Guidline_sstd_bref Version 2

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KREC-Norsk Bergindustri 1/110 March 2015 Report Number 2 from Norsk Bergindustri/Norwegian Mineral Industry in a series regarding effects of sea disposal of mine tailings. The report is version 1 of a guideline for characterization of tailings intended for sub-sea deposition, the deposition site and receiving environment The report has been put together by Ingar Walder in Kjeøy Research and Education Center, commissioned by Norsk Bergindustri. KREC-Norsk Bergindustri 2/110 March 2015 This report is number 2 in our series regarding sea disposal. The initiative to this series has been taken by Norsk Bergindustri/Norwegian Mineral Industry in order to document the Norwegian practice of disposal of mine tailings in the sea. Norsk Bergindustri has several committes, which are made up by internal and external specialists in different areas. A full overview of these committees and their responsibilities is available at www.norskbergindustri.no There is a special committee, deponiarbeidsgruppa/Deposition Working Group, which is open for all members that practice disposal of mine tailings. The mandate of this committee is as follows: advisor of the board relating to the disposal of mineral waste - as well as the sharing of experience and development of best practices regarding this matter. Elisabeth Gammelsæter Roar Sandøy Secretary General Norsk Bergindustri KREC-Norsk Bergindustri 3/110 Leader, Deposition Working Group March 2015 prSN/TR-9432 SUB-SEA TAILINGS DEPOSITION EVALUATION GUIDELINE A guideline for characterization of tailings intended for sub-sea deposition, the deposition site and receiving environment. Version 2 March 2015 Guide prepared by: Ingar Walder, Ph.D. Geochemist Director R&D Kjeøy Research & Education Center Kjeøy, 8412 Vestbygd Norway. Reference/Review Group - Sverre Høstmark, Norsk Industri - Roar Sandøy, Sibelco Nordic - Mona Schanche, Nordic Mining - Arnstein Amundsen, Hustadmarmor - Ann Heidi Nilsen, Titania KREC-Norsk Bergindustri 4/110 March 2015 FORWARD This guideline document (prSN/TR-9432:2012) has been prepared by Dr. Ingar Walder at Kjeøy Research & Education Center. The document has been reviewed by Norsk Bergindustri (Norwegian Mining Association) Waste Facility Group and by the Scottish Association of Marine Studies. This Guideline, written as a Technical Report according to the European Standardization system, is intended to supplement the existing series of four CEN Technical Reports/Specifications dealing with characterization of waste from extractive industries: • CEN/TR 16376:2012, Characterization of waste - Overall guidance document for characterization of waste from extractive industries. • CEN/TR 16365:2012, Characterization of waste - Sampling of waste from extractive industries. • CEN/TR16363:2012, Characterization of waste - Kinetic testing for sulfidic waste from extractive industries. • CEN/TS16229: 2011, Characterization of waste - Sampling and analysis of cyanides (WAD) discharged into tailings ponds. This Guideline focuses on the technical issues related to the recommended characterization for evaluating sub-sea deposition of tailings from the extractive industries. General issues concerning characterization of the waste are laid out in the above listed CEN-documents. This Guideline considers a range of potential approaches and tools for the characterization of a prospective receiving sub-sea environment; e.g. bottom flora, fauna, fish, water current, and water conditions; in addition to, methods for characterization of waste that will potentially be placed in a sub-sea tailings facility. This approach enables the project manager to tailor the sampling plan and characterization to a specific testing scenario. It also allows for flexibility in the selection of the sampling approach, sampling point, method of sampling and equipment used, to characterize the receiving environment. It helps generate the necessary KREC-Norsk Bergindustri 5/110 March 2015 background information pertaining to factors influencing the chosen characterization approach required for characterizing the receiving environment. The Guideline also makes references to the overall guidance document for characterization of waste from extractive industries (CEN/TR 16376), which provides guidance and recommendations on the application of methods for the characterization of waste from extractive industries. This document provides guidance, not required procedures. It gives recommendations on what to evaluate during characterization of possible sub-sea deposition environments for waste from extractive industries. It provides a toolbox with different methods that may or may not be applicable in a specific case. It is not a legally binding document. There are many issues specific to sub-sea tailings deposition which are not covered in the CEN mine-waste guidelines but are covered in this document: • • • • • Sediment dispersion in a Marine environment; Fish affected by suspended sediments and the effect of suspended sediments of the Pelagic system; Leaching of chemicals used during the processing and thickening of tailings; Release of metals from the tailings due to biogeochemical cycling; Covering of bottom flora and fauna by sediments. It is important to understand these issues pertaining to specific sites when evaluating sub-sea deposition for storage of the tailings. KREC-Norsk Bergindustri 6/110 March 2015 TABLE OF CONTENT FORWARD 5 INTRODUCTION 10 1. SCOPE 14 2. ADMINISTRATIVE PROCEDURES AND LEGAL CONSIDERATIONS 15 2.1. EU LEGAL DOCUMENTS 2.1.1. RELEVANT EU-DIRECTIVES AND BAT-DOCUMENTS 2.1.2. COMMISSION DECISIONS RELATED TO WASTE FROM EXTRACTIVE INDUSTRIES 2.1.3. CEN DOCUMENTS 2.2. INTERNATIONAL CONVENTIONS 2.2.1. OSPAR, LONDON, HELCOM AND BARCELONA CONVENTIONS 2.3. NORWEGIAN LAWS, BYLAWS AND GUIDELINES 2.3.1. NORWEGIAN MINERALS ACT 2.3.2. POLLUTION CONTROL ACT WITH BYLAWS 2.3.3. GUIDELINE FOR CLASSIFICATION OF BOTTOM SEDIMENT 2.3.4. GUIDELINE FOR DEPOSITING CONTAMINATED SEDIMENTS IN THE SEA 2.3.5. CONTAMINATED FJORD COVER DEPOSITION GUIDE 2.3.6. CONCLUDING REMARK 2.4. OTHER NATIONAL REGULATIONS ON SSTD 2.4.1. PAPUA NEW GUINEA DEEP SEA TAILINGS PLACEMENT GUIDELINE 2.4.2. PHILIPPINES 2.4.3. TURKEY 2.4.4. USA 2.4.5. CANADA 2.4.6. AUSTRALIA 2.4.7. JAMAICA 15 15 16 17 18 18 19 19 20 20 21 22 23 24 25 26 26 26 26 27 27 3. HEALTH AND SAFETY 28 4. ENVIRONMENTAL ISSUES 29 4.1. TAILINGS CHARACTERISTICS 4.1.1. PARTICLE TRANSPORT / SILTATION / TURBIDITY 4.1.2. ACID/NEUTRAL ROCK DRAINAGE AND POTENTIAL RELEASE OF HEAVY METALS 4.1.3. PROCESS CHEMICALS 4.2. TAILINGS DISCHARGE SYSTEMS 4.2.1. PLUME DENSITY 4.2.2. PIPELINE BREAK 4.3. RECEIVING ENVIRONMENT 4.3.1. FJORD CIRCULATION 4.3.2. VERTICAL WATER COLUMN 4.3.3. CHANGES IN CURRENTS DUE TO DEPOSITION 4.3.4. EFFECTS ON FISH DEPENDENT ON FISH TYPE 4.3.5. SPAWNING AREA (PERMANENT – VARIABLE) 29 30 32 33 35 35 36 36 36 37 37 37 38 KREC-Norsk Bergindustri 7/110 March 2015 4.3.6. ECOSYSTEM EFFECTS 4.4. RECOLONIZATION 38 38 5. CHARACTRIIZATION OF DEPOSITION SITE 41 5.1. 5.2. 5.3. 5.4. 5.5. 5.6. 43 43 44 44 45 46 BACKGROUND INFORMATION MINERAL DEPOSIT EXPLOITATION METHOD MINERAL PROCESSING DEPOSITION SITE DEPOSITION 6. CHARACTERIZATION OF TAILINGS 48 6.1. SAMPLING PLAN 6.2. PHYSICAL AND HYDRAULIC PROPERTIES 6.2.1. COMPRESSIBILITY AND FRICTIONAL BEHAVIOR 6.2.2. IN-SITU INVESTIGATION OF DEPOSITED WASTE 6.2.3. GRAIN SIZE / SPECIFIC SURFACE AREA 6.3. MINERALOGICAL COMPOSITION AND TEXTURAL INFORMATION 6.4. CHEMICAL ANALYSIS 6.4.1. ANALYSIS OF SOLIDS 6.4.2. ANALYSIS OF LIQUIDS 6.4.3. SULPHUR (TOTAL, SULFATE AND SULFIDE) 6.4.4. ORGANIC AND INORGANIC CARBON 6.4.5. PROCESS CHEMICALS 6.5. A/NRD TESTING METHODS 6.5.1. STATIC TESTING - ACID BASE ACCOUNTING (EN15875) 6.5.2. KINETIC TESTING 6.5.3. SALTWATER/SEAWATER KINETIC TESTING 6.6. LEACHING BEHAVIOUR AND LEACHING TESTS 6.6.1. COMMON LEACHING TESTS 6.7. DISCHARGE SETTLING 6.8. FIELD EXPERIMENTS 6.8.1. EXISTING WASTE FACILITY 6.8.2. SMALL-SCALE FIELD TESTING 6.9. AQUATIC TOXICITY TESTS 6.9.1. ACUTE TOXICITY TESTS 6.9.2. CHRONIC EFFECT TESTS 6.9.3. BIOACCUMULATION TESTS 49 50 51 51 52 52 54 55 55 56 56 56 57 57 58 60 65 65 66 68 68 69 69 70 72 73 7. CHARACTERZATION OF THE RECEIVING ENVIRONMENT 74 7.1. FISH AND FISH RESOURCES 7.2. BOTTOM SEDIMENTS 7.3. BOTTOM FLORA AND FAUNA 7.3.1. SOFT-BOTTOM FLORA AND FAUNA 7.3.2. HARD-BOTTOM FLORA AND FAUNA 7.4. WATER QUALITY 7.5. OCEAN-FJORD CURRENTS 75 76 77 77 78 78 79 KREC-Norsk Bergindustri 8/110 March 2015 7.6. BATHYMETRY 80 8. DATA QUALITY 81 9. INTERPRETATION, APPLICATION, AND EVALUATION 83 9.1. PARTICLE TRANSPORT 9.2. ACID/NEUTRAL ROCK DRAINAGE AND LEACHING RISK 9.2.1. A/NRD EVALUATION 9.2.2. LEACHING EVALUATION 9.2.3. MARINE ECO-TOXICOLOGY 9.3. UNCERTAINTY – LIMITATIONS 84 88 89 92 94 96 10. OPERATION, MONITORING AND CLOSURE 98 DISCHARGE SYSTEM FIELD VERIFICATION MONITORING EMERGENCY RESPONSE PLANS 98 99 101 101 11. DOCUMENTATION AND REPORTING 103 12. REFERENCES 105 13. WORDS 110 10.1.1. 10.1.2. 10.1.3. 10.1.4. List of Figures Figure 1. Flow-chart showing the outline of the SSTD evaluation guideline Figure 2. Simplified sub-sea tailings deposition setting from a mine Figure 3. Flow chart for a baseline evaluation. Figure 4. Characterization flow chart. Figure 5. Experimental setup for long-term leaching tests for SSTD Figure 6. Flow chart for the steps within the Evaluation of SSTD data Figure 7. Acid potential vs. neutralization potential Figure 8. Display of level of organisms and eco-toxicity and leach tests. 10 33 34 40 52 74 79 84 List of Tables Table 1. List of the main aspects to be covered in a sampling plan KREC-Norsk Bergindustri 9/110 41 March 2015 INTRODUCTION Waste from the extractive industries can only be managed properly if sufficient knowledge about its geochemical and physical properties and behaviour is available, together with knowledge of whether or not the receiving environment can handle the impact of the waste deposition. Such knowledge can be obtained through proper waste and receiving environment characterization. The Mining Waste Directive, MWD, (Directive 2006/21/EC of the European Parliament and the Council of March 15, 2006 on the management of waste from extractive industries) and the associated Commission Decisions (waste facility classification, inert waste definition and waste characterization) include requirements related to characterization of waste from the extractive industry. As a follow-up a series of guidelines have also been developed in order to assist regulators, consultants, and mining operators to characterize the mining waste. These guidelines have focused on issues regarding land deposition; Sub-sea tailings deposition has not been specifically addressed. Norway has a relatively long history of depositing tailings in fjords with approximately such 22 cases (Kvassnes 2013). Currently, 7 operations are actively depositing tailings in fjords (Kvassnes 2013). Five of these are primarily industrial minerals operations (graphite, nepheline syenite, calcite, quartz); and two are iron mines (magnetite, hematite). Historically tailings from sulphide ore (Cu, Pb, Zn and Ni) and ilmenite ore have also been deposited in fjords. The Mining Waste Directive (Directive 2006/21/EC) covers the management of waste arising from land-based extractive industries. A sub-sea tailings facility is not specified as “excluded” from the scope of the Mine Waste Directive; and therefore, such facilities are also covered in the Mining Waste Directive. The Water Framework Directive (Directive 2000/60/EC) does not preclude sub-sea tailings deposition (Klima- og forurensningsdirektoratet 2012). In this document, sub-sea tailings deposition (SSTD) is used to define tailings from extractive industries being deposited below the lowest water mark registered for an ordinary outgoing low tide. However, as described in this guideline, a more ideal placement is considerably deeper than this. The term submarine tailings placement (STP) and submarine tailings deposits (STD) are also used to mean the same (Ellis, 1995). Deep submarine tailings placement (DSTP) refers to tailings being deposited on the seafloor with a discharge point of more than 100 m depth (Shimmield, 2010). KREC-Norsk Bergindustri 10/110 March 2015 The European Commission Decision on waste characterization (CD 2009/360) states that: “The purpose of the characterization of extractive waste is to obtain the relevant information on the waste to be managed in order to be able to assess and monitor its properties, behaviour and characteristics and thereby ensure that it is managed under environmentally safe conditions in the long term. Furthermore, the characterization of extractive waste should facilitate the determination of the options for managing such waste and the related mitigation measures in order to protect human health and the environment.” A multitude of methods and tools are available for various waste characterization purposes – some are standardised and some are not. Many methods are developed for characterization of non-mineralogical material and not applicable for waste from the extractive industry. Tradition, geography, and experience often determine which method is used. In some cases, the use of specific methods is required by legislation; for example, “Characterization of waste from extractive industries”. Within EU legislation, European (CEN) standards and methods are generally preferred, if they are available. The main methods for the characterization of waste have been included in this SSTD evaluation guideline. Also included are specific methods used for the evaluation of a SSTD as a waste disposal method. This Sub-Sea Tailings Deposition Evaluation Guideline document has been developed for Standard Norway to support stakeholders in Norway involved in the characterization and management of extractive waste, in selecting the appropriate tools (standards or methods) for evaluating the potential for Sub-Sea Tailings Deposition; and to satisfy the requirements of Directive 2006/21/EC and associated Commission and the Norwegian implementation of this directive and Commission decisions. It is further meant to provide information on the possibilities and limitations of the methods, and some guidance on where to find further information on the interpretation and application of the waste characterization results. The purpose of the document is to provide authorities, regulators, operators/waste producers, consultants and testing laboratorieswith a summary of the specific aspects of characterising waste from the extractive industries and its suitability for SSTD at a given site. The outline of the document follows, to a large extent, the outline used in the three CEN guidelines developed for the characterization of waste from extractive industries (Fig. 1). There are a total of nine chapters. The first chapter, The Scope, is followed by a KREC-Norsk Bergindustri 11/110 March 2015 chapter (Chapter 2) on European and other international legal documents and guidelines including a review of the Norwegian regulations of sea and fjord issues. Chapter 3, a short chapter on health and safety issues related to sampling, is followed by a chapter (Chapter 4) on environmental issues related to mining and sub-sea tailings deposition. Chapter 5 discusses the baseline issues of waste characterization as described in the Commission Decision. This guideline further discusses the baseline issues of the receiving waste facility site. The baseline chapter is followed by an extensive chapter, Chapter 6, Characterization. This chapter reviews sampling procedures and methods that can potentially be used for characterizing the waste and the potential receiving environment. The Chapter 7 is on data quality, with issues relating to quality control/quality assurance of the characterization data; while Chapter 8 goes through the evaluation, application and interpretation of the characterization data. Chapter 9, the last chapter of the document provides information for proper documentation and an outline of a report form. KREC-Norsk Bergindustri 12/110 March 2015 Figure 1. Flow-chart showing the outline of the SSTD evaluation guideline. KREC-Norsk Bergindustri 13/110 March 2015 1. SCOPE This Guideline document/Technical report provides guidance and recommendations on the application of methods for the characterization of mine waste and deposition site when sub-sea tailings deposition is considered. The document covers characterization methods for both physical and geochemical properties of the waste together with characterization of the deposition site and receiving environment. Other significant aspects, from planning to interpretation and reporting, that are not covered in other Norwegian or European official documents, are also included. The main purpose of this document is to aid extractive industries and regulatory agencies on how to plan, determine, perform and evaluate the necessary characterization for potential sub- sea-tailings deposition. The document includes a discussion on when and why characterization may be needed, and on the contexts within which characterization data may need to be applied. The extractive industry covers many different sectors with very different waste categories; and characterization may be carried out with many different objectives. For this reason, a guidance document on characterization cannot be prescriptive or provide generally applicable instructions on how waste characterization should be performed in each and every case. KREC-Norsk Bergindustri 14/110 March 2015 2. ADMINISTRATIVE PROCEDURES AND LEGAL CONSIDERATIONS There are very few legal international documents that directly discuss sub-sea/deep sea tailings deposition. The most important legal documents that have an impact on how characterization and evaluation of Sub-sea tailings deposition is to be performed are described below. The EU directives and regulations, together with documents from the European Standardization Commission, make up the bulk of the documents. This section also includes a short discussion on how other countries outside Europe have been dealing with the potential of sub-sea/deep sea tailings disposal. 2.1. EU Legal Documents There are several types of documents that legally define the characterization of waste and the facilities to handle the waste from extractive industries. The first of these are the EU-directives and Commission Decisions. There is also the European BREF/BAT (2004) document for specific issues decided by the Commission. This reference document was decided/accepted by the EU-commission and formed the basis for the EU-directive on Waste from Extractive Industries (2006). Furthermore, the European Standardization Commission (CEN) issued standards to be followed, if applicable, and technical specifications and reports considered as guidelines. These documents are further described in the following sub-sections. 2.1.1. Relevant EU-Directives and BAT-documents There are several EU-directives that affect the evaluation of mine waste management in Norway. The most important directives are: • EU-Directive on Waste from Extractive Industries (Directive 2006/21/EC) • EU-Water framework directive (Directive 2000/60/EC) The Mining Waste Directive was adopted in April 2006, and was to be implemented from June 2012. As a part of the implementation of the directive, four CEN technical reports/guidelines and one standard (acid base accounting) have been developed. The Mining Waste Directive (Directive 2006/21/EC) covers the management of waste arising from land-based extractive industries. In article 3.15 the directive defines a KREC-Norsk Bergindustri 15/110 March 2015 deposition area as a waste facility: “Such facilities are deemed to include any dam or other structures serving to contain, retain, confine or otherwise support such a facility, and also to include, but not to be limited to, heaps and ponds, but excluding excavation voids into which waste is replaced, after extraction of the mineral, for rehabilitation and construction purposes.” A sub-sea tailings facility is thus included in the scope of the Mining Waste Directive. According to the directive, inert waste should have less rigorous guidelines, unless classified as Category A waste facility. Non-hazardous noninert waste may have reduced or waived requirements (Bullet 9) unless classified as category A waste facility. Bullet 23 states that it is necessary to define when a waste facility should be closed, and the obligations and responsibilities of the operator after closure. The Water Framework Directive (Directive 2000/60/EC) has been in effect from October 23rd, 2000; and part of the scope of the Directive is to protect territorial and marine waters (Article 1). Article 11.6 states that member states should take all appropriate measures not to increase pollution to marine waters, unless these requirements result in an allowed increase in pollution of the environment as a whole. The directive also specifies the characterization needed for classification of fresh water bodies and marine waters. The BAT (2004) document on management of tailings briefly mentions sub-sea tailings deposition (SSTD), but does not include the SSTD as a Best Available Technique due to lack of information on the method. However, the Bref/BAT (2004) document does not exclude SSTD as a best available technique for tailings management. The document does, in general terms, describe the Hustadmarmor SSTD system, and states that SSTD is used since there is no space for land-based deposition. In addition, the document also states: “This technique is applicable where the tailings slurry will form a high density plume that will descend to the bottom of the sea, leaving a clear water area above the pipe outlet.” This Bref/BAT document is under revision. 2.1.2. Commission Decisions related to Waste from Extractive Industries The EU-Commission has made several decisions as part on the implementation of the EU-Mining Waste directive that also impacts the evaluation of waste handling in Norway. These are: • Commission decision on waste characterization (CD 2009/360/EC) KREC-Norsk Bergindustri 16/110 March 2015 • Commission decision on classification of waste management facilities (CD 2009/337/EC) • Commission decision on inert waste (CD 2009/359/EC) • Commission decision on financial assurance (CD 2009/335/EC) These four Commission Decisions (CD) describe, in some more detail, issues that are only briefly mentioned in the Mining Waste Directive. The Commission Decision (CD) on waste characterization describes, in general, the issues that need to be addressed with regards to waste characterization in order to make a mine-waste management plan. These issues have been incorporated into CEN Guidelines for characterization of waste from extractive industries (chapter 2.1.3). The CD on waste management facilities describes the criteria for classification of the facilities. The classification involves determining whether a facility is an A-Facility or not. An A-Facility, a facility that has the potential risk to cause significant harm to human health or the environment, has to comply with more stringent regulation and member states cannot make variances to the EU directives or commission decisions. The CD on inert waste describes the criteria to be used for classifying waste from extractive industries as inert. It specifies a maximum content of sulfide, minimum ratio between acid potential and neutralizing potential, and a list of elements whose concentrations must be low enough to insignificantly affect human health or the environment. However, it does not specify methods to be used or threshold values; these are to be decided by each member state. The CD on financial assurance outlines the requirement to perform an assessment of the costs of closure and post closure monitoring and care. The cost is to ensure land rehabilitation is performed at closure and after closure, including post-operational monitoring; and/or that treatment of contaminants can be performed. 2.1.3. CEN Documents As part of the implementation of the mining directive the European standardisation committee, CEN has developed several documents via the committee CEN/TC292. CEN/TC292 handles waste issues and issues related to waste from extractive industries. The documents developed by CEN as part of the implementation are: KREC-Norsk Bergindustri 17/110 March 2015 • • • • • 2.2. CEN/TR 16376:2012, Characterization of waste - Overall guidance document for characterization of waste from extractive industries. CEN/TR 16365:2012, Characterization of waste - Sampling of waste from extractive industries. CEN/TR16363:2012, Characterization of waste - Kinetic testing for sulfidic waste from extractive industries. CEN/TS16229: 2011, Characterization of waste - Sampling and analysis of cyanides (WAD) discharged into tailings ponds. EN15875 2011, Characterization of waste – Static testing for determination of acid potential and neutralization potential of sulfidic waste. International Conventions There are several International Conventions treating dumping of wastes in marine waters. None of these conventions prohibit deposition of tailings materials in the sea. 2.2.1. OSPAR, London, HElcom and Barcelona conventions The Oslo Convention (1974) and the Paris Convention (1978) were established in order to reduce the input of contaminant material to the sea (North Sea in particular) (OSPAR Convention from 1992). The HELCOM convention applies for the Baltic area, and the Barcelona Convention for the Mediterranean Sea. In 1996 these conventions were followed up by the “1996 Protocol to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, 1972" (replacing the 1972 London Convention), having similar text as the Oslo Convention, but for international waters in general. The London Convention has a series of Annexes that list hazardous or potentially hazardous elements and compounds, and specifies limits of those for accepted deposition. The London Convention also specifies methods of testing. Among the most important additions of the 1996 Protocol is the inclusion of the "precautionary approach" and the "polluter pays principle." A major structural revision of the Convention was the so-called "reverse list" approach. Instead of prohibiting the dumping of certain (listed) hazardous materials, the dumping of any waste or other matter that is not listed in Annex 1 ("the reverse list") of the 1996 Protocol was prohibited. Dumping of wastes or other matter on this reverse list requires a permit. KREC-Norsk Bergindustri 18/110 March 2015 The London Convention of 1972, with the Protocol from 1996, sets limits on waste being disposed in the sea in national and international waters. Article 4, dumping of wastes or other matters, states: “Contracting parties shall prohibit the dumping of wastes and other matters with the exception of those listed in Annex 1.” Annex 1, Wastes and other matters that may be considered for dumping (the reverse list), states: “The following wastes or other matter are those that can be considered for dumping ….. 5. Inert inorganic geological material (e.g. mining wastes)…” However, the protocol does not specify what criteria to be used for defining inert inorganic geological material. The European commission has made definitions for inert waste from extractive industries (CD-Inert Waste, 2009, see Ch. 2.1.2) that can be applied in cases evaluating SSTD. The London Protocol applies for all marine waters other than the internal waters of States, and in this respect it thus not apply for sub-sea tailings deposition in Norwegian fjords. 2.3. Norwegian Laws, Bylaws and Guidelines There are several Norwegian laws that include environmental impact from mining operations. 2.3.1. Norwegian Minerals Act The Norwegian Minerals Act (NFD, 2009), as previously mentioned, primarily regulates the mineral rights and the exploitation of a deposit. The law briefly discusses the environmental issues, restating other Norwegian laws that an Environmental Impact Assessment is required if the disturbed area is above 200 hectares, more than 2 Mm3 material is to be exploited, and/or significant adverse effects on the environment may occur. The Mining Law states that the operator is required to clean up the site after closure. The Directorate for Mineral Resources (DMF) is the agency that sets the requirements for the restoration and cleanup, and oversees such work. DMF can also require financial assurance for such restoration and cleanup measures. The Norwegian Ministry of Trade, Industry and Fisheries (NFD) has issued a guideline that briefly explains the Norwegian Mining Law (NFD, 2011). KREC-Norsk Bergindustri 19/110 March 2015 2.3.2. Pollution Control Act with bylaws The Pollution Control Act (Forurensningsloven) of 1981 is designed to protect the environment against pollution, where discharge of solids and liquids are included as pollution. It states that it is illegal to pollute (discharge) unless environmental pollution authorities have issued a permit. The limits for discharge in a permit are commonly based on mass per time and total concentrations. The Norwegian waste regulation (Avfallsforskriften) is a follow up to the Norwegian Pollution Control Act. The Norwegian waste regulation, updated in 2012, is the implementation of the EU Waste Directive of 2001, and the EU Mining Waste Directive of 2006. The latest version of the Norwegian waste regulation incorporates the mine waste issues referred to in the Mining Waste Directive, and the commission decisions described above in section 2.1.2. There is no specific description in the Norwegian Waste Regulation on how to characterize a potential sub-sea waste facility or how to monitor a SSTD. The Norwegian water regulation (Vannforskriften) of January 2007 is the Norwegian implementation of the EU Water Framework Directive (2000). The Norwegian water regulation does not preclude sub-sea tailings deposition (Klima- og forurensningsdirektoratet 2012), but includes issues that impact sub-sea tailings deposition. There are several other Norwegian regulations (forskrifter) and guidelines (veiledere) that may be used for parts of characterization for evaluating SSTD at a particular site. Several of them are discussed in the following sub-sections. 2.3.3. Guideline for Classification of Bottom Sediment The Water Framework Directive was implemented in Norway via the Water Regulation (2010; Vannforskriften). The Norwegian Guideline for Classification of Bottom Sediments (TA-3001/2012) is a further implementation of the Water Framework Directive to ensure that all fresh water, groundwater, and coastal water have good ecological and chemical conditions. This classification follows to a large extent the Environmental Quality Standard (EQS) Report 55-2011. The system used for classification of sediments and water is applicable to SSTD. The KREC-Norsk Bergindustri 20/110 March 2015 guideline uses distribution coefficients between pore water and sediments to derive the classification. Tailings to be deposited would also be classified by the same system. Where there is no data, or there are questions regarding the listed distribution coefficient, the classification can be derived according to the following equation: PNECsed = PNEC H2O * Kd PNEC (Predicted No Effect Concentrations) in the sediments (PNECsed) is based on PNEC in water (PNEC H2O) and the distribution coefficient (Kd) between sediment and water for the element/component in question. If the Kd is not known, the Kd can be derived from sorption tests according to EQS 55-2011. The classification system uses five different classes: • • • • Class I Class II Class III Class IV • Class V Natural background concentrations No toxicological effects; PNEC Chronicle effects from long term exposure; PNCacute Acute toxicological effects at short term exposure; PNECacute*Safety factor Severe toxicological effects This classification system is focused around equilibrium between sorbate and sorbant, and does not take into account the precipitation-dissolution/weathering, which may be as important for mine-waste material as sorption processes. . 2.3.4. Guideline for depositing contaminated sediments in the sea The Norwegian Environment Agency (Miljødirektoratet) has developed a guideline for depositing contaminated sediments in the sea (TA-2624/2010). This guideline was developed to ensure that the experience and knowledge gained from recent sea/fjord deposition of contaminated sediments from harbor dredging was maintained and utilized in future contaminated sediment cleanup. This guideline applies to the deposition of sediments, Class III or higher, in accordance with the sediment classification, TA- KREC-Norsk Bergindustri 21/110 March 2015 3001/2012 (see Chapter 2.3.3), which is not applicable to the deposition of tailings from current mining operations. The Sediment Deposition Guideline specifies the characterization needed for both the deposition site and the material to be deposited. It also specifies the monitoring framework during the deposition and after the deposition has been completed. Some of the required information from a characterization investigation for evaluating deposition is as follows: • Seasonal variations in the deposition site, to include biological, physical and chemical. • Salinity, temperature, oxygen content, physical oceanography to include currents • Geotechnical stability of the bottom sediments and natural sedimentary rates. • Potential for affecting salmon and sea-trout and other fish types The main purpose for monitoring after deposition is to: • Evaluate if the sediment deposited is stable; • Determine if there is leaching of contaminants; and • Determine re-colonization rates by biota. The requirement is that there be a natural barrier in the deposition zone so that contaminated sediments are deposited in a confined area; and that the natural sediments are not coarser than the sediments to be deposited. If the natural sediments are coarser than the contaminated sediments, there is a possibility that turbulence of the contaminated sediments with the natural sedimentation will occur; and the rate of natural cover development will be slowed down. 2.3.5. Contaminated fjord cover deposition guide The Norwegian Environment Agency (Miljødirektoratet) has developed a guideline to characterize material to be used as cover for contaminated sea-sediments (Klif, TA2143/2005). This guideline describes, in several steps, how to characterize the physical and geochemical characteristics of a material, so as to be accepted for use in covering KREC-Norsk Bergindustri 22/110 March 2015 contaminated sediments. The guideline has also included specifications on ecotoxicological tests. This guideline discusses the following material: • Rock crushed, milled and physically separated without addition of chemicals; • Loose material which also includes the fine fraction of sieved material, including natural sandy material and dredged sea material; and • Process material, e.g. tailings, smelter slag, and recovered fluidized bed material. The guideline requires that the material be tested through a series of steps; where if accepted within a set of criteria at one step level, there is no need to perform tests at the next step level. If the material is not accepted at one level, it can be tested further to evaluate if it can be accepted as cover material. The levels of testing are as follows: • General physical and chemical characteristics • Chemical stability – leaching potential • Eco-toxicological characteristics All suggested cover material needs to be site specifically evaluated. In general, the characterization of “cover material” is similar to that needed for the characterization of material evaluated for SSTD. However, since the amount of material to be deposited from a mining operation commonly constitutes a much larger volume than the material used for covering contaminated harbor/sea sediments, and the mine material is likely to be deposited in an area without contaminated sediments, the testing is more rigorous. In addition, some of the characterization methods described in this guideline are not appropriate for the purpose designed. The guideline states that mineralogical analyses are to be performed using X-Ray Diffraction Analysis. However, the detection limits for this method are too low for the minerals that are often in question, and this may lead to erroneous results and wrong conclusions. 2.3.6. Concluding remark There is no specific regulation on mine waste characterization except what has been incorporated in the waste regulation (Avfallsforskriften). These regulations are relatively vague without specific guidelines on how to characterize the waste or the KREC-Norsk Bergindustri 23/110 March 2015 environment potentially receiving the waste. Chapter 17 does specify the following requirements: • • • • Make a waste management plan, Evaluate the facility classification, Design a closure plan, and Specify financial assurance It also specifies general issues to be included as part of these requirements, which have been adopted from the EU-requirements as specified in the EU-Mining Waste Directive and the following Commission decisions (See 2.1.2). 2.4. Other National regulations on SSTD Papua New Guinea (PNG) is currently the only country that has specific regulations for tailings deposition in the sea. These regulations are for Deep Sea Tailings Placement (DSTP). DSTP is practiced at two operating mines in PNG. These regulations were developed under an EU-funded project (SYSMIN). SYSMIN’s aim was to characterize and assess the impacts of DSTP at three mine sites (two active and one closed operation), and develop a regulatory framework for DSTP. The Scottish Association for Marine Science, Research Service (SRSL), Scotland was funded by the European Commission (8th European Development Fund, 2007-2010) to produce ‘best-practice’ guidelines of DSTP for the Department of Environment and Conservation and the Mineral Resource Authority in PNG,. The general guidelines that were produced by SRSL in 2010 have since been accepted by the PNG government, and are presently being adopted as regulation within PNG’s legislation. The International Marine Organisation (IMO) and the Scientific Group of the London Protocol have also acknowledged the guidelines. More recently, SRSL has been commissioned to produce a number of site-specific guidelines for individual mines, as a consequence of the highly site- and conditions dependent nature of DSTP environmental impacts. Both USA and Canada give an opening for sub-sea tailings deposition in their environmental regulation, where SSTD may be the most environmentally friendly option for tailings deposition. The London Dumping Convention also includes SSTD as a potential viable method for inert inorganic geological material. There are also a few KREC-Norsk Bergindustri 24/110 March 2015 countries practicing sub-sea tailings deposition, however, without any specific regulations for this practice (e.g. Indonesia and Turkey). 2.4.1. Papua New Guinea Deep Sea tailings placement guideline A general Deep Sea Tailings Placement (DSTP) guideline for Papua New Guinea (Guide PNG, 2010) is written to provide developers with a framework for deciding whether DSTP is an option; and it is different from this guideline and the EU-guidelines for waste characterization. It is a guideline for 1) evaluating DSTP at a particular site; and 2) detailing the conditions that must be met to ensure maximum efficiency of deposition of tailings. The guideline requires the use of an Environmental Impact Assessment process to ensure best practice development for a potential DSTP project. However, there are a set of specific guidelines for each operational mine which details the environmental monitoring and operation that must be carried out at a specific mine. The PNG guideline discusses the operational requirements in general terms. The discharge point needs to be sufficiently deep to ensure the following: • No entrainment or advection of tailings into euphotic zone; • Minimal production of plumes due to density differences in the water column; and • There is acceptable small diffusion of dissolved toxic material into the euphotic zone. The guideline specifies that DSTP should be at a minimum depth of 120 meters, where the euphotic zone is 80 meter or less. Where the euphotic zone is deeper than 80 meters, the discharge point should be at a minimum of an additional 50% depth. In addition, it suggests there should be two discharge pipes. The guideline also states that there should be no potential for long-term adverse effects of the natural bio resources. The guideline also specifies that the physical oceanographic environment in close proximity and further away should be monitored for a minimum of 1 year. This 1-year monitoring also includes weekly monitoring of stratified surface layers. Furthermore, the guideline also states that the benthic community should be enumerated and characterized for the three major organism body size classes (meso-fauna, macro-fauna, and mega-fauna). KREC-Norsk Bergindustri 25/110 March 2015 2.4.2. Philippines The Philippines have covered the environmental issues under the Mining Law in Chapter XI. All operations are required to perform an Environmental Impact Assessment regulated by the Environmental Impact Assessment System of the Local Government Code of 1991. All operating mining companies are required to pay a fee for generating tailings and mine waste. The fee is to cover potential damages to land, water and marine environment; and to cover the cost of re-vegetation, rehabilitation, etc. Even though the Philippines have active sub-sea tailings deposition, there is no specific law / regulation / guideline for such tailings deposition. 2.4.3. Turkey Turkey has one location with tailings deposition, where tailings are deposited at a 350 meters depth in the Black Sea. There has been some consideration to reduce the depth of the outfall from 350 meters to 250 meters depth. The final tailings deposition zone is in anoxic water at a depth of over 2000 m. Turkey has no specific regulations for the sub-sea tailings deposition, but is working on implementing the EU-Mining Waste directive with the follow-up commission decisions. 2.4.4. USA USA has no specific regulation for sub-sea tailings deposition; however, there are general requirements on the amount of solids in a discharge effluent (15 mg/l). The result is that sub-sea tailings deposition is practically banned. However, there is an opening for evaluating sub-sea tailings deposition if no other options are available. This has been done in a couple of locations: A.J. Gold mine project, Alaska in 1996; and Quartz Hill molybdenum prospect, Alaska, USA. Both of these projects were halted due to low metal prices in the mid 1990´s (Ellis and Robertson, 1999). 2.4.5. Canada Environment Canada has published a guide to understanding the Canadian environmental Protection Act of 1999. This guide discusses the practical use of the Canadian Environmental Assessment Act. Section 8.2.2 explains that deposition of KREC-Norsk Bergindustri 26/110 March 2015 mine waste into the sea is subject to a permitting system, based on an environmental impact assessment. There is currently no active mining operation with SSTD in Canada, but there are several closed large scale mining operations (Britannia Copper mine, BC; Jordan River Copper Mine, BC; Island Copper Mine, BC, Kitsault Molybdenum Mine, BC, Canada), which have provided a lot of experience/information that is used in currently active SSTD (Ellis and Robertson, 1999). (Den siste setningen er litt selvmotsigende hvis det fortsatt er snakk om Canada) 2.4.6. Australia Australia has no laws or regulations that specifically prevents the use of SSTD as an option for tailings displacement, as long as, the project conforms with the Australian and New Zealand Environmental and Conservation Council´s Interim Disposal Guideline (December, 1998). There are no active sub-sea tailings disposals or current proposals for SSTD. The Australian Best Practice Environmental Management of Mining Modules (2008) do not mentioned SSTD. 2.4.7. Jamaica United States Agency for International Development (USAID) has developed guidelines for dredging in coastal and estuarine region for the Government of Jamaica (USAID, 1992). This guideline includes sections on dredging mineral resources and disposal of the waste material generated from such dredging. The guideline identifies the characterization necessary for evaluating base-line conditions, and the issues that should be a part of an impact evaluation. The guideline also specifies the importance of long term monitoring during and after dredging cessation and deposition. The document also states that it is extremely important to do bioaccumulation studies using fish, crustaceans and molluscs typical of the disposal site. The Jamaica guideline for dredging builds upon the World Bank document 0126/1990 on dredging. (World Bank 1990). KREC-Norsk Bergindustri 27/110 March 2015 3. HEALTH AND SAFETY The specific health and safety issues related to the sampler in the context of a sub-sea waste deposition characterization are mainly related to both the sampling of the waste and the waste deposition site. During sampling, there are physical and chemical risks to be aware of. The physical risks related to the waste sampling may be: • • • • • • • • • Movement of large vehicles, e.g. trucks; Collapse of waste rock heaps/slopes during sampling; Trace metal dust inhalation and/or digestion; Inhalation of dust (e.g. silica, asbestos fibre); Active waste dumping; Sink holes and cavities; Unstable wet tailings etc.; Safety issues at sea; and Deployment of sampling gear. There may also be chemical issues related to the use of potentially hazardous chemicals in the process, or off-gases resulting from processes in the waste (e.g. hydrogen sulfide or carbon monoxide). The majority of sampling at a site, potentially employing deep-sea tailings deposition, will be performed from a ship utilizing appropriate sampling gear. In this case, the Ship’s Master will have the final say with respect to health and safety issues on board. The sampling plans should identify all relevant physical and chemical health and safety risks; and safety measures should be specified. Health and safety issues should be streamlined with the health and safety procedures of the operator. Good practice, when planning a characterization-sampling program, would be to develop a project and sitespecific health and safety plan. It is recommended that, at an operating site, waste sampling should never be performed by a single individual and that at least one member of the sampling team should be a local employee. These issues are further discussed in the sampling standard EN 14899. KREC-Norsk Bergindustri 28/110 March 2015 4. ENVIRONMENTAL ISSUES Sub-sea tailings deposition constitutes a different set of environmental risks not considered in the CEN/TR 16376:2012, Overall guidance document for characterization of waste from extractive industries. The environmental effects of sub-sea tailings deposition depend on how the tailings interact with the receiving environment. The impact the tailings will have on the receiving environment will be dependent on their composition, physical characteristics, and volume, as well as on the tailings discharge systems and waste-material management. There are mainly two environmental effects of tailings deposition; smothering of benthic biota and fauna in the deposition area, and environmental effects from suspended particles. The environmental issues are described in the following paragraphs. The different issues described comprise the physical and chemical characteristics of the tailings that combined with the characteristics of the receiving environment may potentially affect the water quality and/or the flora and fauna in the affected area, as well as the recolonization of the affected area. Each issue is described individually below; and some overlap may exist. Data obtained from the following issues are further discussed in Chapter 6. 4.1. Tailings characteristics When sediments are deposited, fine particles may remain in the water column for an extended period of time. Suspended particles may directly affect pelagic biota such as plankton and fish; and indirectly, by reducing light necessary for growth of flora and fauna. Discharge into the marine environment below the euphotic zone has generally less environmental effect since deposition is done below the zone of highest primary production (Ellis 2008). Never the less deposition will have a negative impact on benthic biota and fauna in the area of deposition. If the tailings system is not managed correctly suspended material may rise to shallower water depths and be transported longer KREC-Norsk Bergindustri 29/110 March 2015 distances. Correct management and monitoring is therefore important to ensure controlled deposition in intended area. Heavy metal contamination from tailings may have en environmental effect if metals are mobilized in to the environment in harmful concentrations. However, metals in sulfidic tailings are less likely to be released when placed under water as a result of less oxygen available for sulfide oxidation. Another important aspect is to evaluate potential environmental effects related to processing chemicals that may follow the tailings in to the marine environment. Some chemicals may have adverse effects on marine life, may not be biologically degradable and may accumulate in the environment, and may thus be linked with environmental risk. 4.1.1. Particle Transport / Siltation / Turbidity Particle transport by rivers, erosion, landslides and glacial activity are common natural processes. Substantial amounts of particles are continually being deposited naturally in lakes, fjords and at sea.. Negative effects of suspended particles are linked to concentrations that can cause reduction in the growth of the flora and fauna due to reduced photosynthesis in the euphotic zone. Other effects may be negative effects on predation caused by reduced visibility, and negative effects on gills. Particles dispositioning on the sea bottom will smother benthic fauna and flora that are not mobile and able to move away from the deposition area. Some organisms are adapted to high turbidity and sedimentation rates; however, these may not be common in the area where discharged tailings are planned, and will not be the only species within the receiving environment. The impact from particle transport and turbidity on pelagic and benthic biota needs to be assessed before any discharge. Generally a sandy/muddy seabed (sedimentation environment) is more suitable for deposition than a rocky bottom (high energy erosion environment) (Ellis 2008). Suspended particulate material has a direct effect on the fish by affecting the outer protective layer, skin and gills; and indirectly by affecting the ecosystem itself. The indirect effects may be: • Reduced visibility with reduced food uptake KREC-Norsk Bergindustri 30/110 March 2015 • • Siltation covering the bottom reducing or destroying the spawning and growth areas, smothering benthic biota and reduced productivity in deposition area Reduced primary production due to reduced light through the water. Tailings deposition can to some extent be compared with river deltas, where large amounts of sediments are being discharged into the sea. Flora and fauna is adapting to this system; however, the growth is commonly low where there is a high sedimentation rate, e.g. river deltas. Particle transport is closely linked to grain size together with the flow system, and the density difference between the discharge material and the seawater where discharge is taking place. The amount of fine-grained (less than 20 micron) particles within the tailings affects the dispersion in the marine environment). The amount of fine-grained material is a result of the milling and processing techniques required for extraction of the target minerals. A known effect on fine particles in sea water is flocculation. This is a process where particles because of their electrostatic charge and inherent stickiness floc together to form larger particle clusters. This effect increases the sinking velocity of the particles. Models predicting particle transport should therefore consider this effect that will largely affect the area of deposition and the concentration of particles in the water column. In addition to natural flocculation, additional flocculation may occur due to the use of flocculation additives in the tailings. The flocculation agent is often used for recovering fresh water, and causes the fine grained tailing to floc together. This will also affect the tailings settling velocity upon depositing. However, somefine-grained particles may not flocculate and can be transported with currents outside of intended deposition area. The concentration of which these particles appear will predict whether the particles will have a potential environmental effect or not (Skei and Syvitski 2014, Klif 2010). There are limited studies that investigate how suspended particles affect fish. It is known that fish have an avoidance behavior in relation to elevated particle concentrations. There are studies that show that fish seem to be unaffected by moderate elevations of suspended particles (~25 mg/l) (Hessen 92, Smith et. al 2008). Change in turbidity may result in a change in spawning areas, and in the areas where fish are located (Søvik et al., 2012). Fish that live and swim in the upper layers will likely be much less affected than the fish living/swimming at a lower depth. KREC-Norsk Bergindustri 31/110 March 2015 4.1.2. Acid/Neutral rock drainage and potential release of heavy metals Acid/neutral drainage is one of the largest environmental issues from mines with sulfidecontaining ores, waste material and wall-rock, and is a well know problem related to land depositing The exploitation of a mineral deposit results in an increased availability of surface areas for oxidation of sulfide minerals and, thereby, a potential increase in element release. Sulfide mineral oxidation can result in acid generation and release of heavy metals into the environment, especially if the sulfide minerals consist of pyrite and pyrrhotite. This process is called Acid Rock Drainage (ARD). Sulfide oxidation will commonly halt if the sulfide containing material is placed under water, due to low oxygen solubility and a slow oxygen diffusion rate in water. Strong water currents with oxygenated water will, on the other hand, increase the rate of oxygen transport to the sulfides and maintain some sulfide oxidation. The sulfide oxidation rate may also be affected by the salinity of the water due to electrochemical processes. Seawater has, however, a strong acid buffering capacity, so that acid generation will not take place in the seawater where there is a relatively high degree of water replacement. Acid drainage is primarily a problem related to land deposition, but should be evaluated and examined before tailings are placed in marine environment, if there is a concern about minerals (metals) possibly leaching during and after deposition (Walder et al, In prep.). Heavy metal contamination from tailings may have en environmental effect if metals are mobilized in to the environment in elevated concentrations. However, metals in sulfidic tailings are less likely to be released when placed under water as a result of less oxygen available for sulfide oxidation. This is especially true for anoxic water. Biogeochemical cycling of elements, including metals, takes place within a marine environment. This occurs when the redox condition of the water and/or the sediment changes, causing the elements to be released from particulates/sediments to the surrounding water; or conversely, elements are removed from the water to the solid phase. The minerals may be sulfides that oxidize in the saline alkaline seawater, releasing elements into the seawater, creating a similar condition to neutral rock drainage. There may also be other minerals that are unstable in the oxidizing highly saline setting that would release elements/constituents of concern during alteration. In addition, anoxic conditions in the sediment will affect the metal cycling. KREC-Norsk Bergindustri 32/110 March 2015 For some minerals the weathering processes is faster in salt water than fresh water , and tailings containing these minerals may therefore be in risk for metal contamination. Chemical alteration and settling rate may be linked. If minerals stay in the water column for a prolonged period of time before settling they will have a longer exposure time for alteration/ dissolution if unstable under the oxidizing saltwater conditions. The waste characterization needed for proper sub-sea tailings deposition is similar to that described within the Overall guidance document (CEN/TR 16376:2012). However, some special materials tests of tailings material, and a thorough characterization of the receiving environment is required in order to properly evaluate the impact of sub-sea tailings deposition. 4.1.3. Process chemicals Process chemicals are mainly used in two operations in mineral processing; froth flotation for selectively separating economic minerals from waste, and flocculation to remove fine-grain material in wastewater treatment. Froth flotation chemicals There is commonly a need to add chemicals at different stages in the mineral processing, especially during processing by flotation. When processing is performed by flotation, chemicals having different functions are added in several steps. These functions may be the following: • • • To generating the foam/froth; As collectors so that certain minerals stick to the bubbles; To suppress certain minerals from sticking to the foam (e.g. lime to suppress pyrite from other sulfide minerals); and Even though many of these chemicals are biodegradable, there is a potential for these to leach into the environment, whether in a land based tailings pond or sub-sea tailings disposal. KREC-Norsk Bergindustri 33/110 March 2015 The flotation process is strongly dependent upon the type of minerals to be recovered. In the case of iron ore, this can either be performed with fatty acids or amines as collectors, or by activation, converting the oxide surface to e.g. a sulfide surface, and using thiocomplexes as xanthates. There are four main processes used on an industrial scale in order to separate hematite from primarily quartz in a non-surface activated system (Somasundaran and Luo, 1999): • • • • Flotation of hematite using sulfonates as the collector at pH 2-4; Flotation of hematite with fatty acids as the collector at pH 6-8; Flotation of quartz with amines as the collector at pH 6-8; and Flotation of quartz with calcium ions at pH 11-12, using soaps as the collector with starch to depress the hematite. There are many different chemicals used for sulfide flotation. The three main collectors are xanthate, dithiophosphate and thionocarbamate. By sequentially using additional chemicals or stronger solutions of collectors, different sulfides can be separated and collected. Polypropylene glycol methyl is the standard frother used. New research has shown enhanced recovery in coarser sulfide particles by using different amounts of frothers (Klimple, R, 1999). Success of the flotation depends on the differences in surface charges of the minerals to be separated. The surface charge depends upon the pH of the solution and is given by the zeta potential. The pH of the flotation liquid is commonly controlled by the addition of a low-cost base (lime for raising the pH and hydrochloric acid for lowering the pH). The tailings water can, therefore, be acidic or basic depending upon the flotation process (Klimple, R, 1999). A method for separating chalcopyrite from pyrite using microorganisms has also been developed. Thiobacillius ferrioxidance rapidly colonizes pyrite but not chalcopyrite. Pyrite will, therefore, not have a surface charge; while chalcopyrite will maintain the surface charge and can then be separated from pyrite (Chander, 1999). Excess chemicals are used in the flotation process. Chemicals that are not associated with the concentrate will, to a large extent, be collected with water in the thickener. KREC-Norsk Bergindustri 34/110 March 2015 This is especially true if the ore minerals are enriched with the collectors. However, if the collectors used are for the separation of gangue minerals, the recovery of the chemicals in the thickener will likely be less effective. What is not recovered in the thickener will be discharged with the tailings material. Some collectors for silicate flotation, i.e. cationic surfactants, like quaternary ammonium compounds, are strongly absorbed on the mineral surface and are to a very low extend effecting the surrounding environment in a deposit for mineral waste. The biodegradability is ruled by the desorption rate, which is slow, and these molecules can hardly bio accumulate as they will be stopped on biological membranes. The chemical equilibrium is strongly shifted towards the solid material and these chemicals can hardly be found in the water phase. Flocculation chemicals Milling may result in a large volume of fine-grained material. In order to reduce the water content it may be necessary to run the material through a thickener with the addition of a flocculation chemical (flocculent). Flocculants are polymers that will flocculate the fine-grain material (colloids to clay- size minerals) with larger grains and, thereby, improve the water recovery from the tailings. The flocculants is commonly used in connection with a thickener. There are many producers of flocculant agents. There are organisms living near the bottom that are likely to eat/digest fine-grained tailings material near the bottom or directly digest bottom sediments. The larvae and small fish again eat these organisms and; therefore, existing contaminants can be bioaccumulated up the food chain. 4.2. Tailings discharge systems The type of tailings discharge system and waste-material management may reduce or enhance the potential environmental issues of sub-sea tailings deposition. 4.2.1. Plume density KREC-Norsk Bergindustri 35/110 March 2015 Upwelling, having the potential of transporting fine-grain tailings particles to surface waters, is a concern partly from a fjord current issue and, as well as, a potentially poor waste-material management issue. If there are air bubbles in the material when depositing, the bubbles will rise after discharge and pull tailings upwards. Upwelling may also take place if the interstitial water in the tailings material has lower specific weight than the water at the discharge point. This will result in upward migration of the water that will pull tailings material along and possibly spreading the material in the upper part of the seawater column. Commonly modern tailings discharge is mixed with seawater prior to deposition to ensure that the plume forms a density plume that settles on the sea bottom. 4.2.2. Pipeline break There is a potential for damage to the pipeline transporting the tailings material from the processing plant to the discharge point. This may be due to wear and tear of the material, accidents with boats and onshore equipment, as well as, weather related incidents. Depending on the damage point, such situations can easily result in a spill to shallow areas or upwelling from an uncontrolled spill from the designated outfall depth to shallower waters. These types of pipe breaks have taken place in Papua New Guinea and Turkey. 4.3. Receiving Environment All of the issues described above relate to the tailings deposited into the receiving environment. The receiving environment must also be characterized well enough to be considered a suitable waste disposal site for tailings deposition. 4.3.1. Fjord circulation Upwelling may also be caused by deep water being pushed upwards to shallower areas. Typically a fjord environment consists of several layers due to salinity and temperature differences. This layering will commonly result in reduced vertical transport and the mixing occurring primarily within the layers. Depositing should preferentially be done below the surface layer since this layer form a barrier for upward transportation of tailings. KREC-Norsk Bergindustri 36/110 March 2015 Fjord circulation can be complex. Environmental factors, such as size of catchment, fresh water runoff and occurrence of sills at mouths of basins will determine the circulation and level of mixing between different density layers within the fjord. Depth to the thermocline and halocline in the fjord are important parameters to obtain. The depth at which changes occur in temperature (thermocline) and salinity (halocline) are important when determining whether the receiving environment is suitable for deposition of tailings, and at what depth a discharge point should be set. Occasionally deep water replacements can cause deep water to be pressed upwards and being replaced by water from the sea. This shift may cause fine particles from tailing to be transported upwards to more shallow layers of the fjord. It is important to determine the effect of these events on the dispersion of the tailings. 4.3.2. Vertical water column Vertical mixing may result in vertical plankton migration together with transport of oxygen and chemical compounds. This may result in increased oxidising conditions at the bottom, and transport of potentially harmful elements to higher water layers in the sea. These mixings may be induced by tidal water flow, variable fresh water input from rivers throughout the year, and overturn of the water column due to temperature change in the surface water. 4.3.3. Changes in currents due to deposition If the amount of sediments discharged is considerable relative to the capacity of the receiving environment, the deposition may result in a change in the current pattern that again, may have an effect on flora, fauna, and organisms in the water column. 4.3.4. Effects on fish dependent on fish type There are many different fish types with different habitats and living patterns. Fish that live in the upper part of the water column are less affected by sedimentation from the deeper tailings deposition than bottom-dwelling fish. Migrating fish may be affected KREC-Norsk Bergindustri 37/110 March 2015 differently from permanent fish types. The different fish types to be concerned about may include: o o o o o 4.3.5. Pelagic fish (e.g. herring, mackerel) Farmed fish (salmon, sea trout) Bottom fish (e.g. flat fish, cat fish) Stationary fish (e.g. cod, pollock) Migrating fish (e.g. salmon, sea trout, cod) Spawning area (permanent – variable) Fish with different habitation systems also have different spawning requirements. The spawning areas may be permanent or may move, depending on the environmental conditions from year to year. Therefore, tailings deposition may affect the spawning, depending on fish type. 4.3.6. Ecosystem effects There may be cumulative effects that are difficult to see without looking at the ecosystem as a whole. Blocking off part of a fjord bottom may result in a lack of bottom migration of flora –fauna that are essential to other flora-fauna-fish in a different part of the fjord; and therefore, the tailings deposition may have an indirect effect on certain species. 4.4. Recolonization Where tailings deposition is greatest, the benthic biota will be smothered and suffer major impacts. The recolonization of an area will depend on the environmental conditions that exist post-operation (change in sediment type, change in nutrient level, sea current change, depth change, etc.). Investigations performed in the Jøssingfjord, Norway; Bøkfjord Norway; and Island Copper Mine, Canada, after closure of the sub-sea disposal indicates that the natural revegetation of a barren tailings deposition, to reach a sustainable ecological succession, KREC-Norsk Bergindustri 38/110 March 2015 can take place relatively rapidly, over 2-5 years. The species are often as varied and rich as before depositing but may have a different composition compared with the original flora and fauna. This may be due to: • Change in sediment type (grain size and chemistry from the natural sediments; • No nutrient in the new sediments (tailings material); • Leaching of elements/compounds that are effecting species differently; • Shallower than original topography which can result in more sunlight and change in natural habitats and higher growth; and • The weathering may result in change to a mineralogy that forms a crust – hardpan, as indicated at the shoreline deposit from the former Nussir deposit flotation plant (Øystein Rushfeldt, Nussir ASA, Pers. Com., 2012). This hardpan, on land-based tailings, is commonly a mix of gypsum, calcite and iron hydroxide; however, other minerals can as well be a part of the crust. The sub-sea tailings deposition described in this document relates to more confined areas, such as fjord environments, not deep-sea conditions, as is the case of Papua New Guinea’s tailings deposition. Tailings deposition in Norway will most likely be within a confined fjord/sea area (Figure 2), where there is some type of geological barrier. This barrier reduces the spread of tailings material; and it is similar to an on-shore tailings dam, where tailings material is contained within a constructed dike. Titania considered an artificial barrier in the Dyngadypet deposit closing off Knubedalsrenna, in order to reduce spread of tailings material. (Evaluated by Havnelaboratoriet i 1986) There may be different options of rehabilitating the tailings by • Re-introducing the species that where there before; • Develop a reef that will increase growth; and • Fertilize the tailings sediment, before or after deposition, e.g., by establishing a fish farming plant above the tailings- KREC-Norsk Bergindustri 39/110 March 2015 Figure 2. Simplified sub-sea tailings deposition setting from a mine, via processing plant, thickener, and discharge pipeline to deposition. It also shows mixing in the upper part of the water body, layering in the sea due to salinity differences, and general flow direction out of the fjord. KREC-Norsk Bergindustri 40/110 March 2015 5. CHARACTRIIZATION OF DEPOSITION SITE Obtaining baseline information is an essential part of waste characterization, which again is essential for developing waste management plans. The EU-Commission Decision on waste characterization has included several areas that, in addition to understanding the waste properties, will help in determining the short and long term behaviour of the waste, and the potential impact on soil, surface water, groundwater and seawater. The CD decision 2009/360/EC specifies five categories of information: • • • • • Background information; Geological background of deposit to be exploited; The waste and its intended handling; Geotechnical behaviour of waste; and Geochemical characteristics and behaviour of waste. The first three categories cover supporting information that is discussed briefly in the Overall Guideline (CEN/TR-16376/2012). The last two categories listed above cover what is generally considered as waste characterization, and are discussed in detail in the four CEN guidelines on mine-waste characterization. Information from the disposal site is briefly mentioned but only for onshore deposition. Figure 3 shows the flow chart for a baseline evaluation. KREC-Norsk Bergindustri 41/110 March 2015 Figure 3. Flow chart for a baseline evaluation. When evaluating sub-sea tailings deposition, on-shore deposition should also be evaluated so that it is feasible to compare the potential impacts between the main alternatives to determine the option that is the safest and has the least environmental impact. General background information about the deposit to be exploited is as important when evaluating a sub-sea tailings deposition as for an on-shore tailings deposition. With new operations, information is gathered during exploration. The amount of information is variable depending on the type of deposit and how far in the exploration process a project may be. The amount of information increases as production gets closer. It is important that specific environmental issues are evaluated as part of the exploration process. For on-going operations, gathering information about the deposit is often a natural part of the operation; and characterization data from produced waste may already exist. The existing information may not meet current characterization standards, and additional information may be needed which can be integrated into the operation. Examples of useful information gathered during exploration and production may be: KREC-Norsk Bergindustri 42/110 March 2015 • • Three-dimensional geological mapping combined with mineralogical and geochemical analysis, which is normally an essential part of the exploration data gathering; Groundwater and surface water information collected and evaluated before and during the operation, e.g.; o Evaluation of process water access; o Assessment of pumping capacity for open pits and underground operations; or o Evaluation of runoff water quality from underground or open pit operations. Use of existing information should be complemented with a field visit for verification; and geochemical/mineralogical data should also be verified by additional analysis. 5.1. Background Information General background information and objectives of the extractive operation is helpful in order to put the waste and the waste characterization process into context. The background information would typically include general information about the following: • • • 5.2. On-going or planned prospecting, extraction, or processing activity; Type and description of method of extraction and process applied/planned; and Intended product. Mineral Deposit General Information of the mineral deposit is aimed at identifying waste units that will be exposed by extraction and processing, as specified in the EU-Commission Decision on waste characterization: • • Nature of surrounding rocks, their chemistry and mineralogy, including hydrothermal alteration of mineralised rocks and barren rocks; Style of mineralisation and morphology of mineral deposits, including mineralised rocks or rock-bearing mineralization; KREC-Norsk Bergindustri 43/110 March 2015 • • • Mineralisation typology, including physical properties such as density, porosity, particle size distribution, water content, economic minerals, gangue minerals, hydrothermal newly-formed minerals; Size and geometry of deposit; and Weathering and supergene alteration from a chemical and mineralogical point of view. Not all of this information is relevant for all types of operations. The level of detail of information to be gathered should be adapted to the type of waste, the potential environmental risk, and the intended waste facility. 5.3. Exploitation method The Exploitation method needs to be described. In general, this is underground and surface/open pit mining. However, it is also important to describe the mining plan, as this has a bearing on the amount and potentially the quality/variability of the waste being generated. The exploitation method needs to combine information about the potential resources within the deposit to show how economical the mineral resources are, and to supply information for a waste minimization evaluation. 5.4. Mineral Processing The type of mineral processing depends, to a large extent, on the economic minerals or elements to be extracted, the mineral assemblage, morphology, grades, the size of deposit and type of deposition feasible. The mineral processing also affects the type of waste generated and the type of waste management strategies chosen. Information about the origin of the waste and the processes generating such waste is, therefore, a natural part of the waste characterization. A practical approach could be to document predicted quantities (annual and total) of site specific waste categories based on factors that affect the waste handling: e.g. mineralogical characteristics, and type of process the waste has gone through before being deposited. KREC-Norsk Bergindustri 44/110 March 2015 The waste transportation system (e.g. transport by trucks, conveyer belts or pipe lines) needs to be specified with quantities within each waste stream and transport system. It is recommended that planned or existing waste transportation systems are documented. Mineral processing may involve the use of chemical substances: e.g. collectors, frothers, suppressing agents, flocculants and leaching agents. The substances can end up in the product which is sold or in the waste stream which is deposited, depending on whether it is a direct flotation or a reverse flotation. It is, therefore, necessary to list all process chemicals, where they are used, in what quantities they are being used, and where they will end up. In addition, under EU legislation, information should be provided on the classification of the waste according to the Commission Decision 2000/532/EC, including the hazardous properties (the so called European Waste Catalogue). The CD also requires the waste characterization to include information on “type of waste facility, final form of exposure of the waste and method of deposition of the waste into the facility”. It should be noted, that for new operations, even though preliminary plans and information may be available at an early stage, these are management decisions that should be made based on the results of the waste characterization and characterization of the waste disposal site. 5.5. Deposition Site Information regarding baseline properties of the intended waste disposal site (or alternative sites where relevant) is necessary to evaluate the potential impact from future waste disposal. The appropriate level of detail will depend on the type of waste and the disposal scenario planned. Relevant information regarding potential on-shore disposal sites may include (but not limited to): • • • • • • Site topography, surface and groundwater hydrology Climatic conditions; Dimensions of the planned waste facility, Physical properties of the foundation soils and bedrock. Geochemistry of foundation soils and bedrock, Surface and groundwater geochemistry. KREC-Norsk Bergindustri 45/110 March 2015 Relevant information regarding potential sub-sea disposal sites (described in more detail in Chapter 6.8 and 6.9) may include (but not limited to): • • • • • • • • 5.6. Bottom topography and depths; Water current variations (vertical and horizontal; seasonal and daily); Environmental conditions in the water column; Environmental conditions near the bottom sediments; Bottom sediment physical and chemical characteristics Bottom flora and fauna identification and abundance; Fish density and fish types and other pelagic species such as zooplankton; and Potential symbioses between different populations within the fjord system. Deposition The method of deposition needs to be described in detail. The deposition method needs to take into consideration the characterization of the waste and waste disposal location. For a SSTD, this includes the following: • • • • • • • Thickener o Capacity o Efficiency of water/chemical removal o Additives De-aeration system Saltwater addition system (mixing tank) Pipeline o Material o Dimension o Length o Anchoring o Floating bodies o Pipe extension systems o Pipe outlet design; diffusor, branches etc o Maintenance management system Discharge point/location/depth Emergency response system if failure occurs Twin pipe systems for safe operation KREC-Norsk Bergindustri 46/110 March 2015 The whole area assigned for deposition may not be active at the same time. The depositional system for changing the discharge point needs to be described, if applicable. KREC-Norsk Bergindustri 47/110 March 2015 6. CHARACTERIZATION OF TAILINGS This chapter describes the characterization of the waste and of the potential sub-sea deposition area. The characterization of the waste follows the CEN/TR 16376:2012 (Mine waste characterization guideline). However, when evaluating sub-sea deposition, there are specific waste characterization issues that are not covered in the CEN/TR 16376:2012 and are, therefore, highlighted within this document. The most common methods used for mineralogical, geotechnical and geochemical analysis in the extractive industry are presented in this chapter, together with a discussion of their applicability, together with the methods used for sub-sea disposal site characterization (Fig. 4). Figure 4. Characterization flow chart. The Water Framework Directive specifies many issues that need characterization. The methods to use in such characterizations are described in section 6.8 and 6.9. KREC-Norsk Bergindustri 48/110 March 2015 The methods described should be seen as a set of tools. Which tools to use in a specific case will depend on the characterization objectives, type of operation, available disposal scenarios, and other site-specific conditions. However, before any characterization is performed, a sampling plan must be developed, as discussed below. 6.1. Sampling Plan To obtain sufficient data for performing a required waste characterization or characterizing a site for deposition of waste, a sampling plan needs to be developed. A field visit will be required as part of developing a sampling/ survey plan. A specific sampling guideline for the characterization of waste from extractive industries has been developed (CEN/TR 16365:2012). This guideline builds upon EN14899, “Sampling of Waste Materials”. The guideline focuses on the development of the sampling plan but includes sections on sampling equipment, storage, and transport. The sampling plan guideline does not describe sampling for characterization of a waste disposal site; however, many of the issues described for a sampling plan are also applicable for developing a sampling plan for a waste disposal site characterization. Issues related to sampling of the sub-sea waste storage site are further described in section 6.8 and 6.9. According to the sampling guideline, a plan for characterization of waste from extractive industries should normally cover the aspects listed in Table 1: ASPECT Identification of stakeholders Identify general objectives Background information Specific objectives Determine generic level Identify constituents and analytical methods Identify health and safety precautions Select sampling approach Identify sampling techniques Sub-sampling Sample preparation Transport sample Document sampling plan and produce instructions for the KREC-Norsk Bergindustri EXPLANATION List with contact information of all stakeholders General objectives as described in Clause 2, Information of the process type, waste types, known geology, mineralogy, previously performed characterization etc. Detailed objectives such as prediction of drainage quality, ARD potential, mineralogy Sampling for screening, detailed characterization, confirmation etc. Elements/constituents of concern e.g. total metal content, pyrite content, and analytical methods to determine these constituents; animal count, flora count Health and safety issues for the sampler and the storage and transport of the samples Judgemental, unbiased, etc. Sampling from drill core, auger, shovel, grab etc. Splitting system of samples after collection for reduction of volume/mass Freezing, drying, splitting for different analysis, storage requirements Transport system to the lab and transport documentation Details on sampling procedure for the sampler 49/110 March 2015 sampler Produce a field sample record Complete sample record and document changes List of information to be included in the field sample record List deviations to the sampling plan and reasons for the deviation Table 1. List of the main aspects to be covered in a sampling plan, summarized from CEN/TR 16365, 2012. 6.2. Physical and hydraulic properties Obtaining physical and hydraulic properties for on-shore deposition is described in the Overall Guidance document (CEN/TR 16376:2012). Many of these properties are also important in assessing sub-sea tailings deposits. These issues are important in evaluating the physical stability of the disposal sites. Only a few of the parameters included in physical and hydraulic properties can be obtained prior to generating the waste deposit. Many of the parameters are included in the waste design and are verified by sampling and testing afterwards. It is necessary, for example, to assess the potential buildup of sediments around the discharge pipe. This can be determined using parameters such as discharge velocity, sediment grain size distribution, specific gravity, sea current and topography. Geotechnical investigations may be divided into laboratory and in situ investigations. Laboratory characterization and testing of the waste material may measure properties such as: compressibility, shear strength, angle of friction, grain size distribution, density (bulk density and specific weight), Attenberg limits, plasticity, fracturing, liquefaction potential, permeability, and erosion potential. Also an accurate composition of the material must be made. While laboratory investigations, in general, make more accurate measurements possible, the average sample size is generally small. Therefore, an accurate sampling strategy to ensure representative samples is crucial. The sampling plan should be constructed to avoid possible replication, and analyses should be replicated to allow statistical analyses of the data. Up scaling of the results should, however, always be done with care. In-situ tests are, in principle, only applicable to waste already present in existing waste dumps and tailings storage facilities. Their relevance for initial testing in the planning stage is limited. However, with advances in ‘smart technology’, it is possible to make KREC-Norsk Bergindustri 50/110 March 2015 in-situ measurements of the seabed; and this should be considered as part of the baseline study of the deposition site. This short introduction to field and laboratory investigations indicates that there is no perfect methodology for the characterization of physical properties of the waste material. There are different, more or less adequate, investigation strategies. All include some level of inaccuracy that can only be reduced using well-educated and highly experienced professionals. It is important to consider the strong interdependence between physical and geochemical properties. While the physical properties of the waste may have a significant impact on the long term geochemical performance, chemical weathering of the waste may lead to changes of the physical properties. Different sets of testing may be considered for physical characterization of tailings material for sub-sea deposition. 6.2.1. Compressibility and frictional behavior Compressibility and frictional behavior are key parameters for the assessment of the behavior of tailings impoundments. The internal friction is a key element of physical stability, and in turn, is strongly linked to the level of compaction and dependent on other processes taking place. Several factors are important in understanding the compressibility and self-compaction properties of the waste materials, including: the overall compressibility; its dependence on moisture content; the possible migration velocity of moisture (seepage velocity); and the grain-size distribution. 6.2.2. In-situ Investigation of Deposited Waste Sediment core sampling is one way to get direct information from already deposited waste. Disturbed and undisturbed samples can be collected using core samplers. The stratigraphy of the impoundment material may be described using a bore log. Disturbed samples are used to determine the Atterberg-limits, Proctor type, bulk density and compressibility. From these values, bearing capacity, plastic and elastic soil parameter values can be estimated. Undisturbed samples can be used for triaxial or uniaxial tests to determine internal friction and cohesion of the materials. The above mentioned KREC-Norsk Bergindustri 51/110 March 2015 properties of disturbed samples or loose soils can also be investigated using shear tests. In specific cases it may be best to avoid boring. Besides boring, Cone Penetrometer Testing and Standard Penetrometer Testing can be used to characterize larger areas. Since they are quick and rather cheap testing methods, they can be used to refine information from borehole investigations. Moreover, indirect information on bearing capacity vs. depth can be recorded by special sensors. To sample tailings deposition on the seabed, specialized multi-corers are used to preserve the sediment water interface. In addition, multibeam and acoustic seabed surveys are used to monitor the tailings footprint on the seabed. 6.2.3. Grain Size / Specific Surface Area Grain size is important for both geotechnical and geochemical evaluations. Grain size analysis can be performed with a set of sieves for the coarser fraction, and pipette method for the clay size fractions. Laser diffraction size analysis can also be used for both coarser and finer fractions. Sieving can be performed either wet or dry. However, dry sieving results in less finer fraction. Surface area, used for evaluating reactive surfaces, can be calculated from grain size analysis (Lapakko and Antonson, 2006), or by using the EMS method (Brunauer et al., 1938). Both will provide the total surface area, however, surface area of individual minerals may not be the same as the percentage composition of each mineral. Morphological analysis is necessary to evaluate available surface area for reactive minerals within the waste material analyzed. 6.3. Mineralogical Composition and textural information Knowledge of mineral composition and mineral chemistry is essential in interpreting chemical composition or leach tests data, and for predicting short and long-term drainage water quality from waste material. Mineralogy, therefore, provides supporting information for waste characterization and for the assessment of long-term behavior at a waste facility, whether on-shore or sub-sea deposition is selected. Detail on mineralogical analysis related to mine waste characterization is described in the Overall Guidance document (CEN/TR 16376:2012) and briefly in the following paragraphs. KREC-Norsk Bergindustri 52/110 March 2015 Mineralogical information together with physico-chemical conditions may, for example, provide evidence of the occurrence of weathering processes (weathering potential) like: • • • • • Oxidation (sulfides); Dissolution (carbonates, sulfates, oxides); Hydrolysis (silicates); Sorption (clay minerals, metal oxides); and Mineral stability/reaction rates. This information, in combination with geochemical data and leach test results, can be used to evaluate; long-term leaching potential within the waste material, metal transport within the waste and into the surrounding environment, and attenuation in the surrounding material (bedrock, soil etc.). There are many different mineralogical analyses that can be performed; and their usefulness varies with the type of issues needing to be solved. However, understanding the mineralogy, the mineral texture, and mineral assemblages is instrumental in understanding and predicting geochemical and physical stability. These methods can provide reliable information on bulk mineralogical composition, especially on specific questions of mineral heterogeneity and alteration processes. This guideline provides background information on the capabilities and limitations of the analytical methods to facilitate dialogue with specialists. The mineral sciences have become very equipment-focused. The analytical methods are being developed towards high accuracy determination of small quantities. Having a well-established purpose with the mineralogy investigation will aid in choosing the right method(s). Below is a brief summary of the methods: Microscopic analysis is often the basic form for mineralogy analysis. The microscopy analysis can give information on the type of minerals and if these minerals have undergone any alteration/weathering; mineral intergrowth and mineral assemblages. In addition to microscopy, X-ray diffraction (XRD) methods are commonly used to identify minerals. This method, however, has detection limits of 2-3 wt %. This means that the method may not detect minerals that could be of concern even at lower concentrations, e.g. sulfide minerals. XRD methods are only semi quantitative, and KREC-Norsk Bergindustri 53/110 March 2015 additional chemical analyses are necessary to quantitatively (e.g. Rietveld method) identify minerals when using XRD. An electron probe micro-analyzer, EPMA, is a micro-beam instrument used primarily for in situ chemical analysis of minute solid samples. The primary advantage of an EPMA is the ability to acquire precise, quantitative elemental analyses at very small "spot" sizes (as little as 1-2 microns), combined with the ability to create detailed images of the sample. EPMA analysis makes it feasible to evaluate in what mineral form hazardous elements may be located; and thereby, evaluate the availability of these elements. Assessing the texture of the waste material may be important when characterizing the waste material; as the texture of the rock provides information about the actual availability of minerals for leaching, and generating acid or neutralizing acidity. If the reactive minerals are fine grained, this will lead to a large surface area when crushed, i.e. high availability. If the reactive minerals occur basically encapsulated within nonreactive minerals, they may remain unavailable. It may also be relevant to assess the degree of liberation; i.e. if the surfaces of the mineral grains are available for surface reactions. This is relevant for neutralizing minerals, acid producing minerals, or leachable minerals. Analysis of the texture of the waste material is commonly performed by classifying the texture of hand specimens and from microscopic analysis of polished thin sections. However, MLA (Mineral Liberation Analysis) is becoming more common, as an addition to traditional methods. 6.4. Chemical Analysis Chemical composition of water and solids can be assessed by a variety of methods. Solids can be analyzed directly using, e.g. X-Ray Fluorescence (XRF), Atomic Absorption Spectrometry (AAS) with graphite furnace or digestion followed by analysis of the dissolved substances. There are different options for digestion and which method to choose partly depends on the objective of the study, and on analytical methods chosen in earlier studies (to produce comparable data). There are also many options for chemical analysis of solutions; and which method to choose, again, depends also on the objective of the study. There are numerous publications on chemical analysis; and KREC-Norsk Bergindustri 54/110 March 2015 CEN/TR16376:2012 lists applicability of CEN and ISO standardized tests methods for waste from extractive industries. 6.4.1. Analysis of Solids It is important to recognize that different digestive methods can give very different results. For example, the most common digestive method for waste characterization is using aqua regia. Aqua regia is a strong acid, however, it will not dissolve silicate minerals. Hydrofluoric acid is needed for silicate mineral digestion. Microwave digestion is a standard method for total digestion of all types of minerals and is recognized internationally as a reliable and accurate method for sample dissolution. Handheld XRF can be a very useful tool in the field for both water and solid analysis. However, the detection limit is poor. It may, therefore, be necessary with follow-up analysis in the laboratory, using equipment with better detection limits. Assessing chemical speciation may also be necessary, e.g. Chromium (III)/Chromium (VI), Iron (II)/Iron (III); and dedicated analytical techniques or several techniques may be necessary. Speciation may also include evaluating distribution of elements between different minerals; e.g. lead sorbed to metal oxides, in sulfide minerals and in silicate minerals. This may be performed with a combination of mineral analysis, EPMA, XRD, and sequential chemical extraction, and possibly together with geochemical modeling (Lichtner et. al. 1996, Moritz et al, 2009). 6.4.2. Analysis of liquids Chemical analysis of water and the digested solid solutions with a focus towards multielement approaches can be performed using Induced Couple Plasma atomic emission spectrometry (ICP-AES) or mass-spectrometry (ICP-MS). However, some elements commonly found in very low concentrations (mercury, arsenic, antimony and selenium) are better analysed with cold vapor atomic fluorescence AAS (CV-AAS), e.g. mercury; and hydride-generation AAS (HG-AAS) for the other elements. Analysis of trace elements in seawater needs to follow a separate approach due to the very high chloride and sodium contents. A common approach is to dilute the seawater sample 1:9 with purified water. Trace element analyses with AA-graphite furnace will also require the use of modifiers. ICP-MS is routinely used for the analysis of seawater, KREC-Norsk Bergindustri 55/110 March 2015 and has very low detection limits allowing accurate analysis of very low concentration of elements. 6.4.3. Sulphur (total, sulfate and sulfide) In the characterization of sulfide containing waste, analyzing sulfur and the mineral forms of sulfur is crucial in assessing acid potential together with determine short term and long-term acid neutralizing potential. These types of acid potential and neutralizing potential analysis forms the basis for Acid-Base Accounting (ABA) and acid/neutral rock drainage (A/NRD) evaluations. ABA analyses are required for most types of wastes form the extractive industry. Analysis of ABA is described in the EU standard CEN15875:2011 (Static testing for determination of acid potential in sulfidic waste), and a discussion on how to evaluate the data is described in the Overall Guidance document (CEN/TR16375:2012). 6.4.4. Organic and Inorganic Carbon Total organic carbon can be analyzed using high temperature combustion (1350 dC). This takes both organic and inorganic carbon. It may be necessary, therefore, for a pretreatment stage, where the sample is acidified, and thereafter, CO2 gas is vented, prior to combustion. Alkalinity analysis of a water sample and subtracting the carbon content from alkalinity will also make it feasible to obtain total organic carbon. Total inorganic carbon in a solid sample would consist of carbonate minerals. Analysis of this can be performed using high temperature combustion, assuming that there is no organic carbon present. Otherwise, the sample can be analyzed using the ABA method (CEN-15875) section 6.5.1. 6.4.5. Process chemicals Additives may be used in many different steps in mineral processing, especially in a flotation process: collectors, frothers, modifiers, depressants, activators, and flocculants. Flotation collectors are made of polar groups and one or more non-polar hydrocarbon groups. Activators may be copper sulfate or sodium sulfide for many of the sulfide minerals and some carbonate minerals. Collectors are often amyl, butyl, or ethyl xanthates or in some settings kersosene or tall oil. Modifiers are commonly lime or soda ash. The frothers used are commonly a type of oil, pine oil, beret oil etc. The type and KREC-Norsk Bergindustri 56/110 March 2015 amount of additives used depends strongly upon the type of economic minerals to be recovered and the gangue minerals to remove. The analysis of these will vary depending upon the components. Some of the additives will be difficult to detect because the elements are already within the mineral matrix. Some collectors, i.e. for silicates will be very difficult to detect as they are strongly bound to the mineral surfaces. Often only the producer of the chemicals can do the analyses. The additives used for leaching may be strong acids (sulfuric acid, hydrochloric acid) or strong bases (soda ash, lime) often with carbonate as a complexing agent for anions, or cyanide for precious metals. Analysis of most inorganic additives is included in section 6.5.2, while cyanides analysis is described in CEN/TS16229: 2011 (Sampling and analysis of cyanides discharged into tailings ponds). Analysis of organic additives depend upon the type of chemical but may be analyzed by ion-chromatography, gas chromatography, and ICP-MS, depending upon what compounds are analyzed. 6.5. A/NRD Testing Methods The EU Mining Waste directive (2006) requires the use of a new static test method for evaluating A/NRD potential. As part of the implementation of the directive, a static test method was developed EN15875 (2011) which is built upon the most commonly used ABA methods in the mining industry, Modified Sobek (Lawrence and Wang, 1998). The Overall Guidance document (CEN/TR 16376:2012) describes how to interpret the data and when to use kinetic testing for further evaluation of the A/NRD potential. These methods are described within the next few sections. 6.5.1. Static Testing - Acid Base Accounting (EN15875) Static testing is a requirement in the EU Mining Waste directive and included in the Norwegian law in the updated Avfallsforskriften, 2012. In addition to the method EN15875 (2011), developed for the Mining Waste directive, the Overall Guideline for KREC-Norsk Bergindustri 57/110 March 2015 characterization of mine waste (CEN/TR 16376:2012) describes other methods. However, these methods are not recommended for basic characterization, but are recommended for verification during production. 6.5.2. Kinetic Testing Kinetic tests are experiments set up to allow naturally occurring reactions to take place, and are a special form of leach tests designed for mineral reactions that has a strong rate change with time. These reactions will commonly change the behavior of the tested material over time. The concept of kinetic tests could include any test that allows for, and measures, changes over time. Commonly, kinetic testing refers specifically to tests run to evaluate acid generation behavior of sulfidic wastes, i.e. to quantify reaction rates for acid producing and buffering reactions and to evaluate if the material actually will go acidic or not. However, these tests can also have other more specific objectives, and the design can be tailored to achieve these objectives. Both long-term and short term leaching takes place during sub-sea tailings deposition. This has not been described in the mine waste guidelines. • Long-term leaching from bottom material after settling • Short-term leaching from the material while settling The Overall Guideline (CEN/TR 16376:2012) specifies the use of kinetic testing if the neutralizing potential (NP) to acid potential (AP) is NP:AP<3. In the case of depositing tailings under water, specific kinetic tests for sub-sea tailings deposition should always be performed. Kinetic testing to evaluate long term leaching behavior from tailings deposited under water is different than the kinetic testing described in CEN/TR16363:2012; where the purpose is primarily to achieve a maximum sulfide oxidation. In a sub-sea tailings deposition, mine waste material will be permanently placed under water shortly after production; and as long as, the deposition system works according to the handling plan, there will be no change to this. Usually, kinetic testing is commonly performed under optimal conditions for sulfide oxidation where leaching of reactive material takes place once a week (typical humidity cell test). KREC-Norsk Bergindustri 58/110 March 2015 Even though the intended handling of the mine waste material is placement under water, the material should be tested under atmospheric conditions, as well, if the acid generation is more than 1/3 of the acid neutralizing potential (CEN/TR 16376:2012). This testing should then follow the Kinetic testing guideline (CEN/TR16363: 2012). The more standardised kinetic test methods (ASTM 2001, 2011: USEPA 1978, Morin and Hutt, 2002) are designed to evaluate/calculate (as mentioned above) the maximum sulphide oxidation rate relative to neutralising reactions, and not to simulate waste behaviour under field conditions (Lapakko, 2004). Adjustments to the standardised methods are being used to evaluate leaching rates (Price, 2009); adjustments that take into account more site-specific conditions such as airflow, grain size and climate. Information on leaching rates and drainage chemistry is also achieved from scaled up experiments and field tests. More information on running kinetic tests under strongly oxidizing conditions can be found in the Overall Guidance document, CEN/TR 16376:2012 and the Kinetic testing guideline (CEN/TR16363: 2012). In order to simulate and evaluate the leaching potential from sub-sea tailings deposition, it is suggested to place tailings in the bottom of a Plexiglas tube. To avoid the experiment being affected by oxygen diffusion through the Plexiglas and to control temperature, experiments can be place in a water bath. The bottom water in the area of deposition may be oxygenated or reduced depending upon the organic activity and the current in the area. Site-specific information is needed for input parameters. Sulfide oxidation rates will be higher in an oxygenated setting than in reduced setting for tailings deposition containing sulfides. Oxygenated condition is, therefore, recommended for the experiments, however it may be very useful to run parallel experiments with reducing conditions for comparison, especially if the seabed measurements indicate reducing conditions, a setting that may change seasonally. The following parameters should be monitored on a frequent basis during kinetic tests for sub-sea tailings deposition, : • • • • • Temperature; Salinity; pH; pe; Oxygen content; and KREC-Norsk Bergindustri 59/110 March 2015 • Element concentrations. These leach tests should be run for several months until they reach a steady release rate. Due to the high alkalinity and carbonate content in seawater, the seawater will not become acidic; however, secondary minerals may, thereby, control the long-term release rate. Sulfur release is commonly the best way of monitoring and calculating sulfide oxidation rates. However, sulfate in seawater is in the range of 2-3000 mg/l. The release of sulfate into the column may be in the order of a few mg/l to maybe a few tens mg/l. It may, therefore, be beneficial to run such tests with water spiked with NaCl and Na2CO3. This can give the chloride content of water with its corrosive capabilities and the alkaline seawater a pH of around 8. Unpublished ongoing work by Repzka and Walder (2013) indicate that the sulfide oxidation rate is lower in such designed saline water compared with normal seawater possibly due to differences in the ionic strength of the solutions. A more detailed look at Kinetic tests for sub-sea tailings deposition is described in the following section. 6.5.3. Saltwater/Seawater Kinetic Testing It is necessary to perform specific leach tests designed for sub-sea tailings deposition in order to evaluate the potential for mineral weathering and element leaching from material potentially placed under water. The CEN guidelines (ref) only mention this issue, referring to this specific guideline for more detailed information. Salt water has a corrosive effect possibly enhancing the reaction rate of minerals. This has been analyzed primarily by comparing reaction rates in high ionic strength solutions relative to low ionic strength solutions (Langmuir, 1997). High chloride and sulfate content has an additional effect where the corrosive processes are increasing. In addition, the high ionic strength of the water will result in increased solubility of minerals. It is, therefore, recommended that long-term leaching tests are run using salt/seawater and in replicated environmental conditions of the tailings deposition site. This requires physical and chemical information of the proposed location described in Section 6.9. KREC-Norsk Bergindustri 60/110 March 2015 There are several issues that should be evaluated as part of the parameters controlled in these leaching experiments for sub-sea tailings disposal. These could be: • • • • • • • • Salinity, Flow rate, Oxygen concentration, Temperature, Grain size/surface area, Deposition area, Mineralogy/mineral chemistry, and Amount and quality of organic matter at deposition site. . A leaching set-up can monitor or control the first four parameters (Figure 5). The last three are input parameters for evaluating the result of the leach tests. Figure 5. Experimental setup for long-term leaching tests for sub-sea tailings deposition. As mentioned before, salinity is an important parameter, due to the corrosion issue of chloride and the ionic buffering capacity of seawater. If deposition is suggested in narrow fjords, there may be a high influx of fresh water reducing the salinity. One option is to use the seawater from the potential location of deposition. If there is a potential for sulfide oxidation, this can be assessed by monitoring the sulfate content in the leachate. However, seawater has relatively high sulfate content (average 2600 mg/l, KREC-Norsk Bergindustri 61/110 March 2015 Stumm and Morgan, 1998) and the excess sulfate from the sulfide oxidation is likely to be insignificant relative to the background value of the seawater. To circumvent this, salt water consisting of only sodium chloride to achieve the appropriate ionic strength and carbonate-bicarbonate to buffer the pH at level of the applicable seawater is a possible option. Local seawater (from site of deposition) or other seawater of similar properties can be used. Using local seawater will have the benefit of having the correct starting water quality with the microbial activity from the site. However, using seawater collected from another area with similar quality should give a similar result. The seawater needs to be filtered preferably with filter size of 0.2 µm to remove most colloids, as well as, other particles in the water. Water with the same salinity and pH as from the site of deposition can also be used. Since the reaction process, especially for sulfides in salt water is poorly known, salt water should only be used to evaluate the sulfate release rate and seawater should be used to assess metal release rates. Water current measurements are a natural part of evaluating potential impact from a sub-sea tailings deposition (See section 6.9). Some areas may be stagnant, while other areas may have a relatively high flow rate. These measurements are usually performed both in upper part of the water body and deeper part of the water body, but seldom at the bottom. However it is important to understand the currents near the seabed as these may redistribute tailings after deposition. The experiments could easily be set up with a flow through system if that is the condition of the potential deposition area. The flow would ensure that there is a constant mix of water near the tailings surface such that the water does not become stagnant. High flow rates, as measured in the Kvalsund, a potential tailings deposition site for the Nussir mine, have a flow rate of 50-150 m/hour 2 meters above the bottom (Akvaplan-Niva, 2011). Implementing this flow rate in column experiments would require larger pumps. Lower flow rate would, therefore, be more applicable for laboratory experiments. However, there is no point in carrying out laboratory experiments that do not replicate conditions. Oxygen content in the water is an indication of bacteriological decomposition and organic activity growth together with a mixing rate. Oxygen content is an indication of the redox content, which affects mineral stability. Sulfide minerals will not oxidize and release elements in reducing conditions. Therefore, monitoring and controlling the KREC-Norsk Bergindustri 62/110 March 2015 oxygen content is important for understanding the processes and evaluating the result from the leaching experiments to predict and assess any potential impact to the receiving environment. Temperature will affect the reaction rate of minerals. The temperature is a component that can be controlled, however, high pumping rates commonly generate higher temperature in the lines transporting the leachate, making it more difficult to control the lower range temperatures. Grain size – surface area can be used to calculate reaction rate relative to the mass of certain grain-size or to a mineral surface area. However, as described in the mineral section 6.3, only the available mineral surface of the reacting minerals is of interest. Therefore, the best option is to run the tests with tailings material from flotation experiments following the designed outline of the processing scheme. There are two possible leaching scenarios taking place when using SSTD; 1) Short term leaching during deposition that is related to the tailings mass, and long-term leaching rates that are related to the tailings area (Walder and Repzka, in prep.). Probably, only the upper part of the tailings will be a part of the reacting system after the tailings has settled to the bottom. However, as the tailings are buried along with organic material, the sediments become sub-oxic then anoxic. How deep in the sediments this occurs is dependent on the amount of organic material, the oxygen content of overlying water, currents and the degree of bioturbation of the sediments. When the tailings become anoxic, the biogeochemical cycling of the elements will take place. This can lead to a release of metals to the pore water and diffusion upwards in the pore water, where it may re-precipitate in oxygenated sediments or be released to the overlying water column. The surface area of the tailings in the column, relative to the total area of deposition, can be useful in calculating the long-term release rate and in the impact evaluation. However, the long-term redox condition of the sediments containing the tailings is extremely important, as there can be currents affecting the oxygen content of the near surface water; bioturbation of the sediments increases oxygen availability. This again can lead to biogeochemical cycling of elements and possible transport of elements to the surface. KREC-Norsk Bergindustri 63/110 March 2015 Mineralogy and mineral chemistry together with the leachate chemistry is important in evaluating the leaching processes taking place. Mineralogy and mineral chemistry together with sequential chemical extraction (SCE) can be very valuable in understanding the processes taking place during the experimental period. In particular, SCE analysis can be very informative on evaluating the amount of mineral transformation and secondary mineral precipitation. The high carbonate and sulfate concentration in the seawater with high pH measurements, results in sulfate and carbonate minerals being formed at very low metal concentrations. The length of time for these tests can be several months depending upon the results. As for kinetic tests, these leach tests evaluate mineral reaction rates and should, therefore, also be run until there is a stable release rate of the primary elements of concern. For kinetic tests, the activity is commonly dependent upon a microbial process, which takes place in a reduced pH environment setting. This can take 6 months to years in an oxygenated freshwater setting. Similar microbial processes are also taking place in seawater. Leaching in seawater is likely not affected by the same high microbial buildup, or a change in pH. Therefore, these tests may have to be run for as long as tests run in a fresh water setting. Buildup of secondary carbonate and sulfate minerals on the surfaces of the sulfide minerals are likely to result in encapsulation of the sulfide minerals. These again will result in reduced release rate and improved long-term condition. The duration of the tests should be long enough to ensure that these processes can be evaluated. Field scale/pilot scale testing is the type of testing that is closest to practice, as it considers natural exposure conditions. This type of test includes pilot scale tests with exposure of waste rock or exposed rock surfaces to the atmosphere (O2) and local weather conditions or imposed rainfall regimes. Tailings may also be placed in a smaller confined area in a fjord during pilot scale operations to evaluate actual leaching and settling. However, these types of tests are costly and must run for a long period of time (years) before meaningful results may be obtained. This can be circumvented by using mesocosum tests which allows for the assessment of leaching, eco-toxicity, and physical effects in-situ. KREC-Norsk Bergindustri 64/110 March 2015 6.6. Leaching Behaviour and Leaching Tests Constituent leaching from waste materials is a natural part of an A/NRD evaluation; however, leaching can also be of environmental significance where there are no sulfide minerals. Wastes from the extractive industry can, for example, be very alkaline where strong bases are used in processing (e.g. alumina refining or gold leaching), very salty (salt mines), or acidic where acids have been used for leaching metals from oxide minerals and silicate minerals. The tests discussed here are short-term leach tests that will be applicable for older waste or waste that will reach a constant leach rate within the leach test time. For new wastes, where there may be a lag-time before reaching longterm stable leaching conditions, these tests would be not applicable. 6.6.1. Common Leaching Tests Leaching tests may in principle, be applicable to any type of residue from the extractive industry. If they are appropriate or not will depend on whether they offer an efficient way, with sufficient accuracy, to produce the information sought after in a specific case. The percentage of a specific constituent that can be leached from a waste at a relevant pH is a measure of the potential leachability. The leachability varies strongly for each material and each element. It may range from close to 100 % to 0,001 %, demonstrating that total composition is a poor measure for predicting the potential environmental impact of an element. There are a large number of standardized leaching tests available. The characterization leaching tests comprise methods for measuring: • • • solid-aqueous partitioning as a function of pH; solid-aqueous partitioning as a function of liquid to solid ratio (L/S); and mass transfer rates for monolithic or compacted granular materials. Most of these tests have been developed for the characterization of waste in general, but not specifically for waste from extractive industries. The preferred and most commonly applied leaching test for waste characterization is the CEN/TS 14405 column-leaching test. KREC-Norsk Bergindustri 65/110 March 2015 The column-leaching test (CEN/TS 14405) is an up-flow percolation test designed to resemble common percolation scenarios. The liquid to solid ratio can be related to a time scale via the infiltration rate, density and height of the material. The liquid used in these types of tests is distilled/de-ionized water, but in this case, it may be applicable to use salt water. It should be noted that, in the case of oxidizing waste material, e.g. sulfide mineral containing waste, this test (CEN/TS 14405) does not capture the change of leachability over time. In addition, this test is not very replicable to the environmental conditions at the bottom of the sea, where the flora and fauna may be using/interacting with the 5-10 cm upper part of the bottom sediments. Different tests use different solutions for leaching, e.g. acetic acid, sulfuric acid, carbonic acid (rain water) etc. None of the tests have been specifically designed for leaching evaluations in sea/saline waters. However, running tests with salt water instead of meteoric water or distilled water may be applicable for evaluating leaching for tailings to be stored in seawater. The first eluate collected from a column test reflects the pore water conditions of the material considered; while eluates collected later are more representative of the leaching rate in a flow through system. Control measures can be taken for testing materials sensitive to oxidation to avoid changes in initial conditions, e.g. using pH or Eh-buffers. The effect of preferential flow can be difficult to quantify. Preferential flow may be generated in sub-sea tailings deposits from bio-turbation (e.g. sea-cucumbers) from boring into the sediments or stirring up the top surface of the bottom sediments. 6.7. Discharge settling The discharges material settles via two different routes: Given high solid content the discharge will form a high density current, and most of the discharge will follow this current to the seabed. A minor fraction will disperse from the density plume and mix with the seawater. These particles will settle at a slower rate and may be transported longer distances, by way of water currents. The speed of the turbidity current is governed by: KREC-Norsk Bergindustri 66/110 March 2015 C = 0.7√((d1-d2)/d2*gh) where: d1 is density of the turbidity current; d2 is density of the ambient fluid (seawater); g is gravity(980 cm/s2); and h is thickness of the head of the current. The settling rate of the tailings sediments is often a critical parameter for modeling sediment transport. Stokes law defines settling rates: V0 = ((ds-dw) g D2)/18µ, where V0 terminal settling velocity (cm/sec); ds is density of the solid (gr/cm3); dw is density of the water (gr/cm) – seawater; g is gravity(980 cm/s2); D is particle diameter (cm) ; and µ is molecular velocity (gr/sec*cm). Experiments can be set up to determine the terminal settling velocity; however, the tailings have a grain size range, and different minerals have different densities. Flocculation: The particles have primarily a negative surface charge and with the high salinity of the seawater, will act as a flocculant. Sea currents in the deposition area may sea current in affect the settling rate (given a vertical component) and the settling point. Can be modeled, provided data for current direction, strength and distribution There are different methods designed for performing settling tests. However, the bulk of the material from a tailings deposition is thick and heavy and settles in a way most experimental setups are not designed to replicate. The majority of the effluent will form a density current and travel to the seabed, provided the tailings density is greater than the seawater. However, fine material will shear off at density changes within the water column and will travel further and take longer to settle. This material will, therefore, be subjected to more a common settling system and experiment. KREC-Norsk Bergindustri 67/110 March 2015 The following issues need to be evaluated when designing settling tests: • Use of different flocculation chemicals and seawater for control • Tests combined with evaluation of mineral dissolution • Settling experiments should be performed with a stirring that is similar to the measured current in the deposition area. Salt water is, by itself, a good flocculation agent. Therefore, saltwater should be used in these experiments. However, it would be useful to also run, simultaneously, freshwater experiments for comparison, which would aid in modeling the particle transportation. The key variable for the models is understanding of the water masses and currents. 6.8. Field experiments Field experiments may be difficult to design in a mining setting where sub-sea tailings deposition is proposed, since it is not common to build a pilot plant prior to a full-scale operation. However, if the processing method is somewhat new or with a new ore type, it may be beneficial to start with a pilot scale operation, e.g. Kolsvik Gold, Bindalen, Northern Norway. At Kolsvik Gold deposit, the plan has been to start with a pilot scale operation processing 20-50.000 tons of material on-site. It is planned to discharge most of this material in the fjord, where the mine is hoping to obtain a discharge permit for full scale operation. It is important to use monitoring systems to evaluate the sediment spread during a test operation. Measurements of current and other parameters that vary over time need to be monitored also during a test deposition (see Chapter 6.9). 6.8.1. Existing waste facility Investigation of existing extractive waste facilities may be part of the monitoring/ confirmation to follow up on an earlier comprehensive waste characterization and predictions of future drainage/leaching water quality. It may also be a part of characterizing the waste in closed facilities, with no or insufficient existing information. This may be former sub-sea/shore line tailings deposit (e.g. Nussir deposit, Sydvaranger mine). A detailed study of the behavior of the deposited tailings and their effect/impact on the surrounding environment will give valuable information for evaluating how a new or increased operation using the same ore will behave. KREC-Norsk Bergindustri 68/110 March 2015 Investigations of existing SSTD sites may be seen as the ideal field scale test set up providing the receiving environment’s conditions are the same or similar especially salinity, water masses, currents, natural sedimentation rates, biology etc. In the existing facility it may be possible to evaluate the sea conditions, geotechnical stability, and geochemical processes that are taking place, much depending on how long the facility has been in place. This information may then be used for evaluation and verification of models and predictions for continued deposition, adjustment to the deposition system, or to evaluate new SSTD sites. 6.8.2. Small-scale field testing Tests performed in the field during field experiments of sub-sea tailings deposition would be similar to those performed for water quality and water current analysis. These could be: • • • • • • • • • Turbidity analysis; Water current measurements; Water quality analysis; Temperature; Salinity; Sediment settling pans; Effect on the marine life from sediment transport and settling; Characterization of natural sedimentation material; and Identification and abundance of benthic and pelagic biota. These methods are discussed in Chapter 6.9. Solid sample collection should be performed from near the discharge point, to a point in transect away from the discharge, to a site far enough away so as not to be impacted by tailings. The last sampling point is a control site. 6.9. Aquatic Toxicity Tests Aquatic toxicity tests are used to evaluate the impact of anthropogenic chemical substances and sediments/water affected by human activity. Common tests include; standardized short time acute and acute test, to longer time chronic tests (OECD 201, 2006; OECD, 202, 2004; OECD, 203, 1992; OECD 204, 1984; ISO 10253). These tests KREC-Norsk Bergindustri 69/110 March 2015 measure endpoints, such as survival, growth, reproduction, of each concentration in a gradient, along with a control test. It is common, and recommended, to use organisms with ecologically relevant sensitivity to toxicants, with a well-established literature background. There are several aquatic toxicity tests available, and several of them are commonly performed in parallel to evaluate the toxicity. There are three toxicological issues that may need to be evaluated. • • • Acute toxicity; Chronic toxicity; and Bioaccumulation. It is important to test fish, crustacean, mollusk, and algae that occur at the site of potential deposition. These tests can be performed following the leach tests, that can indicate potential concentrations of the compounds/elements that potentially will increase due to the tailings deposition, both compounds (organic or inorganic) used as part of the processing of the ore and easily leached, and elements/compounds released due to digenesis (e.g. desorption, mineral dissolution). When designing toxicity tests, as well as, preparing samples prior to the tests, it is important to remember the complexity of the material to be discharged. EN-14735/2006 is a background document describing steps to be performed before performing the ecotoxicity tests. This standard provides guidance on taking a sample, transport, and storage, and defines preparation of a sample. The standard is for both solid and liquid samples. 6.9.1. Acute Toxicity Tests Acute toxicity tests are short-term tests, from a few hours to a few days. Acute toxicity tests can be performed as static non-renewal, static renewal, and as a flow through system. Each setup has their benefits and drawbacks: • • Static non renewal o May result in depletion of oxygen o Loss of toxicants o Buildup of metabolic waste o Easy and inexpensive Static renewal KREC-Norsk Bergindustri 70/110 March 2015 • o Improved conditions for oxygen, loss of toxicants and metabolic buildup o Require greater volume of effluent Flow through tests o Maintain O2 conditions o Require large volume of effluent More representative tests for an acute toxicity evaluation will require more space and volume of effluent, normally used for onsite tests. However, there are sophisticated mesocosm experimental setups that can replicate onsite conditions, and are more appropriate than the smaller laboratory setups. A mesocosm is an experimental tool that brings a small part of the natural environment under controlled conditions. Mesocosms provide a link between observational field studies, with or without replication, and controlled laboratory experiments performed under un-natural conditions (http://mesocosm.eu/node/17). The toxicity tests may also vary depending upon the contaminants being introduced into the water column, compared with what may be sorbed/assimilated with the solid phase. Pelagic organisms would rarely come in direct contact with sediment-associated contaminants; but indirectly they would, by feeding on the benthic organisms or material suspended in the water column. Effluent acute toxicity is generally tested using multi-concentrations, consisting of a control and at least five concentration levels. The test should provide dose-response information, expressed as the percent effluent that is lethal to 50 % of the organisms within the prescribed period of time (commonly 1-4 days). It may also be prescribed as the highest effluent concentration in which survival is not statistically significantly different from the control. Negative results from this test do not preclude chronic toxicity or bioaccumulation effects. The “Marine algal growth inhabitation tests with Skeletonema costatum and Phaeodactylum tricornutum” (ISO 10253) is a screening test for readily water-soluble substances or mixtures of substances. The substances should not be significantly degraded or eliminated in any other way from the test medium. KREC-Norsk Bergindustri 71/110 March 2015 6.9.2. Chronic effect tests There are several tests that are designed to evaluate chronic toxicity on marine life. The most commonly used tests are: • • • • EPA 600/R-01/020, method for assessing the chronic toxicity of marine and estuarine sediment-associated Contaminants with the Amphipod Leptocheirus plumulosus EPA821 chronic toxicity test for water soluble pollutants USEPA-USACE 2001 determination of the chronic toxicity of contaminants associated with whole sediments with the amphipod Leptocheirus plumulosus in laboratory exposures OECD 204, Fish toxicity testing framework, 14 days test period The EPA 600/R-01/020 guideline describes chronic toxicity of contaminants with whole sediments. The sediments may be from marine environments or estuarine environments, or could be spiked with compounds in the laboratory. The method is based on using the amphipod Leptocheirus plumulosus. The test is performed in a 1 liter glass chamber containing 175 ml sediments and 725 ml of overlying water, with 28 days of testing. The endpoint in the tests is survival, growth, and reproduction of amphipods. The test is applicable for sediments from oligohaline to fully marine environments with silt content >5% and clay content <85%. EPA821 is a chronic test designed for five species for which toxicity test methods are provided: the sheepshead minnow, Cyprinodon variegatus; the inland silverside, Menidia beryllina; the mysid, Mysidopsis bahia; the sea urchin, Arbacia punctulata; and the red macroalga, Champia parvula. The EPA821 states further: “Four of the methods incorporate the chronic endpoints of growth or reproduction (or both) in addition to lethality. The sheepshead minnow 9-day embryo-larval survival and teratogenicity test incorporates teratogenic effects in addition to lethality. The sea urchin sperm cell test uses fertilization as an endpoint and has the advantage of an extremely short exposure period (1 h and 20 min).” USEPA-USACE 2001 is a chronic toxicity test designed for a 28 days test period, in a 1-liter glass chamber containing 175 ml of sediment with about 775 mL overlying seawater. Four hundred milliliters of the seawater is renewed three times per week. The KREC-Norsk Bergindustri 72/110 March 2015 organisms are fed at time of seawater renewal. Tests are initiated with neonate amphipods that mature and reproduce during the 28-d test period. After the 28 days survival rate (percentage of amphipods that has survived), growth rate, and reproduction are determined. 6.9.3. Bioaccumulation Tests If there are organics or chemicals present that are not included in priority lists, and bioaccumulation is not already known for the biota, bioaccumulation potential tests may be necessary. Two tests designed for testing bioaccumulation are described in the following paragraphs. • • OECD (2012),Test No. 305. Standard for bioaccumulation testing of fish ASTM-E1688 − 10, Standard Guide for Determination of the Bioaccumulation of Sediment- Associated Contaminants by Benthic Invertebrates The OECD (2012), Test No. 305 describes a procedure for characterizing bioaccumulation potential of substances in fish, using an aqueous or dietary exposure, under flow-through conditions. The test is divided in two phases; bioaccumulation and post-exposure. During the uptake phase (usually 28 days but can be extended), a group of fish of one species is exposed to the test substances at one or more chosen concentrations (depending on the properties of the test substance). For the depuration phase, they are then transferred to a medium free of the test substance, or fed with clean, untreated feed. Concentration of the test substance in the fish is followed through both phases of the test. The aqueous exposure test yields a bioconcentration factor (BCF) and the dietary approach yields a biomagnifications factor (BMF); greater emphasis is put on kinetic BCF estimation (when possible), estimating the BCF at steady state. The ASTM-E1688−10 is a toxicity tests design to evaluate the bioaccumulation from sediment-associated contaminants using benthic invertebrates digesting sediments. The method design is such that it can use single or multiple species. There should always be a control column without contaminants. Light, temperature oxygen content, and flow rate (if not static setup) need to be controlled. Test period may be between 10 to 78 days, with food supplied and water replaced at certain intervals. The method describes how to determine the amount of duplicates, and what invertebrates to use for specific contaminants. The tissue of the benthic invertebrates is tested for the contaminant in question. The guideline describing the method provides an extensive description on KREC-Norsk Bergindustri 73/110 March 2015 how to calculate the results of bioaccumulation, and issues to be aware of to obtain best test result. 7. CHARACTERZATION OF THE RECEIVING ENVIRONMENT The receiving environment is defined in this guideline, as the area for tailings deposition. Even though the onshore receiving environment from tailings dams and waste rocks are poorly described in other EU documents and guidelines, it is outside the scope of this guideline. The characterization of the receiving environment, as referred to in this guideline, is focused on sub-sea tailings deposition sites. The main issues that need investigating with regards to the receiving environment for sub-sea tailings deposition are: • • • • • • • • • Visual observations of the bottom ecological system (corals, sponges, etc.) Fish resources (quantities, types, spawning areas, economics etc.); Bottom flora-fauna; Zooplankton (types and concentrations etc.); Indicator species; Bottom sediments (grain size, chemical composition, pore water chemistry etc.); Ocean (e.g. eufotic-afotic zone, thermocline, oxycline, halocline); Water quality; Water currents, including identifying different water masses, circulation and potential for turnover in the fjord; and • Bathymetry. Visual observations of bottom marine activity such as corals and sponges give an indication of the natural nutrient conditions in the area potentially used for SSTD. The observations can be used to evaluate spawning and feeding areas. This gives a starting point for evaluating the potential impact from tailings deposition, e.g. potential for spawning areas. Visual observations can be performed with sub-sea cameras, small submarine vessels and divers. In addition, a complete benthic survey should be carried out using sediments collected by an appropriate corer that recovers sediment with sediment water interface samples. The samples should then be analyzed for micro and macro fauna using internationally recognized methods. KREC-Norsk Bergindustri 74/110 March 2015 It is important to identify flora-fauna indicator species (and agree upon) during the characterization. These indicator species should then be monitored during operation and after closure. Methods to obtain this information are described in the following sub-sections. 7.1. Fish and Fish Resources Particle discharge may affect the fish by irritating the gills; while increased turbidity may result in the fish moving to areas with better water quality. Particles from crushing and milling have sharper edges than natural formed fine particles. Due to the sharper edges, tailings particles may be more harmful to gills than natural fine particles. The discharge may also affect the growth potential by reducing light and covering the sea bottom, which again affects the fish habitat and food supply. Different species of fish will often use area potentially affected by tailings deposition in different ways. For Atlantic salmon and sea trout, the area may only be used as a transport route near the surface, while other fish may have spawning or feeding areas at the bottom, where the tailings potentially will be deposited. The fish resource in the potential depositional area should, therefore, be studied. This can be done by investigating records describing catches, and interviewing local fishermen. The information to obtain should include: • • • • • Historically sizes/amount of fish catches combined with boat types and fishing equipment used; Identify the type of fish that is in the area (local and migrating fish) and in what depth that they typically exist in potentially affected areas; Spawning areas and feeding areas for the different fish types should also be identified; Identify salmon protected areas within the potentially affected area; and Identify areas designated for fish farming. There may be a need to actually fish within the designated area to better evaluate the type of fish that exist within the potentially affected area. All of this information can KREC-Norsk Bergindustri 75/110 March 2015 then be used to evaluate the potential impact of fish resources from tailings deposition. Salmonid fish (Atlantic salmon, sea trout, arctic char) have been protected by the Norwegian legislation with the introduction of the National Salmon Water Courses and National Salmon Fjords legislation. No negative impact will, therefore, be allowed for salmon as a result of tailings material deposition. Salmon is also protected via the North Atlantic Salmon Convention (NASCO) established in 1983. Atlantic salmon smolt, sea trout, Tout and arctic char can be tagged with acoustic tags, and an array of receivers along the migration route can be deployed throughout the fjord area. This will indicate migration routes, residence time, migration periods, and depths of the salmonides, all information to be used for evaluating potential impact. It may be beneficial to divide the salmon cycle into the juvenile stage (larvae to smolt), post-smolt (migration stage), and spawning stage. The information for pelagic fish (herring, mackerel, etc.), white fish (cod, red fish, haddock etc), and bottom fish (flat fish, halibut) is commonly collected from local fishermen and government records of fish catches. The information to be collected should follow Norwegian guideline for fish resource mapping (Fiskeridirektoratet 2010). Chemical analysis should be performed primarily of liver and muscles of the local fish to evaluate baseline conditions. This will also be used as a reference level for monitoring during mining and after secession of the mining operation. 7.2. Bottom Sediments Physical and chemical analyses of bottom sediments should be performed for monitoring purposes and environmental assessments. ISO 5667-19:2004 provides guidance for bottom sediment sampling. The guideline encompasses sampling strategy, requirements for sampling devices, observations made and information obtained during sampling, sediment sample handling, and sediment packaging and . It should be noted, that it is extremely important to use correct sampling equipment, otherwise the results may be useless. The amount of samples and locations can be estimated based on different statistical approaches described in the waste sampling guidelines (EN 14899:2005; CEN/TR 16376:2012) and other geo-statistical sampling documents. KREC-Norsk Bergindustri 76/110 March 2015 Sediment cores should be described visually prior to analysis. Bottom sediment sampling should be performed using a multi or mega-corer that is hydraulically dumped, and recovers undisturbed sediment with the sediment water interface intact. Common practice for the sediment analysis is to use the upper 0-2 cm layer for grain size, total organic carbon (TOC) and metals, when carrying out a baseline study. Down core analysis should be undertaken, as this will provide information on the redox conditions of the sediments and indicate what biogeochemical cycling is taking place. Pore water samples should also be collected and analyzed. Mineralogical analysis e.g. MLA (mineral liberation analysis; see Chapter 6.3) would also be advantageous. This will give a good indication of the environmental condition (environmental classification system SFT 97:03) at present and provide background data prior to potential tailings deposition. There is also a need to select one or several locations as reference stations that will be outside the expected tailings deposition influence area. These reference stations should have similar bottom fauna and geochemical characteristics as within the influence area. Pore water analysis is also recommended for evaluating background conditions. Pore water can be extracted from core samples of bottom sediments and analyzed as water samples, as described under Chapter 6.4.2. 7.3. Bottom Flora and Fauna 7.3.1. Soft-Bottom Flora and Fauna The bottom fauna (for the same samples as described above) should be sorted and species abundance determined. The data should be presented in species lists together with univariate parameters, amount of species, amount of individuals, Shannon Wiener diversity indexes, and Hulberts diversity indexes. There should be 3-5 replicates for each sample location for the soft bottom analysis, where each sample represents at least 0.1 m2. In some cases, this may be increased to 10 replicates if there is a considerable variation between replicates. This can be performed by sampling more replicates at one time, and storing them until results are obtained from KREC-Norsk Bergindustri 77/110 March 2015 the initial 3-5 replicates analysis. The amount of stations to be sampled will depend upon the variation of conditions and fauna in the potential influence area. Sampling should be performed according to the standards NS 9422 (ISO 5667-19:2004) and NS 9423. 7.3.2. Hard-Bottom Flora and Fauna The hard bottom flora and fauna evaluation is divided into the littoral zone (0-5 meters depth) and the sub-littoral zone (to 20-25 meters depth). Permanent macro-algae and animals are to be analyzed by species types and amounts. The analyses of species types, and amounts of flora and fauna in the littoral zone, should be performed within a set frame of 0.5*0.5 m, divided into 25 squares. All squares should be analyzed according to NS 9424. These frames should be set at every onemeter depth to below the tidal water area (with one replicate for each depth level). The amount of stations required depends on the potential influence area and variation within the influence area. In addition, reference areas should also be selected and analyzed. The analysis of the sub-littoral zone (below the littoral zone described above) can be performed by a specialist (e.g. diver/marine biologist) using visual analysis, together with photo image analysis for each meter depth. 7.4. Water Quality Assessment of the water quality in the potential affected area needs to be performed. The water quality should be taken into account when sampling. Sampling can be performed according to ISO-5667-9, 1992 Guidance on sampling marine water. Water quality data is used both as input for water current modeling and for evaluating geochemical leaching potential: • • • • • Salinity; Turbidity; Temperature; Redox potential –oxygen content; and Chemical composition. KREC-Norsk Bergindustri 78/110 March 2015 The first four parameters can be measured using probes, while chemical composition requires samples to be analyzed in a laboratory. The first four parameters can be measured in continuous depth profiles, from the top to bottom, in selected locations. All of these parameters should be performed within the potential influence area, at different locations, during different seasons. 7.5. Ocean-Fjord Currents Current measurements are necessary to evaluate particle transport in the potential impact area. Current measurements should be performed using both stationary measurement and mobile devices, e.g., gliders or AUVs. Both current direction and velocity need to be monitored at different depths. Measurements should be performed at several locations within the potential influence area. The data from these measurements can then be used to plot direction velocity maps for different depths. There are commonly large seasonal differences due to snow melting in the spring (wet season) and freezing conditions in the winter (dry season) and low fresh water input. Measurements need to be taken during both of these seasons, over a minimum of a two month period. There are moon cycles affecting tidal water currents with daily, monthly and yearly cycles that may need to be assessed. These may be evaluated during the 2 by 2 month monitoring explained in the above paragraph. In addition, the possible occurrence of internal waves needs to be explored. By deploying mooring lines with different instruments at different depths, it is possible to gather the required information by high-resolution monitoring. Examples of stationary equipment that may be used include the RCM9 current meter from Aanderaa instruments. Current velocity can be measured using an Acoustic Doppler Current Profiler (ADCP), a hydroacoustic current meter similar to a sonar. Water current velocities are measured over a depth range using the Doppler effect of sound waves bouncing off off particles within the water column. There are no moving parts, so biofouling is not an issue. Such an instrument is enough to cover up to 1000 m of water column, this allows for more accurate estimations of flow patterns. The ADCP is an acoustic instrument which may affect cetacean navigation and ecolocation (Hogan, 2011). However, if the water KREC-Norsk Bergindustri 79/110 March 2015 column is layered, e.g. with thermocline or halocline, mechanical instruments may be more appropriate. The length of time for the current measurements will vary based on locations for deposition. One year monitoring may be enough at one place; while other potential locations may need measurements collected over several years, especially if there are large variations from year to year and more accurate data is needed for performing transport modeling. If the potential area for deposition is strongly affected by tidal cycles, it may be necessary to take several full month measurements. If the potential area for deposition is strongly affected by variation in freshwater input, it may be necessary to have current measurements taken over several years to see the difference from one year to another. It is difficult to describe, in general terms, where to place monitoring systems. However, if there is a threshold that is used to enclose the sediments, the current velocity and direction across it should be monitored. The potential of upwelling needs to be monitored, as well as, the current near the sea bottom where deposition is taking place. Surface current data is also important in order to develop a possible threedimensional flow system. This flow system can be used to model particle transport. 7.6. Bathymetry Mapping the bottom topography is an important part of evaluating the potential impact. Bottom topography data can be used in identifying potential thresholds that can be used as dykes for the deposition; estimating potential volume for deposition, and identifying locations for bottom test locations. Kartverket (Norwegian Map Authority) has produced hydrographic maps for most areas of the Norwegian coast. However, more detail information may be necessary. One method for performing more detailed mapping is using, e.g. Simrad 38/200 kombi D transducer and an EA400SP transceiver. Collected data is then transferred to a map using a computer mapping programme. For the Simrad 38/200, the mapping programme Nobeltec is commonly used. Depth measurements can also be performed using sonar in connection with the OLEX system. Depth maps using color differences for depth variations are recommended. KREC-Norsk Bergindustri 80/110 March 2015 8. DATA QUALITY The Overall Guidance document, CEN/TR 2012 for characterization of waste states: “Assessing current physical and geochemical properties and predicting how these will develop in the future under the influence of weathering, with possible different closure alternatives, is a complex undertaking. Especially, the prediction of future behaviour is no exact science and will always include a level of uncertainty. The level of accuracy and precision that is required /acceptable will vary depending on the context. In situations where the test result and predictions will be the key factor in the choice between different management options, a high level of accuracy will be needed (alternatively high safety factors will have to be applied). On the other hand, in clear-cut cases, whether clearly benign or clearly problematic material, there may be no need for a high precision. This may be the case when assessing if drainage collection and treatment will be needed (while dimensioning of a treatment system will still require a higher level of precision)”. This statement also applies to the SSTD Evaluation Guideline, where the precision of the species and amount of species, may not have the high precision requirement; while metal leaching and particle transport may need high precision, especially in sensitive environments. . Data quality and uncertainty can be understood in several ways ISO 5667-14:1998. • • • • • Uncertainty related to the representativeness of the samples that are collected; Uncertainty of a specific test result (e.g. leaching and analysis); Variability in materials taken at different times or locations; Seasonal variation; and Uncertainty in the prediction of release behaviour under field conditions. These uncertainties are not easy to measure or calculate; however, the sampling plan needs to address the issues and design an approach for the possible uncertainties. The sample representativeness can often give a higher uncertainty than the lab analysis, where uncertainties are routinely dealt with. Predictive modeling will often be a part of developing waste management plans and closure plans (e.g. particle transport; long-term leaching rates; ground-water transport). Considerable uncertainty is inherent in determining many of the parameters that are required for modeling drainage quality from waste rock or tailings. The inherent uncertainty in model predictions is rarely stated or recognized; however, sensitivity KREC-Norsk Bergindustri 81/110 March 2015 analysis should be a part of the modeling, evaluating important output parameters that are sensitive to the input parameters. The uncertainties of modelling outputs may stem from incomplete characterization or incomplete knowledge of the geochemical conditions, lack of data on thermodynamic/ kinetic properties, and/or insufficient knowledge of the sea conditions at the potential deposition site. The Overall guidance document for waste characterization (CEN/TR16367, 2012) states: “Methods used to evaluate or account for model uncertainty include Monte Carlo analysis, stochastic methods, and an evaluation of a range of model parameters to develop a range of deterministic outcomes. Rather than parameters being described by a single value, as required in the model, parameters are better described with a probability distribution (i.e., a mean value with standard deviation, etc.)”. Model uncertainty should be described in predicting leaching quality of waste material. These uncertainties should include the different potential setting for the waste management options and for the closure scenarios. Field verification is commonly needed to reduce uncertainties in the conceptual model, as omission of an important release controlling process may lead to a faulty prediction. In this context, the interrelations between laboratory test results, field studies, and actual measurements at full scale operations can provide a higher level of understanding, and thus increase the reliability of data developed to support management decisions, keeping in mind that management options are strongly reduced by the time full scale operation begins. The uncertainty level and type of uncertainties change at different stages of the characterization process (GARD Guide, 2009; MEND Prediction Manual, Price, 2009). The MEND Prediction Manual emphasizes the use of sensitivity analysis and risk assessment as part of the characterization program; and both the MEND and the GARD Guide recommends using characterization and modeling results cautiously. Quality Control/Quality Assurance (QA/QC) is important in this context, dealing primarily with measurable quantities, such as physical parameters, chemical analysis and leaching test results; and helping to create a process where sampling or laboratory analysis are performed consistently. General laboratory practice is important in this context and described in EN17025. KREC-Norsk Bergindustri 82/110 March 2015 9. INTERPRETATION, APPLICATION, AND EVALUATION Data from the many different analyses will not mean much if it is not evaluated, interpreted and used in the correct context. Specialist in the different disciplines should perform this work. When there is a possibility for a land-based deposition, then an environmental cost-benefit analysis for these main two deposition forms should be performed. Some of the issues that would be incorporated in such an evaluation may be: • Fine grained tailings on top of natural fine-grained material/slime etc.; • Stability at the bottom of the sea/fjord relative to dam failures from land based deposition • Temporary destruction of sea-bottom relative to temporary destruction of a surface area housing a tailings dam; • Difference in the air/water flow through a land based deposition relative to subsea tailings deposition, where this is close to non-existent. • Leaching from a SSTD in a high acid buffering capacity sea, compared with a land-based weathering setting; • Natural geological barrier that reduces sediment migration and provides high stability relative to a land based tailings dam failure; • Shallow area (tailings filling) gives higher biological activity; and • Recovery after sub-sea deposition ends relative to reclamation of a surface tailings dam. This guidance document will aid in obtaining proper information from the potential SSTD, while the CEN documents will guide in obtaining the proper information for the land based tailings dams. One of the purposes with the SSTD evaluation is to develop acceptance criteria for the different tailings deposition issues. Such criteria may be: • • • • • Solid concentrations near and far from the deposition area Element concentration near and far from the deposition area Amount of discharge relative to environmental limits (how much the area can take without significantly being impacted, short term and long term. Metals in the food chain Process chemicals KREC-Norsk Bergindustri 83/110 March 2015 Developing such acceptance criteria could be through an open dialog with regulatory agencies, interest groups (NGOs) and experts in the different fields. The basis for such discussions would be the data and interpretations obtained through the SSTP evaluation report guided by this document (Fig. 6). Fig. 6. Flow chart for the steps within the Evaluation of SSTD data Through this type of an SSTD evaluation, it is recommended that indicator species for flora and fauna are identified. Monitoring should then focus on these indicator species on a frequent basis. Non- indicator species could be monitored on a less frequent basis; however, this is open for debate. The type of indicator species would depend on type of environmental issues that are dealt with. There may be a need for several indicator species, where environmental issues, e.g. turbidity, siltation, metal leaching, and organic contaminant leaching (additives) exist. 9.1. Particle Transport Particle transport is an important part of the sub-sea tailing evaluation because: KREC-Norsk Bergindustri 84/110 March 2015 • • • • Particles may transport contaminants a long distance; Enhance the length of time for leaching; Affect the gills of fish; Reduce the light to and growth of the bottom flora and fauna and depending on the amount and rate of deposition; and • Smother the flora and fauna in the deposition area. It is necessary to understand the sea current at least throughout the year, the structure in the sea (e.g. layering and internal mixing), bottom topography, water salinity in addition to the effluent characteristics to be able to evaluate the particle transport distance and residence time in the water column. This information will then be used as input to particle tracking modeling programs. Some of the sea-current particle tracking programs are as follows: • • • • • • • • CORMIX/CDFATE (Schroeder et al, 1998) PLUMES (VISUAL PLUMES) (USEPA) BJET (developed by DNV and NTNU, documented by Sørgård, 1992) DREAM –and Sintef, Trondheim NCOM - Navy Coastal Ocean Model (Martin, 2000) BOM-Bergen Ocean Modeling (Berntsen, 2000) MOHID – Instituto Superior Técnico, Technical University, Lisbon GEMS - NIVA program There are likely more programs available, or programs that could be modified to serve the purpose of modeling fjord current. The following is a brief description of these modeling programs. CORMIX/CDFATE is a numerical modeling program developed to evaluate dilution and spreading from a continuous discharge of particles from a discharge point. The model simulates the spread and dilution at different layering and current velocities. The input data to CDFATE and BJET are: • Receiving Environment o Current direction and velocity o Temperature variations KREC-Norsk Bergindustri 85/110 March 2015 • o Salinity variations Discharge material o Particle grain size (silt:clay ratio) o Salinity o Temperature o Amount of discharge with solid to liquid ratio o Discharge velocity o Diameter of discharge pipe Visual Plumes (VP), (USEPA) is a Windows-based computer application for modeling a mixing zone system. VP simulates single and merging submerged aquatic plumes in arbitrarily stratified ambient flow and buoyant surface discharges. It contain features such as graphics, time-series input files, user specified units, a conservative tidal background-pollutant build-up capability, a sensitivity analysis capability; and a multistressor pathogen decay model that predicts coliform bacteria mortality based on temperature, salinity, solar insolation, and water column light absorption. VP includes the DKHW model based on UDKHDEN (Muellenhoff et al., 1985. Initial mixing characteristics of municipal ocean discharges. EPA/600/3- 85/073a and b), and the surface discharge model PDS (Davis, 1999, Fundamentals of environmental discharge modeling. CRC Press). . MOHID is a three-dimensional water modeling system, developed by MARETEC (Marine and Environmental Technology Research Center) at the Instituto Superior Técnico, Technical University of Lisbon. The MOHID modeling system allows the adoption of integrated processes modeling (physical and biogeochemical), at different scales (e.g. use of nested models) and systems (estuaries and watersheds). The integration of MOHID’s different tools, (MOHID Water, MOHID Land and MOHID Soil) can be used to study the water cycle in an integrated approach. Since these tools are based on the same framework, coupling them is easily achieved (www.mohid.com). MOHID includes a baroclinic hydrodynamic module for the water column, a module for the sediments, and corresponding eulerian and lagrangian transport modules. The system is composed of pre-processing and post-processing systems plus a graphical interface for KREC-Norsk Bergindustri 86/110 March 2015 the implementation of the model (Neves et al., 2008). The model has been used in several fjord sediment transport investigations (Marin, 2012) Bergen Ocean Model (BOM) can be used as a mean in investigating the dynamic interaction between the slope, shelf, and fjord, thereby aiding interpretation of the observational data (Cotier et al., 2005). The primitive equations used in the BOM, sigma-coordinate ocean model, assumes Boussinesq and hydrostatic approximation, and solves for the barotropic field at higher resolutions in time than the baroclinic field (Berntsen, 2000). This model does not include particle transport, only current movement. DREAM model is developed by SINTEF, Trondheim, Norway and currently used in the offshore industry to evaluate spreading of drill-mud material from the North Sea drilling. Also used for tailings Hustad, Nordic Mining The modeling program is tailings deposition. The DREAM model can be used to potentially describe the following (Rye, 2012): • Near zone characteristics: content of particles, grain size distribution, content of chemicals, fresh water, seawater, discharge system, creation of sub-sea plume. • Testing of chemicals. Chemicals used in the production should be tested for toxicity, biodegradation, and bioaccumulation. What is used for the oil industry can also be used in the evaluation of SSTD. • The DREAM model can simulate spreading of fine particles from a point source discharge taking into account plume behavior of the discharging material. This modeling will include near zone deposition and far zone transport of fine grained particles, e.g. clay fraction to colloids where input data can include: e.g. salinity layering, temperature layering, sea current at different levels, and flocculation potential for the particles • Simulation may also include environmental effect from chemicals used, where data from toxicity tests and sorption onto particles of the chemicals are included, as well as, the above input factors. The choice of modeling program depends on the complexity of the modeling required. Important issues that may need to be handled by the program are as follows: KREC-Norsk Bergindustri 87/110 March 2015 • • • • • • • • • The grid spacing needs to be small enough that that it will catch the processes taking place, Pipe discharge Dual density fluids, Salinity variations, Temperature variations, Tidal variations, Fresh water input from rivers, Variable depth, Particle transport, Other necessary issues may include fate and transport of chemicals, either from additives or from weathering and leaching of minerals. Mineral precipitation and dissolution may also be included in the modeling evaluation in order to understand the potential environmental impact of SSTD. 9.2. Acid/Neutral Rock Drainage and Leaching Risk Understanding the mineralogy is essential in performing prediction on material stability, A/NRD, and/or leaching behaviour. Using the methods described within this document and/or other guidelines will give the basic mineralogical information required for characterization. This mineralogical information may need to be combined with chemical, leaching, and reaction rate analysis of the waste material to perform any longterm behaviour prediction. The tests will often give indications of the geochemical processes that are or could take place. This will commonly have to be followed up by geochemical modeling to predict long-term behaviour. Geochemical modeling will commonly be the tool used when predicting how different closure scenarios may affect the long-term behaviour. This section discusses the interpretation of the required ABA (EN15875) test for potential waste from the extractive industry; and the required test if there is less than three times the neutralising capacity relative to acid production capacity based on the ABA test. There is then a discussion on the use of leach tests, followed by the use of geochemical modelling for A/NRD prediction. KREC-Norsk Bergindustri 88/110 March 2015 9.2.1. A/NRD Evaluation A/NRD can be a major environmental effect from mining operations if not understood and handled properly. ABA accounting gives a first evaluation of the acid and neutralising potential for analysed material. It is not always applicable, as a lot of mine waste material, especially from industrial minerals operations, does not contain sulfides; and therefore, the issue of A/NRD does not apply. Inert waste is defined by EU-commission decision (CD 2009/359/EC on inert waste) as waste material that has less than 0.1 wt.% sulfide, or waste with maximum 1 wt.% sulfide content and the neutralizing potential is 3 times higher (based on method EN15875). In addition, the contents of potentially harmful elements (Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, and Zn) are insignificant. If the waste material has a significantly high content of these potentially harmful elements, the availability of these potentially harmful elements should be evaluated by leaching and /or kinetic testing methods. The level of insignificance is to be defined by each member state. This insignificance is commonly defined by the contaminant levels classification for soils not affected by contamination. (e.g., background level). If the waste cannot be classified as inert waste, further A/NRD evaluation is needed. A first step in this evaluation is to have an understanding of the mineral phases that can potentially leach elements, and/or affect the chemical condition of water, e.g. neutralization or acidification. The data should be evaluated based on acid (producing) potential (AP) relative to (acid) neutralization potential (NP) (EN15875). The data is commonly plotted in a diagram where AP vs NP and AP vs Net Neutralizing Potential (NNP = NP-AP). If the ABA analyses are using total sulfur content for calculation of AP (that means all sulfur is as pyrite sulfur), the AP will be a conservative estimate. If sulfide is used, the result may not be conservative, depending upon the mineralogy (Fig. 7). KREC-Norsk Bergindustri 89/110 March 2015 AP (tCaCO3 eq./1000t) Potentially acid generating 1:1 C - sulfate addition D - carbonate reduction. Uncertainty zone B - Non-carbonate neutralization A - sulfide reduction 3:1 Non-acid generating NP (tCaCO3/1000t) Figure 7. Acid potential (AP) relative to neutralization potential (NP) based on ABA analysis. In addition, included are the mineralogical effects on AP and NP that are not included in the ABA analysis. A-sulfide reduction – material containing sulfide minerals that are not acid generating; B-Noncarbonate neutralization – long term silicate weathering consuming hydrogen ions; C-Sulfate addition – acid generating sulfate minerals; D-carbonate addition – iron carbonate and dolomite (Modified from Walder et al., 2005). The method required in Europe to be used is the same as most other methods; it analyzes only for the rapid carbonate neutralizing potential. This is not necessarily a conservative estimate, since it depends upon the carbonate mineralogy. Some carbonate minerals can be acid generating (iron carbonate mineral- siderite; D Fig. 7), and some have very low reaction rate (dolomite - calcium magnesium carbonate). In a slow moving water system, (e.g. groundwater or tailings flow), either in seawater or onshore, a long residence time for the acid production will result; silicate minerals may also be acid consuming (B, Fig. 7). When there is a potential for element leaching and/or acid generation, kinetic tests should be run as specified in CEN/TR 16376 (Overall Guidance document). The method for kinetic testing is described in CEN/TR16363 (Kinetic Testing guideline). This document specifies the issues to be dealt with for an on-shore placement of tailings; while sub-sea tailings placement are not dealt with, but rather described within this document. Data from kinetic testing for SSTD evaluation should be plotted as cumulative concentration relative to time. This will show immediate release rate and afterwards, long-term release rate (2-3 months). Since the seawater is highly alkaline, acid rock drainage is not likely to be an issue when tailings are placed under water in the sea. KREC-Norsk Bergindustri 90/110 March 2015 There may be microbial buildup in these environments, however, not in the same way as in on-shore placement, where the neutralization is only from the minerals within the waste material. There are likely two different element/metal leaching processes taking place (Walder et al, 2013; Repzka et al, 2013): • • Short term leaching is based on the initial leaching of the material either from secondary minerals and/or from leaching taking place in the tailings prior to deposition. This short term leaching rate is relative to the total mass of the material deposited. Long-term leaching is from metal desorption, mineral digenesis, dissolution, and oxidation. This process will primarily take place near the surface of the tailings, which are in contact with fresh seawater, and also where the products of the mineralogical processes can be incorporated into the water column. Microbial processes and bio-turbation in the upper 5-10 cm of the bottom sediments may result in an exchange of compounds of leach elements in the water column. Since the second process is dependent on three geochemical processes: transport of reactant to the surface, mineral transformation, and transport of products away from the surface, this process will likely slow down with time. If the reactive minerals on the surface layer of the tailings are being consumed, there will be a propagation downwards dependent only upon diffusion. This will slow down the reaction process. If the products are elements-compounds that are becoming saturated in the high alkalinity, high sulfate setting, these will precipitate and potentially encapsulate either individual minerals or the surface of the tailings (possibly forming a hardpan). This will slow down both the transport of reactants to the surface and products away from the surface. However, bio-turbation and microbial processes may also be involved. There may be a lag-time as well for these processes, as seen for sulfide oxidation in aerated conditions. Native sediments may, therefore, also be included in the kinetic cell tests to make sure that the specific microbes are included. If microbial processes are significant to the metal leaching rates, it is important that the tests are run long enough to be able to evaluate what mineralogical and geochemical processes are taking place within the tailings material. It is also necessary to evaluate if KREC-Norsk Bergindustri 91/110 March 2015 the leaching rates observed are in a setting similar to the expected setting in the tailings deposition area. • • 9.2.2. There may be mineral precipitation taking place in the tests that is not likely to take place in the natural setting because of buildup of element concentrations in the leach solution that would be removed by high water current. The flow near bottom in the experiments may be higher than in the natural setting and, therefore, mineral saturation is not reached in the experiments that may take place in the natural environment, a common issue for kinetic tests run under aerated conditions as well. Leaching Evaluation The potential impact on water (surface water, groundwater, seawater) is a key aspect in the waste characterization evaluation. The concentrations of different elements in the waste material (tailings and waste rocks) are controlled by the water in contact with the waste. The concentration in the water can be equilibrium based (if water flow is low relative to the rate of solid solution exchange); or reaction rate based, by weathering and diffusion (reacting elements to the surface of the minerals e.g. oxygen), and products transported away from the reacting surface. In many cases, these reaction rate processes are biologically mediated, especially for sulfide oxidation. Many factors control the resulting concentrations in water that come in contact with the waste, such as pH, Eh, EC, L/S, minerals, and sorptive phases. Only a few leaching tests have been designed specifically for waste from the extractive industry, and most have been designed for specific purposes. All tests have to be used cautiously, since they are designed for specific purposes, and not necessarily for the required purpose. All test results have to be used carefully since leaching of the material is mineralogically controlled mineral precipitation and dissolution, together with the physiochemical conditions both in the laboratory and in the field. There is often a large difference between the laboratory-controlled condition and what is taking place in the natural setting. Leaching addresses the release of substances by dissolution from the surface of particles. These substances may be dissolution of primary waste minerals or secondary minerals formed after short term/long term weathering. When evaluating the water quality, it is the dissolved elements that are of concern. Factors controlling solubility under realistic KREC-Norsk Bergindustri 92/110 March 2015 exposure conditions are: mineral precipitation/dissolution, sorption on iron-oxide phases, binding to clay surfaces, ionic strength of the solution, and cation exchange. Dissolution of mineral phases and ingestion by bottom fauna and fish can also be of concern. This information is not obtained through the normal leaching methods described for the waste characterization. Bioavailability tests may be needed for this purpose. The short-term leach tests are most useful for older mine waste that has been exposed to on-shore weathering or mineralisation and digenesis in a marine environment, for some time (months to years) and are in a quasi-stable leaching mode. Test results can then be used to evaluate leachability during the operational phase (short to medium term); e.g. to assess what will be released in the water phase during the next rainfall on land. Shortterm leach tests may also be used to evaluate the immediate leaching potential when depositing the tailings in seawater, but the result cannot be used to evaluate the longterm leaching after deposition. When evaluating short-term storage of new waste material, or when the release rate is controlled by equilibrium reactions of sorption, dissolution/precipitation etc., the shortterm leach tests can be useful. Results from leaching tests can be used as input to geochemical modelling programmes, as a calibration of parameters used in geochemical modelling. Calibration in geochemical modelling can be done through comparing modelling results with leach test results. If leach test results are used for calibration, geochemical modelling of the leaching tests data should be adjusted at least for the water: rock ratio and the grain size/surface area used in the modelling. Kinetic testing of waste material in saltwater generates difficulties in the interpretation and in the quality of the data. Seawater has high concentrations of chloride, sulfate and bicarbonate-carbonate. Chloride may complex with some of the positively charged elements (Cu, Ag, Zn, Cd) increasing the solubility of minerals that otherwise would precipitate e.g. tenorite (copper oxide), and other copper minerals. Also the high ionic strength may result in an increased dissolution relative to dissolution in fresh water. On the other hand, sulfate and carbonate in solution results in the formation of secondary minerals like azurite, malachite, and cerrusite. These minerals may, therefore, reduce the availability of elements of concern. The leach solution needs to reflect this by either KREC-Norsk Bergindustri 93/110 March 2015 using seawater from the location, or design seawater with the components that affects the solubility of these elements. To understand the result, it is often necessary to run geochemical modeling programs to specifically evaluate saturation index of easily soluble or precipitating minerals. The bottom seawater is usually oxygenated; and there is a water current at the bottom. It is, therefore, essential to obtain information about the bottom water oxygen level to reflect this in the reaction rate/leaching tests. Leaching of tailings at the bottom of the sea is very different than for tailings (and waste rocks) deposited on shore, where water and air can freely flow through and more easily generate A/NRD. Tailings deposited in a lake or a tailings pond with a water table above the surface of the tailings, have a very slow through-flow. Tailings deposited in the sea would have little or no water flow-through, resulting in mineral reactions occurring only near the surface depending on colonization and bio-turbation. 9.2.3. Marine Eco-toxicology Marine eco-toxicity tests may be a natural step after leach tests have been performed. The concentrations of compounds from the applicable leach tests should be reflected in the eco-toxicity tests (short term and long term). The type of test(s) may vary with the results of the leach tests. • Compounds used in the processing may decompose rapidly and, thereby, rapidly reduce in concentration. In those settings, acute toxicity may be the most applicable. • Compounds used in the processing may slowly leach, and therefore, the concentration used in the tests needs to reflect this. • Minerals may, with time, weather and release elements. The release may increase with time or reduce with time and the tests needs to reflect this. The connection between the different eco-toxicity test types, leach tests, and the level of marine life forms are displayed in Figure 8. The eco-toxicity tests are commonly performed on water-soluble compounds; however, the bottom sediments may, through the digestive system of several species at different levels, enter the food chain. EcoKREC-Norsk Bergindustri 94/110 March 2015 toxicity tests should also be set up to reflect this, depending upon the material that is evaluated for sub-sea deposition. Figure 8. Display of the connections between the level of organisms, eco-toxicity tests and leach tests. In the framework of CEN/TC292 (Waste), standardization work was initiated to validate methods to characterize the eco-toxicological properties of waste. While some choose methods predominantly using chemical analyses, others are more in favor of direct ecotoxicological measurements. Observed toxicity may be a final result of a number of processes occurring during all preparation steps, from sampling to the preparation of a concentration series. Critical aspects can be found within the selection of the leaching conditions (for example pH and solid/liquid ratio), and the choice between batch procedures versus percolation tests. Within the EN 14735 (standard for preparation of material for eco-toxicity testing), several choices have already been made concerning these aspects. In order to understand the results of the eco-toxicity tests, the variation of test conditions need to be such that speciation models can be used. This will increase the understanding of the toxicity result, since toxicity often depends on the species available, not the total concentration of a component. This type of speciation modeling may need to include, organic and inorganic components, sorption processes, and solid phases (e.g. LeachXS, Geochemical Work Bench, PhreeqC), Solid –liquid separation has a major influence on DOC and colloid levels in solution. The decision to filter or centrifuge the eluate or to abstain from liquid-solid separation cannot be taken lightly, as these parameters have a major influence on the outcome of an eco-toxicity test. For many decisions on waste use, treatment, and disposal, a low liquid to solid ratio is of importance. Inferring effects at a low L/S from results at L/S=10 is impossible. During tailings deposition, the fine-grained material will shear off and KREC-Norsk Bergindustri 95/110 March 2015 remain suspended for a longer time period indicating that a high L/S ratio would be the most applicable for tailings deposition. When chemicals are accumulated into the bottom sediments, the direct bio-availability for pelagic organisms is reduced. The exposure to benthic organisms, however, is increased. The bioaccumulation into the pelagic organisms is, therefore, dependent upon feeding of the benthic organisms (EPA821). However, suspended fine-grained material from the deposition process may be indigested by pelagic organisms. The bioaccumulation is more complex with respect to human health. There will be an ecologic impact on the communities. Performing bioaccumulation tests based on sediment-associated contaminants is very difficult. Taking natural sediments into the laboratory for controlled bioaccumulation can easily disturb the complex nature of the sediments and, thereby, stress the benthic organisms and change the microenvironments (redox and temperature conditions). This would, thereby, make it difficult to interpret the result. 9.3. Uncertainty – Limitations Uncertainty and limitations are very important issues in a sub-sea tailings deposition evaluation. Much of what is discussed in this section has already been mentioned in Chapter 7. However, due to their importance, the information is repeated here. Assessing current physical and geochemical properties of waste material is relatively straight forward; however predicting how the waste material will develop in the future under the influence of weathering is complex. When adding different closure scenarios, this becomes an even more complex task. The prediction of future behaviour of the waste material is no exact science and will include a level of uncertainty. When the result of the predictions is a key factor in a choice of a waste management option, a high level of accuracy or safety factors will be needed. In clear-cut cases, however, whether clearly benign or clearly problematic material, there may be no need for high precision. Data quality and uncertainty can be understood in several ways. It can be the uncertainty related to the representativeness of the samples that are collected, the uncertainty of a specific test result (e.g. leaching and analysis), the variability in materials taken at different times or locations; and it can relate to the uncertainty in the prediction of release behaviour under field conditions. KREC-Norsk Bergindustri 96/110 March 2015 In case of sea/fjord evaluation uncertainties can include; • • • • Variations throughout the years, when growth potential is variable; Migrating fish; Bottom flora fauna is highly variable between different locations; and Salinity is dependent upon variable currents and freshwater input. These uncertainties are not easy to measure or calculate, but it is important to get a sense of the magnitude of uncertainty when trying to draw conclusions based on test results and predictions. Predictive modeling will, in many cases, be part of the evaluation. The inherent uncertainty in model predictions should be recognized and clearly stated. Considerable uncertainty is inherent in determining many of the parameters that are required for modeling sea currents, sediment transport, and leaching rates from mineral weathering. The uncertainties of modeling outputs may result from: • • • • Incomplete characterization; Incomplete knowledge of the; o Conditions; o Leaching rates; o Thermodynamic data in general or for the specific conditions; Lack of data on flocculation; and/or Insufficient knowledge of the hydrological conditions at the site. The Overall guidance document for waste characterization (CEN/TR16367, 2012) states: “Methods used to evaluate or account for model uncertainty include Monte Carlo analysis, stochastic methods, and an evaluation of a range of model parameters to develop a range of deterministic outcomes. Rather than parameters being described by a single value as required in the model, parameters are better described with a probability distribution (i.e., a mean value with standard deviation, etc.).” The model uncertainties should also recognize and describe the difficulties of up-scaling test results from e.g. leaching tests and flocculation tests. Taking into account the uncertainty in model parameters will still not address uncertainties in the conceptual KREC-Norsk Bergindustri 97/110 March 2015 model. Field verification is commonly needed to reduce uncertainties in the conceptual model, as omission of an important release controlling process may lead to a faulty prediction. In this context, the interrelations between laboratories test results and field tests can provide a greater level of understanding, thus increasing the reliability of data developed to support management decisions. Quality Assurance /Quality Control (QA/QC) is also important, and deals primarily with measurable quantities, such as physical parameters, chemical analysis and leaching test results, and helping to create a process where sampling or laboratory analysis are performed consistently. EN17025 is a European standard that specifies good laboratory practice. Issues of sampling quality are described in CEN/TR 15363 specific for mines waste. There are no specific guidelines dealing with QA/QC in monitoring sea currents. 10. OPERATION, MONITORING AND CLOSURE The characterization of the waste and the area of deposition are essential in evaluating the impact. The level of impact needs to be evaluated based on different types of discharge; electing a method for discharge that gives the minimal impact to human health and the environment. When the system for minimal or accepted level of impact has been decided, the design of the monitoring program should include: • • • • • • • Discharge parameters (salinity, L:S ratio, air content); Turbidity measurements in the surrounding sea; Soft-bottom flora –fauna monitoring in a distant from discharge point at border of no-influence; Fish amount and quality; Water quality; Interstitial water from the tailings; and Redox potential at the bottom and within the tailings sediments. 10.1.1. Discharge System The discharge system includes the transport from the processing plant to the discharge point in the sea. The issues to deal with in the discharge systems are the following parameters: KREC-Norsk Bergindustri 98/110 March 2015 • • • • • Pipeline; Flocculation; Salt water addition; Temperature; and Air bubble trap. The parameters are issues that deal with reduction of material spreading. If there are air bubbles in the tailings then discharging the tailings will result in a greater mixing and possible upwelling. If the tailings are warm, and have low salinity, the water within the tailings will have buoyancy and rise, increasing the mixing and spread. The same effect may take place if fresh water is within the tailings. The fresh water can be partly replaced with cold saltwater, and thereby, reduce the effect of buoyancy, and reduce the effect of mixing. The characterization data of the seawater at a deposition site is part of the input data to be used in evaluating how much seawater is required, and how reduction in temperature is necessary to get an acceptable density to reduce particle spreading. Experiments on flocculation using different flocculation agents will also give input to such modeling. Salt water is assumed to act as a flocculation agent due to the high salinity. If salt-water addition is not efficient enough as a flocculation agent, then other chemicals are needed, causing other effects that will need evaluating based on the chemical used, e.g. Magnafloc, which can be carcinogenic at certain concentrations . 10.1.2. Field verification Most of the analysis and methods described in this document are based on relatively short-term analysis of small samples. Kinetic tests, that may last for a year or more, are considered short term when taking into account that the analysis/methods are in some cases used to evaluate long-term effects over hundreds to thousands of years. Long-term onsite field scale tests can be very useful if there is a potential for mineralization or digenesis affecting the chemical and geotechnical stability of the KREC-Norsk Bergindustri 99/110 March 2015 waste. During the exploration phase, there is usually not enough material available for such tests; however, when a project moves into the feasibility phase and excavation for full production has begun, material will become much more available. Field scale tests can and should then be initiated. These tests can be in place throughout the life of the mine, and provide feedback to update waste handling and closure plans. Information on water chemistry, turbidity, flora-fauna, fish impact etc. provide valuable on going information on the stability of the waste and deposition process. These onsite long-term field-testing would be a natural part of the operational environmental and management plan. The monitoring can be based on indicator species, together with a well-developed accepted criteria system. The long-term stability is both a physical and geochemical issue. Both long-term physical and geochemical stability needs to be evaluated using the receiving environmental setting, design criteria, and leach tests, but primarily from a theoretical and analogue site evaluation with the input of the above listed issues. The geochemical stability is partly evaluated though the long-term leach tests. However, these tests will seldom be run long enough to observe silicate mineral alteration and/or hard pan formation. It is, therefore, necessary to evaluate the geochemical stability using geochemical modeling tools that can incorporate reaction rates. Input parameters for such geochemical modeling will include, but not necessary be limited to: • • • • • • Initial solution geochemistry, Initial mineralogy, Potential secondary mineral precipitation or alteration of primary minerals, Reaction rates of initial and secondary minerals, Seawater chemistry (salinity, alkalinity, oxygen concentration, element concentration etc.) Infiltration rate of seawater into the tailings material and transport mechanism out of the tailings. Geochemical programs that potentially can be used for this evaluation include e.g. PhreeqC, Geochemical Work Bench (Bethke, 2010), FlowTran (Lichtner, 2001), and LeachEX. Cuipers et al, 2005 gives an overview of potential geochemical modeling programs to use. Most of these programs do not include the high salinity issue of KREC-Norsk Bergindustri March 2015 100/110 seawater in the geochemical data base and adjustments to the programs may have to be done. There are few physical stability analyses that can be performed prior to tailings deposition. Ore processing tests will result in data on grain size. If sufficient material is available, stability tests can be performed in salt-water tanks. These tests may be performed alongside the testing for useful flocculants. These types of analyses can then be used to make criteria for a tailings deposition design. However, in many cases, only monitoring will tell if the design fulfils the physical stability criteria. 10.1.3. Monitoring Defining monitoring plans is a natural step in evaluating SSTD. The monitoring plan for SSTD should be designed to evaluate: . • Sea-fjord current and mixing; • Salinity of seawater and possible change in layering over time; • Geochemistry of the discharging material; • Solid transport above the tailings deposition area and away from this area; • Seawater chemistry with a focus on elements that potentially can leach from the tailings – tailings water; • Amount of material deposited; • Fish habitat changes; • Flora – fauna changes relative to reference monitoring stations; and • Water and solids discharge from rivers to the fjord potentially used for tailings deposition. These issues should be monitored on a regular basis during and after closure of the tailings deposition. 10.1.4. Emergency Response Plans There is always the potential for failures in a production system, which is also applicable to a tailings deposition system. A failure in a pipe, especially the tailings pipeline, could have a catastrophic short-term effect, and potentially long-term effect, on the marine environment. It is, therefore, essential to perform a risk assessment for potential KREC-Norsk Bergindustri March 2015 101/110 failures. From there, a response systems should be developed that can effectively be implemented to reduce potential affects due to failures. The emergency response plans may include: • • • • Failure in the pipe line above the sea; Failure in the pipe line below sea level; Failure in the mixing tank; and Failure in the air removal system, KREC-Norsk Bergindustri March 2015 102/110 11. DOCUMENTATION AND REPORTING Proper documentation and reporting is important in building trust between involved parties (operator, regulators, general public, NGOs) and for the credibility and traceability of test results. The documentation of the waste characterization and the characterization of the receiving environment (on-shore and off-shore) should cover all steps, from describing the rationale behind performing the characterization to the evaluation and conclusions. The structure of the documentation of the results and interpretations should follow good reporting practices and any applicable legal requirements. A recommended structure, including the documentation of relevant supporting information, is given below; 1. 2. 3. 4. 5. 6. 7. 8. 9. Introduction Background information of the (future) operation • Type and description of extraction method, • Nature of the intended product Geology of the site • Nature of surrounding rocks • Chemistry and mineralogy, mineralization typology, including physical properties, size and geometry of deposit, • Weathering of the deposit Objective(s) and approach(s) to the characterization Sampling procedures Analytical procedures Baseline data for the site of disposal Presentation of the results of the characterization • Waste characteristics Field data Analytical data • Deposition location characteristics Field data Analytical data Evaluation and discussion of the result • Waste types and its intended handling KREC-Norsk Bergindustri March 2015 103/110 • 10. 11. 12. Mineralogical and geochemical description of the waste including leaches tests/kinetic tests etc. • Volume/mass of different types of waste and when waste is produced • Description of potential geotechnical and geochemical impact • Sub-sea deposition system Pipeline Spreading/settling Chemical effect of additives Conclusions and Recommendations for follow up work References to sited documents Attachment • Laboratory reports • Field reports (field analysis and observations) • Sampling plan Copies of all reports should be stored at the operator’s office for possible future auditing. KREC-Norsk Bergindustri March 2015 104/110 12. REFERENCES ASTM 2001: Bakke, S.M. and Jensen, T., 2004: Titania AS. Miljøundersøkelser i Jøssingfjorden 2003. Report 2004-0083 by Det Norske Veritas. Bref/BAT, 2004: Reference Document on Best Available Techniques for Management of Tailings and Waste-Rock in Mining Activities, Sevilla, Spain, July 2004, Internet: http://eippcb.jrc.es. Brunauer, S., Emmett, P. 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WORDS TAILINGS means the waste solids or slurries that remain after the treatment of minerals by separation processes (e.g. crushing, grinding, size-sorting, flotation and other physico chemical techniques) to remove the valuable material/minerals/metals (from the Mining Waste directive) WASTE FACILITY means any area designated for the accumulation or deposit of extractive waste, whether in a solid or liquid state or in solution or suspension, (from the Mining Waste Directive) HEAVILY MODIFIED WATER BODY means a body of water, which as a result of physical alterations by human activity is substantially changed in character (from the Water Framework Directive) GOOD ECOLOGICAL POTENTIAL means the status of a heavily modified water body or an artificial body of water, so classified in accordance with relevant provisions of Annex V in the water framework Directive. ECOLOGICAL STATE is an expression of the quality of the structure and functioning of aquatic ecosystem associated with surface waters, classified in accordance with relevant provisions of Annex V in the water framework Directive. KREC-Norsk Bergindustri March 2015 110/110