Quarry Southern Africa January 2017 | Page 20

© Nevit Dilmen
The fast-growing fever tree ( Acacia xanthophloea ) is planted across the site for rehabilitation to help improve soil fertility .
Future planning
Another area where DSS is investing heavily is in site rehabilitation . All mines are required by law to remove and store overburden until the LOM is exhausted . At this time , the overburden is spread out over the area it was initially removed from . Once it has been properly flattened out and it gets some rain , all the seeds for grass and other vegetation originally present in the overburden start to grow almost immediately .
In addition to the overburden , DSS is planting fast-growing fever trees ( Acacia xanthophloea ) across the site for rehabilitation . As nitrogen fixers ( able to turn atmospheric nitrogen into nitrogen fertilisers ), these trees help to improve soil fertility . The quarry also has a catchment storage area for rehabilitating soil that has been contaminated by oil or hazardous chemicals . Here , fertiliser ( 2:3:2 ) is added to the soil to neutralise the contaminants . When plants begin growing out of the soil , the previously contaminated soil is removed and added to the current rehabilitation efforts .
Blast-off
Our visit started with a safety briefing and presentation on mine operations by Van Wyk , which is compulsory for all site visitors , contractors and drivers . Following this , we moved on to the blasting cabin from where we watched the blast .
When blasting is going to be done , which is approximately once every week to two weeks , the site is evacuated beforehand to minimise potential accidents and / or injury . Preparation for each blast is extensive , for both safety and cost reasons . Drilling of the 102mm-diametre hole takes six to seven days , and charging takes around six hours . If for any reason the blast is halted , the charge is not permitted to stand over , as the DMR mandates that everything must be washed out . DSS contracts out its drilling to Eagle International Drilling & Blasting , and its load and hauling to KwaMhlanga Quarrying . The blasts are carefully monitored , with each blast being filmed for later examination . As Van Wyk explains , “ Because it ’ s a quarry , your changes or your impact due to a change , are immediate . If I don ’ t pick something up today , tomorrow it ’ s a stuff up — what should have been rectified today turns into a big problem tomorrow .” The blasting cabin , from which the blast is observed and recorded for monitoring purposes , is located within the 500-metre blasting radius .
Van Wyk explained that with a successful blast — like the one that we watched , which achieved good fragmentation — the blast itself is a non-event , and can easily be missed if you aren ’ t watching for it very carefully . A bad blast , on the other hand , is very visible , and occasionally even spectacular . The blast we watched was of the number 3 bench and was blue rock ( granite ). Blasting manager Marnie Viljoen explained the cost associated with blasting . The emulsion used as the explosives for the blast is a mixture of old oil and fertiliser , and the mix for each blast costs around R200 000 .
18 _ QUARRY SA | JANUARY 2017