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An Overview of Acid Mine Drainage Problems within the Witwatersrand Area

An Overview of Acid Mine Drainage Problems within the Witwatersrand Area. February 2010 Marius Keet. BACKGROUND. Mining started more than 100 years ago De-watering to explore reserves No environmental laws Uncontrolled slime deposits Uncontrolled releases

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An Overview of Acid Mine Drainage Problems within the Witwatersrand Area

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  1. An Overview of Acid Mine Drainage Problems within the Witwatersrand Area February 2010Marius Keet

  2. BACKGROUND • Mining started more than 100 years ago • De-watering to explore reserves • No environmental laws • Uncontrolled slime deposits • Uncontrolled releases • No in-stream water quality standards

  3. BACKGROUND • 100 Years later • Re-watering • Newly formed voids filling up • AMD formation • Integrity of geology • Decanting

  4. WHAT IS ACID MINE DRAINAGE (AMD)? Acid generation is caused by the exposure of rock containing certain sulphide minerals, most commonly iron pyrite (FeS2), with air and water, resulting in the production of highly acidified water containing elevated concentrations of sulphate andmetals. AMD largely associated with gold & coal mining.

  5. RISKS ASSOCIATED WITH AMD • Biggest environmental challenge ever • Negatively impacts on quality of water resources & is harmful to ecosystems • Flooding and Decanting • AMD is a concern in Gauteng (Witwatersrand), Mpumalanga & Free State • AMD most problematic in Witwatersrand area

  6. A M D IN THE WITWATERSRAND • Witwatersrand divided into 4 “Basins” (underground reservoirs) • Eastern Basin: Nigel to Germiston • Central Basin: Germiston to Roodepoort (including Johannesburg) • Western Basin: Krugersdorp to Randfontein • Far Western Basin: Westonaria to Carletonville

  7. © CEM

  8. Current Grootvlei is the only mine pumping Part of water is partially-treated and discharged into Blesbokspruit Risks Discharge does not meet standards, but no immediate threat EASTERN BASIN

  9. Current Consists of individual mines which are interconnected Most mines are ownerless or defunct and hence became state liability Basin is currently flooding with no pumping facilities Studies to determine the level of all associated risks (e.g. current status and capacity to accommodate AMD from Western Basin) Risks Flooding of the Basin Structural integrity of buildings and other infrastructure CENTRAL BASIN

  10. Current 12.5 ML/d AMD partially-treated and discharged into Tweelopies Spruit 6 – 20 ML/d untreated AMD decanting into Tweelopies Downstream water users include COH WHS, KGR and private farms Risks Human and animal life Ecological impacts Sinkholes Destruction of heritage value Difficulty for mines to achieve compliance within short time periods Western Basin

  11. 18 Winze

  12. Surface runoff from 18 Winze

  13. Outlet of Krugersdorp Game Reserve (Aviary Dam) before entering COH WHS and Tweelopies Spruit

  14. Far Western Basin Current • Most mines are still operational • Mines at various operating lifespan – up to 50 years • No AMD problem • Mines working on long-term solutions

  15. Upper Vaal - Overall Status Vaal Barrage Vaal Dam Kromdraai Grootdraai © CEM

  16. RECENT DEVELOPMENTS • GTT (DWA, DMR, DEAT, DST, Provincial Environmental Departments) • Interdepartmental Basin Task Teams • Council for Geo-Science • Directives (regulatory measure) issued to mines in the Western Basin • Continued engagements with sister Depts in order to reach a common understanding on addressing AMD and thus common government position • Environmental Critical Levels to be finalized soon

  17. RECENT DEVELOPMENTS • Sub-committee on AMD to concretise recommendations by GTT for presentation to relevant Departments • Regional mine closure strategies developed to ensure that the rehabilitation plans take into account the AMD problem • Establishment of Public-Private Partnership (PPP) (between Government and the applicable Mines) • DWA preparing report on strategy to address AMD

  18. CHALLENGES • Funding • Costs (+/- R3 Billion) • Roles and responsibilities • Between the Mining Houses • Between Government Departments

  19. PLAN OF ACTION Immediate to Short Term: • Support and strengthen partnerships • Rigorous monitoring and reporting on AMD matters • Explore promising technologies and strategies for AMD management • Intervention by DWA to deal with emergency in the Western Basin (R6 Million)

  20. PLAN OF ACTION Medium to Long-term: Investigate the following options: • Evaluate the merits of inter-basin AMD transfer • Treatment of AMD per Basin vs centralised (“massified”) treatment plant • Best use of treated water (What? Where? How?) • Conclusion of any studies in progress • Considerations of funding mechanisms for State liabilities

  21. Think Outside the Box © CEM

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