Arizona mining BADCT guidance manual : aquifer protection program 2004 |
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ARIZONA MINING GUIDANCE MANUAL BADCT Publication # TB 04-01 ARIZONA DEPARTMENT OF ENVIRONMENTAL QUALITY 1110 West Washington Street Phoenix, Arizona 85007 (602) 771-2300 or 1-800-234-5677 in Arizona TDD Number (602) 771-4829 ARIZONA MINING BADCT GUIDANCE MANUAL Aquifer Protection Program ACKNOWLEDGMENTS The publication of Arizona’s new mining BADCT (Best Available Demonstrated Control Technology) document represents a milestone in protecting groundwater under the state's Aquifer Protection Permit (APP) program. Its successful completion combined the efforts of ADEQ staff and members of the mining community in an unprecedented cooperative venture to develop guidance for protecting groundwater for future uses. ADEQ is greatly indebted to the “Small BADCT Committee” for the thousands of hours its members invested in the preceding 18 months to produce this guidance manual. Without their patience, cooperation and perseverance, this project could not have been completed. SMALL BADCT COMMITTEE ADEQ PARTICIPANTS MINING INDUSTRY PARTICIPANTS Dennis L. Turner, Chairman George H. Beckwith, P.E. Michael D. Greenslade, P.E. Derek J. Cooke James F. Dubois Colleen D. Kelley Michael J. Wood Robin A. Kettlewell Richard N. Mohr Dirk Van Zyl, P.E., Ph.D. This document also greatly benefited from an independent technical review performed by TRC Environmental Solutions, Inc., lead by Dr. Ian Hutchison. Dr. Hutchison, along with Dr. Richard D. Ellison, edited “Mine Waste Management,” a publication sponsored by the California Mining Association. Drs. Hutchison and Ellison are internationally recognized water quality management experts and designers of mine waste management units, as well as authorities in developing mine waste regulations appropriate to those issues. The technical editorial team consisted of: Ian P. G. Hutchison, Ph.D., P.E. Joseph L. Stenger, R.G. Michael L. Leonard Sr., P.E. Deanna Stamboulian Joe Gelt of the University of Arizona’s Water Resources Research Center edited and formatted the final copy; Ken Seasholes of WRRC designed the cover. Deborah L. Patton of ADEQ was responsible for the final edit and press preparation. i USE OF MANUAL At a minimum, readers are encouraged to read the following sections: • Introduction • Part 1 - General BADCT Information Thereafter, if they intend to submit a Prescriptive BADCT design they should review: • Part 2 - Prescriptive BADCT Criteria • Section 2.1 - Introduction • The sections that apply to their facilities selected from 2.2 to 2.5 If they intend to submit an Individual BADCT design they should review: • Part 3 - Individual BADCT Guidance • Section 3.1 - Introduction • The sections that apply to their facilities selected from 3.2 to 3.6. The Appendices are available for further detailed review. The more important are: • Appendix B: Solution Ore and Waste Characterization • Appendix C: Liner Design, Principals and Practice • Appendix E: Engineering Design Guidance ii TABLE OF CONTENTS PAGE NO. INTRODUCTION Purpose and Scope ........................................................................................................1 BADCT Selection Process Overview...............................................................................2 How to Use This Manual..................................................................................................3 Facilities Requiring BADCT ............................................................................................5 PART 1 - GENERAL BADCT INFORMATION.................................................................1-1 1.1 The BADCT Process...............................................................................................1-1 1.1.1 Prescriptive BADCT...................................................................................1-3 1.1.2 Prescriptive BADCT Review Process ........................................................1-3 1.1.2.1 Determination of Prescriptive BADCT .......................................1-6 1.1.3 Individual BADCT Review Process For New Facilities ............................1-6 1.1.3.1 Site Selection ...............................................................................1-8 1.1.3.2 Development of Reference Design .............................................1-11 1.1.3.3 Estimation of Aquifer Loading ...................................................1-11 1.1.3.4 Alternative Design(s) Selection ..................................................1-17 1.1.3.5 Estimation of Aquifer Loading for Alternative Design(s)..........1-17 1.1.3.6 Selection of BADCT Design ......................................................1-17 1.1.3.7 Economic Considerations ...........................................................1-18 1.1.3.8 Discussion...................................................................................1-19 1.1.4 Individual BADCT Review Process for Existing Facilities ......................1-19 1.1.4.1 Steps 1 & 2: Identifying Current Discharge Controls and Assessing Their Performance - The Reference Design........1-20 1.1.4.2 Step 3: Identifying Technically Feasible DCTs for Improvement .........................................................................1-21 1.1.4.3 Step 4: Use Candidate List to Arrive at One or More Alternative Discharge Control Systems......................................1-22 1.1.4.4 Step 5: Weigh Cost vs. Discharge Reduction by Calculating Aquifer Loading for Alternative System(s) and Calculating Cost for New DCTs ..........................................1-22 1.2 Using Site Characteristics as a part of the BADCT Design...................................1-22 1.2.1 Waste Types and Process Solution Characteristics ...................................1-22 1.2.2 Water Resource Values..............................................................................1-25 1.2.3 Climatic Conditions ...................................................................................1-26 1.2.4 Site Factors.................................................................................................1-28 1.2.4.1 Topography.................................................................................1-29 1.2.4.2 Geology/Stability ........................................................................1-30 1.2.4.3 Soil Properties.............................................................................1-31 1.2.4.4 Surface Hydrology......................................................................1-31 1.2.4.5 Hydrogeology .............................................................................1-32 1.2.4.6 Barriers........................................................................................1-35 1.2.5 Passive Containment..................................................................................1-35 1.3 Using Liners as a Part of the BADCT Design .......................................................1-36 PART 2 - PRESCRIPTIVE BADCT CRITERIA .................................................................2-1 2.1 Introduction.............................................................................................................2-1 TABLE OF CONTENTS (Continued) PAGE NO. iii 2.2 Non-Storm Water Ponds.........................................................................................2-5 2.2.1 Siting Criteria..............................................................................................2-5 2.2.1.1 Site Characterization....................................................................2-5 2.2.1.2 Surface Water Control .................................................................2-6 2.2.1.3 Geologic Hazards.........................................................................2-6 2.2.2 Design, Construction and Operations Criteria............................................2-7 2.2.2.1 Solution/Effluent Characterization ..............................................2-7 2.2.2.2 Capacity and Storage Design .......................................................2-7 2.2.2.3 Site Preparation............................................................................2-7 2.2.2.4 Liner Specifications .....................................................................2-7 2.2.2.5 Stability Design............................................................................2-8 2.2.3 Facility Inspection Criteria .........................................................................2-9 2.2.4 Closure/Post-Closure Criteria ....................................................................2-11 2.3 Process Solution Ponds..........................................................................................2-17 2.3.1 Siting Criteria.............................................................................................2-17 2.3.1.1 Site Characterization...................................................................2-17 2.3.1.2 Surface Water Control ................................................................2-18 2.3.1.3 Geologic Hazards........................................................................2-18 2.3.2 Design, Construction and Operations Criteria...........................................2-19 2.3.2.1 Solution/Effluent Characterization .............................................2-19 2.3.2.2 Capacity and Storage Design ......................................................2-19 2.3.2.3 Site Preparation...........................................................................2-19 2.3.2.4 Liner Specifications ....................................................................2-19 2.3.2.5 Leak Collection and Removal System (LCRS) ..........................2-21 2.3.2.6 Stability Design...........................................................................2-21 2.3.3 Facility Inspection Criteria ........................................................................2-23 2.3.4 Closure/Post-Closure Criteria ....................................................................2-23 2.4 Heap Leach Pads....................................................................................................2-31 2.4.1 Siting Criteria.............................................................................................2-31 2.4.1.1 Site Characterization...................................................................2-31 2.4.1.2 Surface Water Control ................................................................2-32 2.4.1.3 Geologic Hazards........................................................................2-32 2.4.2 Design, Construction and Operations Criteria...........................................2-32 2.4.2.1 Solution and Waste Characterization..........................................2-33 2.4.2.2 Site Preparation...........................................................................2-33 2.4.2.3 Liner Specifications ....................................................................2-33 2.4.2.4 Perimeter Containment ...............................................................2-35 2.4.2.5 Stability Design...........................................................................2-35 2.4.3 Facility Inspection Criteria ........................................................................2-36 2.4.4 Closure/Post-Closure Criteria ....................................................................2-38 2.5 Tailing Impoundments ...........................................................................................2-43 2.5.1 Siting Criteria.............................................................................................2-43 2.5.1.1 Site Characterization...................................................................2-43 2.5.1.2 Surface Water Control ................................................................2-44 2.5.1.3 Geologic Hazards........................................................................2-44 2.5.2 Design, Construction and Operations Criteria...........................................2-45 TABLE OF CONTENTS (Continued) PAGE NO. iv 2.5.2.1 Solution and Tailing Characterization ........................................2-45 2.5.2.2 Capacity and Storage Design ......................................................2-45 2.5.2.3 Site Preparation...........................................................................2-45 2.5.2.4 Liner Specifications ....................................................................2-45 2.5.2.5 Stability Design...........................................................................2-47 2.5.3 Facility Inspection Criteria ........................................................................2-49 2.5.4 Closure/Post-Closure Criteria ....................................................................2-49 PART 3 - INDIVIDUAL BADCT GUIDANCE...................................................................3-1 3.1 Introduction.............................................................................................................3-1 3.2 Heap Leach Pads.....................................................................................................3-2 3.2.1 Introduction.................................................................................................3-2 3.2.2 Solution and Waste Characterization..........................................................3-2 3.2.3 Siting Considerations..................................................................................3-3 3.2.3.1 Climate and Surface Hydrology...................................................3-4 3.2.3.2 Subsurface Conditions .................................................................3-4 3.2.3.3 Geologic Hazards.........................................................................3-4 3.2.3.3.1 Landslides ..................................................................3-5 3.2.3.3.2 Subsidence and Settlement ........................................3-5 3.2.3.3.3 Earthquake-Induced Ground Failure..........................3-6 3.2.3.3.4 Collapsing Soils .........................................................3-7 3.2.4 Design, Construction and Operations Considerations ................................3-7 3.2.4.1 Site Preparation............................................................................3-7 3.2.4.2 Surface Water Control .................................................................3-8 3.2.4.3 Discharge Control ........................................................................3-8 3.2.4.3.1 Natural Containment and Liners................................3-9 3.2.4.3.2 Leachate Collection/Hydrostatic Head Control ........3-10 3.2.4.3.3 Solution Control and Storage....................................3-11 3.2.4.4 Stability Design...........................................................................3-11 3.2.4.5 Operational Measures .................................................................3-12 3.2.4.6 Operational Monitoring ..............................................................3-13 3.2.5 Closure/Post-Closure .................................................................................3-14 3.2.5.1 Physical Stability ........................................................................3-15 3.2.5.2 Chemical Stability.......................................................................3-16 3.2.5.2.1 General......................................................................3-16 3.2.5.2.2 Rinsing/Detoxification..............................................3-17 3.3 Dump Leaching Facilities ......................................................................................3-18 3.3.1 Introduction................................................................................................3-18 3.3.2 Solution and Spent Ore Characterization...................................................3-19 3.3.3 Siting Considerations.................................................................................3-19 3.3.3.1 Climate and Surface Hydrology..................................................3-20 3.3.3.2 Subsurface Conditions ................................................................3-21 3.3.3.3 Geologic Hazards........................................................................3-21 3.3.3.3.1 Landslides .................................................................3-21 3.3.3.3.2 Subsidence and Settlement .......................................3-22 3.3.3.3.3 Earthquake-Induced Ground Failure.........................3-22 TABLE OF CONTENTS (Continued) PAGE NO. v 3.3.3.3.4 Collapsing Soils ........................................................3-23 3.3.4 Design Construction and Operations Considerations ................................3-24 3.3.4.1 Site Preparation...........................................................................3-24 3.3.4.2 Surface Water Control ................................................................3-26 3.3.4.3 Discharge Control .......................................................................3-26 3.3.4.4 Stability Design...........................................................................3-28 3.3.4.5 Operational Measures .................................................................3-29 3.3.4.6 Operational Monitoring ..............................................................3-30 3.3.5 Closure/Post-Closure .................................................................................3-31 3.3.5.1 Physical Stability ........................................................................3-31 3.3.5.2 Chemical Stability.......................................................................3-32 3.3.5.2.1 General......................................................................3-32 3.3.5.2.2 Rinsing/Detoxification..............................................3-33 3.4 In-Situ Leaching.....................................................................................................3-34 3.4.1 Introduction................................................................................................3-34 3.4.2 Types of In-Situ Leaching Operations.......................................................3-35 3.4.2.1 In-Situ Leaching With Deep Well Injection ...............................3-35 3.4.2.2 In-Situ Leaching Using the Water Table for Capture.................3-35 3.4.2.3 In-Situ Leaching With Capture Above The Water Table ...........3-36 3.4.3 Solution Characterization...........................................................................3-40 3.4.4 Siting Considerations.................................................................................3-40 3.4.4.1 Climate and Surface Hydrology..................................................3-41 3.4.4.2 Subsurface Conditions ................................................................3-41 3.4.4.3 Geologic Hazards........................................................................3-41 3.4.4.3.1 Landslides .................................................................3-42 3.4.4.3.2 Subsidence and Settlement .......................................3-42 3.4.4.3.3 Earthquake-Induced Ground Failure.........................3-43 3.4.4.3.4 Collapsing Soils ........................................................3-44 3.4.5 Design, Construction and Operations Considerations ...............................3-44 3.4.5.1 Site Preparation...........................................................................3-44 3.4.5.2 Surface Water Control ................................................................3-45 3.4.5.3 Discharge Control .......................................................................3-45 3.4.5.3.1 Discharge Control - In-Situ Leaching With Deep Well Injection .........................................3-46 3.4.5.3.1.1 Injection Well Mechanical Integrity - Design .................................3-46 3.4.5.3.1.2 Injection Well Construction.................3-47 3.4.5.3.1.3 Injection Well Operation......................3-47 3.4.5.3.2 Discharge Control - In-Situ Leaching Using the Water Table for Capture .....................................3-48 3.4.5.3.3 Discharge Control - In-Situ Leaching With Capture Above The Water Table .....................3-48 3.4.5.4 Stability Design...........................................................................3-49 3.4.5.5 Operational Measures .................................................................3-49 3.4.6 Closure/Post-Closure .................................................................................3-50 3.5 Tailing Impoundments ...........................................................................................3-50 TABLE OF CONTENTS (Continued) PAGE NO. vi 3.5.1 Introduction................................................................................................3-50 3.5.2 Solution and Tailing Characterization .......................................................3-52 3.5.3 Siting Considerations.................................................................................3-52 3.5.3.1 Climate and Surface Hydrology..................................................3-53 3.5.3.2 Subsurface Conditions ................................................................3-53 3.5.3.3 Geologic Hazards........................................................................3-54 3.5.3.3.1 Landslides .................................................................3-54 3.5.3.3.2 Subsidence and Settlement .......................................3-54 3.5.3.3.3 Earthquake-Induced Ground Failure.........................3-55 3.5.3.3.4 Collapsing Soils ........................................................3-56 3.5.4 Design, Construction and Operations Considerations ...............................3-56 3.5.4.1 Site Preparation...........................................................................3-57 3.5.4.2 Surface Water Control ................................................................3-57 3.5.4.3 Discharge Control .......................................................................3-58 3.5.4.3.1 Base Metal Tailing Impoundments...........................3-58 3.5.4.3.2 Precious Metals Tailing Impoundments ...................3-59 3.5.4.3.3 Uranium Tailing Impoundments...............................3-60 3.5.4.4 Stability Design...........................................................................3-61 3.5.4.5 Operational Measures .................................................................3-66 3.5.4.6 Operational Monitoring ..............................................................3-66 3.5.5 Closure/Post-Closure .................................................................................3-67 3.6 Surface Ponds.........................................................................................................3-68 3.6.1 Introduction................................................................................................3-68 3.6.2 Solution Characterization...........................................................................3-68 3.6.3 Siting Considerations.................................................................................3-69 3.6.3.1 Climate and Surface Hydrology..................................................3-69 3.6.3.2 Subsurface Conditions ................................................................3-70 3.6.3.3 Geologic Hazards........................................................................3-70 3.6.3.3.1 Landslides .................................................................3-70 3.6.3.3.2 Subsidence and Settlement .......................................3-71 3.6.3.3.3 Earthquake-Induced Ground Failure.........................3-72 3.6.3.3.4 Collapsing Soils ........................................................3-72 3.6.4 Design, Construction and Operations Considerations ...............................3-73 3.6.4.1 Site Preparation...........................................................................3-73 3.6.4.2 Surface Water Control ................................................................3-74 3.6.4.3 Discharge Control .......................................................................3-74 3.6.4.3.1 Liners ........................................................................3-74 3.6.4.3.2 Leak Collection and Removal System (LCRS) ........3-75 3.6.4.4 Stability Design...........................................................................3-76 3.6.4.5 Operational Measures .................................................................3-77 3.6.4.6 Operational Monitoring ..............................................................3-77 3.6.5 Closure/Post-closure ..................................................................................3-77 3.6.5.1 Closure by Removal....................................................................3-78 3.6.5.2 Closure In-Place..........................................................................3-78 TABLE OF CONTENTS (Continued) PAGE NO. vii PART 4 - APPENDICES A COMPARISON OF COPPER LEACHING FACILITIES B SOLUTION, ORE AND WASTE CHARACTERIZATION C LINER DESIGN PRINCIPLES AND PRACTICE D CONSTRUCTION QUALITY ASSURANCE AND QUALITY CONTROL E ENGINEERING DESIGN GUIDANCE F FEDERAL, STATE AND LOCAL ENVIRONMENTAL PERMITS PART 5 - GLOSSARY OF TECHNICAL TERMS PART 6 - REFERENCES INDEX TABLE OF CONTENTS (Continued) PAGE NO. viii LIST OF TABLES TABLE NO. TITLE 1-1 Example Table of Contents - Prescriptive BADCT Demonstration.......................1-5 1-2 Example Table of Contents - Individual BADCT Demonstration..........................1-9 1-3 Examples of Demonstrated Control Technologies ................................................1-13 2-1 Examples of Engineering Equivalents ....................................................................2-2 2-2 Non-Storm Water Ponds Prescriptive BADCT .....................................................2-12 2-3 Process Solution Ponds Prescriptive BADCT .......................................................2-25 2-4 Heap Leach Pads Prescriptive BADCT .................................................................2-39 2-5 Tailing Impoundments Prescriptive BADCT ........................................................2-50 LIST OF FIGURES FIGURE NO. TITLE PAGE NO. 1-1 Example of Prescriptive and Individual BADCT “Zones” ....................................1-2 1-2 Schematic of BADCT Selection Process For New Facilities ..................................................................................................1-7 2-1 Example of Non-Storm Water Pond Cross-Section...............................................2-10 2-2 Example of Process Solution Pond Cross-Section.................................................2-22 2-3 Example of Heap Leach Pad Cross-Section ..........................................................2-37 2-4 Example of Tailing Impoundment Cross-Section..................................................2-48 3-1 Example of Dump Leach Facility Cross-Section...................................................3-25 3-2 Example of In-Situ Leaching With Deep Well Injection.......................................3-37 3-3 Example of In-Situ Leaching Using the Water Table for Capture ........................3-38 3-4 Example of In-Situ Leaching With Capture Above the Water Table....................3-39 3-5 Tailing Dam Construction Method .......................................................................3-63 3-6 Upstream Tailing Dam Construction Using Cyclones ..........................................3-64 INTRODUCTION ________________________________________________ INTRODUCTION (1) INTRODUCTION Purpose and Scope This guidance manual describes the process that an Aquifer Protection Permit (APP) applicant should follow in selecting the Best Available Demonstrated Control Technology (BADCT) for a specific mining facility(1) and site(1) in accordance with Arizona Revised Statute (A.R.S) 49-243.B.1. This statute requires all permitted facilities to utilize BADCT in their design, construction and operation while considering various factors depending on whether the facility is new or existing. The requirements of BADCT are met, according to A.R.S. 49-243.B.1, if it is demonstrated: AThat the facility will be so designed, constructed and operated as to ensure the greatest degree of discharge reduction achievable through application of the best available demonstrated control technology, processes, operating methods or other alternatives, including, where practicable, a technology permitting no discharge of pollutants. In determining best available demonstrated control technology, processes, operating methods or other alternatives the director shall take into account site specific hydrologic and geologic characteristics and other environmental factors, the opportunity for water conservation or augmentation and economic impacts of the use of alternative technologies, processes or operating methods on an industry-wide basis. However, a discharge reduction to an aquifer achievable solely by means of site specific characteristics does not, in itself, constitute compliance with this paragraph. In addition, the director shall consider the following factors for existing facilities: (a) Toxicity, concentrations and quantities of discharge likely to reach an aquifer from various types of control technologies. (b) The total costs of the application of the technology in relation to the discharge reduction to be achieved from such application. (c) The age of equipment and facilities involved. (d) The industrial and control process employed. (e) The engineering aspects of the application of various types of control techniques. (f) Process changes. (g) Non-water quality environmental impacts. (h) The extent to which water available for beneficial uses will be conserved by a particular type of control technology.@ Arizona Administrative Code (A.A.C.) R18-9-A202(A)(5) requires that an application for an APP include a description of the BADCT to be employed at the facility. The procedures and information presented in this guidance manual are intended for use in determining the appropriate BADCT, and to assist the applicant=s development and the Arizona Department of Environmental Quality's (ADEQ=s) review of permit applications. (2) INTRODUCTION____________________________________ Demonstrating that a facility will be designed, constructed, and operated in accordance with BADCT requirements is one of five demonstrations required for obtaining an APP permit. Other required demonstrations include: $ The facility will not cause or contribute to an exceedance of Aquifer Water Quality Standards (AWQS) at the point of compliance or, if AWQS for a pollutant has been exceeded in an aquifer, that no additional degradation will occur (A.A.C. R18-9- A202(A)(8)(a and b)); $ The person applying for the APP is technically capable of carrying out the conditions of the permit (A.A.C. R18-9-A202(B)); $ The person applying for the APP is financially capable of constructing, operating, closing, and assuring proper post-closure care of the facility (A.A.C. R18-9-A203); and $ The facility complies with applicable municipal or county zoning ordinances and regulations (A.A.C. R18-9-A201(A)(2)(c)). The above four demonstrations are outside the scope of BADCT and are not further addressed. Additional information on these demonstrations is available from the referenced rules and statutes, and the ADEQ=s AAquifer Protection Permits Application Guidance Manual.@ The ADEQ will use both this AMining BADCT Guidance Manual@ and the AAquifer Protection Permits Application Guidance Manual@ to evaluate APP applications. In the event of an inconsistency between this manual and applicable rules and/or statutes, provisions from rules and/or statutes will prevail. The AAquifer Protection Permits Application Guidance Manual@ provides procedures for pre-application meetings and coordination between the ADEQ and the applicant, at the applicant=s request. This early coordination is strongly encouraged by ADEQ to provide assurance that the applicant=s efforts are focused on relevant issues and necessary data collection, including those requirements related to the determination of appropriate BADCT. BADCT Selection Process Overview To achieve BADCT, mining facility owners and operators should use demonstrated discharge control elements utilized on an industry wide basis to limit or, where practicable, eliminate discharge to aquifers. When considering technologies, processes, operating methods and other alternatives for purposes of demonstrating BADCT, a facility must be evaluated in terms of 1) siting, 2) design, construction, and operation, and 3) closure/post-closure. A range of considerations must be taken into account in demonstrating BADCT for a facility, including characteristics, water conservation and augmentation, and economic impacts associated with the implementation of the various design elements being considered. ________________________________________________ INTRODUCTION (3) Key concepts reflected in this manual regarding determining BADCT for a facility are that: $ BADCT must be determined on a site specific basis by evaluating the degree that alternative discharge control systems minimize the addition of pollutants to the protected aquifer; $ Negotiation between the applicant and ADEQ is usually necessary because of subjective judgments inherent in some BADCT analyses. This means that no single technology or group of technologies can be mandated as appropriate for all discharge control systems. Rather, multiple DCTs (Demonstrated Control Technologies) may be appropriately used to arrive at a BADCT design for a specific facility at a given site. Then, based on a facility=s status as new or existing, the criteria described in A.R.S. 49-243.B.1 must be applied to that particular site to determine which DCTs are appropriate for that facility. It is, however, important to note that the DCTs presented in this manual are simply alternatives which may or may not be required at any specific facility; and $ Monitoring is generally not regarded as part of the BADCT design, unless it is performed as a specific feedback mechanism to adjust the design or operational aspects of the facility. The reader is referred to the AAquifer Protection Permits Application Guidance Manual@ for further discussion on monitoring. A mining APP applicant may choose between two general approaches to demonstrate BADCT: $ Prescriptive BADCT criteria (provided the criteria have been developed and are included in this manual); or $ Individual BADCT criteria. Either approach has merit and may be applied to different facilities at a given site. Only one of the approaches can be applied to a specific facility. The following sections describe the general processes for developing a BADCT demonstration for a mining facility. How To Use This Manual The APP applicant should use this manual as guidance in developing BADCT for a mining facility for the purposes of fulfilling the application requirements in A.A.C. R18-9-A202(A)(5), and demonstrating compliance with A.R.S. 49-243.B.1. If any questions arise, do not hesitate to contact ADEQ Aquifer Protection Program. This manual will also be used by ADEQ personnel to review BADCT demonstrations and to draft permits. This guidance manual is subdivided into four parts, each containing several sections to assist the applicant in selecting the best route to determining BADCT. The General BADCT Information (4) INTRODUCTION____________________________________ described in Part 1 should be read first, because the principles discussed apply to whichever process the applicant chooses to comply with the BADCT requirements. After reading Part 1, and deciding which BADCT process to use, read Part 2 if you are using the Prescriptive BADCT process, or read Part 3 if you are using the Individual BADCT process. Part 1, Section 1.1, broadly discusses the two BADCT processes which are available to the applicant; namely, the APrescriptive@ and AIndividual@ processes. The APrescriptive@ process is a prescribed approach that utilizes pre-approved DCTs and design criteria to obtain an APP permit, largely independent of site specific conditions. It should not be confused with APresumptive@ BADCT (as defined in A.R.S. 49-243.01). Pursuant to A.R.S. 49-243.01.A, the Director may only establish Presumptive BADCT by rule. The AIndividual@ process, on the other hand, is performance based, and allows the applicant to select from all available DCTs that constitute BADCT. This process considers site specific characteristics, operational controls, and other DCTs. The AIndividual@ process allows designs to be tailored to a specific facility and site, and allows for the distinction between BADCT for new and existing facilities. Part 1, Section 1.2, describes how site, technical and economic considerations are applied, on an industry-wide basis, to a BADCT analysis for a specific facility, with discussions of waste types, process solution characteristics, water resource values, climatic conditions, site factors and passive containment. Such factors may affect the BADCT selection for a facility seeking an APP permit. Part 2 discusses how to select control technologies for the Prescriptive BADCT process that results in a conservative BADCT, largely independent of its site specific characteristics. Part 2 contains individual sections for the different types of mining facilities (e.g., heap leach pads, process solution ponds) for which Prescriptive BADCT criteria have been developed. These sections have been prepared in a stand-alone format, each intended for use in conjunction with Part 1. For example, if information is required for applying Prescriptive BADCT criteria to a heap leach pad, the necessary information is contained within Part 1 and Section 2.4, and the other sections in Part 2 do not need to be consulted. Prescriptive BADCT criteria have been developed for the following types of mining facilities: $ Non-Storm Water Ponds (Section 2.2) $ Process Solution Ponds (Section 2.3) $ Heap Leach Pads (Section 2.4) $ Tailing Impoundments (Section 2.5) Part 3 identifies the specific control strategies or designs that may be used for individual BADCT for new and existing facilities. Discharge control strategies are discussed in individual sections for each mine facility type (e.g., heap leach pads, tailing impoundments, etc.). These sections have also been prepared in a stand-alone format, each intended for use in conjunction with Part 1. For example, if information for applying individual BADCT to a heap leach pad is needed, the necessary information is contained within Part 1, and Section 3.2, and the other sections in Part 3 are not needed. This manual addresses individual BADCT development for the following types of mining facilities: ________________________________________________ INTRODUCTION (5) $ Heap Leach Pads (Section 3.2) $ Dump Leaching Facilities (Section 3.3) $ In Situ Leaching Facilities (Section 3.4) $ Tailing Impoundments (Section 3.5) $ Surface Ponds (Section 3.6) The fourth part of the manual is the appendices. These are intended as supplementary information in developing a BADCT demonstration. Appendix A (Comparison of Copper Leaching Facilities) discusses and compares the principal types of copper leaching methods practiced in the United States. Appendix B (Solution, Ore and Waste Characterization) provides guidance on the rationale and the extent of characterization required for solutions, ores and wastes. These requirements are dependent on the type of discharge being considered. Appendix B also discusses the various test methods available to the applicant (such as acid-base accounting, humidity cell tests and leach procedures). Appendix C (Liner Design Principles and Practice) presents details helpful to the applicant pertaining to liner system types, their design and maintenance for environmental protection. The customary and appropriate provisions for construction quality assurance/quality control required in a BADCT demonstration are discussed in Appendix D (Construction Quality Assurance and Quality Control). In Appendix E, (Engineering Design Guidance) the engineering design requirements including hydrologic and stability considerations are described as they may apply to any type of facility and especially as they relate to tailing impoundments. Finally, applicable federal, state and local permits and approvals are discussed in Appendix F (Federal, State and Local Environmental Permits). Facilities Requiring BADCT One of the fundamental assumptions utilized in developing this guidance manual is that an applicant has already determined that an APP is needed for the facility in question. The following facilities may be present at mining, processing, or smelting and refining operations and are considered, or deemed by A.R.S. 49-241.B, to be categorical discharging facilities requiring an APP, unless exempt pursuant to A.R.S. 49-250: $ Surface impoundments(2) including holding, storage settling, treatment or disposal pits, ponds and lagoons (A.R.S. 49-241.B.1); $ Solid waste disposal facilities except for mining overburden and wall rock that has not and will not be subject to mine leaching operations (A.R.S. 49-241.B.2); $ Injection wells (A.R.S. 49-241.B.3); $ Mine tailing piles and ponds(2) (A.R.S. 49-241.B.6); $ Mine leaching operations(2) (A.R.S. 49-241.B.7); $ Sewage or sludge ponds and wastewater treatment facilities (A.R.S. 49-241.B.11); $ Septic tank systems with a capacity of greater than two thousand gallons per day (A.R.S. 49-241.B.8); $ Facilities which add a pollutant to a salt dome formation, salt bed formation, dry well or underground cave or mine (A.R.S. 49-241.B.5); and $ Point source discharges to navigable waters (A.R.S. 49-241.B.10). (6) INTRODUCTION____________________________________ The APP and BADCT requirements apply to both new and existing mining operations. The designations Anew,@ Aexisting,@ and Aclosed@ are specifically defined in A.R.S. 49-201, as follows: $ New facilities began construction or entered into binding contracts after August 13, 1986. Facilities that have undergone major modifications after August 13, 1986 are also deemed new facilities. $ Existing facilities began construction or entered into binding contracts on or before August 13, 1986. Facilities which ceased operation after January 1, 1986 are also regarded as existing facilities; they must meet BADCT and other APP requirements, including notification to ADEQ of closure. Economic considerations are important to the BADCT process for existing facilities. $ Closed facilities are those which ceased operation before January 1, 1986 with no intent to resume operations for which they were intended. Closed facilities are exempt from the APP requirements; hence, they are not subject to BADCT requirements. Some mining facilities may qualify for the following specific exemptions: $ AMining overburden returned to the excavation site, including any common material which has been excavated and removed from the excavation site and has not been subjected to any chemical or leaching agent or process of any kind.@ (A.R.S. 49-250.B.5) $ ALeachate resulting from the direct, natural infiltration of precipitation through undisturbed regolith or bedrock if pollutants are not added to the leachate as a result of any material or activity placed or conducted by man on the ground surface.@ (A.R.S. 49-250.B.9) $ ASurface impoundments used solely to contain storm runoff, except for surface impoundments regulated by the federal clean water act.@ (A.R.S. 49-250.B.10) $ AClosed Facilities. However, if the facility ever resumes operation the facility shall obtain an aquifer protection permit and the facility shall be treated as a new facility for purposes of section 49-243.@ (A.R.S. 49-250.B.11) $ AStorage, treatment or disposal of inert material.@ (A.R.S. 49-250.B.20) $ AStructures designed and constructed not to discharge, which are built on an impermeable barrier that can be visually inspected for leakage.@ (A.R.S. 49- 250.B.21) $ APipelines and tanks designed, constructed, operated and regularly maintained so as not to discharge.@ (A.R.S. 49-250.B.22) $ Other miscellaneous facilities as referenced in A.A.C. R18-9-102 and 103. ________________________________________________ INTRODUCTION (7) Some mining facilities may qualify for a general permit. The APP rules contain 42 general permits which replace individual permits for several classes of facilities in major industry groups, including mining and other industrial operations. These general permits rely on clear technical standards to ensure that a discharging facility does not violate aquifer water quality standards and that the facility employs BADCT in its design, construction, operation and maintenance. There are four types of general permits (Types 1, 2, 3 and 4) for which facilities may qualify. Consult the following rules for the detailed technical requirements: A.A.C. R18-9- A301 through R18-9-A316 (General Provisions); R18-9-B301 (Type 1); R18-9-C301 through R18-9-C303 (Type 2); R18-9-D301 through R18-9-D307 (Type 3); and R18-9-E301 through R18-9-E323 (Type 4). And, some types of facilities are not required to obtain an APP because they are not considered a discharging facility under the APP program. A Adischarge@ is defined by A.R.S. 49-201.11 as: Athe addition of a pollutant from a facility either directly to an aquifer or to the land surface or the vadose zone in such a manner that there is a reasonable probability that the pollutant will reach an aquifer.@ Mining operations with activities that are neither categorical, exempt, or general permitted may be judged to be discharging in accordance with A.R.S. 49-241.A. All facilities that discharge are required to obtain an APP with BADCT incorporated into their design. If it is uncertain if a facility needs an APP, ADEQ can be requested, in accordance with A.A.C. R18-9-106, to determine the applicability of the APP program to the operation or activity. A non-refundable flat rate fee, in accordance with A.A.C. R18-14-102(C)(3), will be charged for each determination requested. ADEQ expects, however, that determinations of applicability will be rare. Applicants are urged to consult the APP rules first, because in almost all cases, the APP rules clarify whether coverage is required. In evaluating a determination of applicability, ADEQ may request that the waste be characterized. Appendix B, Solution, Ore and Waste Characterization, includes guidance that will be useful for this purpose. If the facility does not discharge, then the facility need not comply with the APP requirements and no further design or analysis is necessary. If the facility does discharge, the characterization will be used to properly design the facility to satisfy the BADCT requirements. The burden of proof lies with the applicant to show that the facility is not a discharging facility. PART I General BADCT Information _______________________________ GENERAL INFORMATION (1-1) PART 1 GENERAL BADCT INFORMATION 1.1 THE BADCT PROCESS When considering technologies, processes, operating methods and other alternatives for purposes of a BADCT design, a facility must be evaluated in terms of 1) siting; 2) design, construction, and operation; and 3) closure and post-closure. Part of the BADCT determination process involves deciding whether to use a “Prescriptive” approach or a site specific “Individual” approach for determining BADCT pursuant to A.R.S. 49-243.B.1. Both approaches have merit and either may be appropriate for the applicant’s facility. • The “Prescriptive” approach requires evaluating and selecting a predetermined discharge control technology as the BADCT design. This approach provides a simplified method for an APP applicant to propose BADCT that will be acceptable to the ADEQ. The prescriptive criteria provided in this manual are designed to be generally conservative, and to minimize the level of site investigation and engineering evaluations that the applicant will be responsible for completing. The Prescriptive BADCT criteria are based on the premise of minimizing any discharge beyond the engineered containment. Therefore, this approach cannot incorporate any natural discharge attenuation that may occur in the vadose zone below engineered containment systems. • The “Individual” approach allows the applicant to evaluate and compare alternatives (alternative discharge control systems) which combine site characteristics with demonstrated control technologies (DCTs) that can be applied to arrive at a BADCT design. This approach provides a method for an APP applicant to utilize a site specific BADCT design that can incorporate water quality protection characteristics that may occur due to the climate, vadose zone conditions beneath the facility, operational procedures, and other factors. While this approach allows the BADCT design to be optimized compared to the generally conservative Prescriptive BADCT criteria, the applicant should realize an increased effort will likely be required for site characterization, facility design, APP application review, etc. In the following sections, general processes for performing a BADCT evaluation for a facility are described. Both the Prescriptive and Individual BADCT approaches can be utilized for different facilities at a given site. For example, an applicant may elect to utilize Prescriptive BADCT for some site facilities such as ponds and Individual BADCT for other facilities such as heap leach pads or a tailing impoundment. Both the Prescriptive and Individual BADCT approaches are based on preventing, or minimizing to the extent practicable, the loading of pollutants to an aquifer. Attenuation of pollutant concentrations within the aquifer itself, the point of compliance for water quality standards and water quality monitoring, and other aspects related to discharge after it encounters the aquifer, are outside the scope of BADCT for most types of facilities. Figure 1-1 schematically illustrates the “zones” typically encompassed by Prescriptive and Individual BADCT designs. Exceptions occur where the aquifer may be part of the BADCT design in the cases of in-situ leaching and passive containment. (1-2) GENERAL INFORMATION ________________________________ _______________________________ GENERAL INFORMATION (1-3) 1.1.1 Prescriptive BADCT Prescriptive BADCT, which is an expedited approach to determining BADCT, allows the applicant to select specific demonstrated control technologies for certain facilities or facility types which ADEQ considers to comply with the BADCT requirements. The objective of this approach is to simplify and expedite the permitting of conventional facilities by minimizing required information gathering, information review, and negotiations, compared to the site specific Individual BADCT approach. The Prescriptive BADCT criteria are defined in Part 2 of this manual. The following facility types are eligible to utilize the Prescriptive approach: • Non-Storm Water Ponds; • Process Solution Ponds; • Heap Leach Pads; and • Tailing Impoundments. If the applicant demonstrates that the design, construction, technology, process, operating method or other elements meet the prescriptive criteria, or an engineering equivalent, and the application incorporates these prescriptive criteria, or equivalents, then the applicant will meet the requirements of A.R.S. 49-243.B.1. The use of Prescriptive BADCT in an APP application is typically more applicable to small and medium size mining operations, existing operations undergoing expansion, or existing operations intending to add facilities. 1.1.2 Prescriptive BADCT Review Process An application for an APP utilizing Prescriptive BADCT must include a proposal of what BADCT is at the facility. This proposal should meet the appropriate prescriptive design criteria for the facility described in Part 2 of this manual. An example Table of Contents for describing in the APP application how the design meets BADCT requirements is provided in Table 1-1. Shallow groundwater conditions, if present, must be documented for design considerations, and may prohibit the use of the Prescriptive BADCT approach. The presence of certain site specific geologic hazards may also prohibit the use of Prescriptive BADCT. When process facilities are intended to be located: 1) in areas known to be prone to excessive subsidence; 2) in the vicinity of active faults; 3) in landslide prone terrain, or 4) in other locations of known geologic instability, ADEQ may request that an application using Prescriptive BADCT include studies specific to the hazard(s) present, to assist in determination of whether or not Prescriptive BADCT is appropriately applied. Provided that the hazard(s) present will not have a significant potential to impact the effectiveness of the Prescriptive BADCT design, it will be considered appropriately applied. (1-4) GENERAL INFORMATION ________________________________ ADEQ’s review begins with an applicability check of the proposed design, and the following questions are considered: Does this facility qualify for a Prescriptive BADCT approach? Is the proposed design correctly chosen from the guidance manual and is it correctly applied? If ADEQ determines that any of the answers are no, the applicant will be notified of the need to make the appropriate corrections, and resubmit the application. Depending on the degree of deficiency, this notification and re-submittal process will vary in the degree of formality but in all cases any final determination must be documented in ADEQ’s files. _______________________________ GENERAL INFORMATION (1-5) TABLE 1-1 Example Table of Contents - Prescriptive BADCT Demonstration(1) 1. Introduction 2. Site Criteria 2.1 Relevant Site Characteristics 2.2 Surface Water Controls 2.3 Geologic Hazards 3. Design Construction and Operational Criteria 3.1 Relevant Solution/Effluent Characteristics 3.2 Storage Components 3.3 Site Preparation 3.4 Liner System Specifications 3.5 Stability Considerations 3.6 Facility Operation and Monitoring 4. Relevant Facility Inspection Criteria 5. Relevant Closure and Post-Closure Criteria Example Appendices: • Solution, Ore and Waste Characterization Data • Groundwater Data • Geologic Hazards Evaluation • Geotechnical Data • Surface Water Evaluations • Construction Procedures and QA/QC • Slope Stability Evaluations • Water Balance and Storage Capacity Evaluations • Equivalent Engineering Evaluations (1) All applicable sections should clearly state the manner in which Prescriptive BADCT criteria are satisfied by the proposed design. (1-6) GENERAL INFORMATION ________________________________ If the APP application and supporting documentation show that the prescriptive criteria are met and appropriately applied, BADCT demonstration in accordance with A.R.S. 49-243.B.1 and the APP application requirement of A.A.C. R18-9-A202(A)(5) are deemed satisfied. ADEQ then proceeds with the processing of the permit application, unless new information warrants an additional applicability check. This processing includes a determination of completeness for other parts of the APP application that are not part of BADCT, such as whether or not applicable water quality standards (AWQS) will be met at the Point of Compliance, and the technical and financial capability of the applicant. 1.1.2.1 Determination of Prescriptive BADCT The determination of BADCT using prescriptive criteria for an APP application is based on meeting the prescribed design, construction, and operating criteria defined in Part 2 of this manual, or where applicable, by rule (A.R.S. 49-243.01). Since the objective of the Prescriptive BADCT determination is to simplify and expedite the BADCT review process and therefore the APP process, the prescriptive criteria are designed to be generally conservative for most site conditions in order to minimize the need for collection and evaluation of site specific data. Some site evaluations, however, are still required to provide enough information for determination that the Prescriptive BADCT is appropriate. As discussed further in Part 2, these include evaluations of key issues related to site conditions such as identification of flood plains and geologic hazards. While the Prescriptive BADCT criteria, in part, include specific design criteria for many of the BADCT elements, engineering equivalents to specific elements are also acceptable. Examples of engineering equivalents, and supporting information that may be required by ADEQ for each, are provided in Part 2 (Table 2-1). The ADEQ may require specific supporting evaluations to demonstrate that the proposed element is at least as protective as the specific Prescriptive BADCT element it replaces. Engineering equivalents cannot rely on seepage attenuation or other geologic properties of the vadose zone as part of minimizing aquifer loading. 1.1.3 Individual BADCT Review Process For New Facilities When submitting an individual application for an APP, an applicant must include a proposed BADCT design to be used at the facility. A.A.C. R18-9-A202(A)(5) requires that the applicant submit, in support of the proposed BADCT, a statement of the technology which will be employed to meet the requirements of A.R.S. 49-243.B.1. This statement shall describe alternative discharge control measures considered, the technical and economic advantages and disadvantages of each alternative, and the justification for selection or rejection of each alternative. The applicant shall evaluate each alternative discharge control technology, relative to the amount of discharge reduction achievable, site specific hydrologic and geologic characteristics, other environmental impacts, and water conservation or augmentation considerations. The economic impact of implementation of Individual BADCT design is further discussed in Section 1.1.3.7. _______________________________ GENERAL INFORMATION (1-7) The development of an Individual BADCT design follows the general principles of engineering design. Engineering principles are adhered to during the design process involving the designer’s professional judgment of contingencies, risks and uncertainties based on education and experience. It is therefore only possible to provide general guidance for the process to be followed. Important aspects of developing an Individual BADCT design are: • Discharge control technologies ordinarily constitute a discharge control system incorporating engineering features, operational measures and site characteristics to achieve BADCT; and, • Alternative designs must be considered to arrive at a BADCT design. Discharge control technologies are those design elements which can be included to reduce loading (discharge of pollutants) to an aquifer (e.g., design aspects such as liners, operational aspects such as desaturated tailing disposal for small projects, and closure aspects such as rinsing gold and silver ore residue on heap leach pads after leaching is completed). Alternative designs can include consideration of alternative technologies or alternative design elements as discussed below, and in some cases, alternative sites. In principle, an Individual BADCT design is developed through the following approach: • Development of a range of alternative discharge control systems which may or may not include different sites on a conceptual basis; • Screening these alternative systems by estimating the relative degree of discharge control; • Selection of the most promising alternative systems for more detailed analysis; • Refinement of designs for the selected alternative systems; • Comprehensive estimates of discharge control for the selected alternative systems; and, • Selection of BADCT design. In conducting these analyses, the following steps are required: • Site selection; • Development of individual site design (“Reference Design”) based on demonstrated control technologies and site conditions; • Estimation of aquifer loading for the Reference Design; • Alternative design(s) selection as outlined above; • Estimation of aquifer loading for the promising alternative design(s); and, • Selection of BADCT design. Figure 1-2 provides a schematic representation of the process. Each of the steps are described below. An example Table of Contents for describing in the APP application how the design meets Individual BADCT requirements is provided in Table 1-2. (1-8) GENERAL INFORMATION ________________________________ 1.1.3.1 Site Selection Site selection is a powerful tool in developing a protective design. It is sometimes possible to select a site with outstanding characteristics which will enhance the containment of stored materials. Maximum advantage should be taken of site selection in development of a BADCT design. Site selection can be conducted by the applicant in a formal or informal manner. The formal process will typically consider sites in areas surrounding the mine and the preferred site will be selected through a process of fatal flaw screening, site evaluation and ranking, and in some cases, also limited site investigations and final ranking. Informal site selection is often necessary because of limited availability of suitable sites in the vicinity of the ore body. _______________________________ GENERAL INFORMATION (1-9) TABLE 1-2 Example Table of Contents - Individual BADCT Demonstration(1) 1. Introduction 2. Relevant Site Factors 2.1 Solution, Ore and Waste Characteristics 2.2 Site Characteristics 2.2.1 Surface Hydrology 2.2.2 Hydrogeology 2.2.3 Geologic Hazards 3. Site Selection 3.1 Alternatives 3.2 Evaluation of Alternatives 3.3 Recommended Site 4. Reference Design 4.1 Design 4.2 Construction Considerations 4.3 Operations and Operational Monitoring 4.4 Closure and Post-Closure Considerations 4.5 Estimated Aquifer Loading 4.5.1 Potential Release 4.5.2 Estimated Travel Times to Groundwater Table 4.5.3 Estimated Attenuation of Pollutants 4.5.4 Estimated Aquifer Load 4.6 Estimated Cost of Reference Design 5. Alternative Designs 5.1 Selection of Alternatives 5.2 Screening of Alternatives 5.3 Description of Most Promising Alternative Systems 5.4 Aquifer Loading of Most Promising Alternative Systems 5.5 Estimated Cost of Most Promising Alternative Systems 6. Selection of BADCT Design 6.1 Selection Criteria 6.2 Evaluation of Reference Design and Alternative Systems 6.3 Selected BADCT Design Example Appendices: • Solution Ore and Waste Characterization Data • Groundwater Data • Geologic Hazards Evaluation (1) All applicable sections should clearly state the manner in which Individual BADCT requirements are satisfied by the proposed BADCT design. (1-10) GENERAL INFORMATION ________________________________ • Geotechnical Data • Surface Water Evaluations • Construction Procedures and QA/QC • Slope Stability Evaluations • Water Balance and Storage Capacity Evaluations _______________________________ GENERAL INFORMATION (1-11) The design documents submitted for APP permitting must describe the site selection process. It is the applicant’s responsibility to develop this information; ADEQ can only give guidance in this regard. 1.1.3.2 Development of Reference Design The development of an individual site design must consider: 1) industry-wide DCTs taking into account differences in industry sectors; 2) the type and size of the operation; 3) the reasonableness of applying controls considering the site climatic conditions; and 4) other site specific conditions. In developing this design, a systems approach should be used. This systems approach should consider all phases of the project including: • Site characterization; • Design, construction and operations; and • Closure and post-closure. The demonstrated control technologies for various facilities are described further in Part 3 of this manual. Table 1-3 provides a “menu” of typical DCTs for each of the above phases. A Reference Design will typically include DCTs selected from the Table 1-3 menu. For example, in developing a Reference Design, site specific DCTs will be included such as selection of a site with low permeability geologic formations, specific design elements such as single synthetic liners, specific operational technologies such as maintaining the low hydraulic head on a leach pad, specific operational monitoring proposals such as regular inspections by the facility operator, and specific closure and post-closure technologies such as bacterial rinsing for a gold heap leach pad. In considering the systems approach to development of a Reference Design it is important to include site characteristics. While it may be important to select a high level of engineered containment for sites underlain by alluvium and shallow groundwater, the same may not be the case when the site is underlain by low permeability bedrock and/or deep groundwater (i.e., a demonstrated geologic barrier). The individual designer will include these considerations in the systems design based on experience as well as industry wide demonstrated control technologies which have been applied for similar site conditions. In developing an individual site design the designer must therefore be encouraged to use creativity to provide the greatest degree of discharge reduction achievable through application of DCTs and, where practicable, an approach permitting no discharge of pollutants. 1.1.3.3 Estimation of Aquifer Loading An evaluation must next be performed to estimate the potential loading of pollutants to the aquifer as a result of implementing the Reference Design. Loading to the aquifer is used as a basis for evaluating the impacts of discharge from a facility. This evaluation can be done at (1-12) GENERAL INFORMATION ________________________________ various levels of sophistication but at a minimum must include the steps outlined below. It is important that this evaluation should consider the total life cycle of the facility (i.e., operations as well as closure/post-closure). For example, during operations a slurry deposited tailing impoundment will contain free water. After closure and during the post-closure period, this free water may be removed and therefore the driving head for pollutant migration will be eliminated. _______________________________ GENERAL INFORMATION (1-13) Page 1 of 4 TABLE 1-3 Examples of Demonstrated Control Technologies Project Phase Element Demonstrated Control Technologies (DCT) Evaluation Procedures to be Selected From Site Characterization Solution, Ore and Waste Characterization 1) These characterizations are required to determine the DCTs for other elements. 1) Procedures to differentiate between oxide and sulfide materials. 2) 1312 Leach Procedure. 3) Meteoric Water Mobility. 4) Acid Base Accounting. 5) Humidity Cell Tests. Geotechnical, Surface Hydrology, Hydrogeologic, and Geologic Hazards Characterizations 1) Siting DCT incorporates selection of locations with: • Low permeability geologic formation • Deep groundwater tables • Naturally poor groundwater quality • Small contributory watershed. 2) Selection of sites which avoid or mitigate geologic hazards. 3) These characterizations are required to determine the DCTs for other elements. 1) Test pitting, drilling, trenching, sampling and testing. 2) In-situ tests of, for example, hydraulic conductivity. 3) Geophysical methods. 4) Water level monitoring. 5) Remote sensing methods. 6) Aerial photography mapping and interpretation. 7) Site reconnaissance. 8) Other standard hydrologic and geotechnical field investigation and data evaluation methods. Site Preparation 1) Strip vegetation. 2) Excavate and replace weak foundation materials. 1) Standard construction QA/QC methods. Design, Construction, and Operations Surface Water Control 1) Diversion ditches. 2) Retention structures. 1) Standard hydrologic design methods. (1-14) GENERAL INFORMATION ________________________________ Examples of Demonstrated Control Technologies Project Phase Element Demonstrated Control Technologies (DCT) Evaluation Procedures to be Selected From Discharge Control 1) DCTs for discharge control vary significantly depending on the type and size of the operation and the reasonableness of applying controls in arid or semi-arid settings, but may include: • Liners for containment. • Natural containment. • Leachate collection and hydrostatic head control systems consisting of: - Manufactured or imported drain rock and perforated pipes. - Ore materials satisfying drainage requirements. - Granular or synthetic leak collection layers for pond liner systems. • Solution conveyance pipes or lined channels and storage capacity. 1) Systems approach to liner system design (Appendix C). 2) Standard engineering measures for surface containment. Stability 1) Specified ultimate slope height. 2) Stability benches. 3) Design to withstand shear forces, e.g., by compaction, use of geosynthetics, etc. 4) Control of pore pressures by drainage. 5) Buttressing. 1) Shear strength analysis. 2) Static stability analysis. 3) Seismic deformation analyses. _______________________________ GENERAL INFORMATION (1-15) Examples of Demonstrated Control Technologies Project Phase Element Demonstrated Control Technologies (DCT) Evaluation Procedures to be Selected From Operations 1) Conduct operations to minimize potential for damage to liners at heap leach sites: • • Geosynthetic and/or gravel protective layers. • • Low ground pressure equipment. • • Limit equipment traffic. • • Load in uphill direction. • • Limit rate of rise. • • Limit maximum height. 2) Control solution applications at heap leach sites: • • Avoid excessive reagent concentrations. • • Avoid application rates or storage conditions that result in excessive hydraulic head. • Sequence leaching activities. 3) Managed tailing deposition: • • Layered or subareal deposition. • • Limit size of water pond. 4) Operational monitoring to allow early detection and correction of problems. 5) Facility maintenance to assure performance is consistent with the design. 1) Consider operational conditions during design of facility. 2) Visual observations. 3) Survey monuments. 4) Instrumentation. Closure and Post-Closure Physical Stability 1) Surface Water Control to reduce erosion. 2) Recontouring to control surface flow. 3) Cover placement (e.g., vegetation or rock armor) to reduce erosion. 4) Erosion protection of ditches. 1) Stability evaluations. 2) Long-term erosion evaluations. (1-16) GENERAL INFORMATION ________________________________ Examples of Demonstrated Control Technologies Project Phase Element Demonstrated Control Technologies (DCT) Evaluation Procedures to be Selected From Chemical Stability 1) Source control: • • Ore residue rinsing and/or detoxification. • • Ore residue removal. 2) Migration control: • • Surface grading to enhance run-off. • • Surface grading to minimize run-on. • • Design cover to minimize infiltration and enhance moisture removal (e.g., increased evapo-transpiration by fine-grained soils and/or vegetation). • • Cap with low permeability cover. 3) Interception (e.g., using shallow trenches; cutoff walls) and water treatment. 1) Column leach tests. 2) Fate and transport evaluations. 3) Cover water balance evaluations. _______________________________ GENERAL INFORMATION (1-17) The steps which should be followed to estimate aquifer loading for the total life cycle of the facility are as follows: • Estimate the potential release from the facility by using empirical equations or other appropriate approximate methods. • Estimate the travel time to the water table beneath the facility by vertical migration using groundwater flow calculation methods such as described in Appendix C of Hutchison and Ellison (1992). • Estimate attenuation of pollutants in the foundation based on published values or laboratory test results. • Estimate the load added to the aquifer of constituents that have the potential to impact water quality, particularly those for which there are water quality standards. The purpose of the load estimation to the aquifer is to provide a consistent method to compare the potential impacts of various designs. It is therefore not intended that this evaluation should turn into a research project or an advancement of the state-of-the-art. However, consistent and realistic approaches should be followed. 1.1.3.4 Alternative Design(s) Selection Alternative design(s) should next be developed and can include the evaluation of alternative control technologies or design elements for each applicable type of facility (Part 3 summarizes various demonstrated control technologies for different types of facilities) or, as may be appropriate, the evaluation of alternative sites. The selection of the alternative design(s) should be based on the systems approach where control technologies as well as realistic site conditions are considered. 1.1.3.5 Estimation of Aquifer Loading for Alternative Design(s) Estimating the aquifer loading for the alternative design(s) follows the same approach as described above for estimation of aquifer loading for the Reference Design. By following the same procedures, comparative aquifer loadings from the Reference Design as well as the alternative design(s) can be developed. 1.1.3.6 Selection of BADCT Design The final step in developing an individual BADCT design is to make a selection from the Reference Design and the alternative design(s). The basis for this selection is loading to the aquifer. The BADCT design will be that design which results in the least amount of pollutant loading (discharge) to the aquifer. For example if an alternative design results in a lower pollutant loading to the aquifer, then that design will be selected as the BADCT design instead of the Reference Design. In cases where the Reference Design and/or the alternative design result in similar loadings to the aquifer, and discharges do not contain materials listed in A.R.S. 49-243.I, the design with the (1-18) GENERAL INFORMATION ________________________________ lowest costs (i.e., capital, operations, closure, post-closure and other applicable costs) may be selected as the BADCT design. In such cases, negligible loadings can be considered similar even if the relative difference between loadings is significant (e.g., where loadings from alternatives are small compared to the highest loading that could still comply with aquifer water quality standards, the fact that the loading from one alternative may be up to orders of magnitude smaller may not preclude these loadings from being considered similar). If the discharge contains materials listed in A.R.S. 49-243.I, the applicant must limit discharges to the maximum extent practicable regardless of cost. The BADCT design is therefore selected based on DCTs, a systems approach including site conditions, and the estimation of aquifer loadings for alternative designs. The requirement for this individual BADCT evaluation process to be demonstrated in APP applications is described in regulation as follows (A.A.C. R18-9-A202(A)(5)): “The applicant shall submit in support of the proposed BADCT a statement of the technology which will be employed to meet the requirements of A.R.S. 49-243.B. This statement shall describe the alternative discharge control measures considered, the technical and economic advantages and disadvantages of each alternative, and the justification for selection or rejection of each alternative. The application shall evaluate each alternative discharge control technology, relative to the amount of discharge reduction achievable, site specific hydrologic and geologic characteristics, other environmental impacts, and water conservation or augmentation. The economic impact of implementation of each alternative control technology shall be evaluated on an industry-wide basis. In addition, a statement for a facility in existence on the effective date of this Article shall reflect consideration of the factors listed in A.R.S. 49-243.B.1(a) through (h).” A.R.S. 49-243B.1(a) through (h) includes the following: (a) “Toxicity, concentrations and quantities of discharge likely to reach an aquifer from various types of control technologies. (b) The total costs of the application of the technology in relation to the discharge reduction to be achieved from such application. (c) The age of equipment and facilities involved. (d) The industrial and control process employed. (e) The engineering aspects of the application of various types of control techniques. (f) Process changes. (g) Non-water quality environmental impacts. (h) The extent to which water available for beneficial uses will be conserved by a particular type of control technology.” As discussed in Section 1.1.2, the BADCT demonstration portion of the application can be deemed complete, and A.A.C. R18-9-A202(A)(5) deemed satisfied without this evaluation where facilities utilize Prescriptive BADCT. 1.1.3.7 Economic Considerations In regard to new facilities, A.R.S. 49-243.B.1. directs ADEQ to consider economic impacts of the application of BADCT with other factors on an industry-wide basis. The determination of economic impact on an industry-wide basis shall take into account differences in industry sectors _______________________________ GENERAL INFORMATION (1-19) (i.e., Copper Sector, Gold Sector, Uranium Sector, etc.), the facility type (i.e., heap leaching, dump leaching, in-situ, copper oxide leaching, copper sulfide leaching, etc.), the size of the operation, and the reasonableness of applying controls in an arid or semi-arid setting (gold mining in Northern California vs. gold mining in Arizona, copper mining in Michigan vs. copper mining in Arizona, etc.). ADEQ considers that use of a technology at many other similar facilities in the same industry sector, same type and size, and in the same climatic setting indicates financial feasibility. As indicated above, if a new facility discharges the pollutants identified in A.R.S 49-243.I, then that facility must meet the criteria of A.R.S. 49-243.B.1 (BADCT) to limit discharges to the maximum extent practicable regardless of cost. 1.1.3.8 Discussion It may be beneficial from a design point of view to include elements which are innovative and therefore may not satisfy the requirement of an industry-wide DCT. In this case, the designer must demonstrate that such technologies will perform as intended. Such demonstration can be based on literature reviews, engineering analyses, laboratory and pilot scale testing, or by providing case histories of analogous applications of the technology. 1.1.4 Individual BADCT Review Process for Existing Facilities An existing facility is defined in A.R.S. 49-201.14. as one that is neither a new or closed facility and at which construction began before August 13, 1986. According to A.R.S. 49-201.18, a closed facility that is reopened does not constitute an existing facility, but is regarded as a new facility. The distinction between existing and new facilities is important in determining BADCT for the following two basic reasons: 1) At an existing facility, determining BADCT requires ADEQ and the applicant to consider potential upgrades to the facility design, and 2) Additional factors for existing facilities apply as listed in A.R.S. 49-243.B.1(a) through (h), such as, weighing cost vs. discharge reduction, the age of equipment, and the engineering aspects of the application of various types of industrial and control processes. Also, the requirement of A.R.S. 49-243.I that a new facility limit discharges of certain listed organic pollutants to the maximum extent practicable regardless of cost does not apply to existing facilities. Note that the option of Prescriptive BADCT also applies to an existing facility. If the facility meets the prescriptive criteria identified for the specific type of facility in Part 2, no further demonstration is necessary. Most existing facilities, however, warrant the individual evaluation process. There are two major differences in approach mandated for determining BADCT for an existing facility, compared to that for a new facility. First, existing design and site conditions offer constraints on what can be achieved with the final BADCT configuration. Second, analysis of cost vs. discharge reduction applies in determining BADCT. To arrive at a BADCT, the existing design and its performance become the basis of comparison for judgments about whether or not to upgrade the design. Possible upgrades must, of course, be limited to those that are feasible from an engineering standpoint given the age, design, and operational controls of the facility. (1-20) GENERAL INFORMATION ________________________________ Complicating matters at an existing facility may be the groundwater impact of past operations. While remedial or mitigative efforts may be needed in areas where groundwater quality does not conform to Aquifer Water Quality Standards downgradient of a facility (see A.R.S. 49-243.L), these activities do not constitute part of BADCT for the facility. The reason for this distinction is that BADCT does not include actions or design features which affect groundwater after pollutants have been released into it, since discharge has already occurred in those instances. Thus, while existing groundwater quality may be an indicator of the performance of the current design, remedial or mitigative technologies do not reduce discharge and should not be considered in the BADCT evaluation. There are five basic steps in the existing facility process. Similar to the new facility process outlined previously, the applicant develops a Reference Design. However, here, the existing configuration of a facility and site represents its Reference Design. Alternatives to the Reference Design are then developed and evaluated as outlined by the following five basic steps: Step 1 Identify current DCTs and site factors; Step 2 Estimate performance (determine aquifer loading); Step 3 Identify technically feasible alternative DCTs and assemble them on a candidate list. Consider water conservation and other environmental factors to reduce or adjust the list; Step 4 Use the candidate list to arrive at one or more alternative systems; Step 5 Weigh cost vs. discharge reduction for each alternative system to arrive at BADCT: - Calculate improvements in aquifer loading expected from one or more alternative systems with new DCTs, and - Determine costs to implement alternative system(s). 1.1.4.1 Steps 1 & 2: Identifying Current Discharge Controls and Assessing Their Performance - The Reference Design As with new facilities, BADCT determination for existing facilities depends on an adequate characterization of the discharge quantity and type. To establish the Reference Design for an existing facility, the applicant should inventory the discharge controls used in the facility’s current design. The control processes and technologies can be identified according to the design elements and site characteristics described in Part 3. Discharge control technologies to consider include process solution controls in conjunction with: solution, ore and waste characterization; site preparation; surface water controls; liners; leachate collection systems; stability design; operational monitoring; closure/post-closure; and site factors. Where original design plans are lacking, the applicant should develop as-built design information for those aspects of the facility which have some bearing on discharge rates and characteristics. To save time and effort, and to promote efficiency, the applicant is encouraged to discuss the level of detail needed with ADEQ prior to developing as-built drawings. Once existing control processes are identified, the applicant should evaluate the overall discharge control performance of the facility. As for the approach for new facilities, the applicant may assess site factors and their performance for pollutant reduction in the manner presented in Section 1.2. Where practicable, this step should involve direct measurement of discharge quantity and quality. Otherwise, the applicant may calculate expected performance based on _______________________________ GENERAL INFORMATION (1-21) industry standards for the engineered controls, test data for components, and site specific characteristics determined from field or laboratory testing. Aquifer loading from the facility for the existing configuration can be estimated by the same methods used in Section 1.1.3. This aquifer loading analysis constitutes the performance of the Reference Design. 1.1.4.2 Step 3: Identifying Technically Feasible DCTs for Improvement The BADCT design for an existing facility may involve instituting additional control technologies to those in current use. This step in the process involves developing a list of alternative DCTs that are technically feasible for application at the facility. In many situations, new controls may not be feasible. For instance, adding a liner to an existing dump leach system is beyond the realm of normal mine design and operation. In such cases an applicant should consider other design elements or operational controls discussed below to achieve discharge reduction. Working with only technically feasible technologies, the applicant should assemble a focused, yet complete, list of candidate DCTs for improvement of the existing facility. Ideas for candidate DCTs may be gained from reviewing the lists of DCTs presented in Part 3. However, many DCTs identified in Part 3 may not work as “retrofitted technologies.” The following are types of DCTs which are often easily implemented and may, depending on the facility design and site, offer considerable improvement in facility performance to control discharge: • Operational controls - physical and chemical (This includes physical controls such as modifying solution application cycles and the amount of solution inventory in the heap or pond storage, and chemical controls such as altering the reagents or reagent dose rates); • Run-on and other storm water management controls; • Closure elements such as removal of free liquids, grading, covering, etc.; • Containment systems for process solution and other potential pollutant sources; and • Stability improvements by, for example, berming, benching or regrading. Aside from technical feasibility, certain other factors may disqualify particular DCTs from making the candidate list. Water conservation may be a factor for deciding whether or not a change in discharge control technology is favorable. Simple dilution of a pollutant to achieve lower discharge concentrations, in itself, may not meet BADCT, nor will technologies that consume or alter the quality of large quantities of water. However, there may be extenuating circumstances in which dilution is desirable, such as to facilitate beneficial use of the water or achieve an environment which could enhance natural treatment. The applicant should also consider other environmental factors. The use of a new discharge control technology at an existing facility may have environmental impacts that are not directly related to aquifer water quality. An example of such a technology is air stripping to remove volatile organic substances from water and mobilize them in air. These environmental tradeoffs must be assessed on a case-by-case basis, and judgments about whether they outweigh discharge reduction are likely to be subjective. Some other common environmental factors that may require consideration are air quality, noise levels, land use, aesthetics, environmentally sensitive areas, endangered species, and the potential for disease transmission. (1-22) GENERAL INFORMATION ________________________________ 1.1.4.3 Step 4: Use Candidate List to Arrive at One or More Alternative Discharge Control Systems The selection of alternative design(s) should be based on a systems approach where technologies, as well as site conditions, are considered. The list of alternative DCTs should be used to identify components that may be incorporated alone or in combination in the existing reference design to arrive at the alternative design(s). This step in the process involves considerable professional judgment and the justification for the selected DCTs may require formal exchange of data, and discussion and negotiation between the applicant and ADEQ, depending upon how obvious the available choices are. 1.1.4.4 Step 5: Weigh Cost vs. Discharge Reduction by Calculating Aquifer Loading for Alternative System(s) and Calculating Cost for New DCTs After selecting alternative design(s) in Step 4, an applicant should prepare additional aquifer loading calculation(s) using the same considerations as for the Reference Design. Where additional DCTs are used, their contribution to discharge reduction should be factored into the aquifer loading calculation(s). Where new DCTs are substituted for existing ones, the estimated performance of the new DCT should be used in the calculation. The aquifer loading(s) of the alternative system(s) need to be compared to the Reference Design. For cost evaluations, the applicant shall compare the total cost/benefit of the application of the technology with the discharge reduction to be achieved from such application, as noted in A.R.S. 49-243.B.1(b). When calculating the total cost/benefit, the applicant may apply acceptable discounting methods used for other accounting purposes within the industry. 1.2 USING SITE CHARACTERISTICS AS A PART OF THE BADCT DESIGN This section, together with Appendix B (Solution, Ore and Waste Characterization), describes site, technical and economic considerations, on an industry-wide basis, applicable to BADCT analysis for a specific facility. It includes discussions on waste types and process solution characteristics, water resource values, climatic conditions, site factors, and passive containment. Such factors may affect the BADCT selection for a facility seeking an Individual APP. 1.2.1 Waste Types and Process Solution Characteristics A.A.C. R18-9-A202(A)(4) requires that a person applying for an APP provide a summary of the known past facility discharge activities and the proposed facility discharge activities indicating: • The chemical, physical and biological characteristics of the discharge; • The rates, volumes, and the frequency of the discharge for each facility; and • The location of the discharge. All applications should include the characterizations necessary to satisfy the requirements described above. In some cases (e.g., new facilities), the applicant may not be able to adequately define the characteristics of the material to be discharged until the facility becomes operational. _______________________________ GENERAL INFORMATION (1-23) In such cases, the applicant must design the facility to be compatible with the characteristics of discharge from similar types of mining facilities. Then, upon start-up, the applicant shall be required to characterize the discharge. However, a discharge containing organic substances referenced in A.R.S. 49-243.I must be identified and characterized in order to design the facility to meet BADCT regardless of cost. ADEQ will use this information to determine if the proposed facility BADCT is compatible with the materials to be contained in the facility. This need for compatibility between the DCT and the waste characteristics is one of the reasons that detailed design specifications for liners and other elements cannot be uniformly prescribed in this manual. The characterization information will also be used to evaluate the quality and quantity of the discharge. In characterizing waste, ore or process solutions that may be discharged, the applicant must define the waste type or mix of types (solutions, wastewater, sludges, tailing, leached ore, waste rock, etc.) including the projected or actual leachate composition that will discharge. Discharges that are not identified will not be incorporated into the permit and will be subject to compliance actions under APP regulations. ADEQ should be contacted to review the required type and frequency of characterization for all materials at the facility. While waste characterization may be appropriate in the case of waste rock or spent ore from a precious metal leach operation, it is not clear that such characterization is beneficial for copper leach ore. In acidic copper leach solutions, high acidity and metals concentrations will be produced (for both oxide and sulfide leach operations) throughout the period of operation, as well as after operations. In the case of a sulfide leach project, it is difficult to predict how long it will take to eliminate all the potential for metal and acid leachate because of the ongoing bacterial action. As a result, characterization of materials to be leached with acidic solutions may be deferred until closure of the leach facility. Proposals for deferring material characterization should be presented to ADEQ during the pre-application period. Below is a tiered list of tests commonly used to characterize materials that may discharge. Other tests may also be proposed by the applicant or required by ADEQ. When characterizing tailing or waste rock that may discharge, or “produce” a leachate that may discharge, the applicant should conduct the appropriate tests listed in Tier #1 (Part A) with additional testing from Tier #2 (Part A) and Part B as necessary to adequately characterize the material. Similarly, if process solutions or waste waters may be discharged, then the applicant should submit the information requested in Part C below. Where necessary, the ore may be characterized in order to assist in characterizing the potential discharge. Further guidance on waste characterization testing is provided in Appendix B. Pre-application coordination with ADEQ is strongly encouraged to finalize characterization testing requirements. (1-24) GENERAL INFORMATION ________________________________ PART A: CHARACTERIZATION OF TAILING, SPENT ORE AND WASTE ROCK TIER #1 Primary Analytical Procedures For Waste Characterization • Description of mineralogy and lithology of the waste and leached ore; • Leach Testing (Leach testing should be performed on all materials which may discharge in order to determine the quality of leachate that may be formed.) Types of leach testing include: - SPLP (Synthetic Precipitation Leaching Potential EPA Method 1312), - Nevada Meteoric Water Mobility Procedure, - Leachable sulfates and soluble solids, - Bottle Roll Tests. • Acid Base Accounting (ABA): - Predictive Static Tests. • Physical Characteristic Tests: - Grain Size Analysis, - Density, - Shear Strength. TIER #2 Miscellaneous Analytical Procedures For Additional Waste Characterization • Predictive Kinetic Tests for prediction and acid generating characteristics; • Analysis of Metals (Total and/or Soluble); • Analysis of Radionuclides; • TCLP; • Miscellaneous Physical Analyses (e.g., Hydraulic Conductivity, Moisture Retention Capacity). _______________________________ GENERAL INFORMATION (1-25) PART B: CHARACTERIZATION OF ORGANIC WASTES OR WASTES CONTAINING ORGANICS • Organic Analyses: - Total Petroleum Hydrocarbons, - Polynuclear Aromatic Hydrocarbons, - Phenol Analyses, - Volatile Organic Compounds and Carbon Disulfide. • Hazardous waste determination testing for wastes not exempted by the Resource Conservation and Recovery Act (RCRA), where applicable. PART C: CHARACTERIZATION OF PROCESS SOLUTIONS, WASTEWATERS AND MINE WATERS • Metals; • Major Cations and Anions; • Physical/Indicator Parameters; • Reagents and Organics; • Radiochemicals; • Cyanide Species; • Nutrients and Bacteria; • Miscellaneous; and, 1.2.2 Water Resource Values As discussed in previous sections, the BADCT determination process is driven by A.R.S. 49-243.B.1 and A.A.C. R18-9-A202(A)(5) The BADCT for a site includes those components of facility siting, design, construction, operation and closure/post-closure that limit discharge to an aquifer. Dilution, attenuation, and other factors that effect discharges after reaching an aquifer are not part of BADCT. Demonstrations related to water quality at the point of compliance pursuant to A.R.S. 49-243.B.2 and B.3 are separate and in addition to BADCT, and are not covered in this manual. Water resource considerations that play a role in BADCT determination are: (1) site surface water flow characteristics that can effect containment and migration of discharges through the vadose zone (e.g., surface water run-on and run-off); and (2) potential opportunities for water conservation or augmentation. The surface water hydrology aspects are discussed further in Section 1.2.4.4. This section provides the objectives and background to the water resource conservation considerations. (1-26) GENERAL INFORMATION ________________________________ A.R.S. 243.B.1 states, in part: “In determining best available demonstrated control technology, processes, operating methods or other alternatives the director shall take into account ... the opportunity for water conservation or augmentation ... .” A.A.C. R18-9-A202(A)(5)(b) states that an applicant shall submit, “An evaluation of each alternative discharge control technology, relative to the amount of discharge reduction achievable, site specific hydrologic and geologic characteristics, other environmental impacts, and water conservation or augmentation.” Because mining generally necessitates the use of large quantities of water, conservation plays a major role in the BADCT design. Water conservation is based on the efficient use of the available water and recycling of water used in processing. Recycling of process water should be maximized in the BADCT design. Pumped mine water should be beneficially used wherever possible. 1.2.3 Climatic Conditions Precipitation rates and evaporation rates (a function of temperature, humidity, and wind) are the two primary climatic factors. An applicant wanting to make a demonstration that climatic factors can reduce potential for discharge should evaluate precipitation and evaporation rates in conjunction with other site characteristics. In areas where precipitation rates are high and evaporation rates are low, there is a higher potential for discharge to impact groundwater. This is because precipitation that does not evaporate or run off, infiltrates into and then percolates through the mine waste. This infiltration may be a major transporter of pollutants to the aquifer where no engineered containment is provided. Generally in these conditions, percolation and subsequent leachate formation are important and must be accommodated in the design of the facility by incorporating leachate collection and containment features. Conversely, in arid and semi-arid environments, where precipitation is low and/or evaporation is high, the potential for surface discharge to impact groundwater is reduced. It is the applicant’s responsibility to demonstrate what impacts, if any, climatic conditions will have on the containment provided by the facility. When analyzing the effects and/or discharge reduction capabilities of climatic factors on a facility design, it is important that the applicant understands and considers the following site-specific conditions: • Precipitation and evaporation rates at the site (or nearest comparable area with historic data). (A measurement that is relevant to standing water conditions is pan evaporation. Other methodologies can be applied to estimating soil moisture evaporation conditions.); • Surface run-off: The applicant must estimate what percent of precipitation will run off the facility, and thereby be removed from water balance considerations for the material. _______________________________ GENERAL INFORMATION (1-27) The percentage of run-off depends on several factors including amount, intensity and duration of storm events (consideration should be given to extended periods of precipitation events during periods of low evaporation, such as winter rains), surface slope, permeability of surface (e.g., bedrock conditions, compacted surface vs. ripped surface), etc. Values of run-off can be determined from existing facilities or obtained using the U.S. Department of Agriculture Soil Conservation Service SCS methodology (“Urban Hydrology for Small Watersheds”, PB87-101580); • Moisture storage condition of the material: Two common terms used to define moisture conditions are saturation (the moisture condition at which all pore spaces are completely filled with liquid) and specific retention (the volume of liquid remaining in the previously saturated material after allowing the liquid to drain out of the material by gravity). Specific retention depends primarily on material grain size, shape and distribution of pores and structure. For example, fine grained tailing piles may have a specific retention of as much as 30% moisture by dry weight, while waste rock may have a specific retention of between 10% (coarse rock with minimal fines) and 20% (coarse rock with fines and loam). An applicant considering arid climatic conditions as a demonstrated control technology must, at a minimum, demonstrate that the material deposited will be at a moisture content below specific retention, or that it will be deposited in a manner that will cause the material to dry to at least specific retention; • Infiltration: The rate of infiltration depends on the grain size distribution, the texture and geometry of the ground surface, the moisture content of the waste material, and the amount and rate of rainfall. Coarser materials tend to have higher infiltration rates than fine-grained materials (or surfaces that are highly compacted); • Percolation: Once fluids infiltrate a material and the moisture content reaches the specific retention capacity of the material, percolation occurs. Whether percolation occurs at the facility depends on several factors including material thickness, frequency and intensity of storm events, “drying” time in between storm events, the amount of layering and permeability of the material, the amount of vegetation (vegetation reduce the potential for percolation through evapotranspiration), grain and rock size, evaporative depth, etc. Methods such as the Hydrologic Evaluation of Landfill Performance (HELP) water balance model (Federal Environmental Protection Agency) and other approaches can be used as a guide to evaluate percolation rates; • Evaporative depth: Evaporative depth is the depth to which evaporation can occur. Beyond this depth, evaporation cannot practicably remove moisture that has infiltrated. This depth is a function of material grain size and density (void space), extent and type of vegetation, and climatic conditions; and • Wind: Wind should be considered in the design of a facility because wind increases the evaporation. The applicant must also take into account over-spray problems and freeboard design (wave action) when constructing a facility in an area prone to high speed winds. If climatic factors are to be used in considering DCTs for a given facility, water balance calculations must be conducted. It is strongly recommended that water balance calculations be conducted with input from ADEQ to help assure that acceptable methods are used. (1-28) GENERAL INFORMATION ________________________________ 1.2.4 Site Factors Site specific factors that may be considered part of the BADCT determination, along with their data requirements, are discussed in this section. The following discussions do not cover all site factors relevant to an APP application, but only those relative to BADCT determination. The applicant may need to gather additional site specific information under the hydrogeologic-study portion of an APP application to determine the point of compliance, likelihood of compliance with aquifer standards, alert levels, monitoring requirements, and the discharge impact area. The “Aquifer Protection Permits Application Guidance Manual” discusses these aspects in more detail. Applicants are strongly encouraged to meet early with ADEQ and submit a proposal for the hydrogeologic study. ADEQ’s comments on the workplan and the negotiations with ADEQ will save much time and effort throughout the BADCT and APP application process. For mining projects, siting is often dictated by the ore body configuration and local topography. However, for certain facets of the surface operation, such as location of tailing impoundments, dump leach and heap leach facilities, etc., limited alternative sites may be available. Site selection and site characteristics will greatly influence individual BADCT determination since it is site specific. To a great extent, the site will control the design of the facility. Site selection influences the design of a facility in that each design element must be adapted, or fit, to the dimensions, layout and characteristics of the chosen site. The adaptation to the site affects the performance of the particular design component being used. In selecting a site, an investigation program needs to be developed and implemented. Much has been published on site investigation methods and there are numerous investigation approaches. General approaches available may include: • Remote sensing; • Geophysical methods; • Drilling and sampling; • Test pits and trenches; • Laboratory testing; • In-situ testing; and, • Monitoring wells and groundwater sampling. The designer must determine the appropriate investigative methods for selecting a site. The methods may vary from site to site but the following is a suggested approach. • Conduct a preliminary study. Review existing geologic and hydrologic information (e.g., available through libraries, USGS, universities, project files, etc.) including reports, maps, aerial photos, etc. • Conduct field reconnaissance of the area. Compare this information with any existing information. • Conduct initial investigations and tests, as needed, to augment existing data. Initial investigations and tests may include: surface mapping; subsurface geotechnical, geologic and hydrogeologic investigations using test pits or trenches, soil or rock borings, geophysics, etc.; laboratory testing of soil and rock samples for physical and geochemical properties; and other efforts, as required to develop the facility design and supporting evaluations. _______________________________ GENERAL INFORMATION (1-29) • Review results of initial investigations and tests, determine if additional work is required to support the development of the design and supporting evaluations (e.g., a higher level of field mapping, additional site specific tests, etc.), and conduct additional investigations and tests, as needed. Examples of site characteristics which may be considered in the ultimate design are summarized below. These examples are not intended to cover all site aspects of a permit application. 1.2.4.1 Topography Identifying the topography and surface characteristics of a site is a crucial step in designing a facility to minimize potential discharge, and to protect human health and the environment. Tailing, dump leach and heap leach facilities, for example, located on relatively steep topography underlain by low permeability geologic formations, may benefit from a natural high rate of drainage that can occur under the tailing, dump leach or heap leach material. This is because of the presence of steep slopes and limited potential for infiltration into the underlying geologic formations. Steep topographic terrain is also generally associated with outcropping bedrock and/or shallow alluvium. Lining of slopes steeper than 2(H):1(V) has not been practiced on an industry wide basis, especially for high slopes, due to high induced shear stresses and the possibility of failure of the underlying geologic materials. Liners can be safely designed for slightly flatter slopes ranging from 2:1 to 2.5:1 for landfills and on embankment faces. Lining of slopes steeper than 2.5:1 can be considered provided the applicant has considered the above factors, amongst others, and can demonstrate the adequacy of the design. However, at larger mining facilities, the height and steepness of the slope may be limited by 1) allowable tensile stresses in the liner, 2) the capacity of anchor trenches at the top of the slopes, and 3) the stability of any LCRS system or liners placed on top of the primary liner. Stability can be improved by constructing a “buttress” on a flatter slope, benching or the application of fill materials to reduce the slope. Textured or sprayed-on liners may also be applicable. Facilities located on relatively flat terrain do not, on their own, benefit from higher drainage rates and generally encounter greater soil depths to bedrock. This type of topography is generally suitable for liner application and such sites may benefit from the presence of naturally occurring, low permeability material within the vadose zone beneath the facility. Other topographic factors to consider include the existing containment offered at the site (e.g., valley fills, canyons, within existing pits), the characteristics of the natural soils (e.g., low permeability clay, high permeability gravel), and availability of low permeability borrow soils for liner construction. Information to evaluate topography and surface characteristics can be obtained from topographic maps, field surveys, aerial photos, USGS, Soil Conservation Service reports, etc. (1-30) GENERAL INFORMATION ________________________________ 1.2.4.2 Geology/Stability To determine how geologic conditions may affect the Individual BADCT design for a facility, the applicant should extensively evaluate the associated physical, hydraulic and geochemical properties. Specific information that may be appropriate to address, and that may be required for an APP application utilizing Individual BADCT, includes: • Structural Geology: The degree to which geologic structures may affect the Individual BADCT design depends on the amount of reliance being placed on geologic containment. Information on major geologic structures can be identified using geologic maps, aerial photographs, and existing geologic reports, etc. Detailed onsite geologic mapping or field investigation programs are required to evaluate site specific structures. The types of structures that need to be considered include: - Faults must be considered in the design of any facility because they affect stability. - Other structures, such as anticlines and synclines which affect rock strata orientation, can influence the rate and direction of liquid migration through the vadose zone and may be important in designing leak detection systems. - Fracture systems in bedrock can be important in determining seepage rates and velocities, and the location of monitoring systems. - Various other geologic structures or discontinuities can affect the areal continuity of low permeability layers. • Lithology: Lithology is the physical and mineralogic makeup of geologic materials, including both unconsolidated deposits (e.g., alluvium) and bedrock. Important lithologic considerations include: - Horizontal and vertical variations in lithology that cause permeability to vary and which can affect the degree of natural containment provided by the site. - Subsurface strength properties that can affect the long-term integrity of the facility (e.g., settlement potential) and seismic stability. - The depth to bedrock, degree of subsurface stratification, and variations in strata characteristics, can be important to the design of a facility. - Certain alluvial materials and rock types may, by themselves or possibly in combination with planned facility operations, possess geochemical characteristics that contribute to a reduction of discharge and/or limit pollutant migration by attenuation. The following are representative methods for determining permeability; site specifics will determine which methodologies are applicable: • Soil and rock classification based on subsurface lithologic logs and the use of literature or other available information to determine approximate permeability values; • Field permeability testing, including pump tests, packer tests, and other in-situ tests; • Laboratory grain size analyses and permeability tests; • Borehole and surface geophysical surveys to define lithologic boundaries, and to characterize the distribution of permeability. _______________________________ GENERAL INFORMATION (1-31) The effects of scale should be considered in interpreting results of permeability testing. The permeability measured in isolated borehole packer tests (e.g., local permeability) may vary from the permeability of the larger scale rock or soil mass (bulk permeability). This is due to differences in the persistence, character and interconnectivity of the fractures near the boreholes as compared to the rock mass or due to heterogeneity in soil masses. It is also important to consider possible horizontal and vertical variations in permeability (i.e., does permeability decrease or increase between varying lithologies or with depth) and how the local and regional groundwater regimes at the site are affected. 1.2.4.3 Soil Properties Soil is generally characterized by relatively high organic content, biologic activity by roots and microorganisms, and concentration of weathering products left by leaching, evaporation or transportation. Soil properties may affect discharge from a facility by physical, chemical and biologic interaction with a pollutant(s). Soil properties with potential to affect discharge include: type, distribution and thickness, structure, grain-size distribution, organic carbon content, chemical composition, mineralogy, cation exchange capacity, specific surface area and permeability. The applicant should evaluate any changes to soil characteristics that may result from interaction with the discharge. If soil characteristics are to be used for attenuation, the attenuation capacity of the material must be predicted using literature data, or laboratory or field tests. In addition to analyzing the ability of soil properties to affect the quantity and/or quality of a potential discharge, shear strength must be analyzed to support stability analyses. Soil tests and data which may be useful in an Individual BADCT determination include: • Studies of degradation of pollutants in the soils; • Batch or column tests to react a simulated discharge with site soils to determine attenuation capacity; • Infiltration tests; • Permeability tests; • Chemical analyses (pH, EC, inorganic analyses, organic analyses); • Material property tests (grain size analyses, moisture content, bulk density, Atterberg Limits); • Maps of soil distribution and depth; • Soil boring logs; • Other pertinent soil information including reference to pollutant attenuation research. 1.2.4.4 Surface Hydrology If surface water enters waste or processing facilities, leachate can be generated. A key to controlling leachate generation is to design, construct, operate and close facilities in a manner that minimizes the potential for contact of surface water with pollutants and excludes surface water from areas where infiltration may affect groundwater quality. The configuration of surface (1-32) GENERAL INFORMATION ________________________________ water control systems for a mining facility depends on the climate and topography of the site area. Computer models may guide the assessment of surface water effects and the need for surface water control systems. County flood maps may also be helpful. In general, surface water should be diverted around and drained from areas where facilities are located using engineered features such as diversions and/or retention structures. Diversions and/or retention structures are usually designed to minimize run-on to the facility. This preserves containment integrity and limits the amount of water that may contact process reagents or other sources of potential pollutants. In some cases, drainage controls may also be necessary to protect against inundation of the facility and nearby low areas where infiltration may contribute to pollutant transport in the vadose zone. This can typically be achieved by providing protective berms or dikes. The design of surface water control systems is influenced by: precipitation (amount, intensity, duration, distribution), watershed characteristics (size, shape, topography, geology, vegetation), run-off (peak rate, volumes, time distribution) and degree of protection warranted. Timely maintenance is necessary for the continued satisfactory operation of surface water control systems. The principal causes of failure of surface water diversions and/or retention structures are inadequate design peak flow capacity, channel and bank erosion, sedimentation, and excessive growth of vegetation reducing the flow capacity. It is recommended that free-draining features (e.g., ditches and dikes) be capable of handling the design peak flow and that impounding features be designed to handle the design storm volume which occurs over a duration resulting in the maximum storage requirement (ADEQ may approve other design criteria). Evaluation of these design peak flows and storm volumes is discussed in Appendix E (Engineering Design Guidance). Data that may be presented to evaluate the need for surface water control include: • Location of any perennial or ephemeral surface water bodies; • Rates, volumes, and directions of surface water flow, including hydrographs, if available; • Location of 100-year flood plain; • Site topography; • Historical precipitation data. Any activities in, or discharges to, waters of the United States require 401 Certification with ADEQ, and may require notification to the Army Corps of Engineers for a 404 Permit, the EPA for a 402 Permit, and/or the respective County Flood Control District. Additional information regarding these permits and certifications is presented in Appendix F (Federal, State and Local Environmental Permits). 1.2.4.5 Hydrogeology Site characteristics are a part of BADCT insofar as they control the quality and/or quantity of discharge before it reaches groundwater. Potentially important hydrogeologic characteristics include vadose zone properties that may help to limit discharge to the aquifer. Dilution, _______________________________ GENERAL INFORMATION (1-33) attenuation and other factors that affect discharges after reaching an aquifer are not normally an inherent part of BADCT. The exceptions, where characteristics within the aquifer may be an inherent part of BADCT, are the case of in-situ leaching of an ore body and passive containment. In-situ leaching is defined as the underground injection of solutions into an ore body in-place for the purpose of extracting the mineral commodity. In-situ leaching is discussed in Section 3.4. Passive containment is defined by regulation and is discussed in Section 1.2.5. The remainder of this section addresses vadose zone hydrogeology that may be important to BADCT for mining operations. Properties of the vadose zone, the unsaturated zone between the land surface and the saturated zone or maximum groundwater table (Figure 1-1), may affect the behavior of a discharge in a number of ways. For example, physical properties of the vadose zone, like the presence of high permeability layers and geologic structures (e.g., faults, fracture zones), may increase movement of a discharge to groundwater. Conversely, the presence of impervious layers and geologic structures (e.g., clay seams, strata boundaries) may retard the movement of a discharge to groundwater or cause the presence of perched water tables; fine grained layers within the zone may physically remove some types of pollutants; and the decrease in bedrock permeability with depth may reduce the possibility of discharge reaching groundwater. Also, chemical and/or geochemical reactions between the discharge and materials in the vadose zone may alter or remove some pollutants; or biodegradation due to microbial interaction with the pollutant may degrade the pollutant. If the vadose zone consists of layers or lenses of different materials, such as stratified soil horizons or rock units, the properties of each unit must be considered separately in addition to describing the general properties of the vadose zone. The applicant should identify lateral and vertical extent of the geologic units and the type of contacts between the units (e.g., gradational, fault, unconformity, facies change). Perched water tables within the vadose zone may be a consideration. The attenuation of chemical constituents in soil and rock is a valid consideration that can be factored into site specific evaluations. If vadose materials are to be used for attenuation, the attenuation capacity of the material must be predicted. Below is a brief description of the four major types of attenuation mechanisms. This is further explained in “Mine Waste Management,” Chapter 5 (Hutchison and Ellison, 1992). • Physical Mechanisms: Physical mechanisms include filtration, dispersion, dilution and volatilization. • Physiochemical Mechanisms: Physiochemical mechanisms are dependent on both physical and chemical conditions and can include adsorption and fixation. • Chemical Mechanisms: Chemical mechanisms are dependent on the chemical interaction of an element or mineral with the soil or pore water and includes solution/precipitation of compounds or the increase/reduction in toxicity of a constituent by changing its valence state, or the removal/addition of ions by cation exchange. (1-34) GENERAL INFORMATION ________________________________ • Biological Mechanisms: Biological mechanisms include biodegradation of a chemical into the basic oxidation product, bacterial consumption of the chemical or cellular uptake. Additional data which may be submitted to characterize the vadose zone or any unit of the vadose zone for consideration as a part of BADCT design may include: • Detailed lithologic logs of borings and/or well logs that describe: - rock type, - grain-size distribution, - stratigraphy, - type and degree of cementation, and - thickness of units; • Description of the structural geology including: - faults, - fractures, - joints, - folds, and - bedding orientation; • Geologic maps and cross-sections which identify: - stratigraphic or formation contacts, and - structural geology; • Borehole geophysical logs; • Surface geophysical surveys; • Physical properties including: - horizontal and vertical permeability, - dispersivity, - porosity (primary and secondary), • Chemical analyses (pH, EC, neutralization potential, inorganic and/or organic analyses); • Results of batch or column tests showing quality of discharge after reacting with vadose zone material and quality of vadose zone material after reacting with discharge; • Material property tests (grain size analyses, moisture content, Atterberg Limits, maximum density); • Analyses of fluid movement and/or chemical transport through the vadose zone. Supportive data may be obtained from: - lysimeters, - neutron log measurements, - observation wells, - packer tests, and/or - analytical or numeric simulations. _______________________________ GENERAL INFORMATION (1-35) Depth to groundwater or the thickness of the vadose zone may be a factor in determining BADCT. The degree of discharge reduction provided by depth will depend on several variables including: depth to the anticipated maximum groundwater elevation, the volume and rate of discharge, the properties of the pollutants in the discharge, the properties of the vadose zone, and the length of time a discharge may continue. Any considerations of depth to water as a part of BADCT will have to show how the hydrologic and geochemical characteristics of the vadose zone in conjunction with its thickness will affect discharge. Data for evaluating depth to water may include: • Static water elevation measurements (including date of measurement, location of well, and elevation of measuring point); • Well hydrographs to document long term and seasonal trends; • Location of pumping wells in vicinity of measured well; • Well construction data (including total depth and location of perforations); • Geophysical surveys such as seismic and resistivity. 1.2.4.6 Barriers Hydraulic barriers (e.g., dewatered open pits, or quarries) and physical barriers (e.g., pit walls, quarries, subsidence zones, or slurry walls) can function as downgradient interceptors of groundwater flows, seepage in the unsaturated zone and/or surface flows. For example, steeply sloping surfaces, depressions or openings created by open pit or underground mining can function as downgradient interceptors of lateral seepage from a facility. Cones of depressions in groundwater or slurry walls can be used to contain in-situ leach solutions. Except for in-situ leaching, the use of a hydraulic or physical barrier as a consideration in BADCT design is appropriate only in the context of discharge reduction prior to a pollutant reaching an aquifer. For facilities other than in-situ leaching, use of barriers to control pollutants after reaching the aquifer or to control impacted groundwater may not be used as a part of BADCT unless the physical barrier also functions as passive containment (see Section 1.2.5). 1.2.5 Passive Containment A discharging facility at an open pit mining operation shall be deemed to satisfy BADCT requirements of A.R.S. 49-243.B.1. if the ADEQ determines that both of the following conditions are satisfied (A.R.S. 49-243.G): 1. “The mine pit creates a passive containment that is sufficient to capture the pollutants discharged and that is hydrologically isolated to the extent that it does not allow pollutant migration from the capture zone. For purposes of this paragraph, “passiv
Object Description
TITLE | Arizona mining BADCT guidance manual : aquifer protection program |
CREATOR | Arizona Department of Environmental Quality |
SUBJECT | Groundwater--Pollution--Arizona--Prevention--Handbooks, manuals, etc.; Groundwater--Pollution--Arizona; Mineral industries--Environmental aspects--Arizona |
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Land and resources Water |
DESCRIPTION | This title contains one or more publications |
Language | English |
Publisher | Arizona Department of Environmental Quality |
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Location | o192095024 |
REPOSITORY | Arizona State Library, Archives and Public Records--Law and Research Library |
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TITLE | Arizona mining BADCT guidance manual : aquifer protection program 2004 |
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RIGHTS MANAGEMENT | Copyright to this resource is held by the creating agency and is provided here for educational purposes only. It may not be downloaded, reproduced or distributed in any format without written permission of the creating agency. Any attempt to circumvent the access controls placed on this file is a violation of United States and international copyright laws, and is subject to criminal prosecution. |
DATE ORIGINAL | 2004 |
Time Period |
2000s (2000-2009) |
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Source Identifier | ENQ 1.2:B 12 A 68 |
Location | o192095024 |
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Full Text | ARIZONA MINING GUIDANCE MANUAL BADCT Publication # TB 04-01 ARIZONA DEPARTMENT OF ENVIRONMENTAL QUALITY 1110 West Washington Street Phoenix, Arizona 85007 (602) 771-2300 or 1-800-234-5677 in Arizona TDD Number (602) 771-4829 ARIZONA MINING BADCT GUIDANCE MANUAL Aquifer Protection Program ACKNOWLEDGMENTS The publication of Arizona’s new mining BADCT (Best Available Demonstrated Control Technology) document represents a milestone in protecting groundwater under the state's Aquifer Protection Permit (APP) program. Its successful completion combined the efforts of ADEQ staff and members of the mining community in an unprecedented cooperative venture to develop guidance for protecting groundwater for future uses. ADEQ is greatly indebted to the “Small BADCT Committee” for the thousands of hours its members invested in the preceding 18 months to produce this guidance manual. Without their patience, cooperation and perseverance, this project could not have been completed. SMALL BADCT COMMITTEE ADEQ PARTICIPANTS MINING INDUSTRY PARTICIPANTS Dennis L. Turner, Chairman George H. Beckwith, P.E. Michael D. Greenslade, P.E. Derek J. Cooke James F. Dubois Colleen D. Kelley Michael J. Wood Robin A. Kettlewell Richard N. Mohr Dirk Van Zyl, P.E., Ph.D. This document also greatly benefited from an independent technical review performed by TRC Environmental Solutions, Inc., lead by Dr. Ian Hutchison. Dr. Hutchison, along with Dr. Richard D. Ellison, edited “Mine Waste Management,” a publication sponsored by the California Mining Association. Drs. Hutchison and Ellison are internationally recognized water quality management experts and designers of mine waste management units, as well as authorities in developing mine waste regulations appropriate to those issues. The technical editorial team consisted of: Ian P. G. Hutchison, Ph.D., P.E. Joseph L. Stenger, R.G. Michael L. Leonard Sr., P.E. Deanna Stamboulian Joe Gelt of the University of Arizona’s Water Resources Research Center edited and formatted the final copy; Ken Seasholes of WRRC designed the cover. Deborah L. Patton of ADEQ was responsible for the final edit and press preparation. i USE OF MANUAL At a minimum, readers are encouraged to read the following sections: • Introduction • Part 1 - General BADCT Information Thereafter, if they intend to submit a Prescriptive BADCT design they should review: • Part 2 - Prescriptive BADCT Criteria • Section 2.1 - Introduction • The sections that apply to their facilities selected from 2.2 to 2.5 If they intend to submit an Individual BADCT design they should review: • Part 3 - Individual BADCT Guidance • Section 3.1 - Introduction • The sections that apply to their facilities selected from 3.2 to 3.6. The Appendices are available for further detailed review. The more important are: • Appendix B: Solution Ore and Waste Characterization • Appendix C: Liner Design, Principals and Practice • Appendix E: Engineering Design Guidance ii TABLE OF CONTENTS PAGE NO. INTRODUCTION Purpose and Scope ........................................................................................................1 BADCT Selection Process Overview...............................................................................2 How to Use This Manual..................................................................................................3 Facilities Requiring BADCT ............................................................................................5 PART 1 - GENERAL BADCT INFORMATION.................................................................1-1 1.1 The BADCT Process...............................................................................................1-1 1.1.1 Prescriptive BADCT...................................................................................1-3 1.1.2 Prescriptive BADCT Review Process ........................................................1-3 1.1.2.1 Determination of Prescriptive BADCT .......................................1-6 1.1.3 Individual BADCT Review Process For New Facilities ............................1-6 1.1.3.1 Site Selection ...............................................................................1-8 1.1.3.2 Development of Reference Design .............................................1-11 1.1.3.3 Estimation of Aquifer Loading ...................................................1-11 1.1.3.4 Alternative Design(s) Selection ..................................................1-17 1.1.3.5 Estimation of Aquifer Loading for Alternative Design(s)..........1-17 1.1.3.6 Selection of BADCT Design ......................................................1-17 1.1.3.7 Economic Considerations ...........................................................1-18 1.1.3.8 Discussion...................................................................................1-19 1.1.4 Individual BADCT Review Process for Existing Facilities ......................1-19 1.1.4.1 Steps 1 & 2: Identifying Current Discharge Controls and Assessing Their Performance - The Reference Design........1-20 1.1.4.2 Step 3: Identifying Technically Feasible DCTs for Improvement .........................................................................1-21 1.1.4.3 Step 4: Use Candidate List to Arrive at One or More Alternative Discharge Control Systems......................................1-22 1.1.4.4 Step 5: Weigh Cost vs. Discharge Reduction by Calculating Aquifer Loading for Alternative System(s) and Calculating Cost for New DCTs ..........................................1-22 1.2 Using Site Characteristics as a part of the BADCT Design...................................1-22 1.2.1 Waste Types and Process Solution Characteristics ...................................1-22 1.2.2 Water Resource Values..............................................................................1-25 1.2.3 Climatic Conditions ...................................................................................1-26 1.2.4 Site Factors.................................................................................................1-28 1.2.4.1 Topography.................................................................................1-29 1.2.4.2 Geology/Stability ........................................................................1-30 1.2.4.3 Soil Properties.............................................................................1-31 1.2.4.4 Surface Hydrology......................................................................1-31 1.2.4.5 Hydrogeology .............................................................................1-32 1.2.4.6 Barriers........................................................................................1-35 1.2.5 Passive Containment..................................................................................1-35 1.3 Using Liners as a Part of the BADCT Design .......................................................1-36 PART 2 - PRESCRIPTIVE BADCT CRITERIA .................................................................2-1 2.1 Introduction.............................................................................................................2-1 TABLE OF CONTENTS (Continued) PAGE NO. iii 2.2 Non-Storm Water Ponds.........................................................................................2-5 2.2.1 Siting Criteria..............................................................................................2-5 2.2.1.1 Site Characterization....................................................................2-5 2.2.1.2 Surface Water Control .................................................................2-6 2.2.1.3 Geologic Hazards.........................................................................2-6 2.2.2 Design, Construction and Operations Criteria............................................2-7 2.2.2.1 Solution/Effluent Characterization ..............................................2-7 2.2.2.2 Capacity and Storage Design .......................................................2-7 2.2.2.3 Site Preparation............................................................................2-7 2.2.2.4 Liner Specifications .....................................................................2-7 2.2.2.5 Stability Design............................................................................2-8 2.2.3 Facility Inspection Criteria .........................................................................2-9 2.2.4 Closure/Post-Closure Criteria ....................................................................2-11 2.3 Process Solution Ponds..........................................................................................2-17 2.3.1 Siting Criteria.............................................................................................2-17 2.3.1.1 Site Characterization...................................................................2-17 2.3.1.2 Surface Water Control ................................................................2-18 2.3.1.3 Geologic Hazards........................................................................2-18 2.3.2 Design, Construction and Operations Criteria...........................................2-19 2.3.2.1 Solution/Effluent Characterization .............................................2-19 2.3.2.2 Capacity and Storage Design ......................................................2-19 2.3.2.3 Site Preparation...........................................................................2-19 2.3.2.4 Liner Specifications ....................................................................2-19 2.3.2.5 Leak Collection and Removal System (LCRS) ..........................2-21 2.3.2.6 Stability Design...........................................................................2-21 2.3.3 Facility Inspection Criteria ........................................................................2-23 2.3.4 Closure/Post-Closure Criteria ....................................................................2-23 2.4 Heap Leach Pads....................................................................................................2-31 2.4.1 Siting Criteria.............................................................................................2-31 2.4.1.1 Site Characterization...................................................................2-31 2.4.1.2 Surface Water Control ................................................................2-32 2.4.1.3 Geologic Hazards........................................................................2-32 2.4.2 Design, Construction and Operations Criteria...........................................2-32 2.4.2.1 Solution and Waste Characterization..........................................2-33 2.4.2.2 Site Preparation...........................................................................2-33 2.4.2.3 Liner Specifications ....................................................................2-33 2.4.2.4 Perimeter Containment ...............................................................2-35 2.4.2.5 Stability Design...........................................................................2-35 2.4.3 Facility Inspection Criteria ........................................................................2-36 2.4.4 Closure/Post-Closure Criteria ....................................................................2-38 2.5 Tailing Impoundments ...........................................................................................2-43 2.5.1 Siting Criteria.............................................................................................2-43 2.5.1.1 Site Characterization...................................................................2-43 2.5.1.2 Surface Water Control ................................................................2-44 2.5.1.3 Geologic Hazards........................................................................2-44 2.5.2 Design, Construction and Operations Criteria...........................................2-45 TABLE OF CONTENTS (Continued) PAGE NO. iv 2.5.2.1 Solution and Tailing Characterization ........................................2-45 2.5.2.2 Capacity and Storage Design ......................................................2-45 2.5.2.3 Site Preparation...........................................................................2-45 2.5.2.4 Liner Specifications ....................................................................2-45 2.5.2.5 Stability Design...........................................................................2-47 2.5.3 Facility Inspection Criteria ........................................................................2-49 2.5.4 Closure/Post-Closure Criteria ....................................................................2-49 PART 3 - INDIVIDUAL BADCT GUIDANCE...................................................................3-1 3.1 Introduction.............................................................................................................3-1 3.2 Heap Leach Pads.....................................................................................................3-2 3.2.1 Introduction.................................................................................................3-2 3.2.2 Solution and Waste Characterization..........................................................3-2 3.2.3 Siting Considerations..................................................................................3-3 3.2.3.1 Climate and Surface Hydrology...................................................3-4 3.2.3.2 Subsurface Conditions .................................................................3-4 3.2.3.3 Geologic Hazards.........................................................................3-4 3.2.3.3.1 Landslides ..................................................................3-5 3.2.3.3.2 Subsidence and Settlement ........................................3-5 3.2.3.3.3 Earthquake-Induced Ground Failure..........................3-6 3.2.3.3.4 Collapsing Soils .........................................................3-7 3.2.4 Design, Construction and Operations Considerations ................................3-7 3.2.4.1 Site Preparation............................................................................3-7 3.2.4.2 Surface Water Control .................................................................3-8 3.2.4.3 Discharge Control ........................................................................3-8 3.2.4.3.1 Natural Containment and Liners................................3-9 3.2.4.3.2 Leachate Collection/Hydrostatic Head Control ........3-10 3.2.4.3.3 Solution Control and Storage....................................3-11 3.2.4.4 Stability Design...........................................................................3-11 3.2.4.5 Operational Measures .................................................................3-12 3.2.4.6 Operational Monitoring ..............................................................3-13 3.2.5 Closure/Post-Closure .................................................................................3-14 3.2.5.1 Physical Stability ........................................................................3-15 3.2.5.2 Chemical Stability.......................................................................3-16 3.2.5.2.1 General......................................................................3-16 3.2.5.2.2 Rinsing/Detoxification..............................................3-17 3.3 Dump Leaching Facilities ......................................................................................3-18 3.3.1 Introduction................................................................................................3-18 3.3.2 Solution and Spent Ore Characterization...................................................3-19 3.3.3 Siting Considerations.................................................................................3-19 3.3.3.1 Climate and Surface Hydrology..................................................3-20 3.3.3.2 Subsurface Conditions ................................................................3-21 3.3.3.3 Geologic Hazards........................................................................3-21 3.3.3.3.1 Landslides .................................................................3-21 3.3.3.3.2 Subsidence and Settlement .......................................3-22 3.3.3.3.3 Earthquake-Induced Ground Failure.........................3-22 TABLE OF CONTENTS (Continued) PAGE NO. v 3.3.3.3.4 Collapsing Soils ........................................................3-23 3.3.4 Design Construction and Operations Considerations ................................3-24 3.3.4.1 Site Preparation...........................................................................3-24 3.3.4.2 Surface Water Control ................................................................3-26 3.3.4.3 Discharge Control .......................................................................3-26 3.3.4.4 Stability Design...........................................................................3-28 3.3.4.5 Operational Measures .................................................................3-29 3.3.4.6 Operational Monitoring ..............................................................3-30 3.3.5 Closure/Post-Closure .................................................................................3-31 3.3.5.1 Physical Stability ........................................................................3-31 3.3.5.2 Chemical Stability.......................................................................3-32 3.3.5.2.1 General......................................................................3-32 3.3.5.2.2 Rinsing/Detoxification..............................................3-33 3.4 In-Situ Leaching.....................................................................................................3-34 3.4.1 Introduction................................................................................................3-34 3.4.2 Types of In-Situ Leaching Operations.......................................................3-35 3.4.2.1 In-Situ Leaching With Deep Well Injection ...............................3-35 3.4.2.2 In-Situ Leaching Using the Water Table for Capture.................3-35 3.4.2.3 In-Situ Leaching With Capture Above The Water Table ...........3-36 3.4.3 Solution Characterization...........................................................................3-40 3.4.4 Siting Considerations.................................................................................3-40 3.4.4.1 Climate and Surface Hydrology..................................................3-41 3.4.4.2 Subsurface Conditions ................................................................3-41 3.4.4.3 Geologic Hazards........................................................................3-41 3.4.4.3.1 Landslides .................................................................3-42 3.4.4.3.2 Subsidence and Settlement .......................................3-42 3.4.4.3.3 Earthquake-Induced Ground Failure.........................3-43 3.4.4.3.4 Collapsing Soils ........................................................3-44 3.4.5 Design, Construction and Operations Considerations ...............................3-44 3.4.5.1 Site Preparation...........................................................................3-44 3.4.5.2 Surface Water Control ................................................................3-45 3.4.5.3 Discharge Control .......................................................................3-45 3.4.5.3.1 Discharge Control - In-Situ Leaching With Deep Well Injection .........................................3-46 3.4.5.3.1.1 Injection Well Mechanical Integrity - Design .................................3-46 3.4.5.3.1.2 Injection Well Construction.................3-47 3.4.5.3.1.3 Injection Well Operation......................3-47 3.4.5.3.2 Discharge Control - In-Situ Leaching Using the Water Table for Capture .....................................3-48 3.4.5.3.3 Discharge Control - In-Situ Leaching With Capture Above The Water Table .....................3-48 3.4.5.4 Stability Design...........................................................................3-49 3.4.5.5 Operational Measures .................................................................3-49 3.4.6 Closure/Post-Closure .................................................................................3-50 3.5 Tailing Impoundments ...........................................................................................3-50 TABLE OF CONTENTS (Continued) PAGE NO. vi 3.5.1 Introduction................................................................................................3-50 3.5.2 Solution and Tailing Characterization .......................................................3-52 3.5.3 Siting Considerations.................................................................................3-52 3.5.3.1 Climate and Surface Hydrology..................................................3-53 3.5.3.2 Subsurface Conditions ................................................................3-53 3.5.3.3 Geologic Hazards........................................................................3-54 3.5.3.3.1 Landslides .................................................................3-54 3.5.3.3.2 Subsidence and Settlement .......................................3-54 3.5.3.3.3 Earthquake-Induced Ground Failure.........................3-55 3.5.3.3.4 Collapsing Soils ........................................................3-56 3.5.4 Design, Construction and Operations Considerations ...............................3-56 3.5.4.1 Site Preparation...........................................................................3-57 3.5.4.2 Surface Water Control ................................................................3-57 3.5.4.3 Discharge Control .......................................................................3-58 3.5.4.3.1 Base Metal Tailing Impoundments...........................3-58 3.5.4.3.2 Precious Metals Tailing Impoundments ...................3-59 3.5.4.3.3 Uranium Tailing Impoundments...............................3-60 3.5.4.4 Stability Design...........................................................................3-61 3.5.4.5 Operational Measures .................................................................3-66 3.5.4.6 Operational Monitoring ..............................................................3-66 3.5.5 Closure/Post-Closure .................................................................................3-67 3.6 Surface Ponds.........................................................................................................3-68 3.6.1 Introduction................................................................................................3-68 3.6.2 Solution Characterization...........................................................................3-68 3.6.3 Siting Considerations.................................................................................3-69 3.6.3.1 Climate and Surface Hydrology..................................................3-69 3.6.3.2 Subsurface Conditions ................................................................3-70 3.6.3.3 Geologic Hazards........................................................................3-70 3.6.3.3.1 Landslides .................................................................3-70 3.6.3.3.2 Subsidence and Settlement .......................................3-71 3.6.3.3.3 Earthquake-Induced Ground Failure.........................3-72 3.6.3.3.4 Collapsing Soils ........................................................3-72 3.6.4 Design, Construction and Operations Considerations ...............................3-73 3.6.4.1 Site Preparation...........................................................................3-73 3.6.4.2 Surface Water Control ................................................................3-74 3.6.4.3 Discharge Control .......................................................................3-74 3.6.4.3.1 Liners ........................................................................3-74 3.6.4.3.2 Leak Collection and Removal System (LCRS) ........3-75 3.6.4.4 Stability Design...........................................................................3-76 3.6.4.5 Operational Measures .................................................................3-77 3.6.4.6 Operational Monitoring ..............................................................3-77 3.6.5 Closure/Post-closure ..................................................................................3-77 3.6.5.1 Closure by Removal....................................................................3-78 3.6.5.2 Closure In-Place..........................................................................3-78 TABLE OF CONTENTS (Continued) PAGE NO. vii PART 4 - APPENDICES A COMPARISON OF COPPER LEACHING FACILITIES B SOLUTION, ORE AND WASTE CHARACTERIZATION C LINER DESIGN PRINCIPLES AND PRACTICE D CONSTRUCTION QUALITY ASSURANCE AND QUALITY CONTROL E ENGINEERING DESIGN GUIDANCE F FEDERAL, STATE AND LOCAL ENVIRONMENTAL PERMITS PART 5 - GLOSSARY OF TECHNICAL TERMS PART 6 - REFERENCES INDEX TABLE OF CONTENTS (Continued) PAGE NO. viii LIST OF TABLES TABLE NO. TITLE 1-1 Example Table of Contents - Prescriptive BADCT Demonstration.......................1-5 1-2 Example Table of Contents - Individual BADCT Demonstration..........................1-9 1-3 Examples of Demonstrated Control Technologies ................................................1-13 2-1 Examples of Engineering Equivalents ....................................................................2-2 2-2 Non-Storm Water Ponds Prescriptive BADCT .....................................................2-12 2-3 Process Solution Ponds Prescriptive BADCT .......................................................2-25 2-4 Heap Leach Pads Prescriptive BADCT .................................................................2-39 2-5 Tailing Impoundments Prescriptive BADCT ........................................................2-50 LIST OF FIGURES FIGURE NO. TITLE PAGE NO. 1-1 Example of Prescriptive and Individual BADCT “Zones” ....................................1-2 1-2 Schematic of BADCT Selection Process For New Facilities ..................................................................................................1-7 2-1 Example of Non-Storm Water Pond Cross-Section...............................................2-10 2-2 Example of Process Solution Pond Cross-Section.................................................2-22 2-3 Example of Heap Leach Pad Cross-Section ..........................................................2-37 2-4 Example of Tailing Impoundment Cross-Section..................................................2-48 3-1 Example of Dump Leach Facility Cross-Section...................................................3-25 3-2 Example of In-Situ Leaching With Deep Well Injection.......................................3-37 3-3 Example of In-Situ Leaching Using the Water Table for Capture ........................3-38 3-4 Example of In-Situ Leaching With Capture Above the Water Table....................3-39 3-5 Tailing Dam Construction Method .......................................................................3-63 3-6 Upstream Tailing Dam Construction Using Cyclones ..........................................3-64 INTRODUCTION ________________________________________________ INTRODUCTION (1) INTRODUCTION Purpose and Scope This guidance manual describes the process that an Aquifer Protection Permit (APP) applicant should follow in selecting the Best Available Demonstrated Control Technology (BADCT) for a specific mining facility(1) and site(1) in accordance with Arizona Revised Statute (A.R.S) 49-243.B.1. This statute requires all permitted facilities to utilize BADCT in their design, construction and operation while considering various factors depending on whether the facility is new or existing. The requirements of BADCT are met, according to A.R.S. 49-243.B.1, if it is demonstrated: AThat the facility will be so designed, constructed and operated as to ensure the greatest degree of discharge reduction achievable through application of the best available demonstrated control technology, processes, operating methods or other alternatives, including, where practicable, a technology permitting no discharge of pollutants. In determining best available demonstrated control technology, processes, operating methods or other alternatives the director shall take into account site specific hydrologic and geologic characteristics and other environmental factors, the opportunity for water conservation or augmentation and economic impacts of the use of alternative technologies, processes or operating methods on an industry-wide basis. However, a discharge reduction to an aquifer achievable solely by means of site specific characteristics does not, in itself, constitute compliance with this paragraph. In addition, the director shall consider the following factors for existing facilities: (a) Toxicity, concentrations and quantities of discharge likely to reach an aquifer from various types of control technologies. (b) The total costs of the application of the technology in relation to the discharge reduction to be achieved from such application. (c) The age of equipment and facilities involved. (d) The industrial and control process employed. (e) The engineering aspects of the application of various types of control techniques. (f) Process changes. (g) Non-water quality environmental impacts. (h) The extent to which water available for beneficial uses will be conserved by a particular type of control technology.@ Arizona Administrative Code (A.A.C.) R18-9-A202(A)(5) requires that an application for an APP include a description of the BADCT to be employed at the facility. The procedures and information presented in this guidance manual are intended for use in determining the appropriate BADCT, and to assist the applicant=s development and the Arizona Department of Environmental Quality's (ADEQ=s) review of permit applications. (2) INTRODUCTION____________________________________ Demonstrating that a facility will be designed, constructed, and operated in accordance with BADCT requirements is one of five demonstrations required for obtaining an APP permit. Other required demonstrations include: $ The facility will not cause or contribute to an exceedance of Aquifer Water Quality Standards (AWQS) at the point of compliance or, if AWQS for a pollutant has been exceeded in an aquifer, that no additional degradation will occur (A.A.C. R18-9- A202(A)(8)(a and b)); $ The person applying for the APP is technically capable of carrying out the conditions of the permit (A.A.C. R18-9-A202(B)); $ The person applying for the APP is financially capable of constructing, operating, closing, and assuring proper post-closure care of the facility (A.A.C. R18-9-A203); and $ The facility complies with applicable municipal or county zoning ordinances and regulations (A.A.C. R18-9-A201(A)(2)(c)). The above four demonstrations are outside the scope of BADCT and are not further addressed. Additional information on these demonstrations is available from the referenced rules and statutes, and the ADEQ=s AAquifer Protection Permits Application Guidance Manual.@ The ADEQ will use both this AMining BADCT Guidance Manual@ and the AAquifer Protection Permits Application Guidance Manual@ to evaluate APP applications. In the event of an inconsistency between this manual and applicable rules and/or statutes, provisions from rules and/or statutes will prevail. The AAquifer Protection Permits Application Guidance Manual@ provides procedures for pre-application meetings and coordination between the ADEQ and the applicant, at the applicant=s request. This early coordination is strongly encouraged by ADEQ to provide assurance that the applicant=s efforts are focused on relevant issues and necessary data collection, including those requirements related to the determination of appropriate BADCT. BADCT Selection Process Overview To achieve BADCT, mining facility owners and operators should use demonstrated discharge control elements utilized on an industry wide basis to limit or, where practicable, eliminate discharge to aquifers. When considering technologies, processes, operating methods and other alternatives for purposes of demonstrating BADCT, a facility must be evaluated in terms of 1) siting, 2) design, construction, and operation, and 3) closure/post-closure. A range of considerations must be taken into account in demonstrating BADCT for a facility, including characteristics, water conservation and augmentation, and economic impacts associated with the implementation of the various design elements being considered. ________________________________________________ INTRODUCTION (3) Key concepts reflected in this manual regarding determining BADCT for a facility are that: $ BADCT must be determined on a site specific basis by evaluating the degree that alternative discharge control systems minimize the addition of pollutants to the protected aquifer; $ Negotiation between the applicant and ADEQ is usually necessary because of subjective judgments inherent in some BADCT analyses. This means that no single technology or group of technologies can be mandated as appropriate for all discharge control systems. Rather, multiple DCTs (Demonstrated Control Technologies) may be appropriately used to arrive at a BADCT design for a specific facility at a given site. Then, based on a facility=s status as new or existing, the criteria described in A.R.S. 49-243.B.1 must be applied to that particular site to determine which DCTs are appropriate for that facility. It is, however, important to note that the DCTs presented in this manual are simply alternatives which may or may not be required at any specific facility; and $ Monitoring is generally not regarded as part of the BADCT design, unless it is performed as a specific feedback mechanism to adjust the design or operational aspects of the facility. The reader is referred to the AAquifer Protection Permits Application Guidance Manual@ for further discussion on monitoring. A mining APP applicant may choose between two general approaches to demonstrate BADCT: $ Prescriptive BADCT criteria (provided the criteria have been developed and are included in this manual); or $ Individual BADCT criteria. Either approach has merit and may be applied to different facilities at a given site. Only one of the approaches can be applied to a specific facility. The following sections describe the general processes for developing a BADCT demonstration for a mining facility. How To Use This Manual The APP applicant should use this manual as guidance in developing BADCT for a mining facility for the purposes of fulfilling the application requirements in A.A.C. R18-9-A202(A)(5), and demonstrating compliance with A.R.S. 49-243.B.1. If any questions arise, do not hesitate to contact ADEQ Aquifer Protection Program. This manual will also be used by ADEQ personnel to review BADCT demonstrations and to draft permits. This guidance manual is subdivided into four parts, each containing several sections to assist the applicant in selecting the best route to determining BADCT. The General BADCT Information (4) INTRODUCTION____________________________________ described in Part 1 should be read first, because the principles discussed apply to whichever process the applicant chooses to comply with the BADCT requirements. After reading Part 1, and deciding which BADCT process to use, read Part 2 if you are using the Prescriptive BADCT process, or read Part 3 if you are using the Individual BADCT process. Part 1, Section 1.1, broadly discusses the two BADCT processes which are available to the applicant; namely, the APrescriptive@ and AIndividual@ processes. The APrescriptive@ process is a prescribed approach that utilizes pre-approved DCTs and design criteria to obtain an APP permit, largely independent of site specific conditions. It should not be confused with APresumptive@ BADCT (as defined in A.R.S. 49-243.01). Pursuant to A.R.S. 49-243.01.A, the Director may only establish Presumptive BADCT by rule. The AIndividual@ process, on the other hand, is performance based, and allows the applicant to select from all available DCTs that constitute BADCT. This process considers site specific characteristics, operational controls, and other DCTs. The AIndividual@ process allows designs to be tailored to a specific facility and site, and allows for the distinction between BADCT for new and existing facilities. Part 1, Section 1.2, describes how site, technical and economic considerations are applied, on an industry-wide basis, to a BADCT analysis for a specific facility, with discussions of waste types, process solution characteristics, water resource values, climatic conditions, site factors and passive containment. Such factors may affect the BADCT selection for a facility seeking an APP permit. Part 2 discusses how to select control technologies for the Prescriptive BADCT process that results in a conservative BADCT, largely independent of its site specific characteristics. Part 2 contains individual sections for the different types of mining facilities (e.g., heap leach pads, process solution ponds) for which Prescriptive BADCT criteria have been developed. These sections have been prepared in a stand-alone format, each intended for use in conjunction with Part 1. For example, if information is required for applying Prescriptive BADCT criteria to a heap leach pad, the necessary information is contained within Part 1 and Section 2.4, and the other sections in Part 2 do not need to be consulted. Prescriptive BADCT criteria have been developed for the following types of mining facilities: $ Non-Storm Water Ponds (Section 2.2) $ Process Solution Ponds (Section 2.3) $ Heap Leach Pads (Section 2.4) $ Tailing Impoundments (Section 2.5) Part 3 identifies the specific control strategies or designs that may be used for individual BADCT for new and existing facilities. Discharge control strategies are discussed in individual sections for each mine facility type (e.g., heap leach pads, tailing impoundments, etc.). These sections have also been prepared in a stand-alone format, each intended for use in conjunction with Part 1. For example, if information for applying individual BADCT to a heap leach pad is needed, the necessary information is contained within Part 1, and Section 3.2, and the other sections in Part 3 are not needed. This manual addresses individual BADCT development for the following types of mining facilities: ________________________________________________ INTRODUCTION (5) $ Heap Leach Pads (Section 3.2) $ Dump Leaching Facilities (Section 3.3) $ In Situ Leaching Facilities (Section 3.4) $ Tailing Impoundments (Section 3.5) $ Surface Ponds (Section 3.6) The fourth part of the manual is the appendices. These are intended as supplementary information in developing a BADCT demonstration. Appendix A (Comparison of Copper Leaching Facilities) discusses and compares the principal types of copper leaching methods practiced in the United States. Appendix B (Solution, Ore and Waste Characterization) provides guidance on the rationale and the extent of characterization required for solutions, ores and wastes. These requirements are dependent on the type of discharge being considered. Appendix B also discusses the various test methods available to the applicant (such as acid-base accounting, humidity cell tests and leach procedures). Appendix C (Liner Design Principles and Practice) presents details helpful to the applicant pertaining to liner system types, their design and maintenance for environmental protection. The customary and appropriate provisions for construction quality assurance/quality control required in a BADCT demonstration are discussed in Appendix D (Construction Quality Assurance and Quality Control). In Appendix E, (Engineering Design Guidance) the engineering design requirements including hydrologic and stability considerations are described as they may apply to any type of facility and especially as they relate to tailing impoundments. Finally, applicable federal, state and local permits and approvals are discussed in Appendix F (Federal, State and Local Environmental Permits). Facilities Requiring BADCT One of the fundamental assumptions utilized in developing this guidance manual is that an applicant has already determined that an APP is needed for the facility in question. The following facilities may be present at mining, processing, or smelting and refining operations and are considered, or deemed by A.R.S. 49-241.B, to be categorical discharging facilities requiring an APP, unless exempt pursuant to A.R.S. 49-250: $ Surface impoundments(2) including holding, storage settling, treatment or disposal pits, ponds and lagoons (A.R.S. 49-241.B.1); $ Solid waste disposal facilities except for mining overburden and wall rock that has not and will not be subject to mine leaching operations (A.R.S. 49-241.B.2); $ Injection wells (A.R.S. 49-241.B.3); $ Mine tailing piles and ponds(2) (A.R.S. 49-241.B.6); $ Mine leaching operations(2) (A.R.S. 49-241.B.7); $ Sewage or sludge ponds and wastewater treatment facilities (A.R.S. 49-241.B.11); $ Septic tank systems with a capacity of greater than two thousand gallons per day (A.R.S. 49-241.B.8); $ Facilities which add a pollutant to a salt dome formation, salt bed formation, dry well or underground cave or mine (A.R.S. 49-241.B.5); and $ Point source discharges to navigable waters (A.R.S. 49-241.B.10). (6) INTRODUCTION____________________________________ The APP and BADCT requirements apply to both new and existing mining operations. The designations Anew,@ Aexisting,@ and Aclosed@ are specifically defined in A.R.S. 49-201, as follows: $ New facilities began construction or entered into binding contracts after August 13, 1986. Facilities that have undergone major modifications after August 13, 1986 are also deemed new facilities. $ Existing facilities began construction or entered into binding contracts on or before August 13, 1986. Facilities which ceased operation after January 1, 1986 are also regarded as existing facilities; they must meet BADCT and other APP requirements, including notification to ADEQ of closure. Economic considerations are important to the BADCT process for existing facilities. $ Closed facilities are those which ceased operation before January 1, 1986 with no intent to resume operations for which they were intended. Closed facilities are exempt from the APP requirements; hence, they are not subject to BADCT requirements. Some mining facilities may qualify for the following specific exemptions: $ AMining overburden returned to the excavation site, including any common material which has been excavated and removed from the excavation site and has not been subjected to any chemical or leaching agent or process of any kind.@ (A.R.S. 49-250.B.5) $ ALeachate resulting from the direct, natural infiltration of precipitation through undisturbed regolith or bedrock if pollutants are not added to the leachate as a result of any material or activity placed or conducted by man on the ground surface.@ (A.R.S. 49-250.B.9) $ ASurface impoundments used solely to contain storm runoff, except for surface impoundments regulated by the federal clean water act.@ (A.R.S. 49-250.B.10) $ AClosed Facilities. However, if the facility ever resumes operation the facility shall obtain an aquifer protection permit and the facility shall be treated as a new facility for purposes of section 49-243.@ (A.R.S. 49-250.B.11) $ AStorage, treatment or disposal of inert material.@ (A.R.S. 49-250.B.20) $ AStructures designed and constructed not to discharge, which are built on an impermeable barrier that can be visually inspected for leakage.@ (A.R.S. 49- 250.B.21) $ APipelines and tanks designed, constructed, operated and regularly maintained so as not to discharge.@ (A.R.S. 49-250.B.22) $ Other miscellaneous facilities as referenced in A.A.C. R18-9-102 and 103. ________________________________________________ INTRODUCTION (7) Some mining facilities may qualify for a general permit. The APP rules contain 42 general permits which replace individual permits for several classes of facilities in major industry groups, including mining and other industrial operations. These general permits rely on clear technical standards to ensure that a discharging facility does not violate aquifer water quality standards and that the facility employs BADCT in its design, construction, operation and maintenance. There are four types of general permits (Types 1, 2, 3 and 4) for which facilities may qualify. Consult the following rules for the detailed technical requirements: A.A.C. R18-9- A301 through R18-9-A316 (General Provisions); R18-9-B301 (Type 1); R18-9-C301 through R18-9-C303 (Type 2); R18-9-D301 through R18-9-D307 (Type 3); and R18-9-E301 through R18-9-E323 (Type 4). And, some types of facilities are not required to obtain an APP because they are not considered a discharging facility under the APP program. A Adischarge@ is defined by A.R.S. 49-201.11 as: Athe addition of a pollutant from a facility either directly to an aquifer or to the land surface or the vadose zone in such a manner that there is a reasonable probability that the pollutant will reach an aquifer.@ Mining operations with activities that are neither categorical, exempt, or general permitted may be judged to be discharging in accordance with A.R.S. 49-241.A. All facilities that discharge are required to obtain an APP with BADCT incorporated into their design. If it is uncertain if a facility needs an APP, ADEQ can be requested, in accordance with A.A.C. R18-9-106, to determine the applicability of the APP program to the operation or activity. A non-refundable flat rate fee, in accordance with A.A.C. R18-14-102(C)(3), will be charged for each determination requested. ADEQ expects, however, that determinations of applicability will be rare. Applicants are urged to consult the APP rules first, because in almost all cases, the APP rules clarify whether coverage is required. In evaluating a determination of applicability, ADEQ may request that the waste be characterized. Appendix B, Solution, Ore and Waste Characterization, includes guidance that will be useful for this purpose. If the facility does not discharge, then the facility need not comply with the APP requirements and no further design or analysis is necessary. If the facility does discharge, the characterization will be used to properly design the facility to satisfy the BADCT requirements. The burden of proof lies with the applicant to show that the facility is not a discharging facility. PART I General BADCT Information _______________________________ GENERAL INFORMATION (1-1) PART 1 GENERAL BADCT INFORMATION 1.1 THE BADCT PROCESS When considering technologies, processes, operating methods and other alternatives for purposes of a BADCT design, a facility must be evaluated in terms of 1) siting; 2) design, construction, and operation; and 3) closure and post-closure. Part of the BADCT determination process involves deciding whether to use a “Prescriptive” approach or a site specific “Individual” approach for determining BADCT pursuant to A.R.S. 49-243.B.1. Both approaches have merit and either may be appropriate for the applicant’s facility. • The “Prescriptive” approach requires evaluating and selecting a predetermined discharge control technology as the BADCT design. This approach provides a simplified method for an APP applicant to propose BADCT that will be acceptable to the ADEQ. The prescriptive criteria provided in this manual are designed to be generally conservative, and to minimize the level of site investigation and engineering evaluations that the applicant will be responsible for completing. The Prescriptive BADCT criteria are based on the premise of minimizing any discharge beyond the engineered containment. Therefore, this approach cannot incorporate any natural discharge attenuation that may occur in the vadose zone below engineered containment systems. • The “Individual” approach allows the applicant to evaluate and compare alternatives (alternative discharge control systems) which combine site characteristics with demonstrated control technologies (DCTs) that can be applied to arrive at a BADCT design. This approach provides a method for an APP applicant to utilize a site specific BADCT design that can incorporate water quality protection characteristics that may occur due to the climate, vadose zone conditions beneath the facility, operational procedures, and other factors. While this approach allows the BADCT design to be optimized compared to the generally conservative Prescriptive BADCT criteria, the applicant should realize an increased effort will likely be required for site characterization, facility design, APP application review, etc. In the following sections, general processes for performing a BADCT evaluation for a facility are described. Both the Prescriptive and Individual BADCT approaches can be utilized for different facilities at a given site. For example, an applicant may elect to utilize Prescriptive BADCT for some site facilities such as ponds and Individual BADCT for other facilities such as heap leach pads or a tailing impoundment. Both the Prescriptive and Individual BADCT approaches are based on preventing, or minimizing to the extent practicable, the loading of pollutants to an aquifer. Attenuation of pollutant concentrations within the aquifer itself, the point of compliance for water quality standards and water quality monitoring, and other aspects related to discharge after it encounters the aquifer, are outside the scope of BADCT for most types of facilities. Figure 1-1 schematically illustrates the “zones” typically encompassed by Prescriptive and Individual BADCT designs. Exceptions occur where the aquifer may be part of the BADCT design in the cases of in-situ leaching and passive containment. (1-2) GENERAL INFORMATION ________________________________ _______________________________ GENERAL INFORMATION (1-3) 1.1.1 Prescriptive BADCT Prescriptive BADCT, which is an expedited approach to determining BADCT, allows the applicant to select specific demonstrated control technologies for certain facilities or facility types which ADEQ considers to comply with the BADCT requirements. The objective of this approach is to simplify and expedite the permitting of conventional facilities by minimizing required information gathering, information review, and negotiations, compared to the site specific Individual BADCT approach. The Prescriptive BADCT criteria are defined in Part 2 of this manual. The following facility types are eligible to utilize the Prescriptive approach: • Non-Storm Water Ponds; • Process Solution Ponds; • Heap Leach Pads; and • Tailing Impoundments. If the applicant demonstrates that the design, construction, technology, process, operating method or other elements meet the prescriptive criteria, or an engineering equivalent, and the application incorporates these prescriptive criteria, or equivalents, then the applicant will meet the requirements of A.R.S. 49-243.B.1. The use of Prescriptive BADCT in an APP application is typically more applicable to small and medium size mining operations, existing operations undergoing expansion, or existing operations intending to add facilities. 1.1.2 Prescriptive BADCT Review Process An application for an APP utilizing Prescriptive BADCT must include a proposal of what BADCT is at the facility. This proposal should meet the appropriate prescriptive design criteria for the facility described in Part 2 of this manual. An example Table of Contents for describing in the APP application how the design meets BADCT requirements is provided in Table 1-1. Shallow groundwater conditions, if present, must be documented for design considerations, and may prohibit the use of the Prescriptive BADCT approach. The presence of certain site specific geologic hazards may also prohibit the use of Prescriptive BADCT. When process facilities are intended to be located: 1) in areas known to be prone to excessive subsidence; 2) in the vicinity of active faults; 3) in landslide prone terrain, or 4) in other locations of known geologic instability, ADEQ may request that an application using Prescriptive BADCT include studies specific to the hazard(s) present, to assist in determination of whether or not Prescriptive BADCT is appropriately applied. Provided that the hazard(s) present will not have a significant potential to impact the effectiveness of the Prescriptive BADCT design, it will be considered appropriately applied. (1-4) GENERAL INFORMATION ________________________________ ADEQ’s review begins with an applicability check of the proposed design, and the following questions are considered: Does this facility qualify for a Prescriptive BADCT approach? Is the proposed design correctly chosen from the guidance manual and is it correctly applied? If ADEQ determines that any of the answers are no, the applicant will be notified of the need to make the appropriate corrections, and resubmit the application. Depending on the degree of deficiency, this notification and re-submittal process will vary in the degree of formality but in all cases any final determination must be documented in ADEQ’s files. _______________________________ GENERAL INFORMATION (1-5) TABLE 1-1 Example Table of Contents - Prescriptive BADCT Demonstration(1) 1. Introduction 2. Site Criteria 2.1 Relevant Site Characteristics 2.2 Surface Water Controls 2.3 Geologic Hazards 3. Design Construction and Operational Criteria 3.1 Relevant Solution/Effluent Characteristics 3.2 Storage Components 3.3 Site Preparation 3.4 Liner System Specifications 3.5 Stability Considerations 3.6 Facility Operation and Monitoring 4. Relevant Facility Inspection Criteria 5. Relevant Closure and Post-Closure Criteria Example Appendices: • Solution, Ore and Waste Characterization Data • Groundwater Data • Geologic Hazards Evaluation • Geotechnical Data • Surface Water Evaluations • Construction Procedures and QA/QC • Slope Stability Evaluations • Water Balance and Storage Capacity Evaluations • Equivalent Engineering Evaluations (1) All applicable sections should clearly state the manner in which Prescriptive BADCT criteria are satisfied by the proposed design. (1-6) GENERAL INFORMATION ________________________________ If the APP application and supporting documentation show that the prescriptive criteria are met and appropriately applied, BADCT demonstration in accordance with A.R.S. 49-243.B.1 and the APP application requirement of A.A.C. R18-9-A202(A)(5) are deemed satisfied. ADEQ then proceeds with the processing of the permit application, unless new information warrants an additional applicability check. This processing includes a determination of completeness for other parts of the APP application that are not part of BADCT, such as whether or not applicable water quality standards (AWQS) will be met at the Point of Compliance, and the technical and financial capability of the applicant. 1.1.2.1 Determination of Prescriptive BADCT The determination of BADCT using prescriptive criteria for an APP application is based on meeting the prescribed design, construction, and operating criteria defined in Part 2 of this manual, or where applicable, by rule (A.R.S. 49-243.01). Since the objective of the Prescriptive BADCT determination is to simplify and expedite the BADCT review process and therefore the APP process, the prescriptive criteria are designed to be generally conservative for most site conditions in order to minimize the need for collection and evaluation of site specific data. Some site evaluations, however, are still required to provide enough information for determination that the Prescriptive BADCT is appropriate. As discussed further in Part 2, these include evaluations of key issues related to site conditions such as identification of flood plains and geologic hazards. While the Prescriptive BADCT criteria, in part, include specific design criteria for many of the BADCT elements, engineering equivalents to specific elements are also acceptable. Examples of engineering equivalents, and supporting information that may be required by ADEQ for each, are provided in Part 2 (Table 2-1). The ADEQ may require specific supporting evaluations to demonstrate that the proposed element is at least as protective as the specific Prescriptive BADCT element it replaces. Engineering equivalents cannot rely on seepage attenuation or other geologic properties of the vadose zone as part of minimizing aquifer loading. 1.1.3 Individual BADCT Review Process For New Facilities When submitting an individual application for an APP, an applicant must include a proposed BADCT design to be used at the facility. A.A.C. R18-9-A202(A)(5) requires that the applicant submit, in support of the proposed BADCT, a statement of the technology which will be employed to meet the requirements of A.R.S. 49-243.B.1. This statement shall describe alternative discharge control measures considered, the technical and economic advantages and disadvantages of each alternative, and the justification for selection or rejection of each alternative. The applicant shall evaluate each alternative discharge control technology, relative to the amount of discharge reduction achievable, site specific hydrologic and geologic characteristics, other environmental impacts, and water conservation or augmentation considerations. The economic impact of implementation of Individual BADCT design is further discussed in Section 1.1.3.7. _______________________________ GENERAL INFORMATION (1-7) The development of an Individual BADCT design follows the general principles of engineering design. Engineering principles are adhered to during the design process involving the designer’s professional judgment of contingencies, risks and uncertainties based on education and experience. It is therefore only possible to provide general guidance for the process to be followed. Important aspects of developing an Individual BADCT design are: • Discharge control technologies ordinarily constitute a discharge control system incorporating engineering features, operational measures and site characteristics to achieve BADCT; and, • Alternative designs must be considered to arrive at a BADCT design. Discharge control technologies are those design elements which can be included to reduce loading (discharge of pollutants) to an aquifer (e.g., design aspects such as liners, operational aspects such as desaturated tailing disposal for small projects, and closure aspects such as rinsing gold and silver ore residue on heap leach pads after leaching is completed). Alternative designs can include consideration of alternative technologies or alternative design elements as discussed below, and in some cases, alternative sites. In principle, an Individual BADCT design is developed through the following approach: • Development of a range of alternative discharge control systems which may or may not include different sites on a conceptual basis; • Screening these alternative systems by estimating the relative degree of discharge control; • Selection of the most promising alternative systems for more detailed analysis; • Refinement of designs for the selected alternative systems; • Comprehensive estimates of discharge control for the selected alternative systems; and, • Selection of BADCT design. In conducting these analyses, the following steps are required: • Site selection; • Development of individual site design (“Reference Design”) based on demonstrated control technologies and site conditions; • Estimation of aquifer loading for the Reference Design; • Alternative design(s) selection as outlined above; • Estimation of aquifer loading for the promising alternative design(s); and, • Selection of BADCT design. Figure 1-2 provides a schematic representation of the process. Each of the steps are described below. An example Table of Contents for describing in the APP application how the design meets Individual BADCT requirements is provided in Table 1-2. (1-8) GENERAL INFORMATION ________________________________ 1.1.3.1 Site Selection Site selection is a powerful tool in developing a protective design. It is sometimes possible to select a site with outstanding characteristics which will enhance the containment of stored materials. Maximum advantage should be taken of site selection in development of a BADCT design. Site selection can be conducted by the applicant in a formal or informal manner. The formal process will typically consider sites in areas surrounding the mine and the preferred site will be selected through a process of fatal flaw screening, site evaluation and ranking, and in some cases, also limited site investigations and final ranking. Informal site selection is often necessary because of limited availability of suitable sites in the vicinity of the ore body. _______________________________ GENERAL INFORMATION (1-9) TABLE 1-2 Example Table of Contents - Individual BADCT Demonstration(1) 1. Introduction 2. Relevant Site Factors 2.1 Solution, Ore and Waste Characteristics 2.2 Site Characteristics 2.2.1 Surface Hydrology 2.2.2 Hydrogeology 2.2.3 Geologic Hazards 3. Site Selection 3.1 Alternatives 3.2 Evaluation of Alternatives 3.3 Recommended Site 4. Reference Design 4.1 Design 4.2 Construction Considerations 4.3 Operations and Operational Monitoring 4.4 Closure and Post-Closure Considerations 4.5 Estimated Aquifer Loading 4.5.1 Potential Release 4.5.2 Estimated Travel Times to Groundwater Table 4.5.3 Estimated Attenuation of Pollutants 4.5.4 Estimated Aquifer Load 4.6 Estimated Cost of Reference Design 5. Alternative Designs 5.1 Selection of Alternatives 5.2 Screening of Alternatives 5.3 Description of Most Promising Alternative Systems 5.4 Aquifer Loading of Most Promising Alternative Systems 5.5 Estimated Cost of Most Promising Alternative Systems 6. Selection of BADCT Design 6.1 Selection Criteria 6.2 Evaluation of Reference Design and Alternative Systems 6.3 Selected BADCT Design Example Appendices: • Solution Ore and Waste Characterization Data • Groundwater Data • Geologic Hazards Evaluation (1) All applicable sections should clearly state the manner in which Individual BADCT requirements are satisfied by the proposed BADCT design. (1-10) GENERAL INFORMATION ________________________________ • Geotechnical Data • Surface Water Evaluations • Construction Procedures and QA/QC • Slope Stability Evaluations • Water Balance and Storage Capacity Evaluations _______________________________ GENERAL INFORMATION (1-11) The design documents submitted for APP permitting must describe the site selection process. It is the applicant’s responsibility to develop this information; ADEQ can only give guidance in this regard. 1.1.3.2 Development of Reference Design The development of an individual site design must consider: 1) industry-wide DCTs taking into account differences in industry sectors; 2) the type and size of the operation; 3) the reasonableness of applying controls considering the site climatic conditions; and 4) other site specific conditions. In developing this design, a systems approach should be used. This systems approach should consider all phases of the project including: • Site characterization; • Design, construction and operations; and • Closure and post-closure. The demonstrated control technologies for various facilities are described further in Part 3 of this manual. Table 1-3 provides a “menu” of typical DCTs for each of the above phases. A Reference Design will typically include DCTs selected from the Table 1-3 menu. For example, in developing a Reference Design, site specific DCTs will be included such as selection of a site with low permeability geologic formations, specific design elements such as single synthetic liners, specific operational technologies such as maintaining the low hydraulic head on a leach pad, specific operational monitoring proposals such as regular inspections by the facility operator, and specific closure and post-closure technologies such as bacterial rinsing for a gold heap leach pad. In considering the systems approach to development of a Reference Design it is important to include site characteristics. While it may be important to select a high level of engineered containment for sites underlain by alluvium and shallow groundwater, the same may not be the case when the site is underlain by low permeability bedrock and/or deep groundwater (i.e., a demonstrated geologic barrier). The individual designer will include these considerations in the systems design based on experience as well as industry wide demonstrated control technologies which have been applied for similar site conditions. In developing an individual site design the designer must therefore be encouraged to use creativity to provide the greatest degree of discharge reduction achievable through application of DCTs and, where practicable, an approach permitting no discharge of pollutants. 1.1.3.3 Estimation of Aquifer Loading An evaluation must next be performed to estimate the potential loading of pollutants to the aquifer as a result of implementing the Reference Design. Loading to the aquifer is used as a basis for evaluating the impacts of discharge from a facility. This evaluation can be done at (1-12) GENERAL INFORMATION ________________________________ various levels of sophistication but at a minimum must include the steps outlined below. It is important that this evaluation should consider the total life cycle of the facility (i.e., operations as well as closure/post-closure). For example, during operations a slurry deposited tailing impoundment will contain free water. After closure and during the post-closure period, this free water may be removed and therefore the driving head for pollutant migration will be eliminated. _______________________________ GENERAL INFORMATION (1-13) Page 1 of 4 TABLE 1-3 Examples of Demonstrated Control Technologies Project Phase Element Demonstrated Control Technologies (DCT) Evaluation Procedures to be Selected From Site Characterization Solution, Ore and Waste Characterization 1) These characterizations are required to determine the DCTs for other elements. 1) Procedures to differentiate between oxide and sulfide materials. 2) 1312 Leach Procedure. 3) Meteoric Water Mobility. 4) Acid Base Accounting. 5) Humidity Cell Tests. Geotechnical, Surface Hydrology, Hydrogeologic, and Geologic Hazards Characterizations 1) Siting DCT incorporates selection of locations with: • Low permeability geologic formation • Deep groundwater tables • Naturally poor groundwater quality • Small contributory watershed. 2) Selection of sites which avoid or mitigate geologic hazards. 3) These characterizations are required to determine the DCTs for other elements. 1) Test pitting, drilling, trenching, sampling and testing. 2) In-situ tests of, for example, hydraulic conductivity. 3) Geophysical methods. 4) Water level monitoring. 5) Remote sensing methods. 6) Aerial photography mapping and interpretation. 7) Site reconnaissance. 8) Other standard hydrologic and geotechnical field investigation and data evaluation methods. Site Preparation 1) Strip vegetation. 2) Excavate and replace weak foundation materials. 1) Standard construction QA/QC methods. Design, Construction, and Operations Surface Water Control 1) Diversion ditches. 2) Retention structures. 1) Standard hydrologic design methods. (1-14) GENERAL INFORMATION ________________________________ Examples of Demonstrated Control Technologies Project Phase Element Demonstrated Control Technologies (DCT) Evaluation Procedures to be Selected From Discharge Control 1) DCTs for discharge control vary significantly depending on the type and size of the operation and the reasonableness of applying controls in arid or semi-arid settings, but may include: • Liners for containment. • Natural containment. • Leachate collection and hydrostatic head control systems consisting of: - Manufactured or imported drain rock and perforated pipes. - Ore materials satisfying drainage requirements. - Granular or synthetic leak collection layers for pond liner systems. • Solution conveyance pipes or lined channels and storage capacity. 1) Systems approach to liner system design (Appendix C). 2) Standard engineering measures for surface containment. Stability 1) Specified ultimate slope height. 2) Stability benches. 3) Design to withstand shear forces, e.g., by compaction, use of geosynthetics, etc. 4) Control of pore pressures by drainage. 5) Buttressing. 1) Shear strength analysis. 2) Static stability analysis. 3) Seismic deformation analyses. _______________________________ GENERAL INFORMATION (1-15) Examples of Demonstrated Control Technologies Project Phase Element Demonstrated Control Technologies (DCT) Evaluation Procedures to be Selected From Operations 1) Conduct operations to minimize potential for damage to liners at heap leach sites: • • Geosynthetic and/or gravel protective layers. • • Low ground pressure equipment. • • Limit equipment traffic. • • Load in uphill direction. • • Limit rate of rise. • • Limit maximum height. 2) Control solution applications at heap leach sites: • • Avoid excessive reagent concentrations. • • Avoid application rates or storage conditions that result in excessive hydraulic head. • Sequence leaching activities. 3) Managed tailing deposition: • • Layered or subareal deposition. • • Limit size of water pond. 4) Operational monitoring to allow early detection and correction of problems. 5) Facility maintenance to assure performance is consistent with the design. 1) Consider operational conditions during design of facility. 2) Visual observations. 3) Survey monuments. 4) Instrumentation. Closure and Post-Closure Physical Stability 1) Surface Water Control to reduce erosion. 2) Recontouring to control surface flow. 3) Cover placement (e.g., vegetation or rock armor) to reduce erosion. 4) Erosion protection of ditches. 1) Stability evaluations. 2) Long-term erosion evaluations. (1-16) GENERAL INFORMATION ________________________________ Examples of Demonstrated Control Technologies Project Phase Element Demonstrated Control Technologies (DCT) Evaluation Procedures to be Selected From Chemical Stability 1) Source control: • • Ore residue rinsing and/or detoxification. • • Ore residue removal. 2) Migration control: • • Surface grading to enhance run-off. • • Surface grading to minimize run-on. • • Design cover to minimize infiltration and enhance moisture removal (e.g., increased evapo-transpiration by fine-grained soils and/or vegetation). • • Cap with low permeability cover. 3) Interception (e.g., using shallow trenches; cutoff walls) and water treatment. 1) Column leach tests. 2) Fate and transport evaluations. 3) Cover water balance evaluations. _______________________________ GENERAL INFORMATION (1-17) The steps which should be followed to estimate aquifer loading for the total life cycle of the facility are as follows: • Estimate the potential release from the facility by using empirical equations or other appropriate approximate methods. • Estimate the travel time to the water table beneath the facility by vertical migration using groundwater flow calculation methods such as described in Appendix C of Hutchison and Ellison (1992). • Estimate attenuation of pollutants in the foundation based on published values or laboratory test results. • Estimate the load added to the aquifer of constituents that have the potential to impact water quality, particularly those for which there are water quality standards. The purpose of the load estimation to the aquifer is to provide a consistent method to compare the potential impacts of various designs. It is therefore not intended that this evaluation should turn into a research project or an advancement of the state-of-the-art. However, consistent and realistic approaches should be followed. 1.1.3.4 Alternative Design(s) Selection Alternative design(s) should next be developed and can include the evaluation of alternative control technologies or design elements for each applicable type of facility (Part 3 summarizes various demonstrated control technologies for different types of facilities) or, as may be appropriate, the evaluation of alternative sites. The selection of the alternative design(s) should be based on the systems approach where control technologies as well as realistic site conditions are considered. 1.1.3.5 Estimation of Aquifer Loading for Alternative Design(s) Estimating the aquifer loading for the alternative design(s) follows the same approach as described above for estimation of aquifer loading for the Reference Design. By following the same procedures, comparative aquifer loadings from the Reference Design as well as the alternative design(s) can be developed. 1.1.3.6 Selection of BADCT Design The final step in developing an individual BADCT design is to make a selection from the Reference Design and the alternative design(s). The basis for this selection is loading to the aquifer. The BADCT design will be that design which results in the least amount of pollutant loading (discharge) to the aquifer. For example if an alternative design results in a lower pollutant loading to the aquifer, then that design will be selected as the BADCT design instead of the Reference Design. In cases where the Reference Design and/or the alternative design result in similar loadings to the aquifer, and discharges do not contain materials listed in A.R.S. 49-243.I, the design with the (1-18) GENERAL INFORMATION ________________________________ lowest costs (i.e., capital, operations, closure, post-closure and other applicable costs) may be selected as the BADCT design. In such cases, negligible loadings can be considered similar even if the relative difference between loadings is significant (e.g., where loadings from alternatives are small compared to the highest loading that could still comply with aquifer water quality standards, the fact that the loading from one alternative may be up to orders of magnitude smaller may not preclude these loadings from being considered similar). If the discharge contains materials listed in A.R.S. 49-243.I, the applicant must limit discharges to the maximum extent practicable regardless of cost. The BADCT design is therefore selected based on DCTs, a systems approach including site conditions, and the estimation of aquifer loadings for alternative designs. The requirement for this individual BADCT evaluation process to be demonstrated in APP applications is described in regulation as follows (A.A.C. R18-9-A202(A)(5)): “The applicant shall submit in support of the proposed BADCT a statement of the technology which will be employed to meet the requirements of A.R.S. 49-243.B. This statement shall describe the alternative discharge control measures considered, the technical and economic advantages and disadvantages of each alternative, and the justification for selection or rejection of each alternative. The application shall evaluate each alternative discharge control technology, relative to the amount of discharge reduction achievable, site specific hydrologic and geologic characteristics, other environmental impacts, and water conservation or augmentation. The economic impact of implementation of each alternative control technology shall be evaluated on an industry-wide basis. In addition, a statement for a facility in existence on the effective date of this Article shall reflect consideration of the factors listed in A.R.S. 49-243.B.1(a) through (h).” A.R.S. 49-243B.1(a) through (h) includes the following: (a) “Toxicity, concentrations and quantities of discharge likely to reach an aquifer from various types of control technologies. (b) The total costs of the application of the technology in relation to the discharge reduction to be achieved from such application. (c) The age of equipment and facilities involved. (d) The industrial and control process employed. (e) The engineering aspects of the application of various types of control techniques. (f) Process changes. (g) Non-water quality environmental impacts. (h) The extent to which water available for beneficial uses will be conserved by a particular type of control technology.” As discussed in Section 1.1.2, the BADCT demonstration portion of the application can be deemed complete, and A.A.C. R18-9-A202(A)(5) deemed satisfied without this evaluation where facilities utilize Prescriptive BADCT. 1.1.3.7 Economic Considerations In regard to new facilities, A.R.S. 49-243.B.1. directs ADEQ to consider economic impacts of the application of BADCT with other factors on an industry-wide basis. The determination of economic impact on an industry-wide basis shall take into account differences in industry sectors _______________________________ GENERAL INFORMATION (1-19) (i.e., Copper Sector, Gold Sector, Uranium Sector, etc.), the facility type (i.e., heap leaching, dump leaching, in-situ, copper oxide leaching, copper sulfide leaching, etc.), the size of the operation, and the reasonableness of applying controls in an arid or semi-arid setting (gold mining in Northern California vs. gold mining in Arizona, copper mining in Michigan vs. copper mining in Arizona, etc.). ADEQ considers that use of a technology at many other similar facilities in the same industry sector, same type and size, and in the same climatic setting indicates financial feasibility. As indicated above, if a new facility discharges the pollutants identified in A.R.S 49-243.I, then that facility must meet the criteria of A.R.S. 49-243.B.1 (BADCT) to limit discharges to the maximum extent practicable regardless of cost. 1.1.3.8 Discussion It may be beneficial from a design point of view to include elements which are innovative and therefore may not satisfy the requirement of an industry-wide DCT. In this case, the designer must demonstrate that such technologies will perform as intended. Such demonstration can be based on literature reviews, engineering analyses, laboratory and pilot scale testing, or by providing case histories of analogous applications of the technology. 1.1.4 Individual BADCT Review Process for Existing Facilities An existing facility is defined in A.R.S. 49-201.14. as one that is neither a new or closed facility and at which construction began before August 13, 1986. According to A.R.S. 49-201.18, a closed facility that is reopened does not constitute an existing facility, but is regarded as a new facility. The distinction between existing and new facilities is important in determining BADCT for the following two basic reasons: 1) At an existing facility, determining BADCT requires ADEQ and the applicant to consider potential upgrades to the facility design, and 2) Additional factors for existing facilities apply as listed in A.R.S. 49-243.B.1(a) through (h), such as, weighing cost vs. discharge reduction, the age of equipment, and the engineering aspects of the application of various types of industrial and control processes. Also, the requirement of A.R.S. 49-243.I that a new facility limit discharges of certain listed organic pollutants to the maximum extent practicable regardless of cost does not apply to existing facilities. Note that the option of Prescriptive BADCT also applies to an existing facility. If the facility meets the prescriptive criteria identified for the specific type of facility in Part 2, no further demonstration is necessary. Most existing facilities, however, warrant the individual evaluation process. There are two major differences in approach mandated for determining BADCT for an existing facility, compared to that for a new facility. First, existing design and site conditions offer constraints on what can be achieved with the final BADCT configuration. Second, analysis of cost vs. discharge reduction applies in determining BADCT. To arrive at a BADCT, the existing design and its performance become the basis of comparison for judgments about whether or not to upgrade the design. Possible upgrades must, of course, be limited to those that are feasible from an engineering standpoint given the age, design, and operational controls of the facility. (1-20) GENERAL INFORMATION ________________________________ Complicating matters at an existing facility may be the groundwater impact of past operations. While remedial or mitigative efforts may be needed in areas where groundwater quality does not conform to Aquifer Water Quality Standards downgradient of a facility (see A.R.S. 49-243.L), these activities do not constitute part of BADCT for the facility. The reason for this distinction is that BADCT does not include actions or design features which affect groundwater after pollutants have been released into it, since discharge has already occurred in those instances. Thus, while existing groundwater quality may be an indicator of the performance of the current design, remedial or mitigative technologies do not reduce discharge and should not be considered in the BADCT evaluation. There are five basic steps in the existing facility process. Similar to the new facility process outlined previously, the applicant develops a Reference Design. However, here, the existing configuration of a facility and site represents its Reference Design. Alternatives to the Reference Design are then developed and evaluated as outlined by the following five basic steps: Step 1 Identify current DCTs and site factors; Step 2 Estimate performance (determine aquifer loading); Step 3 Identify technically feasible alternative DCTs and assemble them on a candidate list. Consider water conservation and other environmental factors to reduce or adjust the list; Step 4 Use the candidate list to arrive at one or more alternative systems; Step 5 Weigh cost vs. discharge reduction for each alternative system to arrive at BADCT: - Calculate improvements in aquifer loading expected from one or more alternative systems with new DCTs, and - Determine costs to implement alternative system(s). 1.1.4.1 Steps 1 & 2: Identifying Current Discharge Controls and Assessing Their Performance - The Reference Design As with new facilities, BADCT determination for existing facilities depends on an adequate characterization of the discharge quantity and type. To establish the Reference Design for an existing facility, the applicant should inventory the discharge controls used in the facility’s current design. The control processes and technologies can be identified according to the design elements and site characteristics described in Part 3. Discharge control technologies to consider include process solution controls in conjunction with: solution, ore and waste characterization; site preparation; surface water controls; liners; leachate collection systems; stability design; operational monitoring; closure/post-closure; and site factors. Where original design plans are lacking, the applicant should develop as-built design information for those aspects of the facility which have some bearing on discharge rates and characteristics. To save time and effort, and to promote efficiency, the applicant is encouraged to discuss the level of detail needed with ADEQ prior to developing as-built drawings. Once existing control processes are identified, the applicant should evaluate the overall discharge control performance of the facility. As for the approach for new facilities, the applicant may assess site factors and their performance for pollutant reduction in the manner presented in Section 1.2. Where practicable, this step should involve direct measurement of discharge quantity and quality. Otherwise, the applicant may calculate expected performance based on _______________________________ GENERAL INFORMATION (1-21) industry standards for the engineered controls, test data for components, and site specific characteristics determined from field or laboratory testing. Aquifer loading from the facility for the existing configuration can be estimated by the same methods used in Section 1.1.3. This aquifer loading analysis constitutes the performance of the Reference Design. 1.1.4.2 Step 3: Identifying Technically Feasible DCTs for Improvement The BADCT design for an existing facility may involve instituting additional control technologies to those in current use. This step in the process involves developing a list of alternative DCTs that are technically feasible for application at the facility. In many situations, new controls may not be feasible. For instance, adding a liner to an existing dump leach system is beyond the realm of normal mine design and operation. In such cases an applicant should consider other design elements or operational controls discussed below to achieve discharge reduction. Working with only technically feasible technologies, the applicant should assemble a focused, yet complete, list of candidate DCTs for improvement of the existing facility. Ideas for candidate DCTs may be gained from reviewing the lists of DCTs presented in Part 3. However, many DCTs identified in Part 3 may not work as “retrofitted technologies.” The following are types of DCTs which are often easily implemented and may, depending on the facility design and site, offer considerable improvement in facility performance to control discharge: • Operational controls - physical and chemical (This includes physical controls such as modifying solution application cycles and the amount of solution inventory in the heap or pond storage, and chemical controls such as altering the reagents or reagent dose rates); • Run-on and other storm water management controls; • Closure elements such as removal of free liquids, grading, covering, etc.; • Containment systems for process solution and other potential pollutant sources; and • Stability improvements by, for example, berming, benching or regrading. Aside from technical feasibility, certain other factors may disqualify particular DCTs from making the candidate list. Water conservation may be a factor for deciding whether or not a change in discharge control technology is favorable. Simple dilution of a pollutant to achieve lower discharge concentrations, in itself, may not meet BADCT, nor will technologies that consume or alter the quality of large quantities of water. However, there may be extenuating circumstances in which dilution is desirable, such as to facilitate beneficial use of the water or achieve an environment which could enhance natural treatment. The applicant should also consider other environmental factors. The use of a new discharge control technology at an existing facility may have environmental impacts that are not directly related to aquifer water quality. An example of such a technology is air stripping to remove volatile organic substances from water and mobilize them in air. These environmental tradeoffs must be assessed on a case-by-case basis, and judgments about whether they outweigh discharge reduction are likely to be subjective. Some other common environmental factors that may require consideration are air quality, noise levels, land use, aesthetics, environmentally sensitive areas, endangered species, and the potential for disease transmission. (1-22) GENERAL INFORMATION ________________________________ 1.1.4.3 Step 4: Use Candidate List to Arrive at One or More Alternative Discharge Control Systems The selection of alternative design(s) should be based on a systems approach where technologies, as well as site conditions, are considered. The list of alternative DCTs should be used to identify components that may be incorporated alone or in combination in the existing reference design to arrive at the alternative design(s). This step in the process involves considerable professional judgment and the justification for the selected DCTs may require formal exchange of data, and discussion and negotiation between the applicant and ADEQ, depending upon how obvious the available choices are. 1.1.4.4 Step 5: Weigh Cost vs. Discharge Reduction by Calculating Aquifer Loading for Alternative System(s) and Calculating Cost for New DCTs After selecting alternative design(s) in Step 4, an applicant should prepare additional aquifer loading calculation(s) using the same considerations as for the Reference Design. Where additional DCTs are used, their contribution to discharge reduction should be factored into the aquifer loading calculation(s). Where new DCTs are substituted for existing ones, the estimated performance of the new DCT should be used in the calculation. The aquifer loading(s) of the alternative system(s) need to be compared to the Reference Design. For cost evaluations, the applicant shall compare the total cost/benefit of the application of the technology with the discharge reduction to be achieved from such application, as noted in A.R.S. 49-243.B.1(b). When calculating the total cost/benefit, the applicant may apply acceptable discounting methods used for other accounting purposes within the industry. 1.2 USING SITE CHARACTERISTICS AS A PART OF THE BADCT DESIGN This section, together with Appendix B (Solution, Ore and Waste Characterization), describes site, technical and economic considerations, on an industry-wide basis, applicable to BADCT analysis for a specific facility. It includes discussions on waste types and process solution characteristics, water resource values, climatic conditions, site factors, and passive containment. Such factors may affect the BADCT selection for a facility seeking an Individual APP. 1.2.1 Waste Types and Process Solution Characteristics A.A.C. R18-9-A202(A)(4) requires that a person applying for an APP provide a summary of the known past facility discharge activities and the proposed facility discharge activities indicating: • The chemical, physical and biological characteristics of the discharge; • The rates, volumes, and the frequency of the discharge for each facility; and • The location of the discharge. All applications should include the characterizations necessary to satisfy the requirements described above. In some cases (e.g., new facilities), the applicant may not be able to adequately define the characteristics of the material to be discharged until the facility becomes operational. _______________________________ GENERAL INFORMATION (1-23) In such cases, the applicant must design the facility to be compatible with the characteristics of discharge from similar types of mining facilities. Then, upon start-up, the applicant shall be required to characterize the discharge. However, a discharge containing organic substances referenced in A.R.S. 49-243.I must be identified and characterized in order to design the facility to meet BADCT regardless of cost. ADEQ will use this information to determine if the proposed facility BADCT is compatible with the materials to be contained in the facility. This need for compatibility between the DCT and the waste characteristics is one of the reasons that detailed design specifications for liners and other elements cannot be uniformly prescribed in this manual. The characterization information will also be used to evaluate the quality and quantity of the discharge. In characterizing waste, ore or process solutions that may be discharged, the applicant must define the waste type or mix of types (solutions, wastewater, sludges, tailing, leached ore, waste rock, etc.) including the projected or actual leachate composition that will discharge. Discharges that are not identified will not be incorporated into the permit and will be subject to compliance actions under APP regulations. ADEQ should be contacted to review the required type and frequency of characterization for all materials at the facility. While waste characterization may be appropriate in the case of waste rock or spent ore from a precious metal leach operation, it is not clear that such characterization is beneficial for copper leach ore. In acidic copper leach solutions, high acidity and metals concentrations will be produced (for both oxide and sulfide leach operations) throughout the period of operation, as well as after operations. In the case of a sulfide leach project, it is difficult to predict how long it will take to eliminate all the potential for metal and acid leachate because of the ongoing bacterial action. As a result, characterization of materials to be leached with acidic solutions may be deferred until closure of the leach facility. Proposals for deferring material characterization should be presented to ADEQ during the pre-application period. Below is a tiered list of tests commonly used to characterize materials that may discharge. Other tests may also be proposed by the applicant or required by ADEQ. When characterizing tailing or waste rock that may discharge, or “produce” a leachate that may discharge, the applicant should conduct the appropriate tests listed in Tier #1 (Part A) with additional testing from Tier #2 (Part A) and Part B as necessary to adequately characterize the material. Similarly, if process solutions or waste waters may be discharged, then the applicant should submit the information requested in Part C below. Where necessary, the ore may be characterized in order to assist in characterizing the potential discharge. Further guidance on waste characterization testing is provided in Appendix B. Pre-application coordination with ADEQ is strongly encouraged to finalize characterization testing requirements. (1-24) GENERAL INFORMATION ________________________________ PART A: CHARACTERIZATION OF TAILING, SPENT ORE AND WASTE ROCK TIER #1 Primary Analytical Procedures For Waste Characterization • Description of mineralogy and lithology of the waste and leached ore; • Leach Testing (Leach testing should be performed on all materials which may discharge in order to determine the quality of leachate that may be formed.) Types of leach testing include: - SPLP (Synthetic Precipitation Leaching Potential EPA Method 1312), - Nevada Meteoric Water Mobility Procedure, - Leachable sulfates and soluble solids, - Bottle Roll Tests. • Acid Base Accounting (ABA): - Predictive Static Tests. • Physical Characteristic Tests: - Grain Size Analysis, - Density, - Shear Strength. TIER #2 Miscellaneous Analytical Procedures For Additional Waste Characterization • Predictive Kinetic Tests for prediction and acid generating characteristics; • Analysis of Metals (Total and/or Soluble); • Analysis of Radionuclides; • TCLP; • Miscellaneous Physical Analyses (e.g., Hydraulic Conductivity, Moisture Retention Capacity). _______________________________ GENERAL INFORMATION (1-25) PART B: CHARACTERIZATION OF ORGANIC WASTES OR WASTES CONTAINING ORGANICS • Organic Analyses: - Total Petroleum Hydrocarbons, - Polynuclear Aromatic Hydrocarbons, - Phenol Analyses, - Volatile Organic Compounds and Carbon Disulfide. • Hazardous waste determination testing for wastes not exempted by the Resource Conservation and Recovery Act (RCRA), where applicable. PART C: CHARACTERIZATION OF PROCESS SOLUTIONS, WASTEWATERS AND MINE WATERS • Metals; • Major Cations and Anions; • Physical/Indicator Parameters; • Reagents and Organics; • Radiochemicals; • Cyanide Species; • Nutrients and Bacteria; • Miscellaneous; and, 1.2.2 Water Resource Values As discussed in previous sections, the BADCT determination process is driven by A.R.S. 49-243.B.1 and A.A.C. R18-9-A202(A)(5) The BADCT for a site includes those components of facility siting, design, construction, operation and closure/post-closure that limit discharge to an aquifer. Dilution, attenuation, and other factors that effect discharges after reaching an aquifer are not part of BADCT. Demonstrations related to water quality at the point of compliance pursuant to A.R.S. 49-243.B.2 and B.3 are separate and in addition to BADCT, and are not covered in this manual. Water resource considerations that play a role in BADCT determination are: (1) site surface water flow characteristics that can effect containment and migration of discharges through the vadose zone (e.g., surface water run-on and run-off); and (2) potential opportunities for water conservation or augmentation. The surface water hydrology aspects are discussed further in Section 1.2.4.4. This section provides the objectives and background to the water resource conservation considerations. (1-26) GENERAL INFORMATION ________________________________ A.R.S. 243.B.1 states, in part: “In determining best available demonstrated control technology, processes, operating methods or other alternatives the director shall take into account ... the opportunity for water conservation or augmentation ... .” A.A.C. R18-9-A202(A)(5)(b) states that an applicant shall submit, “An evaluation of each alternative discharge control technology, relative to the amount of discharge reduction achievable, site specific hydrologic and geologic characteristics, other environmental impacts, and water conservation or augmentation.” Because mining generally necessitates the use of large quantities of water, conservation plays a major role in the BADCT design. Water conservation is based on the efficient use of the available water and recycling of water used in processing. Recycling of process water should be maximized in the BADCT design. Pumped mine water should be beneficially used wherever possible. 1.2.3 Climatic Conditions Precipitation rates and evaporation rates (a function of temperature, humidity, and wind) are the two primary climatic factors. An applicant wanting to make a demonstration that climatic factors can reduce potential for discharge should evaluate precipitation and evaporation rates in conjunction with other site characteristics. In areas where precipitation rates are high and evaporation rates are low, there is a higher potential for discharge to impact groundwater. This is because precipitation that does not evaporate or run off, infiltrates into and then percolates through the mine waste. This infiltration may be a major transporter of pollutants to the aquifer where no engineered containment is provided. Generally in these conditions, percolation and subsequent leachate formation are important and must be accommodated in the design of the facility by incorporating leachate collection and containment features. Conversely, in arid and semi-arid environments, where precipitation is low and/or evaporation is high, the potential for surface discharge to impact groundwater is reduced. It is the applicant’s responsibility to demonstrate what impacts, if any, climatic conditions will have on the containment provided by the facility. When analyzing the effects and/or discharge reduction capabilities of climatic factors on a facility design, it is important that the applicant understands and considers the following site-specific conditions: • Precipitation and evaporation rates at the site (or nearest comparable area with historic data). (A measurement that is relevant to standing water conditions is pan evaporation. Other methodologies can be applied to estimating soil moisture evaporation conditions.); • Surface run-off: The applicant must estimate what percent of precipitation will run off the facility, and thereby be removed from water balance considerations for the material. _______________________________ GENERAL INFORMATION (1-27) The percentage of run-off depends on several factors including amount, intensity and duration of storm events (consideration should be given to extended periods of precipitation events during periods of low evaporation, such as winter rains), surface slope, permeability of surface (e.g., bedrock conditions, compacted surface vs. ripped surface), etc. Values of run-off can be determined from existing facilities or obtained using the U.S. Department of Agriculture Soil Conservation Service SCS methodology (“Urban Hydrology for Small Watersheds”, PB87-101580); • Moisture storage condition of the material: Two common terms used to define moisture conditions are saturation (the moisture condition at which all pore spaces are completely filled with liquid) and specific retention (the volume of liquid remaining in the previously saturated material after allowing the liquid to drain out of the material by gravity). Specific retention depends primarily on material grain size, shape and distribution of pores and structure. For example, fine grained tailing piles may have a specific retention of as much as 30% moisture by dry weight, while waste rock may have a specific retention of between 10% (coarse rock with minimal fines) and 20% (coarse rock with fines and loam). An applicant considering arid climatic conditions as a demonstrated control technology must, at a minimum, demonstrate that the material deposited will be at a moisture content below specific retention, or that it will be deposited in a manner that will cause the material to dry to at least specific retention; • Infiltration: The rate of infiltration depends on the grain size distribution, the texture and geometry of the ground surface, the moisture content of the waste material, and the amount and rate of rainfall. Coarser materials tend to have higher infiltration rates than fine-grained materials (or surfaces that are highly compacted); • Percolation: Once fluids infiltrate a material and the moisture content reaches the specific retention capacity of the material, percolation occurs. Whether percolation occurs at the facility depends on several factors including material thickness, frequency and intensity of storm events, “drying” time in between storm events, the amount of layering and permeability of the material, the amount of vegetation (vegetation reduce the potential for percolation through evapotranspiration), grain and rock size, evaporative depth, etc. Methods such as the Hydrologic Evaluation of Landfill Performance (HELP) water balance model (Federal Environmental Protection Agency) and other approaches can be used as a guide to evaluate percolation rates; • Evaporative depth: Evaporative depth is the depth to which evaporation can occur. Beyond this depth, evaporation cannot practicably remove moisture that has infiltrated. This depth is a function of material grain size and density (void space), extent and type of vegetation, and climatic conditions; and • Wind: Wind should be considered in the design of a facility because wind increases the evaporation. The applicant must also take into account over-spray problems and freeboard design (wave action) when constructing a facility in an area prone to high speed winds. If climatic factors are to be used in considering DCTs for a given facility, water balance calculations must be conducted. It is strongly recommended that water balance calculations be conducted with input from ADEQ to help assure that acceptable methods are used. (1-28) GENERAL INFORMATION ________________________________ 1.2.4 Site Factors Site specific factors that may be considered part of the BADCT determination, along with their data requirements, are discussed in this section. The following discussions do not cover all site factors relevant to an APP application, but only those relative to BADCT determination. The applicant may need to gather additional site specific information under the hydrogeologic-study portion of an APP application to determine the point of compliance, likelihood of compliance with aquifer standards, alert levels, monitoring requirements, and the discharge impact area. The “Aquifer Protection Permits Application Guidance Manual” discusses these aspects in more detail. Applicants are strongly encouraged to meet early with ADEQ and submit a proposal for the hydrogeologic study. ADEQ’s comments on the workplan and the negotiations with ADEQ will save much time and effort throughout the BADCT and APP application process. For mining projects, siting is often dictated by the ore body configuration and local topography. However, for certain facets of the surface operation, such as location of tailing impoundments, dump leach and heap leach facilities, etc., limited alternative sites may be available. Site selection and site characteristics will greatly influence individual BADCT determination since it is site specific. To a great extent, the site will control the design of the facility. Site selection influences the design of a facility in that each design element must be adapted, or fit, to the dimensions, layout and characteristics of the chosen site. The adaptation to the site affects the performance of the particular design component being used. In selecting a site, an investigation program needs to be developed and implemented. Much has been published on site investigation methods and there are numerous investigation approaches. General approaches available may include: • Remote sensing; • Geophysical methods; • Drilling and sampling; • Test pits and trenches; • Laboratory testing; • In-situ testing; and, • Monitoring wells and groundwater sampling. The designer must determine the appropriate investigative methods for selecting a site. The methods may vary from site to site but the following is a suggested approach. • Conduct a preliminary study. Review existing geologic and hydrologic information (e.g., available through libraries, USGS, universities, project files, etc.) including reports, maps, aerial photos, etc. • Conduct field reconnaissance of the area. Compare this information with any existing information. • Conduct initial investigations and tests, as needed, to augment existing data. Initial investigations and tests may include: surface mapping; subsurface geotechnical, geologic and hydrogeologic investigations using test pits or trenches, soil or rock borings, geophysics, etc.; laboratory testing of soil and rock samples for physical and geochemical properties; and other efforts, as required to develop the facility design and supporting evaluations. _______________________________ GENERAL INFORMATION (1-29) • Review results of initial investigations and tests, determine if additional work is required to support the development of the design and supporting evaluations (e.g., a higher level of field mapping, additional site specific tests, etc.), and conduct additional investigations and tests, as needed. Examples of site characteristics which may be considered in the ultimate design are summarized below. These examples are not intended to cover all site aspects of a permit application. 1.2.4.1 Topography Identifying the topography and surface characteristics of a site is a crucial step in designing a facility to minimize potential discharge, and to protect human health and the environment. Tailing, dump leach and heap leach facilities, for example, located on relatively steep topography underlain by low permeability geologic formations, may benefit from a natural high rate of drainage that can occur under the tailing, dump leach or heap leach material. This is because of the presence of steep slopes and limited potential for infiltration into the underlying geologic formations. Steep topographic terrain is also generally associated with outcropping bedrock and/or shallow alluvium. Lining of slopes steeper than 2(H):1(V) has not been practiced on an industry wide basis, especially for high slopes, due to high induced shear stresses and the possibility of failure of the underlying geologic materials. Liners can be safely designed for slightly flatter slopes ranging from 2:1 to 2.5:1 for landfills and on embankment faces. Lining of slopes steeper than 2.5:1 can be considered provided the applicant has considered the above factors, amongst others, and can demonstrate the adequacy of the design. However, at larger mining facilities, the height and steepness of the slope may be limited by 1) allowable tensile stresses in the liner, 2) the capacity of anchor trenches at the top of the slopes, and 3) the stability of any LCRS system or liners placed on top of the primary liner. Stability can be improved by constructing a “buttress” on a flatter slope, benching or the application of fill materials to reduce the slope. Textured or sprayed-on liners may also be applicable. Facilities located on relatively flat terrain do not, on their own, benefit from higher drainage rates and generally encounter greater soil depths to bedrock. This type of topography is generally suitable for liner application and such sites may benefit from the presence of naturally occurring, low permeability material within the vadose zone beneath the facility. Other topographic factors to consider include the existing containment offered at the site (e.g., valley fills, canyons, within existing pits), the characteristics of the natural soils (e.g., low permeability clay, high permeability gravel), and availability of low permeability borrow soils for liner construction. Information to evaluate topography and surface characteristics can be obtained from topographic maps, field surveys, aerial photos, USGS, Soil Conservation Service reports, etc. (1-30) GENERAL INFORMATION ________________________________ 1.2.4.2 Geology/Stability To determine how geologic conditions may affect the Individual BADCT design for a facility, the applicant should extensively evaluate the associated physical, hydraulic and geochemical properties. Specific information that may be appropriate to address, and that may be required for an APP application utilizing Individual BADCT, includes: • Structural Geology: The degree to which geologic structures may affect the Individual BADCT design depends on the amount of reliance being placed on geologic containment. Information on major geologic structures can be identified using geologic maps, aerial photographs, and existing geologic reports, etc. Detailed onsite geologic mapping or field investigation programs are required to evaluate site specific structures. The types of structures that need to be considered include: - Faults must be considered in the design of any facility because they affect stability. - Other structures, such as anticlines and synclines which affect rock strata orientation, can influence the rate and direction of liquid migration through the vadose zone and may be important in designing leak detection systems. - Fracture systems in bedrock can be important in determining seepage rates and velocities, and the location of monitoring systems. - Various other geologic structures or discontinuities can affect the areal continuity of low permeability layers. • Lithology: Lithology is the physical and mineralogic makeup of geologic materials, including both unconsolidated deposits (e.g., alluvium) and bedrock. Important lithologic considerations include: - Horizontal and vertical variations in lithology that cause permeability to vary and which can affect the degree of natural containment provided by the site. - Subsurface strength properties that can affect the long-term integrity of the facility (e.g., settlement potential) and seismic stability. - The depth to bedrock, degree of subsurface stratification, and variations in strata characteristics, can be important to the design of a facility. - Certain alluvial materials and rock types may, by themselves or possibly in combination with planned facility operations, possess geochemical characteristics that contribute to a reduction of discharge and/or limit pollutant migration by attenuation. The following are representative methods for determining permeability; site specifics will determine which methodologies are applicable: • Soil and rock classification based on subsurface lithologic logs and the use of literature or other available information to determine approximate permeability values; • Field permeability testing, including pump tests, packer tests, and other in-situ tests; • Laboratory grain size analyses and permeability tests; • Borehole and surface geophysical surveys to define lithologic boundaries, and to characterize the distribution of permeability. _______________________________ GENERAL INFORMATION (1-31) The effects of scale should be considered in interpreting results of permeability testing. The permeability measured in isolated borehole packer tests (e.g., local permeability) may vary from the permeability of the larger scale rock or soil mass (bulk permeability). This is due to differences in the persistence, character and interconnectivity of the fractures near the boreholes as compared to the rock mass or due to heterogeneity in soil masses. It is also important to consider possible horizontal and vertical variations in permeability (i.e., does permeability decrease or increase between varying lithologies or with depth) and how the local and regional groundwater regimes at the site are affected. 1.2.4.3 Soil Properties Soil is generally characterized by relatively high organic content, biologic activity by roots and microorganisms, and concentration of weathering products left by leaching, evaporation or transportation. Soil properties may affect discharge from a facility by physical, chemical and biologic interaction with a pollutant(s). Soil properties with potential to affect discharge include: type, distribution and thickness, structure, grain-size distribution, organic carbon content, chemical composition, mineralogy, cation exchange capacity, specific surface area and permeability. The applicant should evaluate any changes to soil characteristics that may result from interaction with the discharge. If soil characteristics are to be used for attenuation, the attenuation capacity of the material must be predicted using literature data, or laboratory or field tests. In addition to analyzing the ability of soil properties to affect the quantity and/or quality of a potential discharge, shear strength must be analyzed to support stability analyses. Soil tests and data which may be useful in an Individual BADCT determination include: • Studies of degradation of pollutants in the soils; • Batch or column tests to react a simulated discharge with site soils to determine attenuation capacity; • Infiltration tests; • Permeability tests; • Chemical analyses (pH, EC, inorganic analyses, organic analyses); • Material property tests (grain size analyses, moisture content, bulk density, Atterberg Limits); • Maps of soil distribution and depth; • Soil boring logs; • Other pertinent soil information including reference to pollutant attenuation research. 1.2.4.4 Surface Hydrology If surface water enters waste or processing facilities, leachate can be generated. A key to controlling leachate generation is to design, construct, operate and close facilities in a manner that minimizes the potential for contact of surface water with pollutants and excludes surface water from areas where infiltration may affect groundwater quality. The configuration of surface (1-32) GENERAL INFORMATION ________________________________ water control systems for a mining facility depends on the climate and topography of the site area. Computer models may guide the assessment of surface water effects and the need for surface water control systems. County flood maps may also be helpful. In general, surface water should be diverted around and drained from areas where facilities are located using engineered features such as diversions and/or retention structures. Diversions and/or retention structures are usually designed to minimize run-on to the facility. This preserves containment integrity and limits the amount of water that may contact process reagents or other sources of potential pollutants. In some cases, drainage controls may also be necessary to protect against inundation of the facility and nearby low areas where infiltration may contribute to pollutant transport in the vadose zone. This can typically be achieved by providing protective berms or dikes. The design of surface water control systems is influenced by: precipitation (amount, intensity, duration, distribution), watershed characteristics (size, shape, topography, geology, vegetation), run-off (peak rate, volumes, time distribution) and degree of protection warranted. Timely maintenance is necessary for the continued satisfactory operation of surface water control systems. The principal causes of failure of surface water diversions and/or retention structures are inadequate design peak flow capacity, channel and bank erosion, sedimentation, and excessive growth of vegetation reducing the flow capacity. It is recommended that free-draining features (e.g., ditches and dikes) be capable of handling the design peak flow and that impounding features be designed to handle the design storm volume which occurs over a duration resulting in the maximum storage requirement (ADEQ may approve other design criteria). Evaluation of these design peak flows and storm volumes is discussed in Appendix E (Engineering Design Guidance). Data that may be presented to evaluate the need for surface water control include: • Location of any perennial or ephemeral surface water bodies; • Rates, volumes, and directions of surface water flow, including hydrographs, if available; • Location of 100-year flood plain; • Site topography; • Historical precipitation data. Any activities in, or discharges to, waters of the United States require 401 Certification with ADEQ, and may require notification to the Army Corps of Engineers for a 404 Permit, the EPA for a 402 Permit, and/or the respective County Flood Control District. Additional information regarding these permits and certifications is presented in Appendix F (Federal, State and Local Environmental Permits). 1.2.4.5 Hydrogeology Site characteristics are a part of BADCT insofar as they control the quality and/or quantity of discharge before it reaches groundwater. Potentially important hydrogeologic characteristics include vadose zone properties that may help to limit discharge to the aquifer. Dilution, _______________________________ GENERAL INFORMATION (1-33) attenuation and other factors that affect discharges after reaching an aquifer are not normally an inherent part of BADCT. The exceptions, where characteristics within the aquifer may be an inherent part of BADCT, are the case of in-situ leaching of an ore body and passive containment. In-situ leaching is defined as the underground injection of solutions into an ore body in-place for the purpose of extracting the mineral commodity. In-situ leaching is discussed in Section 3.4. Passive containment is defined by regulation and is discussed in Section 1.2.5. The remainder of this section addresses vadose zone hydrogeology that may be important to BADCT for mining operations. Properties of the vadose zone, the unsaturated zone between the land surface and the saturated zone or maximum groundwater table (Figure 1-1), may affect the behavior of a discharge in a number of ways. For example, physical properties of the vadose zone, like the presence of high permeability layers and geologic structures (e.g., faults, fracture zones), may increase movement of a discharge to groundwater. Conversely, the presence of impervious layers and geologic structures (e.g., clay seams, strata boundaries) may retard the movement of a discharge to groundwater or cause the presence of perched water tables; fine grained layers within the zone may physically remove some types of pollutants; and the decrease in bedrock permeability with depth may reduce the possibility of discharge reaching groundwater. Also, chemical and/or geochemical reactions between the discharge and materials in the vadose zone may alter or remove some pollutants; or biodegradation due to microbial interaction with the pollutant may degrade the pollutant. If the vadose zone consists of layers or lenses of different materials, such as stratified soil horizons or rock units, the properties of each unit must be considered separately in addition to describing the general properties of the vadose zone. The applicant should identify lateral and vertical extent of the geologic units and the type of contacts between the units (e.g., gradational, fault, unconformity, facies change). Perched water tables within the vadose zone may be a consideration. The attenuation of chemical constituents in soil and rock is a valid consideration that can be factored into site specific evaluations. If vadose materials are to be used for attenuation, the attenuation capacity of the material must be predicted. Below is a brief description of the four major types of attenuation mechanisms. This is further explained in “Mine Waste Management,” Chapter 5 (Hutchison and Ellison, 1992). • Physical Mechanisms: Physical mechanisms include filtration, dispersion, dilution and volatilization. • Physiochemical Mechanisms: Physiochemical mechanisms are dependent on both physical and chemical conditions and can include adsorption and fixation. • Chemical Mechanisms: Chemical mechanisms are dependent on the chemical interaction of an element or mineral with the soil or pore water and includes solution/precipitation of compounds or the increase/reduction in toxicity of a constituent by changing its valence state, or the removal/addition of ions by cation exchange. (1-34) GENERAL INFORMATION ________________________________ • Biological Mechanisms: Biological mechanisms include biodegradation of a chemical into the basic oxidation product, bacterial consumption of the chemical or cellular uptake. Additional data which may be submitted to characterize the vadose zone or any unit of the vadose zone for consideration as a part of BADCT design may include: • Detailed lithologic logs of borings and/or well logs that describe: - rock type, - grain-size distribution, - stratigraphy, - type and degree of cementation, and - thickness of units; • Description of the structural geology including: - faults, - fractures, - joints, - folds, and - bedding orientation; • Geologic maps and cross-sections which identify: - stratigraphic or formation contacts, and - structural geology; • Borehole geophysical logs; • Surface geophysical surveys; • Physical properties including: - horizontal and vertical permeability, - dispersivity, - porosity (primary and secondary), • Chemical analyses (pH, EC, neutralization potential, inorganic and/or organic analyses); • Results of batch or column tests showing quality of discharge after reacting with vadose zone material and quality of vadose zone material after reacting with discharge; • Material property tests (grain size analyses, moisture content, Atterberg Limits, maximum density); • Analyses of fluid movement and/or chemical transport through the vadose zone. Supportive data may be obtained from: - lysimeters, - neutron log measurements, - observation wells, - packer tests, and/or - analytical or numeric simulations. _______________________________ GENERAL INFORMATION (1-35) Depth to groundwater or the thickness of the vadose zone may be a factor in determining BADCT. The degree of discharge reduction provided by depth will depend on several variables including: depth to the anticipated maximum groundwater elevation, the volume and rate of discharge, the properties of the pollutants in the discharge, the properties of the vadose zone, and the length of time a discharge may continue. Any considerations of depth to water as a part of BADCT will have to show how the hydrologic and geochemical characteristics of the vadose zone in conjunction with its thickness will affect discharge. Data for evaluating depth to water may include: • Static water elevation measurements (including date of measurement, location of well, and elevation of measuring point); • Well hydrographs to document long term and seasonal trends; • Location of pumping wells in vicinity of measured well; • Well construction data (including total depth and location of perforations); • Geophysical surveys such as seismic and resistivity. 1.2.4.6 Barriers Hydraulic barriers (e.g., dewatered open pits, or quarries) and physical barriers (e.g., pit walls, quarries, subsidence zones, or slurry walls) can function as downgradient interceptors of groundwater flows, seepage in the unsaturated zone and/or surface flows. For example, steeply sloping surfaces, depressions or openings created by open pit or underground mining can function as downgradient interceptors of lateral seepage from a facility. Cones of depressions in groundwater or slurry walls can be used to contain in-situ leach solutions. Except for in-situ leaching, the use of a hydraulic or physical barrier as a consideration in BADCT design is appropriate only in the context of discharge reduction prior to a pollutant reaching an aquifer. For facilities other than in-situ leaching, use of barriers to control pollutants after reaching the aquifer or to control impacted groundwater may not be used as a part of BADCT unless the physical barrier also functions as passive containment (see Section 1.2.5). 1.2.5 Passive Containment A discharging facility at an open pit mining operation shall be deemed to satisfy BADCT requirements of A.R.S. 49-243.B.1. if the ADEQ determines that both of the following conditions are satisfied (A.R.S. 49-243.G): 1. “The mine pit creates a passive containment that is sufficient to capture the pollutants discharged and that is hydrologically isolated to the extent that it does not allow pollutant migration from the capture zone. For purposes of this paragraph, “passiv |