Presentation to the Portfolio Committee: Water& Environment

Presentation byMr N Nepfumbada

Acting Deputy Director-General: Policy & Regulation26 - 27 January 2011

Impact of Current Rainfall / Flooding on Acid Mine Drainage in Gauteng

1

• High rainfall / flooding leads to increased ingress of water into mine workings via:

Surface streams

Shallow groundwater systems

Open pit mining

Leads to increased mine water levels and decant of AMD

2

Status of Western Basin (West Rand)

• Dry season: zero AMD decant or relatively small volume (2 ML / day) + {12.5 ML / day partially-treated mine water}

• Wet season: AMD decant of 15.5 ML / day (Dec 2010) up to 30 ML / day (as at Jan 2011) + {12.5 ML / day partially-treated mine water}

Impacts on Tweelopies Spruit flowing to the Crocodile River system. Recent fish kills not due to AMD.

3

Status of Central Basin (Central Jhb)

Dry season: mine water rises by 0.3 m / day

• Wet season: mine water rises by 0.9 m / day

Current rate of rise is 0.37 – 0.47 m / day

Despite high rainfall, the rate of rise is less pronounced due to delayed ingress or greater void volume at 500 m below surface level (lateral spreading of water)

4

Status of Eastern Basin (East Rand)

• Recent rainfall has increased rate of mine water rise to 0.4 m / day (7 x increase)

• Pump station can flood within 16 days at this rate

Grootvlei Mine has reported urgent measures underway to increase pumping capacity

5

RecommendationsAs per Expert Team report to the Inter-Ministerial Committee on Acid Mine Drainage, interventions include:

• Western Basin: reduce ingress by pit filling and canalising watercourses

• Central Basin: ingress reduction by canalising streams over mining areas + grouting (sealing) of mine paths

• Eastern Basin: immediately expand culvert in Blesbok Spruit to reduce water entering mine

The above recommendations have been included in a Cabinet Memorandum which will be processed shortly

6

The End

Thank you