EXPANDED ENGINEERING EVALUATION & COST ANALYSIS Lilly/Orphan Boy Mine Powell County, Montana Prepared for: Trout Unlimited 111 N. Higgins, Suite 500 Missoula, Montana Prepared by: NewFields Companies, LLC 1120 Cedar Street Missoula, Montana 59802 April 2016 Project 350.0215 EXPANDED ENGINEERING EVALUATION & COST ANALYSIS Lilly/Orphan Boy Mine Powell County, Montana Prepared for: Trout Unlimited 111 N. Higgins, Suite 500 Missoula, Montana Prepared by: NewFields Companies, LLC 1120 Cedar Street Missoula, Montana 59802 April 2016 Project 350.0215 Lilly/Orphan Boy Mine Expanded Engineering Evaluation & Cost Analysis April 2016 TABLE OF CONTENTS 1.0 INTRODUCTION ......................................................................................................................1 1.1 PURPOSE AND OBJECTIVES .................................................................................................................. 1 1.2 DOCUMENT ORGANIZATION ................................................................................................................ 2 2.0 SITE BACKGROUND .................................................................................................................3 2.1 MINING HISTORY............................................................................................................................... 3 2.2 CLIMATE .......................................................................................................................................... 4 2.3 GEOLOGY, HYDROGEOLOGY, AND HYDROLOGY ....................................................................................... 4 2.3.1 Local and Regional Geology ..................................................................................................................... 4 2.3.2 Soils .......................................................................................................................................................... 4 2.3.3 Hydrogeology ........................................................................................................................................... 4 2.3.4 Surface Water Hydrology ......................................................................................................................... 5 2.3.5 Current Site Setting .................................................................................................................................. 6 2.3.6 Location and Topography ........................................................................................................................ 6 2.3.7 Vegetation, Fish and Wildlife ................................................................................................................... 6 2.4 HISTORIC AND ARCHAEOLOGICALLY SIGNIFICANT FEATURES ...................................................................... 7 2.4.1 Land Use and Population ......................................................................................................................... 8 2.4.2 Land Ownership ....................................................................................................................................... 8 3.0 WASTE CHARACTERISTICS AND SUMMARY OF EXISTING DATA .................................................9 3.1 SOLID WASTE SAMPLES .................................................................................................................... 10 3.1.1 Mine Waste ............................................................................................................................................ 10 3.1.2 Surface Soil ............................................................................................................................................. 11 3.1.3 Background Samples .............................................................................................................................. 11 3.2 SEDIMENT ...................................................................................................................................... 11 3.3 SURFACE WATER QUALITY ................................................................................................................ 13 3.4 GROUNDWATER QUALITY ................................................................................................................. 15 3.5 ASSESSMENT OF PHYSICAL HAZARDS ................................................................................................... 15 3.6 REPOSITORY SITING EVALUATION ....................................................................................................... 16 3.7 CONCEPTUAL SITE MODEL ................................................................................................................ 16 4.0 RISK EVALUATION ................................................................................................................. 18 4.1 POTENTIALLY EXPOSED POPULATIONS ................................................................................................. 18 4.2 EXPOSURE PATHWAYS ...................................................................................................................... 19 4.3 SELECTED SCREENING LEVELS ............................................................................................................ 19 4.3.1 Human Health ........................................................................................................................................ 19 4.3.2 Ecological Risk ........................................................................................................................................ 19 4.4 CONTAMINANTS OF CONCERN ........................................................................................................... 20 4.4.1 Human Health ........................................................................................................................................ 20 4.4.2 Ecological Health ................................................................................................................................... 20 4.5 HEALTH EFFECTS OF CONTAMINANTS OF CONCERN ............................................................................... 21 Page | i Lilly/Orphan Boy Mine Expanded Engineering Evaluation & Cost Analysis April 2016 5.0 SUMMARY OF APPLICABLE OR RELEVANT & APPROPRIATE REQUIREMENTS ........................... 24 6.0 RECLAMATION GOALS & OBJECTIVES .................................................................................... 25 6.1 ARAR-BASED RECLAMATION GOALS .................................................................................................. 25 6.2 RISK-BASED RECLAMATION GOALS ..................................................................................................... 25 6.3 RESTORATION GOALS ....................................................................................................................... 26 7.0 DEVELOPMENT & SCREENING OF RECLAMATION ALTERNATIVES ............................................ 27 7.1 IDENTIFICATION AND PRELIMINARY SCREENING OF RECLAMATION TECHNOLOGIES ...................................... 27 7.2 INSTITUTIONAL CONTROLS ................................................................................................................ 27 7.3 ENGINEERING CONTROLS .................................................................................................................. 28 7.3.1 Containment .......................................................................................................................................... 28 7.3.2 Surface Controls ..................................................................................................................................... 28 7.4 EXCAVATION AND DISPOSAL .............................................................................................................. 29 7.4.1 On-Site Disposal ..................................................................................................................................... 29 7.4.2 Off-Site Disposal ..................................................................................................................................... 30 7.5 IN-SITU TREATMENT ........................................................................................................................ 31 7.6 EX-SITU TREATMENT ........................................................................................................................ 32 7.6.1 Reprocessing .......................................................................................................................................... 32 7.6.2 Re-Use .................................................................................................................................................... 33 7.6.3 Physical/Chemical Treatment ................................................................................................................ 33 7.7 RECLAMATION ALTERNATIVE DEVELOPMENT ........................................................................................ 33 8.0 DETAILED ANALYSIS OF RECLAMATION ALTERNATIVES .......................................................... 35 8.1 EVALUATION CRITERIA ...................................................................................................................... 35 8.1.1 Threshold Criteria ................................................................................................................................... 36 8.1.2 Primary Balancing Criteria