DEPARTMENT OF WATER AFFAIRS. Key Indicators, Methodologies to Set Targets and Commodity-based Targets

Transcription

1 REPORT July 2014 DEPARTMENT OF WATER AFFAIRS Targets for Water Conservation / Water Demand Management in the Mining Sector Key Indicators, Methodologies to Set Targets and Commodity-based Targets Submitted to: Department of Water and Sanitation Chamber of Mines of South Africa Report Number: Distribution: 1 x copy to Department of Water and Sanitation 1 x copy to Chamber of Mines of South Africa 1 x copy to Golder Project File 1 x copy to Golder Library

2 Table of Contents 1.0 INTRODUCTION KEY WATER USE EFFICIENCY PERFORMANCE INDICATORS Key Indicators for Defining Water Use Efficiency... 3 Volumetric indicators... 3 Water use efficiency performance indicators SETTING OF NATIONALWATER USE EFFICIENCY TARGETS General description of national target setting process Discussion of national benchmark setting process Step 1: Calculate current baseline total water use efficiency Step 2: Discard invalid/poor water balances Step 3: Rate mines in terms of WC/WDM Status (accuracy and completeness) of water balance Regular (monthly) update of monitoring data into computerised system Use of water balance data in water management decision making Existing WC/WDM plan Use of DWS BPGs Step 4: Calculate national benchmarks Top 3 coal mines Top 3 gold mines Top 3 platinum mines Top 3 other mines Step 5: Determine national benchmark ranges METHODOLOGY FOR MINES TO SET WATER USE EFFICIENCY TARGETS SPECIFICATION OF GENERIC WC/WDM MEASURES Generic Measures Derived from Recent Literature Measures to reduce mine water use Measures to reuse mine water Measures to recycle mine water Water reduction model Generic Measures Derived from Practical Experience Report No. i

3 5.2.1 WC/WDM measures for mining operations WC/WDM measures for ore / mineral processing operations WC/WDM measures for waste, residue disposal and tailings storage operations General WC/WDM measures Generic Measures Evaluated with Water Balance Model Concluding Remarks Regarding Generic Measures CONCLUSIONS TABLES Table 1: Average water usage per tonne mined for all mines... 6 Table 2: Average total water use efficiency(per tonne mined) of all mines, as well as those with valid and invalid water balances... 8 Table 3: Benchmarks for total water use efficiency based on top 3 mines (per commodity) Table 4: Key Indicators for Coal mines Table 5: Key Indicators for Gold mines Table 6: Key Indicators for Platinum mines Table 7: Key Indicators for Other mines Table 8: Standard deviation of key performance indicators per commodity Table 9: National Key Indicator Benchmarks and Ranges for Coal Mining Table 10: National Key Indicator Benchmarks and Ranges for Gold Mining Table 11: National Key Indicator Benchmarks and Ranges for Platinum Mining Table 12: National Key Indicator Benchmarks and Ranges for Other Mining Table 13: Scenario Summary FIGURES Figure 1: WC/WDM Project Phase 2 Deliverables... 2 Figure 2: Generic Water Balances and Key Indicators... 4 Figure 3: Process for Determining National Water Use Efficiency Targets (Benchmarks)... 5 Figure 4: Coal mines with valid and invalid water balances... 9 Figure 5: Gold mines with valid and invalid water balances... 9 Figure 6: Platinum mines with valid and invalid water balances... 9 Figure 7: Other mines with valid and invalid water balances Figure 8: Top 3 selected coal mines Figure 9: Top 3 selected gold mines Figure 10: Top 3 selected platinum mines Figure 11: Top 3 selected other mines Report No. ii

4 Figure 12: National Water Use Efficiency Benchmarks Figure 13: Overall WC/WDM planning & implementation process Figure 14: Internal target setting review process Figure 15: Methodology for the development of a WC/WDM Plan Figure 16: Effect of rehabilitation lag time on total water use efficiency Figure 17: Effect of rehabilitated opencast pit rainfall recharge on total water use efficiency Figure 18: Effect of tailings specific gravity on total water use efficiency Figure 19: Effect of tailings residue solids percentage on total water use efficiency Figure 20: Effect of return water pool size on top of tailings disposal facility on total water use efficiency Figure 21: Effect of dust suppression water use on total water use efficiency Figure 22: Effect of percentage of sewage water reused on total water use efficiency Figure 23: Effect of water usage per worker with shower access on total water use efficiency APPENDICES APPENDIX A Key Indicator Values For All Mines APPENDIX B Variables Matrix APPENDIX C Water Balance Model APPENDIX D Document Limitations Report No. iii

5 1.0 INTRODUCTION Task 8 is a critical component of the project and has the objective to develop the national water use efficiency targets using the data collected in the site engagement process, describe the methodologies that mines should be utilising to develop their site-specific water use efficiency targets and provide guidance on the types of WC/WDM measures that can be considered for incorporation into the mine's WC/WDM plan. The scope of work for this is contained in the project proposal and is reproduced verbatim below: "Based on the information prepared in Phase I and the feedback received from the Project Steering Committee, the stakeholders consulted and the published WC/WDM Guideline, a report will be prepared that proposes the following: A methodology that can be used by mines to set water use efficiency targets. The proposed methodology will be practical and will also indicate how to take account of the variables that were documented as part of the variables matrix. Key indicators that should be used for water target setting and the monitoring and reporting against these targets. Wherever appropriate, the indicators will be linked to other water frameworks (Global Reporting Initiative [GRI], water accounting, etc.). Targets for each mining sub-sector (based on the key variables defined in the variables matrix). The report will also propose generic measures that can be considered for implementation in order to achieve the set targets. Based on information collected during the site visits, the report will present estimates of the quantities of water that can be saved and the probable timeframes over which such water savings can be realised. Wherever possible, the proposed methodology will be illustrated by way of successful case studies, either reported in the literature, or based on experience within the South African mining industry. This report will initially be issued as a draft report for review by the Project Management Committee, whereafter the comments will be incorporated into a final report for submission to the Project Steering Committee." The actual manner in which the above deliverables will be produced draws on the experience gained to date during the project, the information obtained from the literature review, the experiences obtained during the site engagements and the feedback received from the project stakeholders during the Project Steering Committee meetings. It is critical in undertaking a project of this nature to be flexible and to adapt the originally conceived approach to accommodate the insights gained in the execution of the project. In essence, the scope of work as set out in the project proposal will be addressed in the following manner: Step 1: Define the key indicators that will be used to measure water use efficiency in accordance with established protocols and frameworks and also define standardised reporting protocols. Step 2: Establish national water use efficiency target ranges for each of the major commodity groups evaluated during the site assessments, using the key indicators defined in Step 1 and using the water balance data collected during the site assessments. In this context it is recognised that the grouping termed other covers a wide range of different commodities with divergent mining methods and that each of the commodities should ideally have separate targets. However, the density of data for these other commodities does not support this and at this stage there is no alternative but to group them together as other. These national targets are to be used by the mines as reference or benchmark targets when developing the site-specific internal water use efficiency targets. Step 3: Define methodologies that can be used by individual mines to set site-specific internal water use efficiency targets that take account of the site-specific expression of the variables listed in the variables matrix and that will result in the development of site-specific water conservation/water demand management plans. Step 4: Define generic water conservation measures that can be considered by mines for incorporation into their site-specific water conservation/water demand management plans and provide order-of- Report No. 1

6 magnitude water savings measures that can be anticipated from the application of these generic measures. While it is clear that sensible internal water use efficiency targets need to be developed by each mine in accordance with set methodologies that take account of all the site specific variables, it is equally important that the internal targets that are developed, can be benchmarked against national benchmarks that are achievable and that do represent efficient use of water on mines. The above 4-step process provides for this in a logical and consistent manner and utilizes both the data obtained in Phase 1 of the project (which does represent the most up-to-date and comprehensive database on the current status of water use in the South African mining industry) as well as existing guidance documents, most specifically the WC/WDM Guideline and the DWS Best Practice Guidelines. In addition, relevant insights gained from the literature review are also incorporated. Task 9 is very closely linked to Task 8 and the scope of work for this is contained in the project proposal and the outcome is presented in a different report (Task 9 report). This Task 9 report covers those aspects shown in Figure 1 below. The relationship between Tasks 8 and 9 and their deliverables is shown graphically in the Figure below. WC/WDM PROJECT PHASE 2 DELIVERABLES DRAFT TARGETS AND TOOLS REPORT Task 8 Key indicators National targets per commodity Methodology for internal target setting Savings potentials for generic measures DRAFT IMPLEMENTATION GUIDELINE Task 9 Regulatory implementation framework Industry implementation plan Monitoring & reporting requirements 1-day workshop to assist indicator mines in target setting Select indicator mines for Phase 3 Stakeholder Workshop on Task 8 and 9 reports FINAL TARGETS & TOOLS REPORT FINAL IMPLEMENTATION GUIDELINE Figure 1: WC/WDM Project Phase 2 Deliverables This report only deals with Task 8 and is the Draft Targets & Tools Report as shown in Figure 1. The manner in which the target setting methodology will be implemented, the regulatory framework that should support this, as well as the actions that mines will need to take will be described in a separate report that will be compiled as part of Task 9 of the project. Each of the four major deliverables to be included in this report are dealt with in a separate chapter: Chapter 2: Key Water Use Efficiency Indicators Chapter 3: National Water Use Efficiency Targets Chapter 4: Setting of Internal Water Use Efficiency Targets Chapter 5: Potential Savings Associated with Generic Water Conservation Measures Report No. 2

7 2.0 KEY WATER USE EFFICIENCY PERFORMANCE INDICATORS 2.1 Key Indicators for Defining Water Use Efficiency The issue of which water use efficiency targets should be developed for this project has been extensively debated with the Project Management Committee and with the Project Steering Committee and the finalised agreed list of key indicators reflects these different views and inputs. In order to address the various views, it has been decided that this project will focus on two categories of water usage as defined below: 1) Total water use: Total intake of all water entering the operation. This includes rainfall and runoff that is not separated from and diverted around the operation, groundwater make and/or abstraction, water obtained from water supply boards, water abstracted from any surface water resource, wastewater (or any other water) obtained from an external third party. This total water intake is also, by definition, equivalent to the total water output. 2) Consumptive water use: This is water used by the mine which effectively removes the water from the water cycle - thus it is not available for use by other users. Examples are seepage, evaporation and discharge of dirty water. This specifically excludes water supplied to third parties for their use as well as water discharged to the environment that demonstrably meets DWS discharge standards. This category of water use will be lower than the Total Water Use. The key indicators shown below have been agreed to be relevant in terms of water conservation/water demand management and will be used in this project. The manner in which these indicators are determined using the generic water balance used for the site engagements is shown in Figure 2 below. Volumetric indicators Total water use (volume flow as defined above) Consumptive water use (volume flow as defined above) Water use efficiency performance indicators Total water use efficiency per production measure (m 3 per tonne of ore mined {ROM}) Consumptive water use efficiency per production measure (m 3 per tonne of ore mined{rom}) Percentage of the total volume of wastewater generated that is not reused (%) Water recycling ratio (%) The six key indicators listed above can be applied to the total mine (all operations associated with the mine), as well as to individual mining operations (e.g. mining, beneficiation and residue disposal). Note that the production measure used for the individual mining operations will differ, e.g. beneficiation might be expressed per mass of material processed. Data collected during the site visits does allow the setting of targets ranges for total water use efficiency and consumptive water use efficiency per major commodity. However, the quality and completeness of water balance data obtained during the site visit does not support the derivation of similar targets, with the same degree of confidence, for the sub-balances, i.e. mining operations; beneficiation plants and residue disposal. Report No. 3

8 A Board Water River Water Ground Water Rainwater/ Runoff Other known Sources Unspecified Sources INPUTS TOTAL MINE B OUTPUTS Human Consumption Discharges that meet DWA standards Supply to off-site Third Party Evaporative Losses Product & Residue Moisture Unspecified Sinks TOTAL TOTAL Board Water Mine Service Water Return Dam Water Rainwater/ Runoff Mining Slurry Water Other known Sources Unspecified Sources INPUTS ROM Product: BENEFICIATION PLANTS ROM Ore: ROM Slurry: Product: Residues: t/d oz/d t/d t/d t/d t/d OUTPUTS Human Consumption Discharge to River/Groundwater Supply to Other Users Evaporative Losses Product Moisture Unspecified Sinks TOTAL TOTAL Residue Moisture C Discharges that don t meet DWA standards C D Board Water River Water Ground/fissure Water Rainwater/ Runoff Other known Sources Unspecified Sources INPUTS 0 MINING OPERATIONS ROM Ore: Slurry: t/d t/d Slurry solids: % OUTPUTS Human Consumption Discharge to River/Groundwater Supply to Other Users Evaporative Losses Product & Residue Moisture Unspecified Sinks TOTAL TOTAL Water with Residue Ground/fissure Water Rainwater/ Runoff Other known Sources Unspecified Sources INPUTS RESIDUE DISPOSAL Fine Residue: Coarse Residue: Residues Recovered: t/d t/d t/d OUTPUTS Interstitial Storage Point Discharge to River Seepage to Groundwater Evaporative Losses Return to Plant Or Other Users Unspecified Sinks TOTAL TOTAL D D VOLUMETRIC INDICATORS WATER USE EFFICIENCY INDICATORS Total water use = A Total water use efficiency = A B Consumptive water use = A - C Consumptive water use efficiency = ( A - C ) B % Waste water not recycled = {1 [ D ( A - C + D )]} x 100 Recycle ratio = ( D A ) x 100 Figure 2: Generic Water Balances and Key Indicators The calculated values for the key indicators for all the mines included in the site engagements is shown in Appendix A. 3.0 SETTING OF NATIONALWATER USE EFFICIENCY TARGETS 3.1 General description of national target setting process The commodity-based targets set in this step are derived from the information gathered during the site visits to the 39 mines selected for this project. Mines should consider these targets when developing their sitespecific WC/WDM plan. These national targets will be used by DWS in reviewing individual mine WC/WDM plans and site-specific water use efficiency targets to ensure that they are realistic and in-line with industry commodity norms. The methodology of combining the national targets and the individual targets developed by each mine will be described in the guideline for the regulator and industry as part of Task 9. The method that was used to derive national water use efficiency targets is described below: The current baseline water use efficiency per commodity was determined by evaluating the water usage data at each of the 39 visited mines, as well as mine production data (tons of ore mined). This determines the average Current Total Water Use Efficiency for a particular commodity. This baseline water use may also be expressed in terms of individual processes such as mining, minerals beneficiation, residue handling and disposal, etc., wherever data density supports this. Secondly, it was apparent that the water balances obtained for a number of the mines were seriously flawed and an exercise was undertaken to attempt to objectively identify those mines whose water Report No. 4

9 2σ 2σ TARGETS FOR WC/WDM IN THE MINING SECTOR balance data should be discarded due to the fact that inclusion of this data was skewing the conclusions that were being drawn. The information collected from the site visits was then objectively evaluated to identify those mines that have shown good progress with implementation of general water management measures and WC/WDM measures. The water use efficiency of the top three mines was then evaluated in relation to the current average baseline ranges using the complete data set and used to define the initial national water use efficiency targets for each mineral commodity. This exercise was undertaken for the coal, gold, platinum and other (all other mining) commodities. These water use efficiency targets are defined as national targets and a range above and below the average national target was defined in order to set a national target range. This range was derived from consideration of critical variables, including where possible, those described in the variables matrix. A water balance tool that can be used to assess the effects of the key variables on the national targets for the different commodities was developed and used for this exercise. The process described above is shown graphically in the Figure below. PROCESS FOR DETERMINING NATIONAL WATER USE EFFICIENCY TARGETS Water use efficiency data for all coal mines Water use efficiency data for all coal mines with valid water balances Water use efficiency data for top 3 coal mines regarding WC/WDM Water use efficiency target and range for coal mining WATER BALANCE DATABASE INPUTS OUTPUTS 2.70 MAX 2.70 MAX Board Water River Water Ground Water Rainwater/ Runoff Other known Sources Unspecified Sources m 3 /d m 3 /d m 3 /d m 3 /d m 3 /d m 3 /d TOTAL MINE ROM Product: t/d oz/d m 3 /d m 3 /d m 3 /d m 3 /d m 3 /d m 3 /d m 3 /d Human Consumption Discharges that meet DWA standards Discharges that do not Meet DWA standards Supply to off-site Third Party Evaporative Losses Unspecified Sinks TOTAL m 3 /d m 3 /d TOTAL Product & Residue Moisture Extract all water balance data for a single commodity, e.g. coal 0.79 AVE Remove all water balance data for mines with invalid balances 1.13 AVE Determine top 3 coal mines with respect to WC/WDM and use data 1.33 MAX 0.70 AVE Allocate range based on Monte Carlo simulations with water balance model 1.08 MAX 0.70 AVE 0.10 MIN 0.20 MIN 0.20 MIN 0.31 MIN Figure 3: Process for Determining National Water Use Efficiency Targets (Benchmarks) A review of available literature indicates that the approach of setting national targets has not been attempted in any other country, presumably due to the fact that there are such a large range of variables that affect water use efficiency on a mine. As the precise effect of all these variables cannot be explicitly evaluated or quantified, the international approach has been to focus on ensuring that there is a consistent and accurate methodology for measuring and reporting water use and to then use this as a platform for the implementation of methodologies to enable individual mines to set their own internal targets. The approach described here in Chapter 3 is based on an evaluation of the data collected during the site visits in order to identify those mines that represent a more advanced level of WC/WDM and to use their water use efficiency data as a benchmark for other mines within the same commodity group. It is also assumed that the benchmarks derived from the better performing mines do not represent a desirable end point for that commodity as these better performing mines themselves have room for improvement. This implies that the benchmarks will change in future in line with the process of continuous improvement. It must also be remembered that the better performing mines that were used to develop the benchmarks represent very specific mining situations and that there will be mines that have a specific combination of the variables described in the variables matrix who will be unable to meet these benchmarks no matter how much effort they put into implementing WC/WDM measures. Report No. 5

10 Given the abovementioned caveats, it is deemed more appropriate to refer to the outcome of the process described in Chapter 3 as national commodity benchmarks rather than national targets The national benchmarks developed using the method described above will serve as the initial national benchmarks. These national benchmarks will be refined (probably downwards)in line with the principle of continuous improvement as more information becomes available through the individual WC/WDM plans developed by each mine and as the level of WC/WDM on mines matures in future. 3.2 Discussion of national benchmark setting process In order to calculate the benchmarks using the method described above, more than three mines are required per grouping to get meaningful results. Of the mines evaluated, only coal, gold and platinum have more than three mines. Benchmarks will therefore be calculated for these three commodities, whilst all the other commodities will be grouped under other. The commodity-based national benchmarks will therefore be developed for the following commodities: Coal Gold Platinum Other (includes diamonds, chrome, iron ore, manganese, copper, phosphate, heavy mineral sands and dolomite quarries) It is clearly understood that the group other contains a very diverse range of mining commodities which also represent quite a diverse range of mining methods and that it is problematic to include such a diverse set of mines into a single group. However, the data density for the other mining commodities is simply too low to allow the process described in this section to be applied and there are only two possible options available to the project team. Firstly, group all these mines into a single other grouping and highlight the problem and reduced confidence in the data reported for the other grouping. Secondly, benchmark setting could be confined to the three major commodities with no values reported for the other commodities, other than indicating the range of values actually found from the site visit data. The steps that were followed to calculate the water use efficiency benchmarks and the calculated results are explained in detail below. The discussion presented below generally only refers to the total water use efficiency indicator although the same exercise was undertaken for all the listed performance indicators Step 1: Calculate current baseline total water use efficiency The first step in calculating the benchmarks was to determine the current baseline total water use efficiency per commodity. As a first step, this was calculated using all the mines that were evaluated. The results are shown in Table 1. Table 1: Average water usage per tonne mined for all mines Commodity Total input per ton mined Average of all mines Coal 0.79 Gold 2.46 Platinum 1.68 Other 1.23 Report No. 6

11 3.2.2 Step 2: Discard invalid/poor water balances In order to ensure that the benchmarks are based on valid and correct water balances, the total water balance of each mine was evaluated in terms of its accuracy and completeness. This was done as follows: Each mine was given an initial score of five points. Values were subtracted for omissions and discrepancies in the water balance. All mines with a final water balance score of below 1 were discarded as their water balances were considered to be too inaccurate and incorporation of these data would skew and misrepresent the actual total water usage on mines. All outlier mines with extremely high (>400% of average) or low (<25% of average) water use efficiencies (based on total water use per ton of ore mined) were also discarded, since these values are unrealistic and were deemed to most likely be due to incorrect water balance or production data and not representative of the industry in general. The average total water use efficiency per commodity was then recalculated based on the valid water balances. The water balances of the mines were first penalised for omissions of critical inputs and outputs. On a high level, most mines will have the following water inflows and outflows: Typical inflows: Municipal / Water Board River Water Ground Water Rain Water Runoff Other Known Sources Typical outflows: Human consumption Discharge to River/Groundwater Supply to off-site Third Party Evaporative Losses Product & Residue Moisture Dust suppression Other Known Sinks Of the above inflows and outflows, the following data should be present for all mines and are considered essential for an accurate and complete water balance. This approach is validated by the data collected from the site visits and reported in Figures 24 and 25 of the Phase 1 report which clearly shows that these two inputs and two outputs represent a major portion of the water balance for each commodity group. One point was therefore deducted if any of these values were omitted in the water balance. Essential inflows Report No. 7

12 Ground Water Rain Water Runoff Essential outflows Discharge to River/Groundwater (as this includes seepage which will generally occur to some degree at all mines) Evaporative Losses Mines were also penalised for discrepancies in their water balance, such as a difference between the total inflows and total outflows. One point was therefore subtracted for every ten percent difference between the total inflows and total outflows. All the water balances with a score of less than 1 were considered to have too much missing information and too many discrepancies to be used with confidence in the national benchmark setting process. This process resulted in two mines being dropped (1 gold and 1 coal). Outlier mines with a total water input per tonne mined of more than 4 times the average water usage of that particular commodity were considered to be too high to be representative of the industry in general and were thus discarded. One other mine was discarded for this reason. Outlier mines with a total water input per tonne mined of less than one quarter of the average water usage of that particular commodity were considered to be too low to be representative of the industry in general and were thus also discarded. Five mines (3 coal and 4 other) were discarded for the reason that their water usage was less than 25% of the average for their commodity groups. For the 3 coal mines removed, (representing three different mining Groups) one was an underground mine without a beneficiation plant and two were opencast mines with beneficiation plants. Table 2 shows the averages of all the mines per commodity, as well as the averages of the mines with invalid water balances and the averages of mines with valid water balances. From this is can be seen that, for coal and gold, the average of the mines with valid water balances is actually higher than the averages of all the mines. This is due to the fact that the mines with invalid water balances did not include all the water inflows entering the mine water circuits. Using the data from these mines would therefore be incorrect, since it would result in unrealistic low benchmarks. Table 2: Average total water use efficiency(per tonne mined) of all mines, as well as those with valid and invalid water balances Commodity Average of all mines Total water use efficiency per ton mined Average of mines with invalid water balances Average of mines with valid water balances Coal Gold Platinum 1.68 No invalid mines 1.68 Other The detailed water usage of the valid and invalid water balances for each commodity is shown in Figure 4 to Figure 7. This process resulted in the removal of data for four of the eleven coal mines, one of the eight gold mines, no platinum mines and five of the twelve other mines. Report No. 8

13 Total inflows/tonne mined (m3/t) Total inflows/tonne mined (m3/t) Total inflows/tonne mined (m3/t) TARGETS FOR WC/WDM IN THE MINING SECTOR Coal Invalid Valid Averages Figure 4: Coal mines with valid and invalid water balances Gold Invalid Valid Averages Figure 5: Gold mines with valid and invalid water balances 3 Platinum Invalid Valid Averages 0 Figure 6: Platinum mines with valid and invalid water balances Report No. 9

14 Total inflows/tonne mined (m3/t) TARGETS FOR WC/WDM IN THE MINING SECTOR Other Invalid Valid Averages Figure 7: Other mines with valid and invalid water balances Step 3: Rate mines in terms of WC/WDM The national water use efficiency benchmarks will be based on the mines that have shown good progress with implementation of WC/WDM measures, since the water use efficiency of those mines should be better than the average mine. In order to determine the status of WC/WDM of the mines, each mine was rated out of 5 (5 being good and 0 being poor) on the five critical aspects listed below: 1) Status (accuracy and completeness) of water balance (weight = 5) 2) Regular (monthly) update of monitoring data into computerised system (weight = 4) 3) Use of water balance data in water management decision making (weight = 3) 4) Existing WC/WDM plan (weight = 4) 5) Use of DWS BPGs (weight = 2) The above aspects were rated using the results from the questionnaires that were completed during the site visits. The ratings were then totalled using the relative weights shown in brackets to find a single score out of 5 for each mine related to WC/WDM. The decision to base the rating on the above five aspects is motivated by the fact that effective WC/WDM is a process that is dependent on the mines having a good computerised water balance, updating it regularly and ensuring that the results from the water balances are used in guiding water management decisions on the mine. Additionally, specific questions relating to the mine s WC/WDM plan (where these existed) and the extent to which the mines apply best practice in their operations were also considered critical in determining whether or not the mines represented good practice with regard to WC/WDM. A discussion of how each of the above aspects was rated is presented in the relevant sections below Status (accuracy and completeness) of water balance The status of the water balances were determined as described under section All mines were given an initial score of 5. Subtractions were then made for missing data and discrepancies Regular (monthly) update of monitoring data into computerised system The following questions from the questionnaire were used to rate this aspect: Is the water balance computerised, and if yes, what type of software is used? Is there clear evidence that the water balance is updated at least monthly using new monitoring data? Report No. 10

15 Can the mine provide evidence of the frequency and occurrence of calibration of the flow meters installed? For each yes or not applicable answer, a one was given, and for each no answer a zero was given. The score out of 3 was then scaled to a score out of 5 by dividing it with 3 and multiplying with Use of water balance data in water management decision making The following questions from the questionnaire were used to rate this aspect: Was the mine water balance prepared in accordance with the principles and procedures set out in BPG G2 Water and Salt Balances? Is the level of detail in the water balance appropriate as per BPG G2 Water and Salt Balances guidance? Is the water balance capable of accommodating changes made to the mine water reticulation system? Is the water balance capable of predicting effects of system changes on the mine water balance in order to be used as a management decision tool? For each yes or not applicable answer, a one was given, and for each no answer a zero was given. The score out of 4 was then scaled to a score out of 5 by dividing it with 4 and multiplying with Existing WC/WDM plan The following questions from the questionnaire were used to rate this aspect: Does the mine have a Water Conservation and Demand Management Plan with clearly defined goals and objectives? Was the WC/WDM Guideline used in developing the WC/WDM plan? Was BPG H3 Water Reuse and Reclamation used in the development of the WC/WDM plan? Have specific actions been identified to achieve WC/WDM objectives? Are there documented water quality standards available for all of the major water users on the mine and is there evidence that these standards have been derived from suitable research? For each yes or not applicable answer, a one was given, and for each no answer a zero was given. A sixth aspect that was also used to rate the existing WC/WDM plan of each mine was their current target setting methodologies. From the feedback received during the mine visits on this aspect, the current water use target setting methodologies employed by the mines could be divided into five broad categories. The five categories as well as the score that was given to each category are as follows: No targets (score = 1) Targets based on allocations contained in water use license (score = 2) Targets focussed on reducing potable water usage (score = 3) Percentage reduction of water usage based on past water usage (score = 4) Specific calculated targets customised for each mine (score = 5) The scores of the five questions as well as the score for the target setting methodology were then added to give a total score out of 10. This score was scaled to a score out of 5 by dividing it with 2. Report No. 11

16 Use of DWS BPGs The use of the following DWS Best Practice Guidelines (BPGs) was evaluated: BPG A2 Water Management for Mine Residue Deposits (TDF) BPG A3 Water Management in Hydrometallurgical Plants BPG A4 Pollution Control Dams (RWD) BPG A5 Water Management for Surface Mines (Opencast Mine) BPG A6 Water Management for Underground Mines BPG G2 Water and Salt Balances BPG G3 Water Monitoring Systems BPG H2 Pollution Prevention and Minimisation of Impacts BPG H3 Water Reuse and Reclamation For each yes or not applicable answer, a one was given, and for each no answer a zero was given. The responses on the use of the above nine BPGs, together with the response on the questions as to whether the mine has access to the DWS Best Practice Guidelines were then added to obtain a score out of 10.This score was scaled to a score out of 5 by dividing it with Step 4: Calculate national benchmarks The commodity-based national benchmarks are based on the average total water use efficiency of the top 3 mines of that commodity (based on the rating of WC/WDM described in the previous section for only the mines that have valid water balances). The average total water use efficiency of these top three mines would be expected to be lower than the water usage of all the mines with valid water balances. These values are shown in Table 3 compared to the averages of all the mines as well as the averages of the mines with valid water balances. As can be seen from the table, the averages of the top 3 mines are lower than the averages of the mines with valid water balances, except for the platinum mines. For each of the commodity groups, the top 3 mines will therefore be used to define the benchmarks. Due to the many factors that could influence the total water use efficiency of a mine for a particular commodity, a minimum and maximum value for each benchmark is also specified. This will give the benchmark range and it is based on the minimum and maximum value of the top 3 mines of each commodity. A similar exercise was undertaken for the other key performance indicators. Table 3: Benchmarks for total water use efficiency based on top 3 mines (per commodity) Commodity Average of all mines Total water use efficiency per ton mined (m 3 /t) Average of mines with valid water balances Average of top 3 mines of each commodity Benchmark total water input Average Min Max Coal Gold Platinum Other A detailed breakdown of the total water use efficiencies of all mines with valid water balances, as well as the top 3 selected mines, are shown in Figure 8 to Figure 11. Report No. 12

17 Total inflows/tonne mined (m3/t) Total inflows/tonne mined (m3/t) Total inflows/tonne mined (m3/t) TARGETS FOR WC/WDM IN THE MINING SECTOR Coal Valid Top 3 Averages Figure 8: Top 3 selected coal mines Gold Valid Top 3 Averages Figure 9: Top 3 selected gold mines 3 Platinum Valid Top 3 Averages 0 Figure 10: Top 3 selected platinum mines Report No. 13

18 Total inflows/tonne mined (m3/t) TARGETS FOR WC/WDM IN THE MINING SECTOR Other Valid Top 3 Averages Figure 11: Top 3 selected other mines The calculations described above for the key indicator: total water use efficiency were done for all the different key indicators listed in Section 2 above and the results for all the key indicators are presented in Table 4 to Table 7 below for each of the four commodity groupings. Table 4: Key Indicators for Coal mines Coal All mines Valid water balances Top 3 mines Total Mine Total Mine - Total water input per tonne mined Total Mine - Consumptive use per tonne mined Units Ave Min Max Ave Min Max Ave Min Max m 3 /t m 3 /t Total Mine - % wastewater not recycled % 77% 13% 100% 86% 68% 100% 95% 84% 100% Total Mine - Water recycling ratio (recycle/inflow) Mining Mining - Total water input per tonne mined Mining - Consumptive use per tonne mined Beneficiation Beneficiation - Total water input per tonne mined Beneficiation - Consumptive use per tonne mined Residue Disposal Residue Disposal - Total water input per tonne mined Residue Disposal - Consumptive use per tonne mined % 94% 0% 687% 19% 0% 47% 6% 0% 19% m 3 /t m 3 /t m 3 /t m 3 /t m 3 /t m 3 /t Report No. 14

19 Table 5: Key Indicators for Gold mines Gold All mines Valid water balances Top 3 mines Total Mine Total Mine - Total water input per tonne mined Total Mine - Consumptive use per tonne mined Total Mine - % waste water not recycled Total Mine - Water recycling ratio (recycle/inflow) Mining Mining - Total water input per tonne mined Mining - Consumptive use per tonne mined Beneficiation Beneficiation - Total water input per tonne mined Beneficiation - Consumptive use per tonne mined Residue Disposal Residue Disposal - Total water input per tonne mined Residue Disposal - Consumptive use per tonne mined Units Ave Min Max Ave Min Max Ave Min Max m 3 /t m 3 /t % 70% 26% 89% 70% 26% 89% 82% 75% 89% % 65% 10% 280% 68% 10% 280% 22% 10% 33% m 3 /t m 3 /t m 3 /t m 3 /t m 3 /t m 3 /t Table 6: Key Indicators for Platinum mines Platinum All mines Valid water balances Top 3 mines Total Mine Total Mine - Total water input per tonne mined Total Mine - Consumptive use per tonne mined Total Mine - % waste water not recycled Total Mine - Water recycling ratio (recycle/inflow) Mining Mining - Total water input per tonne mined Mining - Consumptive use per tonne mined Beneficiation Beneficiation - Total water input per tonne mined Beneficiation - Consumptive use per tonne mined Residue Disposal Residue Disposal - Total water input per tonne mined Residue Disposal - Consumptive use per tonne mined Units Ave Min Max Ave Min Max Ave Min Max m 3 /t m 3 /t % 59% 45% 78% 59% 45% 78% 63% 48% 78% % 75% 28% 114% 75% 28% 114% 63% 28% 107% m 3 /t m 3 /t m 3 /t m 3 /t m 3 /t m 3 /t Report No. 15

20 Table 7: Key Indicators for Other mines Other All mines Valid water balances Top 3 mines Total Mine Total Mine - Total water input per tonne mined Total Mine - Consumptive use per tonne mined Total Mine - % waste water not recycled Total Mine - Water recycling ratio (recycle/inflow) Mining Mining - Total water input per tonne mined Mining - Consumptive use per tonne mined Beneficiation Beneficiation - Total water input per tonne mined Beneficiation - Consumptive use per tonne mined Residue Disposal Residue Disposal - Total water input per tonne mined Residue Disposal - Consumptive use per tonne mined Units Ave Min Max Ave Min Max Ave Min Max m 3 /t m 3 /t % 42% 10% 81% 45% 26% 81% 52% 30% 81% % 163% 21% 375% 134% 21% 286% 83% 21% 136% m 3 /t m 3 /t m 3 /t m 3 /t m 3 /t m 3 /t An assessment was made of the three mines in each commodity group that were selected as the top 3 mines in order to determine the nature of mining and beneficiation at these top mines as well as to determine what type of water conservation actions and measures had been implemented at these mines and which could have resulted in them being selected as the top 3 mines. It must again be stressed that the selection of the top 3 mines was an objective exercise based on a standardised scoring system for a wide range of aspects that contribute to water management on a mine. Top 3 coal mines The top 3 coal mines represented three different mining Groups. One was an underground mine without a beneficiation plant while two were opencast mines with beneficiation plants. None of these mines had prepared a separate stand-alone WC/WDM plan. The types of WC/WDM actions found at the top three coal mines included the following: Focus on reduction of potable water intake Focus on increasing the reuse and recycle of waste water streams Water use efficiency targets were set externally and not on the mines themselves Two mines had access to desalination plants to treat waste water to enable it to be reused The DWS WC/WDM guideline and BPG H3 was not being used on any of the mines as the primary focus was on potable use reduction Top 3 gold mines The top 3 gold mines represented two different mining Groups. All three mines employ underground mining techniques and all three have beneficiation plants. Two mines had stand-alone WC/WDM plans while one Report No. 16

21 did not. All three mines had internal water use targets and regularly measure and report actual use versus targets. The types of WC/WDM actions found at the top three gold mines included the following: Focus on reduction of potable water intake Replace potable water with fissure (ground water) water in the process plant and fridge plants Eliminate leaking pipelines, use pressure reducing valves, install low flow showers Educate and train staff on WC/WDM principles Appoint water champions who have responsibility for implementing WC/WDM measures, measuring and reporting on the success of these measures Review and assess water management systems against the DWS BPGs Ensure that all discharges meet standards Design for zero overflows from pollution control dams Use a computerised water balance model with simulation capability to evaluate WC/WDM measures Adapt management systems to ensure to ensure that the WC/WDM strategy is implemented Review water use efficiency targets annually No desalination plants employed Plans to intercept, treat and reuse seepage from pollution control dams and tailings disposal facilities Detailed post-closure geohydrological, hydrological and geochemical predictive models are inplkace and being regularly calibrated Top 3 platinum mines The top 3 gold mines represented three different mining Groups. All three mines employ underground mining techniques and all three have beneficiation plants. Two mines had stand-alone WC/WDM plans while one did not. All three mines had internal water use targets and regularly measure and report actual use versus targets, primarily focused on potable water use reduction. The types of WC/WDM actions found at the top three platinum mines included the following: Focus on reduction of potable water intake Two mines use a computerised water balance model with simulation capability to evaluate WC/WDM measures Water use targets are either set using the WETT tool or on an arbitrary annual percentage reduction Aim for zero potable water use and zero water discharge Review water use efficiency targets annually One mine has access to a desalination plant while the other two only apply suspended solids removal as a water treatment technology Reduce pollution at source by intercepting, treating and reusing seepage Lining of all pollution control dams to minimise seepage losses Report No. 17

22 Eliminate or reduce environmental discharges by effective management of the overall mine water balance Top 3 other mines The top 3 other mines represented three different mining Groups. Two mines employed opencast mining methods while one was an underground mine. All three mines had beneficiation plants. Only one mine had a stand-alone WC/WDM plan but did not use the DWS WC/WDM guideline in developing this plan, The types of WC/WDM actions found at the top three other mines included the following: Primary focus was on eliminating environmental discharges No WC/WDM targets were documented WC/WDM targets were being continuously sought but tended to be more on an ad-hoc basis rather than as part of an integrated WC/WDM strategy or plan One mine was planning to implement tailings disposal facility seepage interception and reuse systems Step 5: Determine national benchmark ranges The average national benchmark values were derived using the process outlined in Sections to above and are shown in Table 3. It is recognised that the actual water use efficiency at each mine is dependent on many factors, including those that were previously identified and listed in the variables matrix (attached as Appendix B) and that the effect of these variables needs to be considered when defining the range (minimum to maximum) for the various water use efficiency benchmarks. As the sample of mines visited in this project does not represent the full extent of variation for all the variables in the variables matrix, a water balance simulation tool was developed that was capable of evaluating the effects of these variables on the key performance indicators. A detailed description of this water balance model is provided in Appendix C. The water balance model was configured to allow it to run in a probabilistic (Monte Carlo) mode, with random sampling of all the key variables, in order to simulate the range in the values for the key performance indicators that could be expected across the various commodities. The results from these simulations were then statistically evaluated in order to identify the expected standard deviations in the key performance indicators. As constructed, the generic water balance model was capable of evaluating, amongst others, the effect of the following variables described in the variables matrix: Climate (rainfall & evaporation) Commodity being mined Groundwater make to the water balance Extent of mine cooling required Type of mining (opencast or underground) Opencast pit size Opencast pit rehabilitation rate and efficiency Depth of mining Presence of beneficiation plant Percentage ore to waste rock Report No. 18

23 Tailings density Tailings dam rise rate Tailings dam pool size Product moisture content Water use for dust suppression Consumptive water use per worker Sewage water recycle rate It can therefore be confidently stated that the effects of the variables contained in the variables matrix were properly evaluated and considered. The output from the exercise to consider the effect of the variables matrix parameters was to determine the standard deviation around the key performance indicators for the average mine condition that could be expected due to the effect of these variables. Table 8: Standard deviation of key performance indicators per commodity Standard Deviation Unit Coal Gold Platinum Other Total Mine Total Mine - Total water input per tonne mined m 3 /t Total Mine - Consumptive use per tonne mined m 3 /t Total Mine - % waste water not recycled % 12% 13% 13% 13% Total Mine - Water recycling ratio (recycle/inflow) % 47% 46% 59% 55% Mining Mining - Total water input per tonne mined m 3 /t Mining - Consumptive use per tonne mined m 3 /t Beneficiation Beneficiation - Total water input per tonne mined m 3 /t Beneficiation - Consumptive use per tonne mined m 3 /t Residue Disposal Residue Disposal - Total water input per tonne mined m 3 /t Residue Disposal - Consumptive use per tonne mined m 3 /t Other Activities Other Activities - Total water input per tonne mined m 3 /t Other Activities - Consumptive use per tonne mined m 3 /t The effect of one and two standard deviations above and below the averages for the top 3 mines were then evaluated in order to define the range for the benchmarks for the different key performance indicators. These national benchmarks are shown in the Table 9 to Table 12 below. The benchmark for each key indicator reported in the tables below (per commodity) is based on the averages of the top 3 selected mines for each commodity (reported in previous section). The minimum and maximum values that constitute the range of the benchmarks are based on the standard deviation of each key indicator to allow for the effects of the variables described in the variables matrix. Report No. 19

24 Table 9: National Key Indicator Benchmarks and Ranges for Coal Mining Min Min Coal Mining Units Benchmark (1x ) (2x ) Total Mine Max (1x ) Max (2x ) Total Mine - Total water input per tonne mined m 3 /t Total Mine - Consumptive use per tonne mined m 3 /t Total Mine - % waste water not recycled % 95% 82% 70% 107% 119% Total Mine - Water recycling ratio (recycle/inflow) % 6% 0% 0% 53% 100% Mining Mining - Total water input per tonne mined m 3 /t Mining - Consumptive use per tonne mined m 3 /t Beneficiation Beneficiation - Total water input per tonne mined m 3 /t Beneficiation - Consumptive use per tonne mined m 3 /t Residue Disposal Residue Disposal - Total water input per tonne mined m 3 /t Residue Disposal - Consumptive use per tonne mined m 3 /t Table 10: National Key Indicator Benchmarks and Ranges for Gold Mining Min Min Gold Mining Units Benchmark (1x ) (2x ) Total Mine Max (1x ) Max (2x ) Total Mine - Total water input per tonne mined m 3 /t Total Mine - Consumptive use per tonne mined m 3 /t Total Mine - % waste water not recycled % 82% 69% 56% 94% 107% Total Mine - Water recycling ratio (recycle/inflow) % 22% 0% 0% 69% 115% Mining Mining - Total water input per tonne mined m 3 /t Mining - Consumptive use per tonne mined m 3 /t Beneficiation Beneficiation - Total water input per tonne mined m 3 /t Beneficiation - Consumptive use per tonne mined m 3 /t Residue Disposal Residue Disposal - Total water input per tonne mined m 3 /t Residue Disposal - Consumptive use per tonne mined m 3 /t Report No. 20

25 Table 11: National Key Indicator Benchmarks and Ranges for Platinum Mining Min Min Platinum Mining Units Benchmark (1x ) (2x ) Total Mine Max (1x ) Max (2x ) Total Mine - Total water input per tonne mined m 3 /t Total Mine - Consumptive use per tonne mined m 3 /t Total Mine - % waste water not recycled % 64% 51% 38% 76% 89% Total Mine - Water recycling ratio (recycle/inflow) % 63% 4% 0% 122% 181% Mining Mining - Total water input per tonne mined m 3 /t Mining - Consumptive use per tonne mined m 3 /t Beneficiation Beneficiation - Total water input per tonne mined m 3 /t Beneficiation - Consumptive use per tonne mined m 3 /t Residue Disposal Residue Disposal - Total water input per tonne mined m 3 /t Residue Disposal - Consumptive use per tonne mined m 3 /t Table 12: National Key Indicator Benchmarks and Ranges for Other Mining Min Min Other Mining Units Benchmark (1x ) (2x ) Total Mine Max (1x ) Max (2x ) Total Mine - Total water input per tonne mined m 3 /t Total Mine - Consumptive use per tonne mined m 3 /t Total Mine - % waste water not recycled % 59% 39% 25% 65% 78% Total Mine - Water recycling ratio (recycle/inflow) % 83% 28% 0% 137% 192% Mining Mining - Total water input per tonne mined m 3 /t Mining - Consumptive use per tonne mined m 3 /t Beneficiation Beneficiation - Total water input per tonne mined m 3 /t Beneficiation - Consumptive use per tonne mined m 3 /t Residue Disposal Residue Disposal - Total water input per tonne mined m 3 /t Residue Disposal - Consumptive use per tonne mined m 3 /t The national total and consumptive water use efficiency benchmarks are also shown graphically in Figure 12 below. Report No. 21

26 TOTAL WATER USE EFFICIENCY BENCHMARKS MAX 3.06 CONSUMPTIVE WATER USE EFFICIENCY BENCHMARKS MAX 3.01 AVE 2.09 MAX 2.29 AVE 1.85 AVE 2.02 MAX 2.27 AVE 1.82 MAX 1.08 MIN 1.11 MIN 1.42 MAX 1.36 AVE 0.96 MIN 1.03 MIN 1.38 MAX 1.06 AVE 0.70 MIN 0.31 MIN 0.56 MAX 0.72 AVE 0.38 AVE 0.65 MIN 0.25 COAL GOLD PLATINUM OTHER MIN 0.03 COAL GOLD PLATINUM OTHER Figure 12: National Water Use Efficiency Benchmarks 4.0 METHODOLOGY FOR MINES TO SET WATER USE EFFICIENCY TARGETS The procedure that mines should follow in setting their own internal water use efficiency targets is fully described in the DWS Water Conservation and Water Demand Management Guidelines for the Mining Sector in South Africa. This guideline describes a methodology that mines should follow to set targets and this guideline also extensively draws on the relevant DWS Best Practice Guidelines. The broad procedure set out in the WC/WDM guideline is based on a three-step process as set out in Figure 13 below. ASSESSMENT OF CURRENT WC/WDM STATUS PLANNING FOR WC/WDM MEASURES & OPPORTUNITIES IMPLEMENT & MANAGE WC/WDM MEASURES & MINE WATER SYSTEM Figure 13: Overall WC/WDM planning & implementation process Report No. 22

27 There is no short-cut process that can be followed by mines to develop their own targets and it is considered essential that the step-wise procedure set out in the WC/WDM guideline (especially with regard to the first two phases) be followed. The critical and key requirement that must be in place before a mine can embark on the process is the establishment of a detailed computerised water balance system. As has been demonstrated in this project with the generic water balance model, such a model, if correctly constructed, can be used as a management decision aid tool to assist in the development of a WC/WDM plan. The mine water balance simulation model can be used to determine the probable effect of a range of proposed WC/WDM measures on the key water use efficiency indicators and the results from such simulations, together with data on the estimated costs of each WC/WDM measure, can be used by the mine to prioritise the range of WC/WDM measures and to develop realistic internal water use efficiency targets. Setting of site-specific water use efficiency targets by the mines will be a bottom-up approach, and these targets will need to be aligned with the national benchmarks set in accordance with the methodology defined in Section 4 above and in accordance with the process shown in Figure 14 below. It will be expected of mines to demonstrate that their site-specific water use efficiency targets are aligned with the national benchmarks and this compliance will be evaluated by DWS when reviewing and assessing the annual WC/WDM plans submitted by the mines. It is important for the mines to submit annual WC/WDM plans annually to DWS. This will enable the DWS and the mine to check on the progress/success of their measures and for them to intervene should they be falling behind with the implementation of the plan. Where the site specific water use efficiency targets proposed by the mines deviate negatively from the national benchmarks, such deviation will need to be accompanied by a sound technical motivation. Apply Phases 1 & 2 of WC/WDM Guideline Develop internal water use efficiency targets YES Can additional WC/WDM measures be identified to bring internal targets within the national benchmark range? NO Are the internal targets within the national Benchmark range? NO Prepare motivation to DWA as to why national benchmarks cannot be met and what the proposed plan of action is. YES Implement Phase 3 of WC/WDM Guideline Figure 14: Internal target setting review process This process described above will also be expanded upon in the separate report that will be prepared in accordance with Task 9 of the project and shown in Figure 1 of this report. The more detailed methodology on how the mines should develop their own WC/WDM plans with their own water use efficiency targets is described fully in the WC/WDM guideline and is reproduced in Figure 15 below. Significant additional detail on the methodology to develop mine WC/WDM plans is given in the Implementation Guideline (Task 9) report. Report No. 23

28 Figure 15: Methodology for the development of a WC/WDM Plan There is not much that can be added to what is already stated in the existing guidance documents, the most important of which (for the purpose of developing a WC/WDM Plan) are: WC/WDM Guideline for the Mining Sector in South Africa Best Practice Guideline G2: Water and Salt Balances. Best Practice Guideline G3: Water Monitoring Systems. Best Practice Guideline H3: Water Reuse and Reclamation. Best Practice Guideline H2: Pollution Prevention and Minimisation of Impacts. Best Practice Guideline H4: WaterTreatment. Report No. 24

29 The critical additional element that is required in order to facilitate the Assessment and Planning Phases shown in Figure 15 above, is to ensure that the water balance that is developed is as detailed as possible, that it is computerised using appropriate software (e.g. Goldsim) and that it is configured to run in a simulation mode. Being able to run in a simulation mode simply requires the software to be able to predict the effect of various water conservation measures on the overall mine water balance. Such a computerised model would therefore be broadly similar to the generic water balance model described in Appendix C that was used to evaluate the effects of the parameters in the variables matrix with the following exceptions: The model would be set up to represent the actual mining, water management and water balance situation at the mine in question and would not need to be able to simulate all the variables contained in the variables matrix. The model must, as a minimum, allow the evaluation of the following parameters on the overall water balance: different hydrological cycles (wet and dry seasons) recycling of water from one point in the water balance to any other point changes in the water content of tailings sent to the tailings disposal facility interventions aimed at reducing evaporation and seepage losses from all facilities where these occur It is also recommended that the computerised water balance model be configured such that it prominently displays the calculated results for all the key performance indicators listed in Section 2 of this report, in order that the effect thereon of any evaluated WC/WDM management measures can easily be seen. A detailed methodology for developing the WC/WDM plan is presented in the Implementation Guideline (Task 9 report) that is issued as a separate report. 5.0 SPECIFICATION OF GENERIC WC/WDM MEASURES 5.1 Generic Measures Derived from Recent Literature The processes outlined in the WC/WDM Guideline and the DWS Best Practice Guidelines, will assist mines in identifying and evaluating a variety of site-specific appropriate water conservation measures which take account of the realities on that specific site. The literature review also presented a number of approaches followed by different mines when implementing site-specific water conservation plans. Subsequent to completion of the literature review, a very relevant paper on WC/WDM in the mining industry was accessed and key findings from this paper are summarised and presented below. The paper in question is titled Reducing mine water requirements, authored by Gunson, A.J., Klein, B., Veiga, M. And Dunbar, S. And was published in the Journal of Cleaner Production (Vol 21, 2012, pp71-82). Some critical statements made in this paper that are aligned with the approach and philosophy of this project, are the following: The high rate of water recycling within the mining industry means that water consumption depends not on the amount of water required for individual unit operations, but the amount of water lost to permanent water sinks, such as evaporation, seepage or retention in the concentrate or tailings material. The first step toward improving or designing mine water systems is to develop a good understanding of the mine s existing system. No effort should be undertaken to improve a mine water system until a reasonably accurate site water balance has been completed. Report No. 25

30 Any water management plan should ensure that existing facilities are well run and maintained. Basic steps such as fixing leaky pipes and valves, replacing undersized or worn-out pumps, and improving thickener or clarifier operation can lead to inexpensive and impressive improvements. Better water system design revolves around two key concepts: first, running all processes at the highest solids density possible without negatively impacting the process and, second, supplying all processes with the poorest acceptable quality water, that does not impact process performance. This paper also divides WC/WDM strategies or measures into three categories: strategies aimed at reducing mine water use, strategies aimed at reusing water (water reused without treatment) and strategies aimed at recycling water (treatment before reuse) Measures to reduce mine water use Measures to reduce mine water use include the following: Reducing wet area/open area in the TSF Reducing clay generation during grinding to lower tailings water retention Improving tailings thickener performance Reducing water losses through thickened tailings or paste tailings disposal Reducing water losses through the installation of drains in the TSF Reducing water losses through tailings compaction Reducing water losses through selective tailings size classification Reducing water losses by using tailings filtration Reducing the concentrate moisture content Reducing evaporation through covers (tanks/thickeners/tailings pond) Reducing evaporation through alternative dust suppressants Ensuring no unplanned pipeline water losses Eliminating evaporative cooling Reducing pump gland service water usage Reducing site employee/contractor water use Reducing water consumption through ore pre-concentration Reducing water use through dry processing Measures to reuse mine water Measures to reuse mine water include the following: Collecting and reusing surface runoff water Reusing mine dewatering water Reusing offsite waste water Reusing cooling water Report No. 26

31 Reusing grey water Measures to recycle mine water Measures to recycle mine water include the following: Recycling TSF surface water Recycling TSF seepage water Recycling tailings thickener overflow Recycling concentrate or intermediate thickener overflow Recycling potential mine effluent water Water reduction model The paper presents the outcome of a water balance simulation model (similar to what is advocated in this project) that was used to simulate a hypothetical low grade copper mine in an arid region, treating tons per day of ore, producing a copper concentrate and operating a conventional tailings disposal facility. The model was used to simulate six different scenarios as follows: Scenario 1 Base case: In the base case, no effort is undertaken to reduce water evaporation or otherwise lower water consumption beyond reclaiming water from the TSF and the concentrate dewatering processes. Scenario 2 Traditional Case with Water Conservation: In Scenario 2, the mine has the same processes and equipment as the traditional case, but has eliminated as many sources of water loss as possible, with a focus on evaporation. Scenario 3 Paste Tailings Case: In Scenario 3, the mine has installed a 75 m diameter tailings thickener to produce paste, but left everything else as per Scenario 1. All of the flotation tailings flow to the new thickener - the overflow water is pumped to the process water tank and the paste tailings, at 65% solids by mass, is pumped to the TSF. Scenario 4 Filtered Tailings Case: In Scenario 4, the mine has installed a 75 m diameter tailings thickener to feed a bank of tailings filters, but with no further change to Scenario 1. All of the flotation tailings flow to the new thickener with the overflow water pumped to the process water tank. The thickened tailings are then filtered to 80% solids by mass, and deposited by a stacker conveyor in the TSF. The filtrate can be reused or recycled. Scenario 5 Ore Pre-Sorting Case: In Scenario 5, the mine has installed an ore pre-sorting system after the primary crusher with the purpose of rejecting any ore below a certain grade. This model conservatively assumes that 20% of the ore can be rejected while retaining 98% of the copper. While the mine could increase production to keep the mill running at 50,000 tpd, for the purposes of comparison, the mine production in the model will remain unchanged, dropping the post-sorter mill feed rate to 40,000 tpd. This would allow much of the mill equipment to be reduced in size. However, for simplicity, the surface area of the flotation cells and the fresh and process water tanks will be unchanged. Pre-sorting may also require an additional crushing step not addressed here. Scenario 6 Combined Water Reduction Case: In this final scenario, the water savings options which most reduced water withdrawals in the previous scenarios are combined. The scenario includes the water conservation methods included in scenario 2, the filtered tailings system described in scenario 4, and the ore pre-sorting system described in scenario 5. To summarize the process, the ore is pre-sorted, rejecting 20% of the ore while retaining 98% of the copper, and the flotation tailings are filtered to a solids content of 80% by mass. In addition, an organic binder is applied to the site roads, all site grey water is directed to the process water tank, a fog dust suppression system is installed on the primary crusher dump pocket and the coarse ore stockpile is covered. The concentrate thickener, the water tanks and the flotation cells are Report No. 27

32 covered. Finally, tiles are placed on the tailings thickener to reduce evaporation by 95% and the final concentrate is filtered to 93% solids by mass. The water use efficiencies of the different scenarios were determined with the water balance model and the results are presented in Table 13 below. Table 13: Scenario Summary Water Withdrawal Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5 Scenario 6 m 3 /day m 3 /ton ore m 3 /ton copper % reduction This paper clearly demonstrates that the most significant improvements in water use efficiency are obtained when mines start developing and implementing WC/WDM measures that are directed towards reducing water losses to final sinks and that the best results are obtained when a combined and integrated approach is taken. 5.2 Generic Measures Derived from Practical Experience Years of experience in conducting water management exercises at a variety of mines allows the identification of a range of generic measures that mines can consider when developing their site-specific WC/WDM plans. Not all the listed measures will be applicable at every mine and the benefit in terms of reduced water usage for each measure will vary from mine to mine. Management measures that will have a very significant benefit at one mine may only have very limited benefits at other mines or, in some cases, may not even be applicable. The benefit of the generic measures listed below is to provide the mines with ideas and options that they can consider when developing their site-specific WC/WDM plans. In particular, the potential benefits of each measure should be evaluated using the computerised water balance simulation tool before decisions are made as to whether or not the particular measure can be fruitfully applied at any mine. For the purpose of this report, the identified generic measures have been divided into the following categories: WC/WDM measures for mining operations WC/WDM measures for ore / mineral processing operations WC/WDM measures for waste, residue disposal and tailings storage operations General WC/WDM measures The generic measures are listed in the following sections WC/WDM measures for mining operations The following generic measures have been identified: Pre-dewatering of areas to be mined with beneficial use of the water derived from the dewatering. Mining done to prevent intersection/interconnection to water-bearing strata /aquifers. Where intersection of water-bearing strata/aquifers cannot be avoided, ensure that intersected water is protected from quality deterioration and pumped out of the mine workings for beneficial reuse. Mining done to avoid surface water bodies such as streams, wetlands and dams. Report No. 28

33 Old workings sealed off to prevent ingress into active workings. Surface waters (streams) diverted around mining impacted areas to limit ingress. Ventilation optimised to limit the need for cooling / refrigeration. Recycle and re-use water employed for underground drilling equipment and mining machines. Backfill underground workings to reduce water ingress and cooling requirements. Separate & divert surface water which may enter the opencast pit workings (clean and dirty water separation). Close & rehabilitate opencast & pit workings and rehabilitate to limit recharge/ingress to the workings. Rehabilitate and shape to free drain the rehabilitated land to reduce runoff to opencast workings & pits. Backfill and rehabilitate final voids and pit lakes to evaporation losses. Upgrade standard & quality of mined land rehabilitation to reduce water ingress/ infiltration. Accelerate the disturbed land rehabilitation and reduce the backlog of rehabilitation behind the active mining face/operation. Recycle and re-use mine dewatering for other applications (ore processing, minerals beneficiation, etc.). Employ dry cooling systems on underground mine working/refrigeration circuits, rather than evaporative cooling. Minimise contact time between water and ore in the mining operations in order to reduce water quality deterioration, thereby making the water easier to reuse WC/WDM measures for ore / mineral processing operations The following generic measures have been identified: Employ dry ROM/ore conveyance (such as conveyer belts) methods rather than hydraulic conveyance systems. Minimize footprint of ROM and ore stockpiling to reduce impacted water production. Employ high solids content/consistency processes for ore/mineral beneficiation. Recover water from the ore and minerals products and recycle to the minerals processing plant. Recover water from the waste and tailings and recycle to the ore/minerals processing plant. Employ dry cooling technologies rather than evaporative cooling systems. Ore/minerals processing plant footprint minimized to reduce impacted water generation. Plant spills/overflows captured as close as possible to the point of origin of the spillage and recycled to the ore/minerals plant water circuits. Clear separation of process spillage systems from storm water systems to allow collection of process spillages close to the point of origin for direct reuse and collection of storm water for general reuse within the plant area. Report No. 29

34 Product stockpile footprint areas minimized to reduce impacted water production. Water storage in underground compartments to reduce evaporative losses. Water supply and storage managed by aquifer recharge and abstraction to reduce evaporative losses. Process water intake based on hierarchy to preferentially use mine impacted water and reduce intake of fresh water. Development and adherence to water quality standards for all water users in the beneficiation plant that aims to provide all users with the worst possible quality water that does not affect process performance or cause corrosion/scaling problems WC/WDM measures for waste, residue disposal and tailings storage operations The following generic measures have been identified: Dispose of waste in underground workings (backfill) to reduce the surface footprint of waste/residue disposal facilities. Dispose of waste in old opencast & pit workings to reduce the surface footprint of waste/residue disposal facilities. Thicken and/or dewater residues and tailings to limit the amount of water disposed with the residues and tailings. Reduce the amount of water stored on the residue/tailings disposal facilities to reduce evaporative losses. Reduce the surface area of the free water pool on tailings storage facilities to recue evaporative losses. Collect and intercept seepage from residues and tailings disposal facilities for reuse and recycling. Manage water balance on return water dams to ensure that no water enters the return water dams that was not included in the original sizing and design of these dams (i.e. this will generally mean that storm water runoff and water from mining operations should not be stored in tailings return water dams) General WC/WDM measures The following generic measures have been identified: Implement dry dust control measures (such as binding agents on haul roads) to reduce water use. Supply excess water that cannot be accommodated within the mine s water balance (with or without treatment) to external, off-mine water users. Discharge excess water that cannot be accommodated within the mine s water balance, in compliance with regulatory discharge standards, to streams & rivers for downstream water users. Water use by staff & personnel using a range of water savings devices and methods: Low volume closets Waterless urinals, etc. Development of non-conventional water resources to reduce the use of conventional surface and groundwater resources: Report No. 30

35 Rain harvesting Reclaimed AMD Covers on dams & ponds. Incorporate water conservation and demand management training into standard induction programmes for all employees and contractors Incorporate meeting of WC/WDM targets into the KPIs of key staff on the mines that have responsibility for ensuring that WC/WDM is optimally developed and implemented on mines 5.3 Generic Measures Evaluated with Water Balance Model The water balance model that was developed to evaluate the effects of the parameters listed in the variables matrix, and which is presented in Appendix C, is also capable of evaluating the effect of various water conservation measures on the key indicators at a typical mine. The specific water conservation measures that the model was capable of evaluating include the following: lag time in rehabilitating an opencast mining operation percentage rainfall recharge of rehabilitated opencast pit areas specific gravity of tailings as deposited percentage solids of the residue on the tailings size of the return water pool on the top of the tailings disposal facility amount of water used for dust suppression percentage of treated sewage water reused as process water change in water use by workers with access to shower facilities The outcome of these simulations are shown in Figure 16 to Figure 23 below and give a good indication of which types of water conservation measures will have the biggest impact in improving water use efficiency. Figure 16: Effect of rehabilitation lag time on total water use efficiency Report No. 31

36 Figure 17: Effect of rehabilitated opencast pit rainfall recharge on total water use efficiency Figure 18: Effect of tailings specific gravity on total water use efficiency Figure 19: Effect of tailings residue solids percentage on total water use efficiency Report No. 32

37 Figure 20: Effect of return water pool size on top of tailings disposal facility on total water use efficiency Figure 21: Effect of dust suppression water use on total water use efficiency Figure 22: Effect of percentage of sewage water reused on total water use efficiency Report No. 33

38 Figure 23: Effect of water usage per worker with shower access on total water use efficiency The extent to which the different water conservation measures modelled and presented above can be effectively implemented will vary from mine to mine and the actual water use efficiency improvements that can be achieved will also vary from mine to mine. However, the above simulations do give an indication of the type of water conservation measures that could most productively be considered by mines. It is also important to emphasize that the availability to the mine of a detailed computerised water balance that accurately reflects its real water balance, is one of the most powerful tools available to the mine to evaluate the potential benefits of various water conservation alternatives. 5.4 Concluding Remarks Regarding Generic Measures Both the paper summarised in this section and the results from the generic water balance model shown in the above Figures, clearly illustrate that the most significant improvements in water use efficiency are obtained when the mine addresses losses at the key final water sinks such as pollution control dams and the tailings disposal facilities. Losses to evaporation and seepage need to be minimised in order to improve water use efficiency. Losses to evaporation can be reduced by reducing the volumes of water reporting to facilities where evaporation takes place (e.g. tailings disposal facilities), reducing the surface area of water pools or covering open water pools. Seepage can be prevented by lining of facilities or alternatively seepage from existing facilities such as tailings disposal facilities which cannot now be lined, can be intercepted and recycled after appropriate treatment. All discharge streams should be evaluated with the view towards recycling these streams, with or without treatment, back into the mine s water balance in order to replace cleaner input streams. The results from the generic water balance model and those reported in literature, indicate that addressing these water losses from the system can result in very significant improvements in water use efficiency. The South African mining industry which is currently primarily focused on reducing potable water use and replacing this with alternative sources, needs to consider the abovementioned interventions at the final water sinks if it is to make significant strides in improving its water use efficiency. 6.0 CONCLUSIONS This report provides a set of national water use efficiency benchmarks that are based on a very detailed analysis of the latest and most up-to-date available data on actual current water use efficiencies within the South African mining industry. This data was collected as part of an extensive site engagement process at 39 different mining operations that have been shown, through evaluation of production and water use data, to be truly representative of the national mining industry. Report No. 34

39 This data was then evaluated in order to develop as detailed a set of mine water balances as was possible, given the limitations of the water balances reported by the mines. The data was further refined through a rigorous and objective methodology, in the manner described in this report, in order to identify national water use efficiency benchmarks that represent achievable targets based on current practices within mines which are already reasonably advanced with their WC/WDM plans. A detailed generic water balance model was developed that was able to evaluate the effects of a number of critical variables (as listed in the variables matrix together with many more) on achievable water use efficiencies, both for individual variables, and probabilistically for the complete set of variables. This exercise resulted in the definition of an upper and lower range for the different key indicators that could then be applied to the national benchmarks (which are based on average values) to give a range that should be achievable by the majority of mines in South Africa. The water balance model was also used to evaluate a number of generic water conservation measures in terms of the anticipated impact that they would have on water use efficiency benchmarks. This information can provide valuable inputs to mines when developing their own internal targets. It was confirmed that the procedures set out in the 2011 DWS WC/WDM Guideline are valid and correct and should be used in the internal mine water use efficiency target setting process. It was also emphasized that the most critical component of a mine's WC/WDM plan is a detailed computerised water balance model that can be used to simulate proposed WC/WDM measures. A procedure is also proposed to evaluate mine's internal targets against the national benchmarks. It has also been demonstrated that the most significant improvements in water use efficiency will be attained by addressing water losses to final sinks primarily in the form of point discharges, diffuse seepage and evaporation losses. While basic housekeeping measures top reduce unnecessary water losses forms an integral component of a mine WC/WDM plan, the really significant improvements in water use efficiency will arise when the losses to the final sinks are addressed. In order to make the recycling of discharges and seepages more economical (i.e. minimum water treatment requirement), pollution prevention strategies will need to be considered throughout the mine process in order to protect water quality from deterioration, thereby saving on water treatment requirements when recycling is undertaken. Finally, based on the literature review previously submitted and subsequent reviews of key literature published after the literature review, it would appear that the setting of national water use efficiency benchmarks as has been done in this report is novel and has not been undertaken in other countries. The standard procedure is for mines to develop site-specific internal targets. GOLDER ASSOCIATES AFRICA (PTY) LTD. A Toerien Senior Process Engineer W Pulles Mine Water Specialist BM/WP/bm Reg. No. 2002/007104/07 Directors: SAP Brown, L Greyling, RGM Heath Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation. issued to psc.docx Report No. 35

40 Report No. 36 TARGETS FOR WC/WDM IN THE MINING SECTOR

41 APPENDIX A Key Indicator Values For All Mines Report No. 37

42 Mine Commodity Total water input Consumptive use Recycle flow Total water input per tonne mined Consumptive use per tonne mined Consumptive use as a % of Consumptive use + recycle Water recycling ratio (recycle/ inflow) TARGETS FOR WC/WDM IN THE MINING SECTOR Table A1: Key indicators (Total Mine) m 3 /d m 3 /d m 3 /d m 3 /t m 3 /t % % Mine 03 Coal % 0% Mine 04 Coal % 0% Mine 05 Coal % 0% Mine 06 Coal % 29% Mine 07 Coal % 19% Mine 08 Coal % 42% Mine 09 Coal % 687% Mine 10 Coal % 0% Mine 11 Coal % 0% Mine 12 Coal % 209% Mine 13 Coal % 47% Mine 16 Gold % 33% Mine 17 Gold % 25% Mine 18 Gold % 41% Mine 19 Gold % 10% Mine 20 Gold % 280% Mine 21 Gold % 15% Mine 22 Gold % 23% Mine 23 Gold % 94% Mine 01 Other % 165% Mine 02 Other % 184% Mine 14 Other % 133% Mine 15 Other % 87% Mine 24 Other % 312% Mine 25 Other % 21% Mine 26 Other % 136% Mine 27 Other % 133% Mine 28 Other % 286% Mine 29 Other % 91% Mine 30 Other % 375% Mine 31 Other % 30% Mine 32 Platinum % 107% Mine 33 Platinum % 53% Mine 34 Platinum % 71% Mine 35 Platinum % 52% Mine 36 Platinum % 70% Mine 37 Platinum % 28% Mine 38 Platinum % 102% Mine 39 Platinum % 114% Report No. 38

43 Mine Commodity Total water input Consumptive use Total water input per tonne mined Consumptive use per tonne mined TARGETS FOR WC/WDM IN THE MINING SECTOR Table A2: Key indicators (Mining) m 3 /d m 3 /d m 3 /t m 3 /t Mine 03 Coal Mine 04 Coal Mine 05 Coal Mine 06 Coal Mine 07 Coal Mine 08 Coal Mine 09 Coal Mine 10 Coal Mine 11 Coal Mine 12 Coal Mine 13 Coal Mine 16 Gold Mine 17 Gold Mine 18 Gold Mine 19 Gold Mine 20 Gold Mine 21 Gold Mine 22 Gold Mine 23 Gold Mine 01 Other Mine 02 Other Mine 14 Other Mine 15 Other Mine 24 Other Mine 25 Other Mine 26 Other Mine 27 Other Mine 28 Other Mine 29 Other Mine 30 Other Mine 31 Other Mine 32 Platinum Mine 33 Platinum Mine 34 Platinum Mine 35 Platinum Mine 36 Platinum Mine 37 Platinum Mine 38 Platinum Mine 39 Platinum Report No. 39

44 Mine Commodity Total water input Consumptive use Total water input per tonne mined Consumptive use per tonne mined TARGETS FOR WC/WDM IN THE MINING SECTOR Table A3: Key indicators (Beneficiation) m 3 /d m 3 /d m 3 /t m 3 /t Mine 03 Coal Mine 04 Coal Mine 05 Coal Mine 06 Coal Mine 07 Coal Mine 08 Coal Mine 09 Coal Mine 10 Coal Mine 11 Coal Mine 12 Coal Mine 13 Coal Mine 16 Gold Mine 17 Gold Mine 18 Gold Mine 19 Gold Mine 20 Gold Mine 21 Gold Mine 22 Gold Mine 23 Gold Mine 01 Other Mine 02 Other Mine 14 Other Mine 15 Other Mine 24 Other Mine 25 Other Mine 26 Other Mine 27 Other Mine 28 Other Mine 29 Other Mine 30 Other Mine 31 Other Mine 32 Platinum Mine 33 Platinum Mine 34 Platinum Mine 35 Platinum Mine 36 Platinum Mine 37 Platinum Mine 38 Platinum Mine 39 Platinum Report No. 40

45 Mine Commodity Total water input Consumptive use Total water input per tonne mined Consumptive use per tonne mined TARGETS FOR WC/WDM IN THE MINING SECTOR Table A4: Key indicators (Residue disposal) m 3 /d m 3 /d m 3 /t m 3 /t Mine 03 Coal Mine 04 Coal Mine 05 Coal Mine 06 Coal Mine 07 Coal Mine 08 Coal Mine 09 Coal Mine 10 Coal Mine 11 Coal Mine 12 Coal Mine 13 Coal Mine 16 Gold Mine 17 Gold Mine 18 Gold Mine 19 Gold Mine 20 Gold Mine 21 Gold Mine 22 Gold Mine 23 Gold Mine 01 Other Mine 02 Other Mine 14 Other Mine 15 Other Mine 24 Other Mine 25 Other Mine 26 Other Mine 27 Other Mine 28 Other Mine 29 Other Mine 30 Other Mine 31 Other Mine 32 Platinum Mine 33 Platinum Mine 34 Platinum Mine 35 Platinum Mine 36 Platinum Mine 37 Platinum Mine 38 Platinum Mine 39 Platinum Report No. 41

46 APPENDIX B Variables Matrix Report No. 42

47 The extent to which water conservation (WC) and water demand management (WDM) measures can be successfully implemented at a mine, is dependent on a number of external and internal variables (differentiating factors). Some of these variables are inherent features of the mine and cannot be changed, while others can be changed through the application of management and operational actions. In the process of developing water use targets and practical approaches to implement WC/WDM to meet these targets, knowledge of these variables is critical. The existence of these variables is also the reason why the setting of targets for WC/WDM in the mining sector cannot be undertaken on the basis of a "one size fits all" approach - different targets must be developed for different mining operations in the sector. In order to develop defensible, practical and achievable water use efficiency benchmarks, it is important to be able to identify the variables that have an effect thereon and to differentiate mines on the basis of these variables. To this end, it is proposed to classify the variables that have a potential effect on water use efficiency benchmarks into the following four classes: CLASS 1: Variables that characterise the mine s operations and are difficult to change (especially for existing mines, might be easier to address on new mine) and that have a limiting effect on the extent to which water use efficiency that can be achieved on a mine. These variables should be explicitly considered when setting differentiated water use efficiency targets and benchmarks. CLASS 2: Variables or practices that influence the mine s current water conservation status but that can be changed with considerable planning, effort and/or capital expenditure. There is significant justification in considering these variables as valid inputs to the process of setting water use efficiency targets, especially with regard to timeframes that are allowed for the mines to converge towards compliance with the benchmarks. CLASS 3: Variables or practices that influence the mine s current water conservation status but that can be changed without much effort and/or capital expenditure. These variables influence the WC/WDM status of the mining but should not be considered as variables that have much influence on the water use efficiency targets to be set. CLASS 4: Variables that are often the driving forces for development and implementation of WC/WDM at mines, but which do not influence the differential setting of water use efficiency benchmarks. Presentation of Variables The following list of variables shown in Tables A1 - A4 (classified in terms of Classes 1 to 4) was identified as having a bearing on the implementation of WC/WDM in the mining sector or having an influence on what the water use efficiency target for a mine should be. Data on these variables therefore needed to be captured during the site visits. These variables are also shown in Figure B1, together with the inter-relationship between variables in Class 1 and Class 2. This list might still be expanded upon as the project progresses. Report No. 43

48 CLASS 1 Critical and affects achievable WC/WDM targets CLASS 2 Have major impact on cost & timeframe required to meet WC/WDM targets CLASS 3 Relate to essential tools required to implement measures to meet WC/WDM targets CLASS 4 Driving forces for implementing WC/WDM but do not influence differentiated targets 1. Climate (rain/evap) 2. Groundwater regime 3. Commodity being mined 4. Depth of mining 5. Presence of sulphides 6. Age of mine 7. Presence of metallurgical plant 8. Regional interactions 1. Quality of fresh water 2. Groundwater make 3. Type of tailings disposal facility 4. Mining method employed 5. Technology in use at mine 6. Remaining life of mine 7. Geographical size of mining operations 8. Type of beneficiation 1. Computerised water and salt balance 2. Internal WQ standards for users 3. Reporting practices 1. Availability of fresh water 2. Catchment sensitivity 3. Financial status of mine Figure B1: Variables affecting WC/WDM Table B1: Class 1 Variables - Characterise the mine s operations Variable Description Climate (rainfall and evaporation) Groundwater regime in area where mine is located Commodity being mined Comment A mine located in a high rainfall area may have significant inputs related to runoff into the mine water balance. Depending on how effective the mine's storm water management is, this may result in significant volumes of contaminated water that need to be accommodated in the WC/WDM plan. Conversely, mines in very arid areas will have very little runoff and will be much more dependent on external fresh water sources such as rivers, groundwater, etc. Furthermore, mines located in areas with very high evaporation rates will have a much greater need to import fresh water to counteract the effects of water loss through evaporation. Such mines may also benefit from focusing WC/WDM actions on minimising surface area of water containment facilities. Although the rainfall and evaporation rates cannot be changed, the impact can be managed through proper WC/WDM methods/technologies. A mine located in an area with abundant groundwater resources can expect to have groundwater inflows contributing significantly to the overall water balance. While some actions can be implemented to limit ingress of groundwater into the mine workings, none of these would be entirely effective and high groundwater inflows can be expected for these mines. In certain cases, such as mines in the dolomitic regions, the volume of groundwater entering the mine can become the defining factor in the mine's water management system with significant challenges in preventing this water from becoming contaminated. However, if this water is used efficiently within the mining operations, it will limit the need for additional water intake as well as reduce excessive discharges (unless the external water intake of the mine is already zero). Previous research and work done in implementing WC/WDM in the mining industry clearly indicated that there are significant differences in water use and water management challenges between different mineral/metals commodities. Some commodities such as coal are relatively shallow and are produced at very large tonnages, while other commodities such as gold and platinum are mined at great depth with lower ore extraction rates. However, within a certain commodity, various steps can be taken to improve water use efficiency. Report No. 44

49 Variable Description Extent of mine cooling required Presence of sulphide or other reactive minerals in the ore body being mined Age of Mine Presence of a hydrometallurgical plant Regional interactions Comment The extent of mine cooling required is strongly correlated with the depth of mining, local geothermal gradient and age of mine. Mines that operate at depth such as gold and platinum have elevated underground temperatures and mine cooling is critical. In such mines, the cooling circuits often represent the largest single user/consumer of fresh water and such mines will have an inherently larger requirement for water than mines that have little or no mine cooling requirement. Water consumption for mine cooling is also dependent on the quality of the fresh water available for the cooling systems, although the water can be treated to mitigate this problem. By treating the water, reductions in intake of water can be achieved. Ore bodies that contain sulphides or other reactive minerals will result in water quality deterioration regardless of management measures to control the pyrite oxidation processes. While the water quality deterioration can be managed and controlled by the development and application of effective water management, some degree of water quality deterioration is inevitable. Mine ore bodies with sulphides or other reactive minerals will therefore have greater difficulty in reducing water usage in a cost-effective manner than mines that do not have such reactive minerals. The age of a mine has a number of effects on water usage and WC/WDM. Firstly, old mines are more likely to have been designed without taking into consideration the optimisation / minimisation of water and energy usage. Changing this could incur significant capital cost, which would make it uneconomical if the mine has limited remaining life over which the capital investment can be recovered. Secondly, old mines may be deeper and require more extensive water reticulation and cooling systems with concomitant rising water demand. Thirdly, older mines may have spread out over time, covering a wider geographical area with greater difficulties in implementing infrastructural changes often required in the implementation of WC/WDM measures. The presence of a hydrometallurgical plant is strongly correlated with the commodity being mined. Many commodities require the inclusion of a hydrometallurgical plant in order to recover/extract/refine the product. An example of an exception is a coal mine that has a contract to supply coal for Eskom and where little beneficiation of the run of mine product is required. However, various improvements to beneficiation technologies can be applied to improve water use efficiency. Sections of the mining sector are characterised by mines located adjacent to each other. Often only narrow boundary pillars of questionable integrity separate adjacent mines. In such instances, the WC/WDM strategy of any mine can be influenced and affected by waterrelated activities at the adjacent mine. These problems take on an even greater complexity when adjacent mines fall in the abandoned and ownerless category. Managing these factors are possible, but might require a regional effort. Table B2: Class 2 Variables Considerable effort to implement WC/WDM Variable Description Groundwater make into the mine Comment The volume of groundwater entering the mine is firstly determined by the Class 1 variable - groundwater regime. However, the extent to which groundwater enters the mine workings, can be controlled to some extent by actions undertaken by the mine. Groundwater control measures may include the following: Grouting of water bearing textures; Interception of groundwater by dewatering boreholes on the periphery of the mine workings; Interception of groundwater flows close to the point where they enter the mine workings; Isolation from mine service water circuits; and Priority pumping out of mine workings before contamination can occur. Application of these groundwater control measures can provide good quality water to be re-used in the mine water circuits with limited or no treatment thereby reducing the need for additional water intake. Report No. 45

50 Variable Description Quality of fresh intake water Type of tailings disposal facility being used Type of mining method Size of mining operation Technology in use at the mine Remaining life of mine Comment Mines that have significant mine cooling requirements and which are located in areas where the fresh water quality is poor, will experience a disadvantage when it comes to reducing fresh water intake. Cooling circuits lose water through evaporation and this causes the salinity of the water to increase with each cycle of concentration. All cooling circuits have a maximum allowable water salinity as determined by corrosion and scaling considerations. High fresh intake water salinity will lead to reductions in the cycles of concentration that can be applied before water must be blown down and replaced with fresh water, unless water treatment is applied (which will have a cost impact). In order to improve water efficiency water treatment can be considered. Mines that have a hydrometallurgical beneficiation plant will produce fine tailings that need to be disposed of or stored in a tailings storage facility (TSF). These facilities have a major impact on the water use efficiency that can be achieved, primarily due to the following factors: The need for hydraulic transportation of the tailings requires significant volumes of water; Water losses through evaporation from the pool on top of the TSF and from the return water dam can be significant, depending on how the pool is managed; The TSFs are typically unlined with resultant water losses through seepage into underlying aquifers; Water quality deterioration during the time that water is in contact with the tailings may limit the ability to reuse the water without treatment. While there are alternative options available to reduce water losses in the tailings circuit, they are not always easy to apply within the constraints of existing infrastructure and design of TSFs. However, improvements in the tailings management/disposal can lead to significant improvement in the water use efficiency of the mine. In many instances, the primary type of mining employed is dictated by the nature of the ore body being mined, especially with regard to deep hard rock ore bodies where underground mining is the only practical option. However, even in such mines, mining options are exercised by the mine as to whether they employ traditional stopping methods or mechanised mining. In other instances with shallower ore bodies such as encountered in the coal mining industry, alternative options are available in selecting between underground and opencast mining. In underground mining, further choices can be made with regard to mining method, e.g. bord& pillar versus high extraction. All these options have significant impacts on the mine water balance and the water use efficiency of the mine. The size of mining operation has both positive and negative effects on WC/WDM alternatives. In some instances, large mines offer economy of scale and allow the more cost effective centralised management of water treatment to facilitate recycling and re-use. In other cases, it is found that large mining operations are dispersed over large areas, making it logistically difficult and expensive to optimally reclaim and recycle water as part of a WC/WDM strategy. The technology in use at the mine is strongly correlated with the age of the mine, since many of the older mines were designed and constructed at a time when water and energy efficiency considerations were not deemed critical. While many mines in this category have and can make technology changes due to water and energy efficiency drivers, such options are often difficult and costly to implement. Newer mines, on the other hand, have been compelled to give consideration to environmental and energy efficiency aspects and are more likely to have incorporated cleaner technology into their operations. Such newer mines will have an easier task in meeting more stringent water use efficiency benchmarks than their older counterparts. Mines which are near to the end of their operational life will be less likely to be able to justify making significant and expensive process technology and infrastructure changes in order to achieve water use efficiency benchmarks as capital redemption can then only be applied over a short remaining life of mine. Conversely, mines with longer operational lives can justify more significant capital expenditure with longer times to redeem capital expenditure and benefit from the savings inherent in WC/WDM Report No. 46

51 Table B3: Class 3 Variables - Reasonable effort to complement WC/WDM Variable Description Availability / accuracy of water (and salt) balances on mine Internal water quality standards Mine and corporate reporting requirements Comment Effective and optimised WC/WDM is not possible on mines that do not have accurate and dynamic water (and salt) balances that comply with the Best Practice Guidelines and which are supported by and regularly updated with data from effective monitoring systems. Such water balances will typically be computerised and capable of being updated to reflect water reticulation changes and data inputs. It is also important that the water balance forms the foundation of the mine's water management system and that it be actively used in developing and reviewing water management actions at all levels. The development of suitable water quality standards for internal water users on the mine is a critical prerequisite for the development and implementation of WC/WDM measures. Absence of such standards may result in users demanding and being supplied with a water quality that is better than what is required. As effective WC/WDM essentially entails supplying each user with the appropriate quality water that does not result in reticulation system problems (scaling / corrosion / erosion) or process efficiency problems, knowledge of what these water quality limits are, is essential. Mines that adhere to rigorous corporate reporting requirements (perhaps in line with the GRI) are more likely to be sensitised to their water usage and are more likely to be engaged in a continuous improvement process aimed at systematically reducing water consumption. Conversely, a lack of structured reporting, based on outputs from an unreliable/untested water balance, is most probably indicative of a mine where WC/WDM does not enjoy any priority attention. Table B4: Class 4 Variables Drivers to support WC/WDM Variable Description Availability of fresh water resources Sensitivity of receiving catchment Financial status of mine Comment In areas of the country where fresh water supplies are limited and water use licences have restrictive conditions and mines are forced to develop optimised WC/WDM strategies, water use benchmarks may be quite stringent. While it is tempting to differentiate water use efficiency benchmarks based on the availability of fresh water supplies, this assumption is not logically consistent. An identical mine in a water-rich region should be equally capable of meeting the same WC benchmarks as the mine in the water-scarce region. In fact, allowing the availability of fresh water resources (over which mines have no direct control) to be a differentiating variable in setting WC benchmarks, could be interpreted as offering unfair commercial advantage to mines that happen to be located in areas where fresh water is abundant. The invalidity of this variable is further highlighted by the fact that South Africa is a country with many inter-catchment water transfer schemes which artificially change the fresh water availability status of both the donating and receiving catchments. The arguments against using sensitivity of receiving catchment as a variable that defines WC benchmarks are based on similar principles to those that were put forward for availability of fresh water resources. While the concept of differentiating catchments in terms of receiving water quality objectives as a basis of the water regulatory approach is appropriate, this should not be used to set differentiated water use efficiency benchmarks. The financial status and strength of the mine and whether or not the mine is an established or emergent mine should not have any influence on the water use efficiency benchmarks that are set. Financially weak or young mines should not be able to use these features as a basis for setting less stringent water use efficiency benchmarks, since the impact of such mines on the water resource and other stakeholders is the same regardless of these variables. The ability to achieve water use efficiency benchmarks should, in the interest of protecting the national water resource, rather be viewed as a minimum entry requirement into the mining sector. Report No. 47

52 APPENDIX C Water Balance Model Report No. 48

53 Introduction A generic mine water balance was developed in Excel, using water balance methodology developed by Golder for a wide range of different mines. The model was also constructed so that it could be run in a probabilistic (Monte Carlo) simulation mode. The primary objectives of the water balance model were to determine the following: Determine the effect of variables listed in the variables matrix on the key indicators Determine the variation in the key indicators due to differences between mines for a specific commodity as an input to the benchmark setting approach Quantify the savings that can be expected by implementing generic water conservation measures The generic mine water balance included the following sections (see Figure C1 for a graphical representation of the total mine): Mining (opencast and underground) Figure C2 Beneficiation Figure C3 Residue disposal Figure C4 Other activities Figure C1: Total mine water balance diagram Report No. 49

54 Figure C2: Mining section water balance diagram Figure C3: Beneficiation section water balance diagram Report No. 50

55 Figure C4: Residue disposal section water balance diagram Description of Water Balance Calculations The mine water balance calculations used to calculate each inflow and outflow of the four sections are described intqable C1 to Table C4. The variables that will influence the results of the water flow calculations for each variable are also listed in these tables. These variables are linked to the variables matrix developed in Phase 1 of this project. Table C1: Mining water balance calculations Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables Opencast operations Recharge due to rainfall on active opencast area Recharge due to rainfall on upstream rehab area Inflow Inflow Based on the average annual rainfall, % recharge of opencast pit and active opencast pit area. Opencast area is based on mining rate (t/year), seam height and duration before opencast area is rehabilitated again. Based on % recharge of rehab and upstream rehab area. Upstream rehab area is based on the area disturbed per year, the age of the mine and a factor (between 0 and 1) to cater for portion of rehab area that is downstream of active pit. Mining rate (t/year) Climate (rainfall) % recharge (depends on opencast pit, access ramps, roads, etc.) Seam height Rehab lag Mining rate (t/year) Age of mine Climate (rainfall) % recharge (depend on quality of rehab) Area disturbed per year (depend on seam height on Report No. 51

56 Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables Groundwater/fissure water Moisture in ore Moisture in ore Seepage, evaporation Underground operations Recharge due to rainfall Groundwater/fissure water Moisture in ore Moisture out with ventilation Inflow Inflow Outflow Consumptive Inflow Inflow Outflow Consumptive Mine cooling water loss Consumptive Water used for UG mining Balance Recycled / Raw water / water from 3de party Internal Inflow This value is mine-specific and specified as a volume per tonne mined. Moisture present in the ore that is mined. Calculated from a specified moisture percentage and the mining rate. Moisture out of the mining section due to ore mined. Calculated from a specified moisture percentage and the mining rate. Not considered a consumptive use since the water is sent to another user (beneficiation). Based on a percentage of the water used in the mining process. Based on the average annual rainfall, % recharge to underground operation and active underground area (seen from top). Underground area is based on mining rate (t/year), seam height, reef angle and duration before opencast area is rehabilitated again. This value is mine-specific and specified as a volume per tonne mined. Moisture out of the mining section due to ore mined. Calculated from a specified moisture percentage and the mining rate. Not considered a consumptive use since the water is sent to another user (beneficiation). This value is mine-specific and specified as a volume per tonne mined. This value is mine-specific and specified as a volume per tonne mined. Volume per tonne mined is a function of mine depth, since deeper mines require more cooling. This is an internal recycle flow that is mine-specific and specified as a volume per tonne mined. If the total inflows is less total outflows (outflows + tonnes mined) Mine plan (mining uphill or downhill) Site-specific (geology, groundwater) Size of mine Ore moisture content (sitespecific) Mining rate (t/year) Same as above Climate (evaporation) Site-specific (depend on geology, mining method) Mining rate (t/year) Climate (rainfall) % recharge (depends on underground operation, geology, etc.) Seam characteristics Site-specific (geology, groundwater) Size of mine Ore moisture content (sitespecific) Mining rate (t/year) Site-specific (mining method, thermal gradient) Size of mine Site-specific (mining method, thermal gradient, depth of mine) Size of mine Site-specific (mining method) Size of mine From balance Report No. 52

57 Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables consumptive), then the difference is assumed to come from recycled water from the central surface water dam (part of residue disposal) if excess water is available. If not enough excess water is available, the balances is assume to be raw water or water from a 3de party. Excess water to surface dams Outflow If the total inflows is more than the total outflows (outflows + consumptive), then the difference is to be sent to the central surface water dam (part of residue disposal). This is thus not seen as a consumptive use for mining, since it is sent to another user. All surplus water is reported in the residue disposal section. From balance Table C2: Beneficiation water balance calculations Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables Moisture in ore Inflow Moisture in ore to beneficiation (sum of opencast and underground ore moisture). Calculated in mining section. Waste rock excluded. Rainfall Inflow Considered to be negligible. Water in tailings Water in product Outflow Consumptive Based on SG of tailings and the dry ore and the amount of solids to tailings. Based on SG of product and the dry ore and amount of solids to product. Impacted storm water Outflow Considered to be negligible. Tailings water recycle to process Internal This is an internal recycle flow that is calculated from the SG of the feed to the tailings thickener, the SG of the tailing and the SG Refer to mining section % ore to beneficiation Climate (rainfall) Beneficiation plant design and footprint Tailings SG (depends on beneficiation method and thickening process used for tailings) SG of dry ore Solids to tailings (depends on mining rate, amount of waste rock and amount of solids to product) Tailings SG (depends on beneficiation method and thickening process used for product) Solids to tailings (depends on mining rate, amount of waste rock and amount of solids to product) Climate (rainfall) Beneficiation plant design and footprint SG of ore SG of thickener feed and outflow (depends on beneficiation plant design) Report No. 53

58 Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables of the dry ore. Balance Recycled / Raw water / water from 3de party Inflow If the total inflows is less total outflows (outflows + consumptive), then the difference is assumed to come from recycled water from the central surface water dam (part of residue disposal) if excess water is available. If not enough excess water is available, the balances is assume to be raw water or water from a 3de party. From balance Excess water to surface dams Outflow If the total inflows is more than the total outflows (outflows + consumptive), then the difference is to be sent to the central surface water dam (part of residue disposal). This is thus not seen as a consumptive use for mining, since it is sent to another user. All surplus water is reported in the residue disposal section. From balance Table C3: Residue disposal water balance calculations Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables Tailings Dams Water in tailings Inflow Based on SG of tailings and amount of solids to tailings, calculated in beneficiation section). Refer to beneficiation Rainfall Inflow Calculated from the average annual rainfall and the area of tailings dam. Tailings dam area is calculated from the volume of deposited sludge remaining on the tailings dam and the annual tailings rise rate. The volume of deposited sludge is calculated from the % moisture remaining in the deposited sludge and the SG of the ore. Climate (rainfall) Tailings dam area (calculated form tailings rise rate and volume of deposited sludge) Volume of deposited sludge (function of % solids in deposited sludge and the SG of ore) Seepage Water remaining in tailings Evaporation from pool Consumptive Consumptive Consumptive Based on pool area and the seepage rate. The pool area is calculated as a percentage of the total tailings dam area. Based on % moisture content of deposited sludge remaining on tailings dam. Based on the average annual evaporation and the pool area. Seepage rate (depends on geology) Pool area (depends on how tailings dam is operated and volume of tailings produced) % solids of deposited sludge Climate (evaporation) Pool area (depends on how tailings dam is operated and Report No. 54

59 Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables Evaporation from wet beach Evaporation from dry beach Tailings return water Rock Dumps Water in ore to waste rock dump Rainfall Run-off and seepage to surface dams Evaporation, seepage and interstitial storage Surface dams Direct rainfall Surface runoff Consumptive Consumptive Outflow Inflow Inflow Outflow Consumptive Inflow Inflow Based on the average annual evaporation and the wet beach area and the wet beach evaporation factor. The wet beach area is calculated as a fraction of the total beach area, which in turn is equal to the total tailings dam area minus the pool area. Based on the average annual evaporation and the dry beach area and the dry beach evaporation factor. The dry beach area is equal to the total tailings dam area minus the pool area minus the wet beach area. The difference between the total inflow and the total outflows (outflows + consumptive) for the tailings dam is equal to the tailings return water that is sent to the central surface water dam. Based on moisture content of the ore and the amount of waste rock produced (calculated as a percentage of the total tonnes mined). Calculated from the average annual rainfall and the area of rock dump. The rock dump area is calculated from the waste rock produced and the rock dump rise rate. Based on a percentage of the rainfall that is captured in the pollution control dam through runoff and seepage. Not a consumptive use since the water is sent to another user (surface dam). The difference between the total inflow and the total outflows (outflows + consumptive) for the rock dump is equal to the evaporation, seepage and interstitial storage. Calculated from the average annual rainfall and the area of the surface dams. The area of the surface dams are calculated as a function of the mining rate. Calculated from the average annual rainfall, the catchment volume of tailings produced) Climate (evaporation) Wet beach (depends on how tailings dam is operated and volume of tailings produced) Climate (evaporation) Dry beach (depends on how tailings dam is operated and volume of tailings produced) From balance Ore moisture content (sitespecific) Mining rate (t/year) % of waste rock mined (sitespecific) Waste rock mined (site-specific) Rock dump area % runoff and seepage (depends on waste rock dump design) Rock dump area From balance Climate (rainfall) Area of surface dams (function on mine size and how the surface dams are managed) Catchment area (function of mine size and whether the Report No. 55

60 Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables Tailings return water Rock dump run-off and seepage Surplus water from mining Surplus water from beneficiation Surplus water from other activities Water to 3de party Specified clean discharge Evaporation Seepage Water to mining Water to beneficiation Inflow Inflow Inflow Inflow Inflow Outflow Outflow Consumptive Consumptive Outflow Outflow Water to other activities Outflow Balance Raw water / water from 3de party Clean discharge Inflow Outflow area and the % runoff factor. The catchment area is calculated as a multiple of the area of the surface dams. Return water from tailings dam (calculated under tailings dam) Run-off and seepage from rock dump (calculated under rock dump) Surplus water (if any) from mining. Calculated from balance of mining. Surplus water (if any) from beneficiation. Calculated from balance of beneficiation. Surplus water (if any) from other activities. Calculated from balance of other activities. Specified water to 3de party (not consumptive use since it is used by another user). Specified clean water discharge (not consumptive use since it is a clean discharge). Calculated from the average annual evaporation and the area of the surface dams. The area of the surface dams are calculated as a function of the mining rate. Calculated from the seepage rate and the area of the surface dams. The area of the surface dams are calculated as a function of the mining rate. Available surplus water sent to mining if mining requires make-up water (calculated under mining) Available surplus water sent to beneficiation if beneficiation requires make-up water (calculated under beneficiation) Available surplus water sent to other activities if other activities requires make-up water (calculated under other activities) If the total inflows is less total outflows (outflows + consumptive), then the difference is assumed to come from raw water or water from a 3de party. If the total inflows is more than the total outflows (outflows + consumptive), then the difference must be discharge. The clean clean storm water runoff is diverted) Refer to tailings dam Refer to rock dump Refer to mining Refer to beneficiation Refer to other activities Specified Specified Climate (evaporation) Area of surface dams (function on mine size and how the surface dams are managed) Seepage rate (depends on geology) Area of surface dams (function on mine size and how the surface dams are managed) Refer to mining Refer to beneficiation Refer to other activities From balance From balance and % of discharge that is clean water Report No. 56

61 Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables discharge is calculated as a percentage of this total discharge (this percentage should be 100%). This is thus not seen as a consumptive use since the discharge water is clean (might require treatment). Untreated spillages/discharges Consumptive use The untreated spillages/discharges are calculated as the difference between the total discharge and the clean discharge (this should be zero). This is seen as a consumptive use since the discharge is polluted and not usable by another user. From balance and % of discharge that is dirty Table C4: Other activities water balance calculations Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables Haul road dust suppression Service road dust suppression Human consumption (potable water) Sanitation water reused as process water Consumptive Consumptive Inflow Internal Based on the dust suppression application rate (mm/d) and the total haul roads area. The haul roads area is calculated from the haul roads length and width. The haul roads length is a function of the size of the mine and the nature of the mining operation. Based on the dust suppression application rate (mm/d) and the total haul roads area. The service roads area is calculated from the service roads length and width. The service roads length is a function of the size of the mine and the nature of the mining operation. Water used by workers (potable and for showers). Number of workers depend on mining method and nature of operation. Calculation is based on an average water usage per worker per day with shower access and an average water usage per worker per day without shower access. Based on a percentage of the sanitation water that is reused as process water. This will depend on treatment of sanitation water. The amount of sanitation water is equal to the human consumption minus the water lost through perspiration, breathing and evaporation Dust suppression application rate (depends on climate, whether binding medium is used on roads) Length of haul roads (depends on size of mine and nature of operation) Width of haul roads Dust suppression application rate (depends on climate, whether binding medium is used, tarred, etc.) Length of service roads (depends on size of mine and nature of operation) Width of service roads Number of workers with and without shower access (depend on mining method and size of mine) Average water usage per worker (dependant on climate) Specified Amount of sanitation water and treatment thereof Report No. 57

62 Inflow/outflow (m 3 /year) Type Description of calculations Influenced by these variables Water lost through perspiration, breathing and evaporation Sanitation water discharged Balance Recycled / Raw water / water from 3de party Excess water to surface dams Consumptive Consumptive Inflow Outflow Based on average water lost per worker per day (dependant on climate). Sanitation water not reused If the total inflows is less total outflows (outflows + consumptive), then the difference is assumed to come from recycled water from the central surface water dam (part of residue disposal) if excess water is available. If not enough excess water is available, the balances is assume to be raw water or water from a 3de party. If the total inflows is more than the total outflows (outflows + consumptive), then the difference is to be sent to the central surface water dam (part of residue disposal). This is thus not seen as a consumptive use for mining, since it is sent to another user. All surplus water is reported in the residue disposal section. Number of workers (depend on mining method and size of mine) Amount of sanitation water and treatment thereof From balance From balance Results of Water Balance Simulations Undertaken As mentioned previously, the model was used to undertake the following: Determine the effect of variables listed in the variables matrix on the key indicators Determine the variation in the key indicators due to differences between mines for a specific commodity as an input to the benchmark setting approach Quantify the savings that can be expected by implementing generic water conservation measures The results of these analyses are reported below. Effect of variables in variables matrix on key indicators The model as it was constructed was capable of evaluating the effects of the following variables listed in the variables matrix (Appendix A) on the key indicators: average annual rainfall average annual evaporation ground water / fissure water ingress into mining operations depth of mine (for underground mines) mine cooling requirement Report No. 58

63 The results of these simulations are shown in Figures C5 through to C9 below in terms of the effect of these parameters on the total water input per tonne (total water use efficiency) for the four major commodities. This will give an indication of how sensitive the water usage of a mine is to these parameters and how this will affect the achievable water use efficiency for the different mining operations. and also quantify how much water can be saved by changing these parameters. In each simulation, only the variable under consideration was varied and all other variables were kept at their reference values. Figure C5: Effect of annual rainfall on total water use efficiency Figure C6: Effect of annual evaporation on total water use efficiency Report No. 59

64 Figure C7: Effect of ground water / fissure water make on total water use efficiency Figure C8: Effect of depth of underground mines on total water use efficiency Figure C9: Effect of depth of mine cooling water requirement on total water use efficiency The parameters shown in Figures C5 to C9 are defined as class 1 variables in the variables matrix as they are fixed features of a mine and cannot be changed. This is important insofar as these variables will directly affect the achievable water use efficiency of a mine. For example, with all other variables being the same, it would be expected (as shown in Figure C8) that a deep mine would have a higher water use requirement Report No. 60

65 than a shallower mine. When evaluating the data shown in Figures C5 to C9, the actual predicted variation in water use efficiency is of less significance than the trend, be it for improved or worsened water use efficiency. Effect of natural variation of water balance parameters on key indicators The model was constructed to be capable of operating in a probabilistic (Monte Carlo) mode where all the input values were randomly sampled and the model was then run 500 times for each of the commodity groups. The outputs of the model were then plotted and statistically evaluated to determine the variation in water use efficiency that could be expected, given a natural variation in these input values at different mine sites. The results of these 500 simulations are shown for the coal mining scenario (similar results were obtained for each commodity) in the Figures below and the results for all the simulations are shown in Table C5 below. Figures C10 to C14 show the results of the Monte Carlo simulations for the total mine water balance, the mining water balance, the beneficiation water balance, the residue disposal water balance and the water balance for other water uses. Table C5: Standard deviation of key indicators per commodity Standard Deviation Unit Coal Gold Platinum Other Total Mine Total Mine - Total water input per tonne mined m 3 /t Total Mine - Consumptive use per tonne mined m 3 /t Total Mine - % impacted water not recycled % 12% 13% 13% 13% Total Mine - Water recycling ratio (recycle/inflow) % 47% 46% 59% 55% Mining Mining - Total water input per tonne mined m 3 /t Mining - Consumptive use per tonne mined m 3 /t Beneficiation Beneficiation - Total water input per tonne mined m 3 /t Beneficiation - Consumptive use per tonne mined m 3 /t Residue Disposal Residue Disposal - Total water input per tonne mined m 3 /t Residue Disposal - Consumptive use per tonne mined m 3 /t Other Activities Other Activities - Total water input per tonne mined m 3 /t Other Activities - Consumptive use per tonne mined m 3 /t Report No. 61

66 Figure C10: Effect of variations on total mine water balance key indicators Figure C11: Effect of variations on mining water balance key indicators Report No. 62

67 Figure C12: Effect of variations on beneficiation water balance key indicators Figure C13: Effect of variations on residue disposal water balance key indicators Report No. 63

68 Figure C14: Effect of variations on other use water balance key indicators The purpose of the Monte Carlo simulations was to evaluate the natural variation around the average values for the key indicators that could be expected if a large number of mines were to be evaluated. The standard deviations determined during this exercise are then also applied to define the range that should be allocated to the average national benchmarks set for each of the key indicators. Evaluation of water use savings from generic WC/WDM measures The water balance model was also used as a tool to evaluate the potential effect of various water conservation measures on the key indicators, again by only varying the one variable under consideration while the other variables were held at their default values. The results of this evaluation are presented in Chapter 5 of the main report. Report No. 64

69 APPENDIX D Document Limitations Report No. 65

70 DOCUMENT LIMITATIONS This Document has been provided by Golder Associates Africa Pty Ltd ( Golder ) subject to the following limitations: i) This Document has been prepared for the particular purpose outlined in Golder s proposal and no responsibility is accepted for the use of this Document, in whole or in part, in other contexts or for any other purpose. ii) iii) iv) The scope and the period of Golder s Services are as described in Golder s proposal, and are subject to restrictions and limitations. Golder did not perform a complete assessment of all possible conditions or circumstances that may exist at the site referenced in the Document. If a service is not expressly indicated, do not assume it has been provided. If a matter is not addressed, do not assume that any determination has been made by Golder in regards to it. Conditions may exist which were undetectable given the limited nature of the enquiry Golder was retained to undertake with respect to the site. Variations in conditions may occur between investigatory locations, and there may be special conditions pertaining to the site which have not been revealed by the investigation and which have not therefore been taken into account in the Document. Accordingly, additional studies and actions may be required. In addition, it is recognised that the passage of time affects the information and assessment provided in this Document. Golder s opinions are based upon information that existed at the time of the production of the Document. It is understood that the Services provided allowed Golder to form no more than an opinion of the actual conditions of the site at the time the site was visited and cannot be used to assess the effect of any subsequent changes in the quality of the site, or its surroundings, or any laws or regulations. v) Any assessments made in this Document are based on the conditions indicated from published sources and the investigation described. No warranty is included, either express or implied, that the actual conditions will conform exactly to the assessments contained in this Document. vi) Where data supplied by the client or other external sources, including previous site investigation data, have been used, it has been assumed that the information is correct unless otherwise stated. No responsibility is accepted by Golder for incomplete or inaccurate data supplied by others. vii) The Client acknowledges that Golder may have retained sub-consultants affiliated with Golder to provide Services for the benefit of Golder. Golder will be fully responsible to the Client for the Services and work done by all of its sub-consultants and subcontractors. The Client agrees that it will only assert claims against and seek to recover losses, damages or other liabilities from Golder and not Golder s affiliated companies. To the maximum extent allowed by law, the Client acknowledges and agrees it will not have any legal recourse, and waives any expense, loss, claim, demand, or cause of action, against Golder s affiliated companies, and their employees, officers and directors. viii) This Document is provided for sole use by the Client and is confidential to it and its professional advisers. No responsibility whatsoever for the contents of this Document will be accepted to any person other than the Client. Any use which a third party makes of this Document, or any reliance on or decisions to be made based on it, is the responsibility of such third parties. Golder accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this Document. GOLDER ASSOCIATES AFRICA (PTY) LTD Report No. 66

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