Appendix D. Hatch Report

Transcription

1 Appendix D Hatch Report

2 Building 14, Harrowdene Office Park, Woodmead, Johannesburg Phone: H Kangra Coal Feasibility - FEL3 - Study Transmittal: H RV ZA01 Date: Authorised by: Johann Beukes Transmittal Issue Reason Issued for Client Review To: Address: Attn: Title: Kangra Coal Ramon Silva, Electronic Delivery Kusipongo Expansion Project - Concept Discard Dump Report - Issued for Client Review Comments: Please review and return comments to Project Document Control no later than PLEASE NOTE - This is the correct document and not the document on TRANSMITTAL H RV ZA01 issued on Please return review comments/signed documents to Project Document Control by Copy to: Beukes Johann McGonigal Seamus Hatch - Issued for Information - Electronic Delivery Hatch - Issued for Information - Electronic Delivery Number of Documents: 1 Project Document No Other Document Number Rev Title Status Grade File Type System Ver H A Concept Discard Dump Report Client Review pdf 3 Document Review Grade Codes: C1 - Proceed to next submission and status C2 - Proceed with exceptions as noted to next submission and status C3 - Do Not Proceed. Revise as noted and resubmit next submission and status C4 - Complete. No further submission required Transmittal created by: Du Preez, Carien H RV ZA01 Page 1 of 1

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4 Table of Contents 1. Executive Summary Introduction Scope of Work and Terms of Reference Available Information Site Selection Site Options Site A Site B Site C Site D Site E Site F Site Suitability and Ranking System Ranking Methodology Site Ranking Results Disposal Methodology Co-disposal Wet and Dry (not considered) Integrated Discard Wet (not considered) Integrated Discard Dry Separated Disposal Wet Site 1 and Dry Site 2 (not considered) Concept Design Design Assumptions Dump Configuration and Sizing Preliminary Hazard Classification Seepage Control and Containment Surface Water Controls Clean Water Runoff Dirty Water Run-off Preparatory Works Phases Construction and Operation Methodology Access to the Waste Dump Rehabilitation and Closure Conclusions Recommendations ISO 9001 H , Rev. A, Page ii

5 1. Executive Summary Kangra Coal, located near Piet Retief, Mpumalanga, currently has an approved Environmental Management Programme Report (EMPR) for the current underground mining operations. However, Kangra Group (Pty) Ltd who owns the Savmore Colliery plan to develop the colliery further to include a new coal resource extension. The existing discard facility has a limited calculated Volume of ton (Maquasa West Amendment, Environmental Management Programme Report, Version 1, 03 April 2009, Kangra Coal (Pty) Ltd, ) and a new facility will have to be designed and implemented to accept discard produced from the Future expansion. This concept design is based on a dry co-disposal system whereby coarse coal discard and fine discard material (filter cake) are disposed together on demarcated areas on the same site. The replacement facility, design concept (based on using the same area as is currently used) has been planned in 3 phases. The new waste discard facility has been designed to accept m 3 of coal discard over a period of 15 years at a average rate of m 3 year. This includes: coarse coal discard m 3 per year fine coal discard m 3 per year (filter cake). The total waste product comprises m³ coal discard material which will occupy an approximate area of x 10 3 m 2 ( ha) and a height varying from 0 meter to 44 m across the sloping topography. Alternate sites have been identified from previous studies that may also present feasible options. The basic designs are transferable to any of the alternatives, if required. The discard dump layout, method of development, side profiles, and rehabilitation have been designed to minimise environmental impacts. Ongoing rehabilitation of the waste dump is required during the operational life to restore the site, at closure, to its original vegetated state. At closure the surface of the discard dump will have been shaped to allow adequate drainage of uncontaminated storm water runoff. Design of the clean and dirty water management systems has led to the sizing requirement of the polluted water dam. The dirty seepage water entering these dams will be allowed to evaporate, whilst dirty water from sub soil drains and runoff from the plant area is collected in a separate polluted water dam and sent back to the plant for re-use. The water balance calculations revealed that an additional polluted water dam facility is required to accommodate the plant nun-off due to an increased area. The estimated areas of the new polluted water dams are: Dam m 2 Dam m 2 Dam m 2 The assumed volume estimation of the existing polluted water dams is confined, and the statutory freeboard requirements are satisfied and the plant runoff area remains unchanged. ISO 9001 H , Rev. A, Page 1

6 Capital costs have been estimated and summarised as follows: Phase 1 - R 92 million Phase 2 - R 174 million Phase 3 - R 387 million (This incorporates the existing Discard Dump footprint). The costs, above, including 20% contingency, based on a concept level (FEL 1) of detail. 2. Introduction Kangra Coal plans to develop the colliery to include the Kusipongo resource which will either include an extension of the existing waste dump or the selection of other alternatives. Kangra Coal has appointed Hatch to submit a concept design and costing of the discard waste dump required. As part of our concept design report we have provided information on the following: Site selection Disposal methodology Dump configuration and sizing for the life of the Mine Preliminary hazard classification according to the draft SABS 0286 code of Practice for Mine Residue Deposits Seepage control and containment Clean and dirty surface water controls before start up, during operation, and on Final closure Preparatory construction works before start up Ongoing rehabilitation and closure of the waste dump Operating methodology Determination of capital costs for preparatory construction works. 3. Scope of Work and Terms of Reference The scope of work that are pertinent to this report are as follows: The specialist investigations and site selection The conceptual design. The design limits for the concept design will include: The works within the haul/access road around the perimeter of the discard dump A haul/access road around the perimeter of the discard dump, and also from the Existing plant to the proposed site C A clean water cut-off trench above and along the flanks of the discard dump ISO 9001 H , Rev. A, Page 2

7 A polluted water pipeline from the proposed site C to the existing polluted water Dams, and the silt traps An additional return water dam. However, the scope of work excludes the following: Return water system from the existing polluted water dams to the plant and / or any Pumping upgrade that might be required; the electrical works for the slurry pumps and possible lighting at the discard dump during the night time operations The works associated with the operations of the discard dump Storm water management in and around the existing polluted water dams and plant area. 4. Available Information A report on the existing discard waste dump water balance (refer to SRK report /4) Scale maps with 1 m contour intervals. Aerial Photographs Site Visit 5. Site Selection 5.1 Site Options The various site considerations are shown in Figure 1. Figure 1: Site ISO 9001 H , Rev. A, Page 3

8 Figure 2: Site with aerial photo of the alternatives Site A The site is situated to the east of the current wash plant position and the advantages are: The relatively flat topography The close proximity (±0,2 km) to the proposed plant position The dump cannot sterilise any coal reserves. The disadvantages of the site are: The close proximity (± 0,6 km) to the Heyshope Dam The collected seepage must be handled by a pumping system that must operate after mine closure The visible impact of the dump The polluted surface water and storm water runoff must be handled by a pumping system during operation Site B The site is situated to the north of the current wash plant position and the advantages are: The close proximity (± 0,5 km) to the proposed plant. The dump can blend in with the natural topography to reduce the visible impact. The polluted surface water and storm water run-off can be handled by a gravity system (passive) ISO 9001 H , Rev. A, Page 4

9 The seepage can be handled by a gravity system (passive). The disadvantages of the site are: The major seep zone that will require significant engineering design to overcome, and will have a low confidence level of success The Site is located partially above the old mined out area and the correct as mined out survey should be sourced to establish how many pillars have been left after mining activities stopped. The depth to underground workings is approximately 30 m Site C The site is situated to the north west of the current wash plant position and includes the existing Dumping site, and the advantages are: The dump can blend in with the natural topography to reduce the visible impact. The polluted surface water and storm water run-off be handled by a gravity system (passive) The seepage can be handled by a gravity system (passive). The disadvantages of the site are: That it is (± 1.2 km) from the existing washing area The Site is located directly above the old mined out area and the correct as mined out survey should be sourced to establish how many pillars have been left after mining activities stopped Site D This site is to the west of the current wash plant position and is situated on the coal reserves in the area known as Maquasa West. The advantages of the site are: The dump can blend in with the natural topography to reduce the visible impact The polluted surface water and storm water runoff can be handled by a gravity system (passive) The seepage can be handled by a gravity system (passive). The disadvantages of the site are: The difficulty in containing seepage The distance (± 1.9 km) from the proposed plant position The Site is located partially above the old mined out area and the correct as mined out survey should be sourced to establish how many pillars have been left after mining activities stopped Site E The site is approximately 2.4 km to the west of the current wash plant position in the Maquasa West Open Cast section. This option is to dump the discard into the open cast excavation was not considered further due to the difficulty of controlling the acid mine drainage (AMD) in the open cast excavation. ISO 9001 H , Rev. A, Page 5

10 5.1.6 Site F The site is situated approximately 3.2 km to the west of the current wash plant position and the advantages are: The dump is on a slope which faces away from the Heyshope dam and Driefontein and therefore the visual impact is reduced The two naturally occurring clay layers within the soil profile, and the elevation of the ground water is below the second layer The dump cannot sterilise any coal reserves. The disadvantages of the site are: The distance from the current washing plant position The introduction of a pumping system to, return the seepage to the plant during the operational life. 5.2 Site Suitability and Ranking System The Fatal Flaw and Critical Factor approach is used to assess the suitability of the sites for residue disposal and is defined as follows: "Fatal Flaws" are those factors which eliminate the use of sites for discard disposal because they do not adhere to the environmental and/or safety objectives "Critical Factors" are those factors that do not adhere to the environmental and/or safety objectives, but can be effectively mitigated by engineering solutions Ranking Methodology Firstly, the sites were ranked using the fatal flaw criteria and those sites with fatal flaws were discarded. The remaining sites were then ranked subjectively by considering: Safety classification Environmental classification Design and operation Economics. The critical factors were then weighted out of 10, with I being the least important and J of critical importance Site Ranking Results Site E is omitted when using the fatal flaw criteria shown in Table 7-1 below: Table 5-1: Summary of the Fatal Flaw Ranking Site Fatal Flaw Comment A No No comment B No Steep zone C No Above old mine out area including existing Discard Dump ISO 9001 H , Rev. A, Page 6

11 D No AMD (Acid Mine Drainage) could exclude this site E Yes Unlikely to be able to control the AMD (Acid Mine Drainage) and open cast operation not guaranteed F No No comment 6. Disposal Methodology 6.1 Co-disposal Wet and Dry (not considered) Co-disposal involves the impoundment of slurry within the body of the coarse discard which will lead to acid mine drainage (AMD) during the operating life and a considerable period after closure. 6.2 Integrated Discard Wet (not considered) Integrated discard involves the mixing of slurry and the coarse discard which will be deposited like conventional tailings. The tailings will beach with the coarse product being deposited first followed by the fine product which will accumulate at the pool centre. The integrated discard technique will reduce the permeability of the coarse discard and therefore a reduction in AMD is expected. Although the expected AMD is significantly less than that for codisposal we can also expect AMD to continue after closure. However, this disposal technique is relatively new and unproven technology. 6.3 Integrated Discard Dry Integrated discard Dry process involves dumping coarse discard material the conventional way in layers and mixing the low moisture filter cake fine discard material in layers with the coarse discard. The integrated discard Dry technique will reduce the permeability of the coarse discard and therefore a have a reduction in AMD. Although the expected AMD is significantly less than that for co-disposal we can also expect AMD to continue after closure. 6.4 Separated Disposal Wet Site 1 and Dry Site 2 (not considered) Separated disposal involves the deposition of the slurry into the underground workings or a separate above ground fines slurry pond, and the impoundment of the coarse discard above the ground surface. This reduces the AMD potential of the coarse discard, and the control and containment of AMD from the slurry if it is placed below ground. In the case of Maquasa the fines could be transported and deposited in the form of a slurry back into the underground workings. These areas of disposal will be prepared using the appropriate preplanning and mining methods. The slurry is then deposited at an elevation below the expected working level and remains flooded thereby excluding or limiting the supply of oxygen. However a decision has been made to stop this operation and to dry the slurry and dispose of the filter cake on the Coarse discard dump. Coarse Discard disposal involves impounding the coarse discard on a selected site above natural ground. The coarse discard is then compacted to minimise the risk of spontaneous combustion by limiting the ingress of air and water into the waste dump. The AMD that could be generated from the ISO 9001 H , Rev. A, Page 7

12 coarse discard during operations would be captured and contained within the mine property and once the dump has been encapsulated, the amount of seepage is likely to cease after a short period of time. 7. Concept Design The concept design has been undertaken to include the existing Discard Dump which covers Site B and Site C. 7.1 Design Assumptions The following design parameters were adopted: a m 3 of coarse discard for the life of Mine tons of coarse discard tons/year tons/month tons/day b m 3 of dry fine discard filter cake for the life of Mine tons of filter cake tons/year tons/month 220 tons/day (assumed compacted density of 1.4 tons/m') which equates to tons. 7.2 Dump Configuration and Sizing The waste dump is sized to accommodate a combined production tonnage of tons for the coarse and fine discard over the 15 year life of the mine. Therefore, the volume requirement of the waste dump is m 3 based on a dry density of 1.4 ton/m 3 for the fine and coarse discard material. The concept configuration of the discard facility, if situated at the existing site, is shown on drawing number H and is derived using the following criteria: Conformity with the natural landscape Minimal visual intrusion Minimal floor area Avoidance of the high water table Minimal erosion during exposure of the waste dump Ease of rehabilitation Side slope stability. The waste dump covers a floor area of approximately 125 x 10' m', and varies in height above natural ground level from 44 m at the deepest position and 0 m at the shallowest position and is stepped in 9 m for every 4.5 m in height to provide an overall slope of I in 5.(3 x berms for every 1 road). ISO 9001 H , Rev. A, Page 8

13 7.3 Preliminary Hazard Classification A preliminary safety and environmental classification for the proposed mine residue disposal for site C has been undertaken in line with the draft SABS 0286 code of practice for mine residue deposits. The preliminary safety classification is high because of the assumed number of workers in the zone of influence being greater than 100, and the depth of the underground mine working being less than 50 m. However, it must be realized that the safety classification only focuses on the potential impacts arising from the existence of the deposit, and not the probability of a failure event occurring. Therefore, a high classification stresses the importance of the deposit and the scope of a risk management plan required. The preliminary environmental classification of the residue deposit indicates a potentially significant impact which arises due to the toxicity of the potential leachate that could be generated by the mine residue deposit. A final hazard classification will need to be carried out for detailed design purposes in accordance with the new SABS 0286 code of practice for mine residue deposits. 7.4 Seepage Control and Containment The majority of seepage will originate from coarse and filter cake discard thereby resulting in a low phreatic surface within the waste dump due to the high permeability of the coarse material. A filter drain around the perimeter of the waste dump is expected to collect ant potential seepage and then transport the contaminated seepage water via a HDPE pipeline to the new trapezoidal channel and then to the polluted water dams. The following works will be undertaken to prevent seepage into the ground water system: Provision of a polymer based bentonite mixed liner at the base of the waste dump which will with stand leachate attack and seepage. The polymer based bentonite liner is 450 mm thick below the coarse discard dump with a minimum permeability of 10-6 cm/sec. compacted in 150mm layers to the suppliers specification Grade and shape the coarse discard material to obtain controlled run-off for Collection of the dirty water Ongoing rehabilitation of the dump during the operational life to reduce the dirty storm water catchment area. Seepage will be expected for a long period after closure and at closure the seepage emanating from the waste dump will be redirected via the filter drains and HDPE pipes and the trapezoidal channels to the catchment dams. 7.5 Surface Water Controls Clean Water Runoff Temporary storm water cut-off trenches will be strategically positioned during the operation of the waste dump to collect all clean water run-off, and divert this water away from the waste dump into the natural veld. However, during the operations those storm water cut-off trenches within the confines of the waste dump will be collected and channeled to filter toe drains as the waste dump grows in size, thereby facilitating drainage of contaminated storm water run-off which will be transported to the existing and new dirty water dams. ISO 9001 H , Rev. A, Page 9

14 Part of the philosophy of increasing clean storm water run-off is achieved by the ongoing rehabilitation of the waste dump slopes. Thus reducing the volume of polluted, dirty water due to the ongoing reduction of the waste dump area that would be exposed to storm water run-off. During operation storm-water, take-down chutes will be constructed to drain the side slope berms. At closure the remainder of the exposed waste dump will be rehabilitated and take down chutes constructed to facilitate a clean storm water run-off area Dirty Water Run-off The philosophy during the operational life of the waste dump will be: To reduce those areas causing dirty storm water run-off To correct water management facilities to control and contain the dirty storm water runoff. The site will initially be divided up with storm water cut-off berms to reduce the dirty Storm water catchment area, and allow the dirty water to drain away via the coarse discard material into the filter drains. High density polyethylene (HDPE) pipes will then be used to collect and transport the dirty water to the new dirty water trapezoidal channels draining to the new and existing dirty water dams. The maximum area of the waste dump contributing to the polluted water system during the operating life will be when the downstream side of the dump is level with the upstream side. Upon closure of the site this area will have reduced to zero when the entire site has been rehabilitated, resulting in a clean storm water run-off system Preparatory Works The initial preparatory works for the Coal Discard waste dump is divided into phase 1, phase 2 and phase 3 (see drawing number H ) in order to minimise capital expenditure for the project, and will incorporate the following: Removal of a mm thick topsoil layer and the storage of this material close to the waste dump for future rehabilitation of the side slopes Rip and compact of the a 150 mm thick in situ soil layer Import of selected 450 mm layer and application the polymer based bentonite additive, and compact to an approved density to form a leachate resistant liner with a minimum permeability of 10-6 cm/sec. Import of selected >50 mm to <100 mm sived stone drainage layer Filter fabric Bidum U 20 Import of 300 mm selected permeable protection layer Filter toe drain (16 mm stone raped in Bidum 500 x 500) Outlet pipes 110 mm HDPE (filter toe drain) - drain A dirty water trapezoidal concrete channel for that specific phase An 6 m wide gravel road around the perimeter of the waste dump and back to the proposed plant area Clean storm water diversion berms and trenches strategically positioned around the waste dump. ISO 9001 H , Rev. A, Page 10

15 The filter toe drain allows seepage through into the outlet pipes, thereby preventing a build-up in water behind and under the dump. The outlet pipes exit into the concrete trapezoidal channel at a 45 o angle which prevents the ingress of air to the underside of the waste dump during operations. All the pipeline must also be periodically monitored for the drain flows: Culverts and crossings where required for access roads Silt traps to collect the majority of the silt that is present in the dirty water. Two silt traps are constructed for maintenance purposes and an additional return water dam facility is located alongside the existing dirty water dams, and is lined with HDPE to prevent seepage from occurring Phases Phase 1, phase 2 and phase 3 of the preparatory works are planned as follows: Phase 1 is 8.35 % of the total Coal Discard waste dump volume including: Dump liner Toe drain The new dirty water dam 2 Dam liner Trapezoidal channel Perimeter fence Phase 2 is % of the total Coal Discard waste dump volume including: Dump liner Toe drain The new dirty water dam 3 Dam liner Trapezoidal channel Perimeter fence Phase 3 is % of the total Coal Discard waste dump volume including: Dump liner Toe drain The new dirty water dam 1 Dam liner Trapezoidal channel Perimeter fence Haul road. ISO 9001 H , Rev. A, Page 11

16 7.6 Construction and Operation Methodology Access to the Waste Dump The access to the Coal Discard waste dump is via an 8 m wide gravel haul road from the existing plant area. The coarse discard material is delivered to site in articulated dump trucks, and then levelled off and compacted. On disposal of the waste the articulated dump trucks will enter the dumping area from one flank and exit on the opposite flank thereby creating a free flowing traffic cycle. The sequence of dump development is as follows: At the start of disposal a mixture of coarse and fine discard is placed in the lowest topographical area of the site. By building this area up in the dry season the rainfall has little impact on prohibiting access to the site The ground surface is subdivided into segments of about 100 m by the construction of storm water berms which initially drains into the outer clean water trench. These trenches prevent upstream storm water run-off entering the low lying areas where the coarse discard is deposited The coarse and fine discard is dumped and compacted in layers so the exposed waste surface always slopes from the downstream side of the dump towards the higher ground for control of storm water run-off Side slope shall not exceed 1 in 3 A 9 m wide step-in is constructed with an outer edge bund for every 4.5 m in elevation achieved. The step-in is level and berm is constructed on this step in to form a berm with 1 in 3 side slopes to contain the dirty water run-off. Thereafter the dirty water is directed into the temporary take down chute and then discharged into the ne concrete trapezoidal channel Every 4 th step-in must be a access road and be covered with a 150 mm layer of wearing coarse Average side slope shall not exceed 1 in 5 Side slopes and step-ins of the Coal Discard waste dump are rehabilitated on an ongoing basis during the operational phase rehabilitation includes replacement of a x m layer of topsoil and vegetation. The storm water run-off from these areas is then considered clean, and the ground levels will be altered to divert this water into the clean water drainage system Permanent take down chutes are constructed on those slopes above the highest level of the dump site. The overall design philosophy is that water is not allowed to accumulate on top of the dump before or after rehabilitation this structure should be free draining Rehabilitation and Closure Rehabilitation is an ongoing process as the waste dump grows in height, and must therefore form part of the operating costs. The rehabilitation will include: The covering of the Coal Discard waste dump side slopes with an approximately 300 mm thick layer of top-soil and then grassing the leveled topsoil The planting trees during the life of Coal Discard waste dump to further reduce the visual impact ISO 9001 H , Rev. A, Page 12

17 The modification of the dirty water drainage from the exposed discard step-ins to clean water drainage after completion of the top-soiling The construction of chutes down the side of the discard dump for the collection of storm water where the step-ins do not daylight at natural ground level The grading and shaping of the waste dump to achieve a suitable long term profile Topsoil covering and grassing of the step-ins and the top of the dump at closure. 8. Conclusions The concept design is based on a co-disposal Dry system whereby the coarse and fine discard material are deposited together on the same site The coal discard facility has been designed to accept 18 million m 3 of waste material over period of 16 years The total waste product comprises 1.2 million tons of fine and million tons of coarse discard material respectively Approximate area of the Coal Discard waste dump is x 10 4 m 2, and the height varies from 0 meters to 44 meters across the sloping topography The coal discard facility layout, method of development, side profiles, and rehabilitation are designed to minimise environmental impacts. The facility requires ongoing Coal Discard waste dump must be rehabilitation to restore the site at closure to its original vegetated state as soon as is practical. The surface of the discard dump shall be shaped during construction to allow adequate drainage of storm water run-off The design of the clean and dirty water management systems has led to a reduced requirements in terms of the sizing of the return water dam. The potential contaminated dirty seepage water entering these dams will be allowed to evaporate, however water from the return water dam can be sent back to the plant for re-use Water balance calculations should be revisited to confirm the sizing of the three dams. 9. Recommendations Should the project proceed the following recommendations are made: Confirmation of the design and management of the mine residue disposal system with the SABS "Code of Practice" before detailed design and construction drawings are undertaken. The following actions are required: The production volumes, life of mine, disposal methodology, material characteristics and site selection are to be confirmed The existing dirty water dams are accurately surveyed to confirm estimation of their sizes and capacity Detailed geotechnical investigations and testing is required for the selected sites ISO 9001 H , Rev. A, Page 13

18 Detailed design and preparation of construction drawings Construction supervision and project management Compilation of enquiry documentation and tender letting Compilation of an operating manual Detailed specifications of the plant/equipment required to transport the coarse discard from the plant to the Coal Discard waste dump Details of the extent of under-mining of the area to be determined before final decision is made. ISO 9001 H , Rev. A, Page 14