© 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