Louis Aucamp

OPGOEDENHOOP, HENDRINA STORM WATER MANAGEMENT PLAN CONCEPTUAL PHASE SEPTEMBER 2014 Prepared by: For: REVIEW AND ACCEPTANCE NAME ROLE SIGNATURE DATE Louis Aucamp Compiler 20/09/2014 Sakkie Prinsloo Reviewer 20/09/2014 Dzivhuluwani Takalani Recipient REVISION HISTORY REV DATE DESCRIPTION AFFECTED PAGES ORIGINATOR 0.0 07/09/2014 First draft for review All Louis Aucamp 0.1 19/09/2014 Final draft for review All Louis Aucamp 0.2 20/9/2014 Reviewed All Sakkie Prinsloo ii TABLE OF CONTENTS 1 INTRODUCTION ........................................................................................................................................ 1 2 SCOPE OF WORK ...................................................................................................................................... 1 3 PROJECT METHODOLOGY ......................................................................................................................... 1 4 OBJECTIVES .............................................................................................................................................. 3 5 TECHNICAL SITUATION ANALYSIS ............................................................................................................. 3 5.1 SITE DESCRIPTION AND RAINFALL DATA ................................................................................................. 3 5.1.1 The Site ........................................................................................................................................... 3 5.1.2 Wetland Assessment ....................................................................................................................... 5 5.1.3 Rainfall ............................................................................................................................................ 5 5.2 METHODOLOGY ...................................................................................................................................... 5 5.3 MINING LAND, PITS AND DUMPS (ANNEXURE B) ....................................................................................... 6 5.4 MAJOR CATCHMENTS (ANNEXURE D) ........................................................................................................ 7 5.4.1 Catchment A ................................................................................................................................... 7 5.4.2 Catchment B.................................................................................................................................... 7 5.4.3 Catchment C.................................................................................................................................... 7 5.4.4 Catchment D ................................................................................................................................... 7 5.4.5 Catchment E .................................................................................................................................... 7 5.4.6 Catchment F .................................................................................................................................... 7 5.4.7 Other catchments ........................................................................................................................... 7 5.4.8 Peak flows ....................................................................................................................................... 8 5.5 SUB-CATCHMENTS (ANNEXURE D) ............................................................................................................. 8 5.5.1 Office area ...................................................................................................................................... 8 5.5.2 ROM pad and weighbridge and haul roads .................................................................................... 8 5.5.3 Opencast pit area............................................................................................................................ 9 5.5.4 Waste dump .................................................................................................................................... 9 5.5.5 Workshop ........................................................................................................................................ 9 5.5.6 Sub-catchments: Peak flows and volumes ...................................................................................... 9 5.6 HYDROLOGICAL MODELLING .................................................................................................................. 9 5.7 PREVIOUS WORK AND INFORMATION.............................................................................................................. 10 6 REQUIRED INFRASTRUCTURE AND CONCEPTUAL DESIGN .....................................................................- 7 CATCHMENT D. ......................................................................................................................................... 10 CATCHMENT C ........................................................................................................................................... 10 CATCHMENT E ........................................................................................................................................... 11 OFFICE AREA ............................................................................................................................................. 11 ROM PAD, WEIGH BRIDGE AND HAUL ROADS ................................................................................................... 11 WASTE DUMP ............................................................................................................................................ 11 WORKSHOP AREA ....................................................................................................................................... 12 OPENCAST PIT STORM RUNOFF ...................................................................................................................... 12 POLLUTION CONTROL DAM FOR ROM PAD AND ASSOCIATED AREAS ...................................................................... 12 FEASIBILITY OF REQUIRED INFRASTRUCTURE ......................................................................................... 12 7.1 ISOLATE CLEAN WATER AREAS...................................................................................................................... 12 7.2 ISOLATE AND MANAGE “AFFECTED” WATER.................................................................................................... 13 7.2.1 Rom pad. Weigh bridge and haul roads ....................................................................................... 13 7.2.2 Waste Dumps ................................................................................................................................ 13 7.2.3 Opencast pit area.......................................................................................................................... 13 7.3 ISOLATE DIRTY WATER AND RE-USE .............................................................................................................. 13 7.3.1 Workshop Area ............................................................................................................................. 13 iii 7.4 FEASIBILITY OF THE SOLUTIONS...................................................................................................................... 13 8 CONCEPTUAL DESIGN AND REVIEW ....................................................................................................... 13 9 CONCEPTUAL OPERATIONAL, MANAGEMENT AND MONITORING SYSTEMS AND RESPONSIBILITIES ..... 14 9.1 WATER POLLUTION PREVENTION METHODS ................................................................................................... 14 9.1.1 Storage & handling of waste ........................................................................................................ 14 9.1.2 Storage and handling of hydrocarbons & explosives .................................................................... 15 9.1.3 Opencast pit area.......................................................................................................................... 15 9.1.4 Pollution control dam ................................................................................................................... 16 9.1.5 Transporting coal .......................................................................................................................... 16 9.2 GROUNDWATER MANAGEMENT ................................................................................................................... 16 9.3 MINIMISATION AND REUSE OF MINE WATER .................................................................................................. 16 9.4 EFFLUENT TREATMENT METHODS ................................................................................................................. 16 9.5 PROPOSED DISPOSAL OF EFFLUENT ............................................................................................................... 17 10 STORM WATER MANAGEMENT PLAN ................................................................................................ 17 10.1 ISOLATION OF CLEAN WATER AREAS .............................................................................................................. 18 10.1.1 Isolation of clean water from Catchment D .................................................................................. 18 10.1.2 Isolation of clean water from Catchment C .................................................................................. 18 10.1.3 Isolation of clean water from Catchment E .................................................................................. 18 10.1.4 Handling of clean water from the office area ............................................................................... 18 10.2 ISOLATE AND TREAT “AFFECTED” WATER ....................................................................................................... 18 10.2.1 Silt laden water from the weigh bridge, ROM pad and haul roads .............................................. 18 10.2.2 Waste Dumps ................................................................................................................................ 18  Construct a pollution control dam(s) with silt traps as detailed in section 6.6. .................................... 19  Provide regular clearance and maintenance of the facility. ................................................................. 19 10.2.3 Storm water runoff and flooding in the opencast pit.................................................................... 19 10.2.4 Pollution control dam for the ROM pad. Pit and workshop areas ................................................ 19 10.3 ISOLATE DIRTY WATER AND RE-USE .............................................................................................................. 19 10.3.1 Workshop Areas ............................................................................................................................ 19 10.4 MAINTENANCE AND OPERATING PROCEDURES ................................................................................... 19 10.4.1 Storm water Drainage System ...................................................................................................... 19 10.4.2 Settling Ponds ............................................................................................................................... 20 10.4.3 Return Water Sumps ..................................................................................................................... 20 10.4.4 Waste Dump Run-Off and Siltation ............................................................................................... 20 10.4.5 Pits ................................................................................................................................................ 20 10.5 MONITORING PROGRAMME................................................................................................................. 20 10.6 MANAGEMENT STRUCTURE ................................................................................................................. 20 11 MINE CLOSURE ................................................................................................................................... 21 12 RELEVANT DOCUMENTATION ............................................................................................................ 21 13 RECOMMENDATIONS ......................................................................................................................... 21 14 ANNEXURE A – WORKPLAN FOR OPGOEDENHOOP SWMP ................................................................. 22 15 ANNEXURE B – SITE PLAN ................................................................................................................... 25 16 ANNEXURE C – CALCULATION RESULTS AND DATA SETS .................................................................... 26 - CATCHMENT A ........................................................................................................................................... 26 CATCHMENT B........................................................................................................................................... 27 CATCHMENT C ........................................................................................................................................... 28 CATCHMENT D .......................................................................................................................................... 31 CATCHMENT E ........................................................................................................................................... 34 CATCHMENT F – PIT AREA INITIAL AND FINAL ................................................................................................... 37 CATCHMENT OFFICE AREA ............................................................................................................................ 39 CATCHMENT ROM PAD, WEIGH BRIDGE AND HAUL ROAD AREAS ........................................................................... 40 CATCHMENT WASTE DUMP AREA ................................................................................................................... 41 iv 16.10 CATCHMENT WORKSHOP AREA...................................................................................................................... 42 17 ANNEXURE D – GENERAL MAPS SHOWING RUNOFF AND CATCHMENT AREAS .................................. 43 18 ANNEXURE E – VOLUME CALCULATIONS FOR THE SUB-CATCHMENTS ............................................... 44 19 ANNEXURE F – CONCEPTUAL DESIGN CALCULATIONS FOR SELECTED AREAS ...................................... 46 LIST OF TABLES Table 1: Rainfall Station Data ................................................................................................................ 5 Table 2: Major Catchments Peak Flows (m 3/s)...................................................................................... 8 Table 3: Sub-Catchments, Peak Flows and Volumes ........................................................................... 9 v 1 INTRODUCTION Chatam Construction and The Complete Back Office were appointed by NRR Mining and Consulting to prepare a conceptual Storm Water Management Plan (SWMP)for the proposed coal mine on portion 5 of the farm Opgoedenhoop 205 IS in the district of Hendrina, Mpumalanga. The scope includes review of and incorporation of previous water related studies that has been done for the property. 2 SCOPE OF WORK The scope of work for the SWMP is listed below and reference is made in the paragraphs therafter to the procedures which are to be applied in the process to compile the STORM WATER MANAGEMENT PLAN:- Project Methodology Objectives Technical Situation Analysis Hydrological Modelling Infrastructure Requirements Maintenance and Operating Procedures Relevant Documentation The scope of work is conceptual in nature and will provide indicative recommendations and guidelines rather than detailed prescriptions. Maintenance and operating issues will only be dealt with in the context of the importance thereof for a sustainable SWMP, as the detail design of the infrastructure will dictate the maintenance and operating procedures. Issues relating to the water balance and salt balance, acid water drainage, permits and legal requirements are covered by other consultants and is excluded from the scope of work for the SWMP. 3 PROJECT METHODOLOGY The Department of Water Affairs Best Practice Guidelines for water resource protection in the South African mining industry have been used in the compilation of this document, in particular G1: Storm Water Management, A5: Water Management for Surface Mines and A6: Water Management for Underground Mines. The procedure adopted for this study is that outlined in chapter 4 of the G1 guideline and the abbreviated flowchart shown hereafter in Figure 1. 1 Figure 1: Procedure to develop a conceptual Storm Water Management Plan (BPG1) 2 The work plan to achieve the deliverables according to the outlined procedure is included as Annexure A. The work plan has been drawn up to cover all the eventualities but could only be developed to the extent that information was available. This document must be read in conjunction with the other reports on aspects of the water usage and requirements prepared by other consultants. For the purposes of this report, three types of run-off have been defined for the assessment i.e.:  Clean water – storm water run-off from natural veld.  Affected water – waste dump run-off containing suspended solids from ore dust and waste rock.  Dirty water – polluted water containing diesel, oil or hydro carbons. 4 OBJECTIVES The objectives of the conceptual Storm Water Management Plan are aligned with those propagated in Best Practice Guidelines G1 namely: Objective 1 Isolate clean water from dirty water and route it directly to the nearest natural watercourse. Objective 2 Isolate run-off contaminated with suspended solids (moderately dirty water or “affected water”) from clean water and treat appropriately. Objective 3 Isolate dirty water, contaminated with oil, grease and solvents, from the clean water areas and treat effectively so that it can be re-used in the process water for the mine as far as practically possible. 5 5.1 TECHNICAL SITUATION ANALYSIS SITE DESCRIPTION AND RAINFALL DATA 5.1.1 The Site The proposed Opgoedenhoop coal mine is situated in Mpumalanga to the east of Hendrina town on Portion 5 of the Farm OP Goedenhoop 205 IS approximately 640 ha in size. The study area is situated to the south of the R38 between Hendrina and Carolina and to the east of the N11 between Hendrina and Ermelo and is located within a district utilised for the cultivation of commercial crops and livestock grazing. The location of the area is depicted in Figure 2 on the next page and the site layout is included as Annexure B. The site falls within the drainage area of the Komati River. The farm land is traversed by an unnamed stream that flows from the southern boundary in a North-Eastern direction where it joins with a stream draining the adjacent property on the eastern side. The junction is approximately 600m from the point where the combined streams leave the property on the north-eastern boundary. The northwestern boundary of the farm consist of higher ground which form the water shed between the stream over the property and the adjacent property to the west. There is a small dam in the upper reaches of the stream over the site. 3 Figure 2: Site location in Mpumalanga 4 5.1.2 Wetland Assessment As part of the Environmental Assessment and Authorisation Process, a Wetland Ecological Assessment was conducted by Scientific Aquatic Services, Report Reference: SAS 213318 of January 2014. Their conclusion is quoted below for reference purposes: The SWMP takes cognisance of the findings of the report, does not comment on the possible regulatory requirements and presents recommendations as if permission for the establishment of the mine will be given. 5.1.3 Rainfall Six rainfall stations are situated around the site and are listed in Table 1 . The 24 hour rainfall for the four listed return periods are shown in the table but calculations were also run for the 1:5 and 1:20 year return periods. The rainfall data was extracted from the DESIGN RAINFALL AND FLOOD ESTIMATION IN SOUTH AFRICA, by J C Smithers and R E Schulze, Final Report to the Water Research Commission, WRC Project No: K5/1060, December 2002 Table 1: Rainfall Station Data Station No Description 24 Hour Rainfall in millimetres MAP (mm) 1:2 1:10 1:50 1:100 --W Morgenster 624 49.9 77.7 105.3 118 --W Karina 663 48.3 81.5 119.5 138.6 --W* Hendrina (Mun) 680 54.4 84.7 114.8 128.6 --W Klipfontein 720 52.5 81.7 110.7 124.0 --W Tevreden 693 51.3 79.8 108.2 121.2 --W Schoonoord 692 54.3 84.6 114.7 128.5 *Values for this rain station was used in the Utility Programs for Drainage. 5.2 METHODOLOGY Several methods of calculating rainfall runoff peak flows and volumes are available. In keeping with the general practice the “rational method” has been adopted for most calculations. After carrying out test runs using alternative methods it appears that this method is best for the catchments being analysed for this report. The rural nature of the catchments making up the mining land is well suited to the rational method. It is an accepted method for catchments up to 15km² areas, which covers all the catchments. The Utility Programs for Drainage developed by the University of Pretoria and distributed by Sinotech 5 cc have been created to carry out the calculation methods used in the South African National Road Agency Limited (SANRAL) Drainage Manual. This software has been used to generate the calculation results presented in the appendices. The methodology for the various calculations are well known and fully documented in the above manual and are not be repeated here. The parameters chosen for the applicable variables form part of the calculation printouts provided in Annexure C. The major catchment have been broken down into 3 sub catchments B, C and D to determine the various runoffs for diversion and possible storage. The positions of these catchments are shown on the map of water sampling points. This, together with other run-off data compiled by Digby Wells and Associates in April 2008 are presented in Annexure D. Sub-catchments for defined areas with different drainage characteristics such as pit and dump areas and clean, dirty and affected water areas will be discussed based on the block plan presented in Annexure B. . Flows for these sub-catchments have been calculated based on the software program mentioned above and flow relationships documented in the SANRAL manual. Various rainfall input methods are available for run-off flows. The triangular hyetograph has been used using the relationship i = (7, 5 + 0,034 MAP) R0,3 / (0, 24 + td) 0,89 for the inland region Where i MAP R td is the average rainfall intensity in mm/h over time td is the mean annual precipitation in mm is the recurrence interval in years is the storm duration in hours. For run-off volumes the South African SCS 24 hour (Type 3) rainfall data and the SCS standard unit hydrograph has been used. The rainfall values are as tabulated in Table 1 and the run-off volumes in Table 3. Full data files and analysis files are provided in Annexure C to this report. A summary table of the main peak flows and run-off volumes are included in the body of the report where relevant. It should be noted that a complete, or exact correlation of flow results between different calculation methods is not possible. The parameters for the various methods are not directly interchangeable and so the flows do differ. In terms of this report the “Rational Method” results for the whole catchments are intended for general use for broad planning purposes. For the detail design of a specific structure or drain a more project specific calculation would need to be carried out and the use of more sophisticated analysis programs such as SWMM, HEC-RAS and ISIS are recommended. 5.3 MINING LAND, PITS AND DUMPS (ANNEXURE B) The Site Plan included in ANNEXURE B shows the mine property with streams as well as the main infrastructure such as roads. It also shows the extent of the planned opencast pits and underground workings. Block indications of the major infrastructure areas such as offices, workshop, ROM pad, weighbridge and overburden and waste dumps are shown. In general the open areas outside the mine pit boundaries and the office area are the clean water areas, while the workshop area comprise the dirty area. The ROM pad, overburden and waste dumps, weighbridge and the in-pit areas are the affected water areas. The outlets of the major catchment areas are depicted in Annexure D. Please note that some of these areas depict the initial before scenario. The scenarios during the operation of the mine are discussed in the following section. 6 5.4 MAJOR CATCHMENTS (ANNEXURE D) The whole property has been evaluated in terms of where storm water run-off originates and where it discharges into the streams, or where it exits the mine property. Six catchments have been defined in this evaluation, working from the outlet of the total catchment flow outside the northern border of the property to the upper stretch of the stream where the flow will have to be diverted around the open cast pit and joined with the catchment from the eastern side of the property to exit at position A. The four catchments that model the before scenario has been numbered A to D as shown in Figure 3 which is also included as Annexure D. The catchment on the western side that needs to be diverted past the open pit is labelled E. The open cast pit area which receives storm water directly from downpours are labelled F and is classified as an affected water area that is to be managed together with the ROM area, weigh bridge and dump areas. The following short descriptions summarise the main features of each catchment and indicates where the run-off enters the system: 5.4.1 Catchment A Catchment A is bounded on the south-west by the high ground area, in the north west by the high ground inside the property boundary and in the south east by the division between the site and the adjacent property which follows the border until about 600m from the north eastern boundary where the valley from the adjacent property joins the main flow. The flow accumulates in the valley running south west to north east. At point C the water from the adjacent property joins the stream and flows out of the property. Catchment A will have to be apportioned into the areas C and D where the flow will be diverted around the open pit, E, via a cut off berm and canal 1 on the north western side of the pit. Flow on the pit boundary past the office and workshop areas and between the dump and pit edge is also diverted via trench 1 to point A. The open cast pit area F is to be managed with a sump in the deepest area of the pit and pumped out to the pollution control dam for the dump, ROM pad and weighbridge areas. 5.4.2 Catchment B This is the part of catchment A before the junction with C and will fall away as it will be divided into two parts, catchment D portion to be diverted and part of catchment F in the pit area. 5.4.3 Catchment C This catchment is formed by the divide on the south eastern border and consists of two valleys on the adjacent property that drains into the mine property at Point C and is to be diverted with the water from catchment D via Trench 2 past the open cast area. Catchment C contains 7 small dams. 5.4.4 Catchment D This catchment is formed by the upper reaches of catchment A and B and will have to be diverted around the open pit via Trench 2 and isolated from the shafts and adit of the underground works. 5.4.5 Catchment E This catchment lies on the north west border of the property and is formed by the “portion of catchment A that is cut off by the pit area. It will be drained by a cut off drain, Trench 1, on the edge of the pit that will flow in a south westerly to north easterly direction. 5.4.6 Catchment F This is the operational area of the pit and will be managed by sumps and pumping to the dump/ROM pollution control dam. 5.4.7 Other catchments The areas north west of the divide on the border on that side of the property drains into the adjacent 7 property and does not need to be managed as part of the SWMP except to ensure that the water stays clean and is not channelled or affected in such a way that it can damage the adjacent property. 5.4.8 Peak flows Table 2 presents the major estimated runoffs calculated according to the rational method for the 1:50 and 1:100 year return periods. Flows for 1:5 and 1:20 year return periods have also been calculated and is included in the results and data sets in Annexure C. The results of runoff calculations with other calculation methods are also included in Annexure C. The full alternative methodology has not been applied to every catchment mostly due to size constraints where the catchments are too small. For the open pit an initial estimate, based on the area shown in Annexure D, and a final estimate based on the pit outline on Annexure B are supplied. The runoff for the pit is based on storm water only and does not include for any ground water. Table 2: Major Catchments Peak Flows (m3/s) MAJOR CATCHMENTS 5.5 RETURN PERIOD (YEARS) 2 10 50 100 A 19.04 40.04 87.62 128.78 B 9.40 19.36 42.76 63.19 C 10.68 21.99 48.52 71.67 D 6.75 10.09 30.77 45.52 E 2.35 4.86 10.78 15.97 F initial 14.33 25.48 39.20 48.06 F final 26.75 36.28 72.49 88.55 SUB-CATCHMENTS (ANNEXURE D) The sub-catchments are classified according to the quality of runoff as follows:  Clean water – storm water run-off from open areas and low volume office/industrial areas: Office area  Affected water – waste dump run-off with suspended solids from ore dust and waste rock: Storm water from the pit mining area, ROM pad and weighbridge, haul roads and waste dump.  Dirty water – polluted water containing diesel, oil or hydro carbons: Workshop The discretization of the sub-catchments endeavours to isolate and quantify these flows. The following detail descriptions define the catchments and Table 3 provides flows and volumes for the sub-catchments. Although labelled as a major catchment, the pit area has also been included as a sub-catchment due to the classification of its runoff. 5.5.1 Office area The office area is situated to the north west of the pit mining area and is estimated to cover an area of 2.9 hectare. Runoff from this area is from roofs, parking areas and gardens. The runoff is clean water and the drainage system will be channelled into the cut-off drains for drainage area E, Trench 1. 5.5.2 ROM pad and weighbridge and haul roads The ROM pad and weighbridge cover an estimated area of 0.8 ha while the haul road length is 8 estimated at about 1000m by 40 m wide (including 2 way traffic and safety berms). The runoff from these areas are classified as affected water and needs to be contained in pollution control dams with a sediment settling facility before the water enter the dam. The water can be left to evaporate or can be used on the mining area such as dust control and in wash bays. 5.5.3 Opencast pit area The pit is estimated to cover an area starting from about 50 ha to about 110 ha. The storm water should be managed as part of the mining operational plan. It is classified as affected water. If it is collected in a sump and pumped out it can be combined with the ROM pad and weighbridge water in a pollution control dam. 5.5.4 Waste dump The waste dump is estimated to start at about 6 ha. The final size of the waste dump will depend on the mining plan and the runoff will have to be controlled as it grows. The position of the waste dump dictates that it will require a separate pollution control dam or dams. Settling ponds is required before the water enters the dam to prevent silting up. The runoff is classified as affected water and can be treated as for the ROM pad etc. water. 5.5.5 Workshop The workshop area is estimated to cover an area of about 1 ha. The water from this area, that include the re-fuelling and lubricating areas and wash bays, are classified as dirty water. The workshop runoff must be collected in a closed system and cycled through an oil, diesel, hydrocarbon etc. removal facility. After the oil etc. has been removed, the remaining water can be decanted into the affected water system for the same treatment as the ROM pad/weighbridge water. 5.5.6 Sub-catchments: Peak flows and volumes Table 3 provides a summary of the peak flows and run-off volumes for all the sub-catchments. Volumes have been calculated by use of the SCS peak flow for the 24 hour storm period and the intensities presented in Table 1. The results was calculate by using the TR 55 and TR 20 SCS models from the NRCS. The results are tabulated in Annexure E. Table 3: Sub-Catchments, Peak Flows and Volumes 2 Yr 10 Yr 50 Yr 100 Yr Peak Runoff (m³/s) Runoff Vol (m3) Peak Runoff (m³/s) Runoff Vol (m3) Peak Runoff (m³/s) Runoff Vol (m3) Peak Runoff (m³/s) Runoff Vol (m3) Office 0.37 573 0.63 1 996 1.01 4 780 1.25 6 300 ROM etc. 0.17 14 0.23 86 0.47 203 0.58 255 Pit initial 14.33 156 142 25.48 307 746 39.20 474 523 48.06 555 621 Pit final 26.75 305 530 36.28 602 650 72.49 924 392 88.55 - Waste dump 1.39 1 364 2.40 6 658 3.85 14 704 4.74 19 730 Workshop 0.21 43 0.37 191 0.59 348 0.72 430 Node 5.6 HYDROLOGICAL MODELLING Full data files and analysis files are provided in the appendices to this report as Annexure C. A summary table of the main peak flows and run-off volumes are included in the body of the report. 9 5.7 PREVIOUS WORK AND INFORMATION Three reports have been made available for review of previous work namely:  Water use license application Op Goeden Hoop Colliery, May 2009, prepared by Digby Wells and Associates.  Report on investigation to determine the potential for acid mine drainage at the proposed Op Goeden Hoop Colliery, September 2007, prepared by Digby Wells and Associates.  Wetland ecological assessment as part of the environmental assessment and authorisation process for a proposed colliery on portion 5 of the farm Op Goedenhoop 205 JIS, Hendrina, Mpumalanga, January 2014, prepared by Scientific Aquatic Services CC. The reports have been reviewed and only the Water use license mentions runoff figures for the total catchment as being 83 m3/s at the upper and 86 m3/s at the lower reaches. No indication of the return period is given. The reports deal mainly with issues that although important for various other important areas of the total water use and management, fall outside the scope of the SWMP. The Water use licence does contain recommendations on storm water and effluent management that can be incorporated in the SWMP as applicable. 6 REQUIRED INFRASTRUCTURE AND CONCEPTUAL DESIGN Based on the hydrological analysis performed and documented in Section 5, the conceptual infrastructure required for managing the storm runoff is presented in the following sections. Some indications of size and dimensions will be presented where it is deemed appropriate as an indication of the type of infrastructure required but mostly the design of the infrastructure should be conducted during the pre-feasibility and feasibility phases. Where conceptual sizes are supplied it will be based on the 1:50 years return flows. 6.1 CATCHMENT D. The runoff from this catchment needs to be diverted around the open pit. The channel (Trench 2) should run from about the position of the current dam on the site, along the contours to the south eastern boundary and then continue along the boundary until it meets up with the channel of catchment area C. The excavated material from the channel should be used to construct a berm on the pit side of the channel so that runoffs from larger storm events cannot overtop the channel on that side and drain into the pit area. A natural grassed channel of trapezoidal shape with 1:2 side slopes is recommended. The design flow is 30.77 m3/s. The channel should be 5 m wide and about 2 m deep (including freeboard). The length is approximate 2 300 m with a slope of 1.5%. Detail of the design is presented in Annexure F. The design appears to have super critical flow so energy dissipaters should be incorporated in the detail design stages. 6.2 CATCHMENT C The runoff from this catchment also needs to be diverted around the open pit. The channel (Trench 3) should run from about the link with the diversion from D, along the contours of the south eastern boundary and link up with the main channel of catchment area D. The excavated material from the channel should be used to construct a berm on the pit side of the channel so that runoffs from larger storm events cannot overtop the channel on that side and drain into the pit area. 10 A natural grassed channel of trapezoidal shape with 1:2 side slopes is recommended. The design flow is 79.92 m3/s. The channel should be 15 m wide and about 2 m deep (including freeboard). The length is approximate 1 200 m with a slope of 1.0%. Detail of the design is presented in Annexure F. The design appears to have super critical flow so energy dissipaters should be incorporated in the detail design stages. 6.3 CATCHMENT E The runoff from this catchment needs to be diverted around the open pit. The channel (Trench 1) should run from about the high point at right angles to the current dam on the north western side of the site, along the pit to the north eastern boundary and then continue until it meets up with the natural channel of the waterway at Point A. The excavated material from the channel should be used to construct a berm on the pit side of the channel so that runoffs from larger storm events cannot overtop the channel on that side and drain into the pit area. A natural grassed channel of trapezoidal shape with 1:2 side slopes is recommended. The channel should start with dimensions to meet a design flow of 2 m3/s and be sized progressively bigger until the final design flow of 10.78 m3/s can be accommodated. The channel should about 2 m wide and 1 m deep and finally be 5 m wide and about 1 m deep (all depths including freeboard). The length is approximate 3 200 m with a slope of 2.0%. Detail of the design is presented in Annexure F. The design appears to have super critical flow so energy dissipaters should be incorporated in the detail design stages. 6.4 OFFICE AREA The runoff from the office area should be collected in open V drains and discharged into catchment E in such a way as not to cause erosion. Detail design and layout should be conducted during the follow up phases. A typical size for the drains would be 1:2 side slopes and a depth of 300 to 400 mm and a slope of 1%. 6.5 ROM PAD, WEIGH BRIDGE AND HAUL ROADS The runoff from the Weigh Bridge and ROM pad must be conveyed in lined channels to the pollution control dam. A possible position for the dam is shown on Annexure B. The channel should be a lined V drain capable of conveying 0.5 m3/s. The drain should have side slopes of 1:2, a length of about 200 m and a depth of about 400 mm. Runoff from the haul road should be captured in side channels and conveyed to the ROM pad, work shop, waste dump or back into the pit as is convenient. The design forms part of the next phases. 6.6 WASTE DUMP Channels to intercept the runoff from the waste dump must be constructed on all sides of the dump. The channels can drain to a separate pollution control dam on the north eastern corner of the waste dump. Channels to be lined and sized to convey a flow of about 3 m3/s. It is estimated that about 1 500 m of channels with slopes around 1% will be needed in the initial phase. The channel should be of trapezoidal shape with side slopes of 1:2, a bottom width of 2 m and a depth of 0.8 m including freeboard. The initial pollution control dam (PCD) should be able to contain a minimum of 14 000 m3 of water and be lined. A silt settling pond is required before the dam and must consist of 2 chambers so that one can always be cleaned while the other is in operation. A possible dam size would be 50 m square and 6 m deep. If smaller dams is desired, 2 or 3 PCDs can be constructed. 11 6.7 WORKSHOP AREA The runoff from the separate areas of the workshop area such as refuelling area, wash bay, slab around the workshop and the workshop itself should be contained in the area itself and conveyed to a sump with oil separator. From the sumps, after oil separation, the water can be pumped to the pollution control dam for the ROM pad. The sizing of the channels and runoff conveyance structures, sumps etc. is a function of the total water usage of the area and is beyond the scope of this report. 6.8 OPENCAST PIT STORM RUNOFF The management of the pit runoff is part of the mining operation plan. For a 1 in 50 year recurrence period the volume of water can fluctuate between 500 000 and 950 000 m3 depending on the size of the pit and the particular mining plan being followed at any stage. The size of sump provided will depend on the mining philosophy which will also determine the tempo of pumping, size of pumps, size of pipes and time period to remove a specified volume of water. 6.9 POLLUTION CONTROL DAM FOR ROM PAD AND ASSOCIATED AREAS The size of this dam is unknown as it will depend on the mine operating philosophy regarding the inpit storm runoff. The minimum size should be able to handle about 5 000 m3. Two settling ponds before the entrance to the dam will be required with the same operating philosophy as for the waste dump dam. 7 FEASIBILITY OF REQUIRED INFRASTRUCTURE The storm water problem areas have been identified and compliant solutions presented in section 6. The compliant solutions to the problems is based on effective use of funds, limited land availability, consideration of practical solutions and cognisance of the life of mine. The different storm water problem areas were assessed in terms of the 3 objectives of this Storm Water Management Plan namely:    Isolate clean and dirty water Isolate run-off contaminated with suspended solids and treat appropriately “affected water” Isolate dirty water, contaminated with oil, grease etc. treat and re-use The identification of problems and solutions thereto is based on the current understanding of the scope and layout of the proposed Opgoedenhoop mine. 7.1 ISOLATE CLEAN WATER AREAS The Hydrological Assessment has defined three catchments that drain the mine property. These catchments and the majority of the land for all the catchments can be classified as clean water areas. The run-off from these areas drains via local non-perennial streams and valleys directly over the property and finally to the Komati River. Some of the clean water discharges onto adjacent properties without causing any problems. Catchments C, D and E fall into the clean water category and thus comply with the requirements of GN704 and the Water Act. The isolation and diversion of the water from these catchments have been discussed in section 6. 12 7.2 ISOLATE AND MANAGE “AFFECTED” WATER 7.2.1 Rom pad. Weigh bridge and haul roads Isolate and contain the 1:50 year run-off volume from these “affected” areas, remove suspended solids and re-use the water for dust suppression or evaporate as discussed in section 6. 7.2.2 Waste Dumps If storm water from the waste dump areas of the mine is not controlled it will flow into the adjacent clean water area downstream of the dumps. Silt from these “affected” water areas will then be deposited on the slopes below the dumps causing otherwise clean areas to fall within the “affected” water category. Portions of catchment E are thus affected. As recommended in section 6, provide cut-off berms along the base of the waste dump together with pollution control dams with settling pond facilities and re-use the water for dust suppression or evaporate. 7.2.3 Opencast pit area. Large volumes of storm water accumulate in the mining pit after extreme storm events and would affect the mining activities if not managed properly. Storm water deposited in the pit needs to be managed and re-used according to the mining operational plan. Excess water is to be contained, re-used as appropriate, evaporated or treated and released. 7.3 ISOLATE DIRTY WATER AND RE-USE 7.3.1 Workshop Area Dirty water containing oil and hydro carbons emanate mainly from the workshop area and its related vehicle washing and refuelling facilities. Dirty water from these areas should be contained as close as possible to the source and treated in settling ponds with attached oil separators. Storm water from surrounding areas should not be allowed to impact on these facilities. After treatment the water can be combined with water from the affected areas and used as appropriately. 7.4 FEASIBILITY OF THE SOLUTIONS The infrastructure required to deal with storm water management are presented in section 6 and is based on general accepted practices in the mining industry and complies with the requirements of GN 704 and the Best Practise Guides issued by Department of Water Affairs. 8 CONCEPTUAL DESIGN AND REVIEW The objectives applicable to developing a new mine have been stated in paragraph 4 and the feasibility of their application to the proposed Opgoedenhoop mine have been assessed in section 7. The conceptual design of storm water infrastructure should be based on the following principles:  Make maximum use of existing natural drainage systems.  Maintain existing natural drainage systems to optimise flow.  Maintain existing outlets to the local water resources. 13      9 Isolate dirty water areas and design them to have as small a footprint as possible. Prevent storm water in-flow from adjacent areas where practical possible. Maintain and separate the systems to reduce pollution where practically possible. Re-use water for process or dust suppression where practically possible. Monitor and apply silt control measures where required. CONCEPTUAL OPERATIONAL, MANAGEMENT AND MONITORING SYSTEMS AND RESPONSIBILITIES This section of the document discusses and provides conceptual proposals for operating, managing and monitoring the proposed Opgoedenhoop project. The detail design of the operational, management and monitoring systems should conform to the mining plan and is beyond the scope of this document. The following sections have been extracted from the water use licence application prepared by Digby Wells and Associates in May 2009 and as such remain their intellectual property. Water will be used in all sections of Op Goeden Hoop Colliery. The following have been identified as activities that may impact on the water resources at the above motioned colliery: • Opencast areas; • Dirty storm water runoff from the mine and administration areas; • The pollution control dam; • Coal handling facility. A Crisis and Emergency Management Code of Practice will be set in place which will be applied to Op Goeden Hoop Colliery ones mining commence. Possible environmental emergency situations identified for the various operational areas of the project area include: • Failure of water storage facilities and pipelines; • Excessive leakages in main clean water pipeline; • Discharge of dirty water from failure or overtopping of pollution control dam. The following sections describe the implementation of various water management methods and measures including water pollution prevention, storm water, groundwater, the use of potable and mine water and the disposal of effluent. 9.1 WATER POLLUTION PREVENTION METHODS 9.1.1 Storage & handling of waste Sewage handling during construction will be by means of portable chemical latrines, until such time as more permanent facilities have been constructed. Chemical latrines will be serviced by an outside contractor in accordance with local by-laws. Septic tanks will be used during the operational phase and will be monitored and maintained in order to ensure that it does not by any means discharge contaminated water that may affect the water resources. Domestic and hazardous waste originating from temporary and permanent offices and stores will go through a waste handling and separation system and will be disposed of in appropriately authorised landfill facilities to minimise the risk of water pollution. A waste management system will be implemented which will make sure that domestic and hazardous 14 waste, including sewage, generated during decommissioning and closure is disposed of in a manner that will not cause water contamination. 9.1.2 Storage and handling of hydrocarbons & explosives A hydrocarbon management system will be introduced. Chemicals and hydrocarbons capable of causing water pollution shall be transported, loaded and unloaded, and stored in bunded facilities, which will be constructed in accordance with applicable legislation and SANS codes. This will minimise the potential of accidental spillage of hydrocarbons and subsequent contamination of water resources. Accidental hydrocarbon spillages will be contained and remediated in situ using appropriate microbial technologies, to prevent leaching into the water systems. An emergency spill response plan will be developed and shall form part of the environmental awareness training. Spillages of ammonium nitrate based explosives during charging of holes, misfires and incomplete combustion of explosives will be monitored and managed to minimise the potential of water pollution. 9.1.3  Opencast pit area Groundwater within the pit areas shall be pumped out immediately to the pollution control dam.  To reduce the effects of acid mine drainage (AMD) due to surface run-off from spoils, diversion trenches will be maintained around spoils and all run-off from spoil piles will be directed into dirty water systems.  The occurrence of AMD as a result of the opencast mining cannot be avoided altogether. The following methods will be utilised to minimise the severity of AMD: o When replacing spoils and overburden, as part of continuous rehabilitation activities, a level of compaction will be achieved through the movement of vehicles on replaced material. This serves the purpose of reducing the amount of air trapped in fractures within the spoils, which reduces the oxidation potential of the material. o When designing and mining opencast areas, the final decant point will, as far as possible, be kept above the level of spoil replacement. This is done in an effort to ensure that replaced spoils are completely flooded when groundwater levels recover to reduce the contact of spoils with air, reducing exposure to oxygen. This minimises the oxidation of pyritic material and limits the formation of AMD. o During rehabilitation, the contouring of the surface will be such so as to avoid ponding of water on rehabilitated surface to reduce the infiltration of water into areas where spoils have been replaced and which are prone to AMD.  Create free draining surface conditions as far as possible.  If and where there is the potential for AMD contaminated pit water to decant to surface water features, appropriate freeboard will be maintained by means of pumping arrangements.  Water decanting from the opencast workings where all spoils cannot be flooded, will be collected and treated prior to release, unless monitoring indicates that the water quality meets the water management objectives for the catchments. If such water does not meet quality objectives, it may also be pumped back to underground workings in order to make it 15 part of the inter mine flow.  A dense vegetative cover will be established and maintained on rehabilitated areas to assist with the evapotranspiration of rain water in an effort to reduce the infiltration of water into rehabilitated spoils. 9.1.4 Pollution control dam The pollution control dams will be operated as storage and evaporation dams, with some of the water used for dust suppression. The dam will be operated to ensure that the storage capacity is not exceeded in normal rainfall events. 9.1.5 Transporting coal Trucks transporting coal on access roads in the area and along the planned access road to the crushing and washing plants will be covered. This will reduce any spillages of coal from access trucks, which may affect surface water quality 9.2 GROUNDWATER MANAGEMENT      9.3 MINIMISATION AND REUSE OF MINE WATER     9.4 The removal of vegetation during topsoil and overburden stripping will be minimised as far as possible to increase the recharge of rain water to aquifers. The dewatering of aquifers during the operation of opencast is implicit in the types of mining involved and cannot be prevented. Where such dewatering causes the drying up of boreholes used for domestic, stock-watering and other uses, alternative supplies of water will be provided on a case-by-case basis Pollution control facilities will be maintained until closure and decanting from pits and underground workings will be prevented as far as possible. After mining has ceased underground workings will be flooded and water in the mine will exclude oxygen from the underground workings and the pH of the mine water will be neutral after the flooding phase. Most heavy metals are insoluble at a neutral pH. Manganese and iron are the only ones that would be present at levels higher than the permissible limits, considering the South African Drinking Water Standards. Groundwater will continue to be monitored for a minimum of five years after closure and data will be submitted to the authorities. The amount of water used for dust suppression will be minimised by the use of road surface sealants. Groundwater will be used if additional water is required for the Op Goeden Hoop mining operations. Only potable water will be used for the office buildings and change house. However, if any additional water be required authorities will be informed accordingly. The potable water system is primarily for domestic use. Domestic water after use can be classified as industrial water and uses for various other purposes or pump to the pollution control dam or septic tank system. However, the most fundamental principal will be to prevent utilising freshwater in the mining processes and to increase the amount of water recycled. Other water use minimisation strategies that will be implemented at Op Goeden Hoop colliery will include launching of an awareness campaign and fixing of leaking pipes, taps, etc. EFFLUENT TREATMENT METHODS Contaminated excess mine water arising from the opencast pit will be handled in the pollution control dam. 16 9.5 PROPOSED DISPOSAL OF EFFLUENT Polluted water resulting from the mining operation at Op Goeden Hoop (site runoff, undergroundwater, industrial water and opencast water) will also be stored in a pollution control dam and will be used for dust suppression on access roads and other denuded areas. This water will be kept in the pollution control dam where it will evaporate, a closed dirty water system, unless the storage capacity of the dam is exceeded and the volume necessitates the discharge of effluent into the surface water body. This, however, might only occur in rainfall events outside of the norm and will be treated as an emergency incident. The pollution control dam is not expected to discharge into the environment, unless unusually high rainfall is experienced. Water quality in the pollution control dams will have slightly higher sulphates and heavy metal contents than the recommended DWAF guidelines. 10 STORM WATER MANAGEMENT PLAN This Storm Water Management Plan describes the infrastructure to be established and the management of storm water required to effectively deal with the storm water problems at the proposed Opgoedenhoop mine while taking into account:  The terrain and topography of the mine  What is practical possible The following general management principles are presented:       The removal of vegetation during the construction phase will be kept to a minimum, which will decrease the erodibility of soils thus minimising the effects of silt loading of surface water running over exposed soil. The establishment of dirty water areas will be planned and monitored in order to minimise the effects of reducing the catchment size so that surface water will be able to flow into surface streams. Dirty water areas such as stores and storage facilities will be constructed to have the smallest possible footprint, thus reducing the reduction in catchment yield. Storm water diversion and pollution control facilities will be constructed to divert the flow of water and ensure the separation of clean and dirty water on site. All such facilities will be constructed in such a manner as to handle a 1:50 year storm event. Where a concentration of water occurs during rain event as a result of the existence/operation of hard paved areas, energy diffusers will be installed to reduce water velocity and to mitigate the effects of increased surface water volumes in such areas. Profiling the final topography by means of the establishment of drainage ridges or canals in a manner which will ensure that areas which use to drain to the streams continue too. An effort will be made to effect drainage into the tributaries as high up their respective courses as is possible to attempt to maintain wetland integrity. 17 10.1 ISOLATION OF CLEAN WATER AREAS 10.1.1 Isolation of clean water from Catchment D Problem: The major portion of catchment D lies upstream of the opencast areas and therefore this clean water flows into the pit where it will be contaminated and interfere with the mining operation. Proposed Plan  Construct a diversion channel around the pit area as described in section 6.1.  Isolate the shafts and adit of the underground mining operation with berms around them to prevent the ingress of storm water. 10.1.2 Isolation of clean water from Catchment C Problem: The existing channel for catchment C joins the main water course in the area where the opencast mining will take place and must be isolated. Proposed plan:  Design and construct a diversion channel around the pit area as described in section 6.2 to also accommodate the extra flow from catchment D. 10.1.3 Isolation of clean water from Catchment E Problem: Catchment E drains towards the main water course in the area where the opencast mining will take place and must be isolated. Proposed plan:  Design and construct a diversion channel around the pit area as described in section 6.3. 10.1.4 Handling of clean water from the office area Problem: The office area will increase runoff from the area due to the increase in impervious areas and will drain towards the pit area. Proposed plan:  Design and construct collection drains as described in section 6.4 and direct into the channel for catchment E. 10.2 ISOLATE AND TREAT “AFFECTED” WATER 10.2.1 Silt laden water from the weigh bridge, ROM pad and haul roads Problem: Silt will be washed down from the material spillages during the handling of the coal and must be prevented from contaminating clean water Proposed plan:  Design and construct lined channels and convey the runoff to the pollution control dam as described in section 6.5.  Implement operational procedures to minimise the material spillage. 10.2.2 Waste Dumps Problem: Storm water from the waste dump area of the mine flows into the adjacent clean water areas downstream of the dumps. Silt from these “affected” water areas is then deposited on the slopes below the dumps causing otherwise clean areas to fall within the “affected” water category. Portions of Catchments E and A are thus affected. 18 Proposed plan:  Construct cut –off berms around the waste dump as presented in section 6.6.  Construct a pollution control dam(s) with silt traps as detailed in section 6.6.  Provide regular clearance and maintenance of the facility. 10.2.3 Storm water runoff and flooding in the opencast pit Problem: Runoff from storm water falling directly on the mine pit cannot be diverted out of the pit and interfere with mining operations. The volumes can be substantial. Proposed plan:  Compile operational procedures for the mining on the strategy and philosophy of dealing with the inflows.  Provide a sump and pumping equipment to deal with the inflow as described in section 6.8. 10.2.4 Pollution control dam for the ROM pad. Pit and workshop areas Problem: The affected water from these areas must be treated in a pollution control dam with silt traps but the size of the dam cannot be determined until the mining operation procedure for dealing with inflows is known. Proposed plan:  Compile operations procedures for the mine to be able to size the dam and facilities.  Maintenance and effective management of the pollution control structures will deal with the problem effectively. 10.3 ISOLATE DIRTY WATER AND RE-USE 10.3.1 Workshop Areas Problem: Dirty water containing oil and hydro carbons emanate from the workshop areas and the related vehicle washing and refuelling facilities. Proposed plan:  Construct oil separation facilities and sumps as described in section 6.7.  Prepare operational procedures to manage oil pollution and prevention.  After oil separation decant the water to the pollution control dam as described in section 6.7.  Perform regular cleaning and maintenance activities. 10.4 MAINTENANCE AND OPERATING PROCEDURES 10.4.1 Storm water Drainage System The storm water systems on the mine will need regular maintenance to remain fully operational. This requires that a visual inspection of the systems be carried out at least twice a year, once at the beginning of the rainy season early in September, then early in the new year to confirm that it is still working correctly. The visual inspection must include:  Surface water channels  Covered drains  Catch pits and Manholes  Inlets and outlets of culverts  Drainage pipes Any blockages caused by siltation or debris needs to be cleared, especially in the larger open channels, if growth of grass or reeds has taken hold in the deposited silt which can consolidate the blockage. 19 Minor siltation can usually be left as the first good rains will flush the system out. The follow up inspection will verify this. 10.4.2 Settling Ponds The level of silt deposit in the settling ponds needs to be monitored on a regular basis. The de-sludging or removal of the silt must be part of the operational procedure of the plant. It must be taken to a waste disposal area where it can dry out for possible later re-use. 10.4.3 Return Water Sumps Although not directly related to storm water the operation of the pumps and return water sumps also need to be monitored on a regular basis to keep the system running. Too much silt in the settling ponds limits the through time of the return water and thus also the effectiveness of the settling process. 10.4.4 Waste Dump Run-Off and Siltation As detailed in paragraph 6.4 silt deposition from the waste dump run-off can be a major concern on the mine. The maintenance and monitoring of the storm water berms as constructed is an on-going task. The level of silt in the dams needs to be checked at regular intervals especially after large storms to make sure they are carrying out their function of trapping the silt and that they still have some capacity available. If capacity becomes limited, plans must be made to remove the silt. The overflows need to be checked for stability and scour and also for evidence of silt passing through the dam, which will show the effectiveness of the operation. An assessment also needs to be made from time to time on the general dump run-off and siltation occurring and whether new storm water berms need to be provided to control the situation. This relates also to the dump stability, the amount of scour occurring on the dump face and whether the dump is still active or consolidating. If the dump is not growing then siltation will become less and cleaner run-off will result requiring less control and management. 10.4.5 Pits The operating procedure for controlling storm water within the pit and the maintenance thereof is very much related to the mining operation itself. The position of the sump to collect the storm water will change as the pit excavation progresses. Pumping options should be in place to manage water within the pit and maintain continuity of the mining operation. 10.5 MONITORING PROGRAMME Monitoring of the environmental impact caused by the mining operation should be in accordance with the Water Use License requirements. A water sampling procedure should be compiled. Both surface water and ground water are to be monitored on a quarterly basis. The monitoring positions is to be decided and the work carried out by the office of the Environmental Manager. External laboratories should be used to analyse water samples and they are to be measured against S.A water quality guidelines. The results will be included in the annual DWA report. Water consumption is also monitored and used to compile the water balance. 10.6 MANAGEMENT STRUCTURE A functional management structure need to be developed for the mine. Overall responsibility rests with the General Manager and then the departmental managers 20 11 MINE CLOSURE In terms of the Storm water Management Plan the cessation of operations should also bring an end to the generation of dirty water or the risk of any pollution. When waste dump deposition stops, siltation should get less and cleaner run-off from the dumps should ensue. Monitoring of this run-off should show whether further monitoring after closure would be required. 12 RELEVANT DOCUMENTATION The following reference documents have been used:  National Water Act, 1998 (Act 36 of 1998)  DWAF Regulation GN704  DWAF Operational Guideline No.M6.1 – Regulations on use of water for mining and related activities – May 2000  DWAF Best Practice Guidelines o o o A5 – Water Management for Surface Mines G1 – Storm Water Management H3 – Water Re-Use and Reclamation 13 RECOMMENDATIONS Maintain new constructed storm water facilities. (Housekeeping of the settling ponds, oil separators and process water systems.) Implement the proposed solutions. Monitoring of the surface and underground water form an integral part of storm water management. A comprehensive storm water design to be undertaken with the detail design of the mine infrastructure. The storm water management plan to be reviewed when the mine closure plan is implemented. _______________________ S PRINSLOO Reviewer 20 September 2014 L AUCAMP Compiler 20 September 2014 21 14 ANNEXURE A – WORKPLAN FOR OPGOEDENHOOP SWMP 1. Prepare base plans and gather existing information  Review drawings prepared for previous WULA applications and Storm Water Management Plans  Review WULA application prepared by Digby Wells and Associates in 2009 and extract information that has not been changed for further use. Review the Wetland Assessment, Acid Based activity and Ground water monitoring reports prepared by Scientific Aquatic Services and Digby Wells and Associates respectively for Information and recommendations that can be utilised going forward. Review the Infrastructure Block Plan according to the latest ‘Google’ aerial photography    Review drawings created for the reports mentioned above and obtain permission for use of copy right/intellectual property in new reports  Obtain and collate information regarding current EIA, WULA and water balance investigations conducted by other parties and integrate Deliverable:  Set of existing drawings and information to help define objectives of the Conceptual Storm Water Management Plan and to include in the Storm Water Management Plan Report 2. Data and Information evaluation     Confirm clean and dirty water areas on the mine using the latest info and make allowance for changes in the following phases Review proposed designs of storm water infrastructure and update with any improvements added since the previous reports as mentioned above. Confirm delineation of sub-catchments taking into account changes that have taken place on the mine design and conceptual layouts. Incorporate information into reports and drawings where changes have taken place. Deliverable:  3. Inputs into drawings and reports by other consultants showing existing and proposed infrastructure and catchment delineation to be used for Technical situation analysis and evaluation. Conceptual Design and Verification of Data    Liaise with the Mining Consultant and through them with the other “water” and EIA consultants to verify all information compiled in sections 1 and 2 above. Prepare high level reviews of climate, topography, land use and proposed alternative uses of different areas as proposed in previous studies and current studies by other consultants Prepare conceptual design standards for run-off, demarcation of clean and dirty areas, sizes of pollution control dams, 22 canals and cut-off structures, oil and other pollutant control measures and management philosophies. Deliverables:  4. Design standards to be used for conceptual design and management strategies for further investigations Define infrastructure requirements  Define physical structures that is required to manage the storm water run-off  Define the control and pollution management requirements. Deliverables:  5. Guidelines for conceptual design and inputs to the follow-up more detail design studies Undertake Conceptual Design   Measure areas, lengths and slopes of the main catchments for use in Hydrological Analysis software to obtain peak runoffs. Use various Method to calculate flows for the main catchments of the mining land.  Calculate indicative sizes for diversion canals around the mining area, cut off berms and canals.  Indicate sizing of pollution control dams and control measures based on the available information Deliverables:  6. Input variables to the conceptual Storm Water Management Plan Define conceptual operational, management, monitoring procedures and systems  Define minimum operational requirements and systems.  Provide inputs for design of monitoring procedures and systems Deliverable:  7. Minimum management, operational and monitoring requirements for a conceptual Storm Water management Plan. Design of Storm water System  Collate all drawings, other information and calculations to prepare a basic storm water concept for the mine which will address the following issues: o Delineation of clean and dirty water areas 23 o Provide input on flow routing of clean water to bypass mining operations and plant and workshop infrastructure to natural water courses o Assess methods to deal with dirty water areas in the plant and o Propose high level infrastructure changes required by the conceptual storm water design o Provide input on the design and size of drainage structures such as settling ponds and pollution control dams etc. Deliverable:  All conceptual info, calculations, designs and systems that go to make up the conceptual Storm Water Management Plan. 24 15 ANNEXURE B – SITE PLAN 25 16 ANNEXURE C – CALCULATION RESULTS AND DATA SETS 16.1 CATCHMENT A 26 16.2 CATCHMENT B 27 16.3 CATCHMENT C 28 29 30 16.4 CATCHMENT D 31 32 33 16.5 CATCHMENT E 34 35 36 16.6 CATCHMENT F – PIT AREA INITIAL AND FINAL 37 38 16.7 CATCHMENT OFFICE AREA 39 16.8 CATCHMENT ROM PAD, WEIGH BRIDGE AND HAUL ROAD AREAS 40 16.9 CATCHMENT WASTE DUMP AREA 41 16.10 CATCHMENT WORKSHOP AREA 42 17 ANNEXURE D – GENERAL MAPS SHOWING RUNOFF AND CATCHMENT AREAS 43 18 ANNEXURE E – VOLUME CALCULATIONS FOR THE SUB-CATCHMENTS Calculated from SCS standard unit hydrograph with TR 55 and TR 20 Opgoedenhoop Volumes for the sub catchments 1. Office return period yr Peak flow Time of hydrograph Time of hydrograph hr seconds Volume V m3 2. ROM pad, weighbridge return period yr Peak flow Time of hydrograph hr Time of hydrograph seconds Volume V m3 2 0.36 10 0.57 50 0.77 100 0.87 0.884 1.945 3.449 4.023 3182.4 7002 12416.4 14482.8 572.832 1995.57 - - 2 0.06 10 0.12 50 0.17 100 0.2 0.133 0.398 0.663 0.708 478.8 1432.8 2386.8 2548.8 14.364 85.968 202.878 254.88 2 0.49 10 0.94 50 1.4 100 1.61 1.547 3.935 5.835 6.808 5569.2 14166 21006 24508.8 - 6658.02 14704.2 - 2 0.09 10 0.16 50 0.23 100 0.27 0.265 0.663 0.84 0.884 3. Waste dump return period yr Peak flow Time of hydrograph Time of hydrograph hr seconds Volume V m3 4. Workshop return period yr Peak flow Time of hydrograph hr 44 Time of hydrograph seconds Volume V m3 954 2386.8 3024 3182.4 42.93 190.944 347.76 429.624 2 5.59 10 9.84 50 14.03 - 15.518 17.375 18.79 19.365 55864.8 62550 67644 69714 - 307746 - - 2 10.49 10 18.47 50 26.34 - 16.181 18.127 19.497 19.939 58251.6 65257.2 70189.2 71780.4 - - - - - - - - 5. Pit initial return period yr Peak flow Time of hydrograph Time of hydrograph hr seconds Volume V m3 6. Pit final return period yr Peak flow Time of hydrograph Time of hydrograph hr seconds Volume V m3 Summary Volumes m3 return period yr 1. Office 2. ROM pad, weighbridge 3. Waste dump 4. Workshop 5. Pit initial 6. Pit final 45 19 ANNEXURE F – CONCEPTUAL DESIGN CALCULATIONS FOR SELECTED AREAS Normal Flow Analysis - Trapezoidal Channel Opgoedenhoop Project: Project: Channel ID: Area D diversion channel Channel ID: Design Information (Input) Channel Invert Slope So = 0.0150 Manning's n n= 0.0260 Bottom Width 16.4042 Right Side Slope B= Z1 = Z2 = Freeboard Height F= 3.28 Design Water Depth Y= 3.94 Left Side Slope ft/ft 0.02 m/m 0.03 ft 5.00 m 2.0000 ft/ft 2.00 m/m 2.0000 ft/ft 2.00 m/m ft 1.00 m ft 1.20 m Normal Flow Condition (Calculated) Q = Fr = Discharge Froude Number - Flow Velocity V= 13.98 Flow Area A= Top Width Wetted Perimeter Hydraulic Radius Hydraulic Depth Specific Energy Centroid of Flow Area Specific Force 46 cfs 37.82 m3/s 1.43 4.26 m/s 95.58 fps sq ft 8.88 m2 T= 32.15 ft 9.80 m P= R = D = Es = Yo = Fs = 34.01 ft 10.37 m 2.81 ft 0.86 m 2.97 ft 0.91 m 6.97 ft 2.12 m 1.75 ft 0.53 m 46.67 kip 207.62 kN Normal Flow Analysis - Trapezoidal Channel Opgoedenhoop Project: Project: Channel ID: Area C diversion channel Channel ID: Design Information (Input) Channel Invert Slope So = 0.0100 Manning's n n= 0.0260 Bottom Width 49.2126 Right Side Slope B= Z1 = Z2 = Freeboard Height F= 3.28 Design Water Depth Y= 3.94 Left Side Slope ft/ft 0.01 m/m 0.03 ft 15.00 m 2.0000 ft/ft 2.00 m/m 2.0000 ft/ft 2.00 m/m ft 1.00 m ft 1.20 m Normal Flow Condition (Calculated) Q = Fr = Discharge Froude Number - Flow Velocity V= 12.87 Flow Area A= 224.75 Top Width T= Wetted Perimeter P= R = D = Es = Yo = Fs = Hydraulic Radius Hydraulic Depth Specific Energy Centroid of Flow Area Specific Force 47 cfs 81.86 m3/s 1.22 fps sq ft 3.92 m/s 20.88 m2 64.96 ft 19.80 m 66.82 ft 20.37 m 3.36 ft 1.03 m 3.46 ft 1.05 m 6.51 ft 1.98 m 1.88 ft 0.57 m 98.48 kip 438.05 kN Normal Flow Analysis - Trapezoidal Channel Opgoedenhoop Project: Project: Channel ID: Area E diversion channel start Channel ID: Design Information (Input) Channel Invert Slope So = 0.0200 Manning's n n= 0.0260 Bottom Width 6.5617 ft 2.00 m 2.0000 ft/ft 2.00 m/m Right Side Slope B= Z1 = Z2 = 2.0000 ft/ft 2.00 m/m Freeboard Height F= 1.64 ft 0.50 m Design Water Depth Y= 1.64 ft 0.50 m 144.61 cfs 4.09 m3/s Froude Number Q= Fr = Flow Velocity V= 8.96 Flow Area A= Top Width Left Side Slope ft/ft 0.02 m/m 0.03 Normal Flow Condition (Calculated) Discharge 1.42 1.42 2.73 m/s 16.15 fps sq ft 1.50 m2 T= 13.12 ft 4.00 m Wetted Perimeter P= 13.90 ft 4.24 m Hydraulic Radius R= 1.16 ft 0.35 m Hydraulic Depth D= Es = Yo = Fs = 1.23 ft 0.38 m 2.89 ft 0.88 m 0.73 ft 0.22 m 3.25 kip 14.44 kN Specific Energy Centroid of Flow Area Specific Force 48 Normal Flow Analysis - Trapezoidal Channel Opgoedenhoop Project: Project: Channel ID: Area E diversion channel end Channel ID: Design Information (Input) Channel Invert Slope So = 0.0200 Manning's n n= 0.0260 Bottom Width 16.4042 Right Side Slope B= Z1 = Z2 = Freeboard Height F= 1.64 Design Water Depth Y= 1.97 441.80 Froude Number Q= Fr = Flow Velocity V= 11.03 Flow Area A= Top Width Left Side Slope ft/ft 0.02 m/m 0.03 ft 5.00 m 2.0000 ft/ft 2.00 m/m 2.0000 ft/ft 2.00 m/m ft 0.50 m ft 0.60 m Normal Flow Condition (Calculated) Discharge cfs 1.51 12.51 m3/s 1.51 3.36 m/s 40.04 fps sq ft 3.72 m2 T= 24.28 ft 7.40 m Wetted Perimeter P= 25.21 ft 7.68 m Hydraulic Radius R= 1.59 ft 0.48 m Hydraulic Depth D= Es = Yo = Fs = 1.65 ft 0.50 m 3.86 ft 1.18 m 0.92 ft 0.28 m 52.29 kN Specific Energy Centroid of Flow Area Specific Force 49 11.75 kip