OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

Station pH TDS PO4-P
A2H12 7.6 485 1.4
A2H52 7.7 510 0.7
A2H60 7.9 535 2.0
4.14.6 Implications for water quality and quantity management
There are a very large number of mining operations of differing sizes in this sub-catchment, and a wide variety
of mineral commodities are exploited. In addition to the mining operations listed in Table 4.14, there are also a
relatively large number of mining operations that have either been closed or abandoned (C.J. Vorster, personal
communication). Some prospecting permits have also been issued but no details were available for this report.
Perhaps the most significant impacts associated with mining in this sub-catchment are those linked to chrome
mining and refining. The defunct African Chrome Smelter at Brits, currently being evaluated for refurbishment,
has previously contaminated local ground water resources with toxic hexavalent chrome (Cr 6+ ). Minor
contamination by hexavalent chrome can also be anticipated from the operating chrome mines located near to
the town of Rustenburg. Another contaminant that can pose significant problems is Vanadium, which is known
to be toxic to plants and animals when present in high concentrations. The vanadium mines near Rustenburg,
and those mines where vanadium is a secondary product (Table 4.14) all have the potential to pose vanadium
toxicity problems.
Some minor problems associated with elevated metal concentrations can also be expected from the platinum
mines and the now-closed base metal mines (lead, silver, tin, zinc, copper). All of these mines have sulphide
orebodies and minor acid mine drainage can be anticipated from these mines. The large iron ore mines at
Thabazimbi are likely to contribute elevated concentrations of iron and manganese to local waterbodies via
wind-blown dusts. Minor contamination by elevated fluoride concentrations can be anticipated in the middle
reaches of this sub-catchment, where local streams drain fluoride-rich areas being mined in the western side of
the Waterberg Plateau.
The lower reaches of the sub-catchment are relatively dry, with high Weinert N weathering indices indicating
that mechanical weathering processes dominate. Consequently, any contaminants emitted by mines in this
area would not normally be expected to be very mobile. This contrasts with the lower Weinert N weathering
indices of the upper reaches of the sub-catchment, where chemical weathering processes will dominate and
contaminants would be more mobile.
All of the metal mining operations and those quarrying operations that extract dimension stone (predominantly
granite) as well as dolomite and limestone can be expected to contribute elevated levels of suspended solids to
local waterways.
4.15 The Matlabas-Mokolo sub-catchment
cclvi