NICO Tailings and Mine Rock Co-disposal Facility (CDF) Design Concept

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1 NICO Tailings and Mine Rock Co-disposal Facility (CDF) Design Concept

2 Open pit and underground mine The project has 31 Mt of ore reserve Ore to be processed at a rate of 4,650 t/d Life of mine is 20 years Mine waste streams are: 30 Mt of tailings 97 Mt of mine rock (includes sub-economic mineralized rock) 2

3 Sub-arctic climate with mean annual temperature of -4.7 C and freezing index of 3,500 to 4,000 C-days The site has discontinuous permafrost. Limited ground ice found in a few boreholes Site has low seismicity with PGA of 0.011g for the 1 in 475 year seismic event Rock outcrops are common on hilly areas Bedrock is overlain by overburden soils in valley areas Overburden soil is <10m thick and includes: topsoil, peat, glacio-lacustrine deposits and glacial till or cobble and boulder 3

4 Tailings are silt to sandy silt sized particles Tailings have potential for metal leaching and low potential for acid generation 19% of mine rock (including sub-economic mineralized rock) has an acid generating potential Mine rock has metal leaching potential In the CDF, the tailings layers act to limit the flow of oxygen and water through the mine rock, thus reducing acid generation and metal leaching 4

5 Mine Rock Classification: Classification Solid Phase Composition Description Type 1 mine rock Type 2 mine rock Type 3 mine rock Sub-economic mineralized mine rock < 0.3 % sulphide sulphur < 50 ppm bismuth < 1000 ppm arsenic < 0.3% sulphide sulphur < 1000 ppm arsenic > 50 ppm bismuth > 0.3% sulphide sulphur > 50 ppm bismuth > 1000 ppm arsenic Classified according to grade control cut-off Mine rock with a low potential for acid generation and metal leaching, suitable for construction of seepage collection dams and the perimeter dyke Mine rock with a low potential for acid generation, suitable for construction of the perimeter dyke Potentially acid generating and metal leaching rock, suitable for placement within the codisposal area Sub-economic mineralized mine rock, to be placed within the co-disposal area and a minimum of 20 m offset from the interior of the perimeter dyke 5

6 Several options were considered for management of tailings and mine rock Co-disposal of tailings and mine rock was preferred for the following reasons: Increases the rate of consolidation of the tailings Improves the stability of the disposal facility Reduces metal leaching and acid mine drainage by reducing O 2 flux and infiltration Reduces dust generation Reduces the mine rock hauling distance Allows progressive closure 6

7 The CDF consists of: Perimeter dyke Tailings and mine rock co-disposal area (CDF interior) Reclaim pond, movable pump station and reclaim water pipeline system Thickened tailings delivery and distribution system Seepage collection ponds (five SCPs) Surge pond Emergency spill containment pond Constructed wetland treatment system 7

8 Total tailings: 17.2 M-m 3 Tailings expected to fill mine rock voids M-m 3 Excess tailings deposited in cells M-m 3 Total mine rock (incl. sub-economic rock): 50.3 M-m M-m 3 required for CDF perimeter dike 0.2 M-m 3 required for SCP dams 0.1 M-m 3 required for cemented rock backfill 43.9 M-m 3 available for co-disposal with tailings CDF covers a total footprint area of 139 ha CDF has a maximum height of 90 m Top surface of CDF will slope at 2% to reduce infiltration 8

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11 Co-disposal area will be developed by depositing alternating layers of tailings and mine rock The layered co-disposal will reduce the flux of oxygen and water into the mine rock layers (compared to a conventional mine rock dump) Tailings layers created by constructing a series of tailings disposal cells (typically 200m by 200m and 5m deep) Perimeter dyke will be constructed in advance of the raising of the co-disposal area to provide containment 11

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13 Seepage Collection Pond dams to be constructed with Type 1 mine rock The perimeter dyke to be constructed using Type 2 (or Type 1) mine rock Type 3 mine rock (and uneconomic mineralized rock) to be placed inside the co-disposal area A filter or heavy geotextile will be used between perimeter dyke and the co-disposed area Perimeter dyke is designed to drain freely, but all seepage will be collected in SCPs Design and operation of the CDF will be reviewed by an independent peer review committee 13

14 Excess mine rock - build more tailings cells Shortfalls of mine rock build larger tailings cells Shortfalls of tailings use mine rock to construct multiple tailings cells ahead of schedule Low solids content tailings increase pumping of reclaim water and possibly increase size of cells Tailings spill control tailings delivery pipeline to be placed in a lined twin soil berms, emergency spill containment pond provided to store spill Ice entrainment in winter tailings leave cell uncovered in summer to thaw slightly higher CDF grade 14

15 CDF closure & reclamation takes place progressively Top CDF surface to be covered by 0.5 m glacial till underlain by 0.25 m of sand CDF perimeter dyke to be covered with 1.0 m glacial till >70% of the CDF will be covered by the end of operation, the rest within 2 years post closure 15