MINING WITH BACKFILL MOUNT ISA MINES Challenges, Learnings AND Strategies

Background Mount Isa Copper Operations (MICO) Employs close to 3,000 people Produces ≈6 Mtpa of Cu ore –X41 mine (old mine ”s and early 70’s) –Enterprise mine (new mine started 2000) Mining Method by SLOS –X41 stopes footprint of m X mH –Enterprise stopes footprint of 15-30M X mH

MICO Backfill Systems Backfill Demand ≈ 3.0Mtpa (2.0 Mm 3 pa) of stope voids % backfilled with CHF and PF % backfilled with HF and RF Backfill Systems 1.Hydraulic Fill System (CHF and HF) 2.Paste Fill System (PF) 3.Rockfill (RF) 4.CRF and CHF + Aggregate discontinued in 1990”s

1. Hydraulic Fill “Wetfill” System HYDRAULIC BACKFILL SYSTEM –Online process –CHF and HF Filling areas - supplies most of the X41 mine - some part of Enterprise mine –“Wetfill” Plant - Processes Cu and PB/Zn tailings - Simple cyclone process (passing10 microns) - ≈1.5 Mtpa (≈1Mm 3 pa) - Fill plant flowrate of 240 tph ( m3ph) - Fill RD of 70% (68-72% / )

2. Pastefill System PASTE BACKFILL SYSTEM –Online process Portion of Cu tailings is processed (50%) Portion pumped to wetfill plant/TSF –Pastefill filling areas - Mainly the Enterprise mine –Fill Plant Processes Cu tailings only Production ≈1.25 Mtpa (900Km 3 pa) - Fill plant flowrate of 250 tph ( m 3 ph) - Fill RD of 76% (1.95) - Processing by filtration and *adding back fines

3. Rockfill -Uses mainly mine development waste -Approximately 250Kt-350Ktpa -Occasionally backfilled in CHF stopes - Stope Filling: based on availability of waste as derived availability of LHD distance to haul waste, and

PF processing set up * Optimised Pastefill Processing (unique set up) - High fill production - Optimum sizing 30 % passing 20 µm) - high density of mix (76%) - Low cement 28d cured)

Cu Tailings PSD -Ratio of filter cake (FC) and fines (T/U) to meet 30% passing 20µm 77 : OPC (185:48:7=240t)

Relationship of location of fill plants, reticulations and mining levels Wetfill/HF plant X41 Mine Enterprise Mine

Reticulation schematic Pastefill and Hydraulic fill ( set up to 2009) Issue/problem: - Filling gap in Enterprise Mine started in 2009 due to shift in mining. - PF plant production increased to 290tph but cannot keep up with filling demand in Enterprise, fill plant struggling at increased flowrate

Wetfill Reticulation Extended to Enterprise Mine (2010) * Filling Strategy to close filling gap in Enterprise Mine

Cement Demand, Supply and Cost Annual Cement Demand - 6% cement requires ≈80,000 tpa OPC - 3% cement requires ≈40,000 tpa OPC ============= Total cement demand ≈120,000 tpa OPC cost* at $198/t ≈ $24million pa *CA supplies OPC at bulk price, reviewed every 3 years *Cement transported by QR using 28 cement containers owned by Mount Isa Mines OPC price in $189/t OPC price in 2009 – OPC price in 2013 – 212/t

Cement Partly Replaced by Fly Ash Slags (Cu and Pb) as OPC part replacement– discontinued in 2004 FA derived from old Mica Creek coal fired power plant - 150,000t identified impounded in a creek - Fly ash testwork Trialled in a small stope >>successful *Binder cost reduction (improvement of mix design) -Cement cost reduction of almost $10m from Cost per tonne CHF 4% OPC + 4% FA (new mix) = 6% OPC (standard mix) $ $1.80 = $9.72 $11.88 » Savings $2.16/t of CHF or $2.8miilion pa

Wetfill boreholes wear challenges Two boreholes at 750m long - 120m below collar steel pipe lined - 138m long inner casing, - 150mm Ø carbon steel sched 80 - $80,000/casing change (OPEX) - replaced casing 6X per year - casing lasts 250Kt fill passing - 1.5Mtpa fill ≈$420K annual cost - 12 days downtime >>>>> Borehole reticulation cost - $0.28/t fill passing through

Wetfill boreholes wear challenges Two boreholes at 750m long - 120m below collar steel pipe lined - 138m long inner casing - 150mm Ø ceramic lined - $600,000/casing change (CAPEX) - casing estimated to last 3 million t - 3 days downtime inspection * Improvement to reduce casing cost and downtime M passing $0.20/t fill after 3Mt fill passing savings of $75kpa M passing $0.15/t fill after 5M t fill passing savings of $150kpa Reduce downtimes

Pastefill boreholes wear challenges Two boreholes at 1,220m long m below collar water table - 420m inner casing replacement, - P110mm Ø steel pipe (standard practice) - $140,000/casing change - replaced every 200Kt fill passing - $1m annual cost + 14day downtime High cost of casing per tonne fill passing >>>$0.83/t fill passing

Pastefill boreholes wear challenges Two boreholes at 1,220m long m below collar water table - 420m inner casing replacement, * Improvement to reduce maintenance cost and downtime 1.Ceramic lined 125mm Ø casing - $1.4million pa, 1.3Mt fill passing (Justify as CAPEX at least a year life) >>> $0.93/t fill passing and 3 days d/time 2. Used oil steel casing of 95mm Ø - $700K pa (5 x $140k/change, 1.25Mt fill) >>> $0.58/t fill passing and 10 days d/time 3. Used oil steel casing of 85mm Ø - $500K pa (3.5 X $140k, 1.25Mt fill) >>> $0.42/t fill passing and 7 days d/time (annual savings of $492k)

Pipelines upgrades – hydraulic fill History of pipe types usage –Up to 2003 – standard use of concrete lined pipe –2004 concrete lined pipe supplier closes shop –Early 2005 rubber lined pipe replacing worn out concrete lined pipes –Late 2005 rubber lined pipe started failings (bubbles and debonding) –Mid 2006 polyurethane lined pipes, early 2007 rubber lining failing (debonding on high pressure areas but ok in low pressure areas) 2007 started trialling ceramic lined pipelines>> successful but expensive Justify CAPEX every year ( ) to replace 1,000m of pipes annually * Upgrades of pipelines 1.Ceramic lined 150mm Ø, 12mm thick ceramic lining - $1.2million pa for 1,000m long pipes bought in success >> more than 7.5million already passed through (only a quarter worn) 2. Ceramic lined pipes now a standard wetfill pipeline in Mount Isa Copper operations - thinner ceramic lining (3-6mm)

Rubber lined pipe – hydraulic fill

End of Presentation Questions

Others Other improvement (cost reduction) Bulkhead shotcrete - fibres remove Long pipelines- borehole bypass Borehole switch set up – level and by-pass switch Adding rockfill in some CHF stopes Quality control (rather than quantity) Questions

What Type of Backfill CAPEX - PF high capital, HF fraction of PF, CRF OPEX LOM-short or long term Suitability and availability of tailings Preference of company Requires Options study

Option summary Fill Type Material Source Process and Delivery Advantages Disadvantages Technical Operational Economic Risk Overall Rockfill (RF) Development waste rock Load haul dump into stopes Direct dump or back load from surface to supplement demand No capital cost Very low operating cost Reduces hoisting requirements Suitable for bulk fill only Limited filling rate Traffic congestion FairGoodVery goodLowVery Good (bulk fill only) Cemented Rockfill (CRF) Crushed and Screened Development waste rock Cement Mix rock with cement slurry in mix bays and load haul and dump into stopes. Low capital cost Moderate barricade cost Low risk of barricade failure Tight filling possible with fill pusher High operating cost Limited filling rate Traffic congestion High segregation FairGoodFairMode rate Good Cemented Aggregate Fill (CAF) Crushed and Screened Development waste rock Tailings Cement Mixture of tailings with aggregate and cement slurry delivered underground by trucks. Moderate capital cost Moderate barricade cost Low risk of barricade failure Tight filling possible with fill pusher High operating cost Limited filling rate Traffic congestion Moderate segregation FairPoor Mode rate Fair Hydraulic Fill (HF) OTML tailings Deslimed tailings slurry pump/gravity delivered underground via boreholes and pipelines Lowest capital cost Very low operating cost Low segregation Rapid filling possible Suitable for bulk fill only Highest barricade cost Higher risk of barricade failure High drainage maintenance cost Longer time to fill Fair Very goodHighVery Good (bulk fill only) Cemented Hydraulic Fill (CHF) OTML tailings Cement Deslimed tailings slurry with cement gravity delivered underground via boreholes and pipelines Moderate capital cost Moderate operating cost Low segregation Rapid filling possible Highest barricade cost Higher risk of barricade failure High drainage maintenance cost Difficult and longer time to tight fill PoorFairGoodHighFair Paste Fill (PF) OTML tailings Cement Dewatered tailings mixed with cement gravity delivered underground via boreholes and pipelines Lowest operating cost Low risk of barricade failure No segregation Tight filling possible Rapid filling possible High capital cost High barricade cost Very good FairLowGood

Backfill Operating Cost - Binder % Percentage of cement usage in operating cost

Backfill Types Operating Cost Binder demand and Operating cost comparison

Backfill Types Operating Cost Operating cost comparison Notes: High cost of preparing/mixing, conveying and slow production in CRF High maintenance of pipeline and drainage in CHF operation Medium processing cost (filtering) in PF online mill processing High cost of reclaiming tailings Details of costing and cement dosage, at A$300/t cementCHF PF -online mill tailings PF -reclaim or harvested tailingsCRF Cement dosage6%4% 5% Cost of cement (A$) $18.00 $12.00 $15.00 Cost of processing, conveying and placement (A$) $7.00 $5.00 $10.00 $18.00 Cost of fll per tonne (A$) $25.00 $17.00 $22.00 $33.00 Percent cement in operating cost72%71%55%45%

Burst Disc

PF Utilisation

Build up of fill on pipe

Oversize pipe, low density

250mm pipe, fill build up

Blocked pipe-CHF

Worn out casing-borehole

Switch/By-pass

Old Isa Pictures