Michele du Plessis
Mining affects fresh water through the heavy use of water in processing ore, and through water pollution from discharged mine effluent and seepage from tailings and waste rock impoundments. Increasingly, human activities such as mining threaten the water sources on which we all depend. Mining by its nature consumes, diverts and can seriously pollute water resources. Cyanide extraction of gold through milling of high-grade ores and heap leaching of low-grade ores requires cycling of millions of litres of alkaline water containing high concentrations of potentially toxic sodium cyanide (NaCN), free cyanide, and metal-cyanide complexes.
Modern industrial gold mining destroys landscapes and creates huge amounts of toxic waste. Due to the use of practices such as open pit mining and cyanide heap leaching, mining companies generate about 20 tons of toxic waste for every 0.333-ounce gold ring. To limit the environmental damage, mines often construct dams and place the toxic waste inside. But these dams do not necessarily prevent contamination of the surrounding environment.
In 2009, after heavy rains in February, environmentalists were concerned about a potential leak of cyanide into the Sabie River after a heap leach pad at the Elandsdrift gold mine near Sabie over spilled.
“The greater TGME/Sabie areas are covered by various Prospecting and Mining rights. TGME and Sabie Mines holds 3 Mining Rights in the same geographical are – these are 198MR for the Elandsdrift Heap Leach Pad, 43MR for the Glynn’s Lydenburg Heap Leach Pad and 358MR for the Rietfontein underground mine.
The proposed new Project 10161 mining application will allow TGME to mine for, Zinc ore, Copper ore, Bismuth ore, Stone Aggregate (from the Waste dump), Iron ore, Silver ore and Gold ore.” EIA Stonewall Mining.
“The current surface water monitoring points of TGME and DWS is provided in the surface water report together with the probable runoff paths for the various shafts and adits, should runoff occur. The existing monitoring sites are sufficient except for a background reading before the drainage line originating from the Olifantsgeraamte.” EIA Stonewall Mining.
Heavy metal pollution is caused when such metals as arsenic, cobalt, copper, cadmium, lead, silver and zinc contained in excavated rock or exposed in an underground mine come in contact with water. Metals are leached out and carried downstream as water washes over the rock surface. Although metals can become mobile in neutral pH conditions, leaching is particularly accelerated in the low pH conditions such as are created by Acid Mine Drainage.
Cyanide, in the form of a very dilute sodium cyanide solution, is used to dissolve and separate gold from ore. Mines use as little cyanide as possible for environmental, safety, and economic reasons. Cyanide leaching is usually done along with a physical process like milling, crushing, or gravity separation. The waste, usually a grey liquid sludge or slurry, is laden with deadly cyanide and toxic heavy metals. Toxic waste can easily seep into soil and groundwater, or be released in catastrophic spills.
Arsenic, a naturally occurring element commonly found as an impurity in metal ores, can also be leached out of some metal ores by cyanide or acid rock drainage but can be captured and removed from wastewater before it is released into the environment. Arsenic is poisonous and causes cancer in humans.
While there have been numerous improvements to modern mining practices, significant environmental risks remain. Water pollution from mine waste rock and tailings may need to be managed for decades, if not centuries, after closure.
*Information from various sources, including the FINAL ENVIRONMENTAL IMPACT ASSESSMENT REPORT and DRAFT ENVIRONMENTAL MANAGEMENT PROGRAMME REPORT FOR THE PROPOSED “TGME MINE DEVELOPMENT PROJECT (10161)”: GOLD MINING PROJECT IN TERMS OF PRE-MINED RESIDUE AND HARD ROCK MINING NEAR SABIE, MPUMALANGA PROVINCE PREPARED FOR: TRANSVAAL GOLD MINING ESTATES (Pty) Limited