RESPECT TO DRINKING WATER SUPPLIES IN THE VICINITY OF WORK PLAN TO CHARACTERIZE AND MITIGATE SULFATE WITH MITIGATION ORDER ON CONSENT DOCKET NO. P CONCENTRATOR TAILING STORAGE AREA REVISION 1 WORK PLAN TO CHARACTERIZE AND MITIGATE SULFATE WITH RESPECT TO DRINKING WATER SUPPLIES IN THE VICINITY OF THE COCHISE COUNTY, ARIZONA CONCENTRATOR TAILING STORAGE AREA COCHISE COUNTY, ARIZONA MITIGATION ORDER ON CONSENT DOCKET NO. P-121-07 REVISION 1 Prepared for: FREEPORT-MCMORAN CORPORATION COPPER QUEEN BRANCH 36 West Highway 92 Bisbee, Arizona 85603 - 121 - 07 Prepared by: HYDRO GEO CHEM, INC. 51 West Wetmore Road Tucson, Arizona 85705 (520) 293-1500 July 3, 2008 HYDRO GEO CHEM July 3, 2008 HYDRO GEO CHEM, INC. Environmental Science & Technology TABLE OF CONTENTS 1. INTRODUCTION .............................................................................................................. 1 1.1 Mitigation Order Requirements Pertaining to Work Plan ...................................... 2 1.2 Work Plan Organization ......................................................................................... 4 2. SUMMARY OF EXISTING INFORMATION ................................................................. 7 2.1 Background............................................................................................................. 7 2.1.1 Description of the CTSA ............................................................................ 7 2.1.2 Historical Land Use of the CTSA and Vicinity.......................................... 8 2.1.3 Use of Excess Mine Water.......................................................................... 9 2.1.4 Location of the Sulfate Plume................................................................... 10 2.2 Current Sulfate Mitigation Actions....................................................................... 11 2.3 Geologic Setting.................................................................................................... 12 2.3.1 Recent Alluvium ....................................................................................... 13 2.3.2 Basin Fill Deposits.................................................................................... 14 2.3.3 Bedrock Complex ..................................................................................... 15 2.3.3.1 Cretaceous Sedimentary Rocks................................................. 15 2.3.3.2 Paleozoic Rocks ........................................................................ 18 2.3.3.3 Igneous and Metamorphic Rocks.............................................. 19 2.3.3.4 Structure .................................................................................... 19 2.4 Groundwater Hydrology....................................................................................... 21 2.4.1 Hydrostratigraphic Units........................................................................... 21 2.4.1.1 Basin Fill ................................................................................... 21 2.4.1.2 Bedrock Complex...................................................................... 22 2.4.1.3 Influence of Structure on Groundwater Flow............................ 23 2.4.2 Hydraulic Properties ................................................................................. 23 2.4.3 Potentiometric Relationships .................................................................... 25 2.4.4 Groundwater Flow .................................................................................... 29 2.4.5 Recharge Sources...................................................................................... 30 2.5 Water Quality........................................................................................................ 32 2.5.1 Sulfate Distribution................................................................................... 34 2.5.1.1 Areal Distribution...................................................................... 34 2.5.1.2 Vertical Distribution.................................................................. 36 2.5.1.3 Comparison of Current Sulfate Distribution to Model Predictions ..................................................................... 37 2.5.2 Major Element Chemistry......................................................................... 39 2.5.3 Metals ....................................................................................................... 41 2.6 Preliminary Conceptual Model for the Groundwater Sulfate Plume.................... 43 3. AQUIFER CHARACTERIZATION PLAN .................................................................... 49 3.1 Aquifer Characterization Plan (ACP) Objectives and Data Needs....................... 49 3.1.1 ACP Objectives......................................................................................... 49 3.1.2 Data Needs................................................................................................ 49 3.2 Task 1 - Well Inventory of Drinking Water Supply Wells................................... 52 Copper Queen Branch Work Plan i H:\872000\Work Plan\Work Plan R1\CQB Work Plan.doc July 3, 2008 TABLE OF CONTENTS (Continued) 3.3 Task 2 - Plume Characterization........................................................................... 54 3.3.1 Task 2.1 - Data Compilation and Evaluation............................................ 55 3.3.2 Task 2.2 - Groundwater Monitoring ......................................................... 56 3.3.3 Task 2.3 - New Monitoring Well Installation and Testing ....................... 59 3.3.3.1 Drilling Methods and Reconnaissance Sampling...................... 62 3.3.3.2 Well Design Rationale .............................................................. 64 3.3.3.2.1 General Considerations .......................................... 65 3.3.3.2.2 Wells on the Margin of the Plume ......................... 66 3.3.3.2.3 Wells within the Footprint of the Plume................ 67 3.3.3.2.4 General Construction Guidelines ........................... 68 3.3.3.3 Well Installation, Development, and Testing............................ 70 3.3.4 Task 2.4 Additional Hydraulic Testing..................................................... 71 3.4 Task 3 - Sulfate Fate and Transport Evaluation.................................................... 71 3.4.1 Compilation of Information on Groundwater Pumping and Recharge..... 72 3.4.2 Sulfate Transport Under Current and Future Conditions.......................... 73 3.5 Task 4 - Reporting ................................................................................................ 74 4. POTENTIAL INTERIM ACTIONS................................................................................. 77 5. FEASIBILITY STUDY FOR SULFATE MITIGATION PLAN .................................... 81 5.1 Identification and Screening of Mitigation Actions and Technologies ................ 81 5.1.1 Mitigation Objectives................................................................................ 82 5.1.2 Mitigation Actions .................................................................................... 82 5.2 Development and Screening of Mitigation Alternatives ...................................... 84 5.3 Detailed Analysis of Mitigation Alternatives ....................................................... 85 5.4 Mitigation Plan...................................................................................................... 86 6. SCHEDULE...................................................................................................................... 87 7. REFERENCES ................................................................................................................. 89 Copper Queen Branch Work Plan ii H:\872000\Work Plan\Work Plan R1\CQB Work Plan.doc July 3, 2008 TABLE OF CONTENTS (Continued) TABLES 1 Generalized Geologic Column in the Vicinity of the CTSA 2 Summary of Hydraulic Conductivity Data 3 Estimated Groundwater Flow Velocities in the Vicinity of the CTSA 4 Analytical Results for 1996 Groundwater Samples Used for Trilinear Diagrams 5 Summary of Data Needs and Proposed Work 6 Proposed Groundwater Monitoring Wells 7 Proposed New Monitoring Well Locations 8 Schedule for Work Plan Deliverables FIGURES 1 Location Map Bisbee-Naco Area 2 Facilities in the Vicinity of the Concentrator Tailing Storage Area 3 Well Location Map 4 Sulfate Plume 2005 5 Geological Map of the CTSA and Vicinity 6 A-A’ Geological Cross Section 7 B-B’ Geological Cross Section 8 Water Level Map 1989 9 Water Level Map 1996 10 Water Level Map 1999 11 Water Level Map September 2005 12 Hydrographs for Wells TM-2, TM-19, BF-2, TM-7, TM-19A, and TM-2A 13 Hydrographs of Monitoring Wells Separated by the Black Gap and the Abrigo Faults 14 Sulfate Concentration Map - July 1989 15 Sulfate Concentration Map - Summer 1996 16 Sulfate Concentration Map - August through November 2005 17 Comparison of 1996 and 2005 Sulfate Plume Boundaries 18 Sulfate Concentrations in Wells BF-1, NWC-3, NWC-4, TM-2, TM-16, and TM-42 19 Measured and Predicted Sulfate Concentrations for Year 2005 20 Trilinear Diagram of Major Ions 21 Schematic Diagram of Conceptual Site Model 22 Proposed Well Locations for Groundwater Monitoring (Task 2.2) at Existing Wells 23 Proposed New Monitoring Well Locations (Task 2.3) 24 Schedule for Aquifer Characterization and Sulfate Mitigation Plans Copper Queen Branch Work Plan iii H:\872000\Work Plan\Work Plan R1\CQB Work Plan.doc July 3, 2008 TABLE OF CONTENTS (Continued) APPENDICES A Summary