6. Water quality
Mines can affect surface runoff and groundwater quality through contamination
with dissolved and suspended materials. Perhaps the commonest surface water
contaminant is sediment or suspended solids. Sediment can smother the beds of
receiving streams, affecting fish and benthic organisms. Apart from runoff from
overburden emplacements and stockpiles, storm water can be contaminated from process
plants, workshops and vehicle wash-down pads. Drainage from oxidization of sulphur or
sulphidic ores is highly acidic and can contain dissolved heavy metals. These are toxic to
aquatic life and impact on the surrounding environment. Mine planners must consider how
their facilities will cope with floods. Mines can de-water groundwater aquifers some
distance from shafts or open pits, which can make nearby wells or groundwater bores run
dry. Mine designers