establishment of stability design criteria for static and seismic loading Establishment of stability design criteria for static and seismic loading y g gy g gconditions based upon laboratory testing, field investigation, and seismic conditions based upon laboratory testing, field investigation, and seismic hazard analysishazard analysis
Development of representative cross sections.Development of representative cross sections.
Completion of static and seismic stability analyses utilizing limit Completion of static and seismic stability analyses utilizing limit equilibrium methods.equilibrium methods.
Slope stability was evaluated using Spencer’s method.Slope stability was evaluated using Spencer’s method.
Dry Stack TSF Stability Analysis MethodologyDry Stack TSF Stability Analysis Methodology
The minimum factors of safety used in accordance with the BADCT The minimum factors of safety used in accordance with the BADCT yyGuidance Manual guidelines are 1.3 and 1.0 for static and seismic Guidance Manual guidelines are 1.3 and 1.0 for static and seismic analyses, respectively with appropriate laboratory and field testing.analyses, respectively with appropriate laboratory and field testing.
The stability of the Dry Stack TSF under earthquake loading was The stability of the Dry Stack TSF under earthquake loading was evaluated using the pseudostatic approach.evaluated using the pseudostatic approach.
The cross sections were developed at the maximum sections of the The cross sections were developed at the maximum sections of the facilityfacility
For conservatism, the tailings 1,100 feet from the crest of the buttress For conservatism, the tailings 1,100 feet from the crest of the buttress d l d h i t thd l d h i t thwere modeled as having no strength.were modeled as having no strength.
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Dry Stack TSF Stability Analysis Material Dry Stack TSF Stability Analysis Material PropertiesProperties
Material Type
MoistUnit Weight
(lbs/ft³)
Effective Stress AnalysisStrength Parameters
Total Stress AnalysisStrength Parameters
Friction Angle(degrees)
Cohesion(lbs/ft2)
Friction Angle(degrees)
Cohesion(lbs/ft2)
Alluvium / Colluvium 130 36 0 - -
Tailings 110 28 0 18 1,300
Compacted Tailings 116 32 0 - -Tailings
No Strength Tailings 110 0 0 - -
Rockfill 125 38 0 - -
Dry Stack TSF Stability Analysis ResultsDry Stack TSF Stability Analysis Results
For tailing impoundment facilities the minimum factors of safety, as required by the For tailing impoundment facilities the minimum factors of safety, as required by the g p y q yg p y q yBADCT Guidance Manual, are 1.3 and 1.0 for static and seismic analyses.BADCT Guidance Manual, are 1.3 and 1.0 for static and seismic analyses.
Cross Section Analysis ModeledStatic
Factor of SafetyPseudostatic
Factor of Safety
Phase IEffective 2.3 1.2
Total 1.9 1.0
Ph IIEffective 2.3 1.2
Phase II Total 1.9 1.0
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Dry Stack TSF Stability Analysis Dry Stack TSF Stability Analysis -- LiquefactionLiquefaction
Liquefaction can be generally defined as the loss of shear strength in loose, Liquefaction can be generally defined as the loss of shear strength in loose, q g y gq g y gsaturated, and saturated, and cohesionlesscohesionless soils due to the generation of excess pore pressures as soils due to the generation of excess pore pressures as a result of large shear strains induced by a result of large shear strains induced by undrainedundrained cyclic loading.cyclic loading.
The dry stack tailings will be unsaturated and will be under large confining pressures The dry stack tailings will be unsaturated and will be under large confining pressures producing a uniformly dense fill, hence the propensity for liquefaction will be very producing a uniformly dense fill, hence the propensity for liquefaction will be very low and is not anticipated to occurlow and is not anticipated to occur
The majority of native foundation soils were very dense or hard for granular and fine The majority of native foundation soils were very dense or hard for granular and fine grained material and are not susceptible to liquefaction.grained material and are not susceptible to liquefaction.
Phase I Stability AnalysisPhase I Stability Analysis
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Phase II Stability AnalysisPhase II Stability Analysis
Dry Stack TSFDry Stack TSFClosure ConceptClosure Concept
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Dry Stack TSF Closure ConceptDry Stack TSF Closure Concept
The primary goal of closure/postThe primary goal of closure/post--closure plan is to eliminate any closure plan is to eliminate any p y g pp y g p p yp yreasonable probability of further discharge from the Dry Stack TSF.reasonable probability of further discharge from the Dry Stack TSF.
Concurrent with operations, portions of the Dry Stack TSF will be Concurrent with operations, portions of the Dry Stack TSF will be reclaimed to reduce erosion due to wind and water.reclaimed to reduce erosion due to wind and water.
The top of the Dry Stack TSF will be graded inward to create an The top of the Dry Stack TSF will be graded inward to create an evapotranspirationevapotranspiration pond capable of containing the PMP.pond capable of containing the PMP.
The top of the Dry Stack TSF will be The top of the Dry Stack TSF will be revegetatedrevegetated with native seed mixes with native seed mixes designed to maximize designed to maximize evapotranspirationevapotranspiration..
