PRESENTED BY : DATE: TEL: Overview of acid mine drainage impacts in the West Rand Goldfield Presentation to the Director General of DWAF: 2 February 2009

2.5 Ml Courtesy of Phil Hobbs - CSIR

West Rand Basin x 10 = 25 Ml/d TDS load ~ 100 t/d Treat. cost R5 M/m

x 100 = 250 Ml/d WITWATERSRAND BASIN

Distilled Water Orange Juice Vinegar Lemon Juice Baking Soda Ammonia Bleach Battery Acid Alkaline Acid pH (Logarithmic) DWAF Guidelines Drinking Water Irrigation Aquatic Ecosystem (Site Specific) Typical Wits Acid Mine Drainage 2.5-4

Pre mining situation Before mining, the water table will have followed a natural piezometric surface Springs may have developed in areas where this surface lies above ground level and where suitable conduits exist by which water can flow to surface Diagram modified after: Hobbs, P. J. and Cobbing, J. E. (2007) A hydrogeological assessment of acid mine drainage impacts in the West Rand Basin, Gauteng Province, CSIR/THRIP, CSIR/NRE/WR/ER/2007/0097/C, Pretoria: 59 p.

During active mining phase During mining, dewatering will have lowered the water table within the mine and surrounding areas Springs will have dried up in the area affected by dewatering During Mining Zone of AMD generation AMD pumped from workings Diagram modified after: Hobbs, P. J. and Cobbing, J. E. (2007) A hydrogeological assessment of acid mine drainage impacts in the West Rand Basin, Gauteng Province, CSIR/THRIP, CSIR/NRE/WR/ER/2007/0097/C, Pretoria: 59 p. Groundwater flow would have been drawn into the mine void owing to dewatering and the creation of a cone of depresion

Post mining situation Water will tend to return to the pre-mining piezometric surface, although this is likely to be flat (or flatter) due to the higher transmissivity of the mined out voids Water will decant from mine openings or other conduits where these lie below the piezometric surface Post Mining Contaminated groundwater flow AMD decanting from low-lying shaft(s) Diagram modified after: Hobbs, P. J. and Cobbing, J. E. (2007) A hydrogeological assessment of acid mine drainage impacts in the West Rand Basin, Gauteng Province, CSIR/THRIP, CSIR/NRE/WR/ER/2007/0097/C, Pretoria: 59 p.

Downstream groundwater pollution Polluted water discharged to the Tweelopie Spruit recharges the Zwartkrans Compartment, leading to contamination of substantial karst groundwater resources and as yet poorly determined impacts on the Cradle of Humankind World Heritage Site Post Mining Diagram modified after: Hobbs, P. J. and Cobbing, J. E. (2007) A hydrogeological assessment of acid mine drainage impacts in the West Rand Basin, Gauteng Province, CSIR/THRIP, CSIR/NRE/WR/ER/2007/0097/C, Pretoria: 59 p. Treatment plant(s) Discharge of partially treated water Recharge of karst aquifer with contaminated surface water

Water pollution management via maintenance of water levels at the ECL This situation may be managed via maintenance of water levels at the Environmental Critical Level (ECL), defined as that level where contaminated mine water will not impact on the environment. The ECL for surface water has been identified for the West Rand only. Additional groundwater investigations are required to determine the appropriate level for groundwater protection however it is estimated to be m below the surface water ECL level. ECLs have not been determined precisely for the other goldfields although there is a good conceptual understanding of issues, particularly in the Central Rand. Level which will prevent decant of mine water to surface via shafts and springs Level which will protect local and regional groundwater Diagram modified after: Hobbs, P. J. and Cobbing, J. E. (2007) A hydrogeological assessment of acid mine drainage impacts in the West Rand Basin, Gauteng Province, CSIR/THRIP, CSIR/NRE/WR/ER/2007/0097/C, Pretoria: 59 p.

pH (Water discharged to the Krugersdorp Game Reserve)

Electrical Conductivity (Water discharged to the Krugersdorp Game Reserve)

Events: January-March 2008 Low pH water released after period of rainfall No significant change in conductivity “High rainfall” period similar to normal years

Downstream groundwater quality (Krugersdorp Brickworks Borehole)

Volumes and loads Polluted water is discharged into a receiving environment –Volume = ~25Ml/d –Salt content = ~4g/l –Salt load = ~100 tons per day Dilution by around 5Ml/d from springs, much of it also contaminated, leading to little dilution This high salinity has had impacts on drinking water quality downstream and has been proposed as the cause of animal deaths and health effects in the Krugersdorp Game Reserve 20t

Regional Closure Strategy Regional Closure Strategies have been developed by the DME in partnership with CGS, CSIR and Mintek. Acknowledge the underground interconnection of mines, leading to cumulative and integrated impacts on the environment and society, with multiple mines responsible for impacts within regions Key aspects –Addresses water management, dust, radioactivity, ground instability, land sterilisation and socio- economic aspects –Water management by integration within the mining industry and other liable parties –Environmental protection can be ensured by the pumping of water to lower the mine void water level to the ECL and treating of water to a standard suitable for discharge (Stock Watering standard or better because of the proximity of the Krugersdorp Game Reserve) or sale to a third party –Establishment of closure and monitoring committees to ensure meaningful stakeholder interactions and to maintain technical oversight of the process. This has already partially been achieved via the Technical Working Group and Monitoring Committee –Apportionment studies found that ALL mines in the Western Basin who had or currently have rights to mine are jointly and severally liable (for example East Champ D’Or is listed as a asset on DRDGold shareholder publications).

Conclusions Pollution is as a result of current and historical mining activities which created and exposed contamination sources connected to an artificial aquifer within a natural groundwater system: –Ingress of water into the mine void –Flooding and decant of contaminated water is driven by natural processes –“Shutting down the mine” won’t work! Enforce the “polluter-pays” principle Ensure that water volume, quality and pollution load issues are adequately captured in all EMPs and Water Use Licenses Enforce legislation to promote the development and implementation of short, medium and long-term solutions Ensure meaningful involvement of stakeholders