The first trial blasting has been undertaken at the Clanwilliam dam construction site in the Western Cape, as the Department of Water and Sanitation (DWS) works to raise the dam wall by 13 m.
The trial blasting kicks off hard rock excavations and formally activates the construction to raise the dam wall after years of unprecedented delays.
“The first blasting at left bank is a significant and noteworthy move, especially since the Clanwilliam project encountered many challenges associated with procuring service providers and materials, said DWS spokesperson Wisane Mavasa.
There were 116 holes drilled in preparation for the blasting activity, each hole had an average depth of four metres, with 920 kg of explosives used for the blasting exercise, which resulted in a total volume of hard rock excavations of 1 253 m3.
Prior to having a major blast, a trial blast had to be done first to determine parameters of future blasting activities in line with security of surrounding infrastructure, mainly the dam, and ensure that there was no damage to the dam, and the dam remained safe and intact.
“Prior to the execution of trial blasting, the blasting sub-contractor submitted blast designs to the engineer and approved professional person (APP) for approval. The APP, through consultation with a third-party blasting specialist, evaluated the designs and gave a go-ahead, looking at aspects such as no blasting is allowed within 100 m from the dam wall, unless it is controlled blasting,” Mavasa explained in a statement issued on Thursday.
“With the blasting exercise, the hard excavations have been triggered on the left bank and regular blasting activities can be scheduled almost monthly through the same process as articulated above. All excavations remaining on the right and left bank are hard excavations and blasting will take place as approved and scheduled.”
Blasting will continue until all hard excavations are completed on both banks, while other activities, such as stripping of overburden at the quarry area and widening of the N7, are underway.