Waste Characterization Data Package The concept for management of waste rock is to classify waste rock

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  • NorthMet Project

    Waste Characterization Data Package

    Version 12

    Issue Date: February 13, 2015

    This document was prepared for Poly Met Mining Inc. by Barr Engineering Co.

  • Date: February 13, 2015 NorthMet Project Waste Characterization Data Package

    Version: 12 Page i

    Table of Contents 1.0  Introduction ............................................................................................................................ 1 

    1.1  Outline ............................................................................................................................ 1  2.0  Regulatory Basis .................................................................................................................... 2 

    3.0  Overburden ............................................................................................................................ 3 

    3.1  Reports............................................................................................................................ 3  3.1.1  Initial Report ........................................................................................................3  3.1.2  2011 Update ........................................................................................................5 

    3.2  Overburden Management Concept ................................................................................. 5  4.0  Waste Rock ............................................................................................................................ 7 

    4.1  Reports............................................................................................................................ 7  4.1.1  Initial Report ........................................................................................................7  4.1.2  2009 Update ........................................................................................................9  4.1.3  2011 Update ......................................................................................................11 

    4.1.3.1  2011 Geochemical Update ...................................................................11  4.1.3.2  Category 1 Concentration Caps Study .................................................12 

    4.1.4  2012 and 2014 Humidity Cell Trends Updates .................................................15  4.2  Waste Rock Management Concept .............................................................................. 15  4.3  Waste Characterization Program as Applied to Waste Rock Stockpiles ..................... 16 

    4.3.1  Waste Characterization by Geologic Unit and Rock Type ...............................16  4.3.1.1  Combination of Units 2 & 3 and 4 & 5 ................................................16  4.3.1.2  Unit 7 ...................................................................................................17 

    4.3.2  Sulfur Content of Stockpiles and Pit Walls .......................................................23  5.0  Flotation Tailings ................................................................................................................. 31 

    5.1  Reports.......................................................................................................................... 31  5.1.1  Initial Report ......................................................................................................31  5.1.2  2009 Update ......................................................................................................32  5.1.3  2011 Update ......................................................................................................34 

    5.1.3.1  Depositional Study ...............................................................................34  5.1.3.2  2011 Geochemical Update ...................................................................39  5.1.3.3  2011 Humidity Cell Trends Update .....................................................39 

    5.1.4  2012 and 2014 Humidity Cell Trends Updates .................................................40  5.2  Flotation Tailings Management Concept ..................................................................... 41 

  • Date: February 13, 2015 NorthMet Project Waste Characterization Data Package

    Version: 12 Page ii

    6.0  Hydrometallurgical Residue ................................................................................................ 42 

    6.1  Reports.......................................................................................................................... 42  6.1.1  Initial Report ......................................................................................................42  6.1.2  2009 Update ......................................................................................................44  6.1.3  2011 Design Update ..........................................................................................44  6.1.4  2013 Water Quality Update ...............................................................................44 

    6.2  Hydrometallurgical Residue Management Concept..................................................... 46  7.0  Geochemical Parameters – Overburden ............................................................................... 47 

    7.1  Leachate Water Quality – Unsaturated Overburden .................................................... 47  7.2  Leachate Water Quality – Peat ..................................................................................... 47  7.3  Leachate Water Quality – Saturated Overburden ......................................................... 49 

    8.0  Geochemical Parameters – Waste Rock .............................................................................. 50 

    8.1  Laboratory Release Rates ............................................................................................. 50  8.1.1.1  Sulfate Release Rates for Category 1, Category 2/3 and Ore ..............50  8.1.1.2  Linear Regression Analysis .................................................................50  8.1.1.3  Combining Data Sets ...........................................................................54  8.1.1.4  Testing Assumptions of Ordinary Least Squares .................................55  8.1.1.5  Correction for Non-Constant Variance ................................................56  8.1.1.6  Application to Probabilistic Modeling .................................................59 

    8.1.2  All Other Release Rates ....................................................................................60  8.1.2.1  Release Rates from Humidity Cells .....................................................61  8.1.2.2  Release Rates from Humidity Cell Release Ratios ..............................63  8.1.2.3  Release Rates from Solid Ratios ..........................................................63 

    8.1.2.3.1  Nickel Release ...................................................................65  8.2  Lab to Field Scale-Up................................................................................................... 66 

    8.2.1  Background .......................................................................................................66  8.2.2  Water Contact Factor .........................................................................................68  8.2.3  Particle Size Factor ............................................................................................68  8.2.4  Temperature Factor ...........................................................................................71  8.2.5  Acidity Factor ....................................................................................................74  8.2.6  Composite “Bulk” Scale-Up Factor ..................................................................77  8.2.7  Scale-Up Model Verification ............................................................................79  8.2.8  MDNR Method for Category 1 Waste Rock Stockpile Scale-Up .....................81 

  • Date: February 13, 2015 NorthMet Project Waste Characterization Data Package

    Version: 12 Page iii

    8.3  Concentration Caps ...................................................................................................... 83  8.3.1  Category 1 Waste Rock .....................................................................................83 

    8.3.1.1  Category 1 Waste Rock Stockpile pH .................................................83  8.3.1.2  Concentration Caps from Category 1 SMWMP Study ........................86  8.3.1.3  Concentration Caps from Modeled Mineral Solubility .......................87  8.3.1.4  Concentration Caps from Analog Site Data .........................................88  8.3.1.5  Concentration Caps Dependent on pH (PolyMet method) ..................89  8.3.1.6  Concentration Caps Dependent on pH (MDNR method) ....................91 

    8.3.2  Duluth Complex Category 2/3/4 Waste Rock and Ore (nonacidic) ..................92  8.3.3  Duluth Complex Category 2/3/4 Waste Rock and Ore (acidic) ........................93  8.3.4  Virginia Formation Category 4 Waste Rock .....................................................93 

    8.4  Additional Model Parameters and Considerations ....................................................... 93  8.4.1  Depletion ...........................................................................................................93  8.4

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