surges of water flow that would follow each rainfall. “In Phase 1 of the project, we cleared reeds and removed sludge, importing pioneer material – or dump rock – from AfriSam to stabilise the access road and gabion areas,” explains Pospech. “The gabion baskets, which are mostly 1 metre by 1 metre by 3 metres in size, were then constructed, after which AfriSam also supplied a clayey overburden material of the appropriate plasticity index.” The work involves extensive earthworks, with some 45 000 m 3 being excavated down to depths of 1 to 1,5 metres. Clearing of reed beds has been conducted using long-boom excavators and articulated dump trucks, which stockpiled the material to drain before reloading onto trucks for removal from site. Earthworks prepare the way for 12 000 m 3 of dump rock for stabilisation – to be covered by around 20 000 m 3 of overburden. About 15 000 tonnes of large stones of up to 200 mm in size are being delivered for the gabion baskets. The contract is also making use of 3 500 m 3 of G4 material, which is stabilised with cement. According to Ian Trimmel, Territory Sales Manager for AfriSam, the range of material required for the project is sourced from the company’s nearby Peninsula quarry. “Material such as dump rock can add complexity to the supply logistics,” says Trimmel. “Not all trucks can accommodate the size and impact of dump rock, for example, and we adjusted our arrangements to ensure that trucks could navigate the quarry to collect certain materials.” As part of AfriSam’s commitment to the project, a dedicated gabion stone plant was established. Traditionally, this size of stone is usually hand-picked from dumps. However, the large volumes required by this project meant AfriSam About 15 000 tonnes of large stones of up to 200 mm in size are being delivered for the gabion baskets.
substantially raising its capacity. It also needs to allow for easier maintenance and periodic clearing of litter. “The design includes two 140 metres long primary sedimentation ponds which will allow heavier suspended matter to settle out,” he says, “while the 460 metre long secondary treatment canal will ensure that finer suspended matter also drops out of suspension as the water passes through.” After passing through the sedimentation ponds, stormwater will flow over a weir into a secondary treatment canal, allowing for the uptake of nutrients and physical filtration of pollutants by the reeds. A new bypass channel of almost 600 metres is also being developed along the eastern boundary of the R27 to bypass the primary and secondary ponds and drain freely directly to Rietvlei when the water level in the Bayside Canal exceeds the weir level of 2,9 m MSL. CSV Construction was handed the site in November in 2023, and earthmoving machines were busy from January 2024. With construction activity taking place directly in the path of a flowing water course, the project was scheduled around the Cape’s rainy season in winter. The bulk of the work has been planned to take place during the dry summer months. Pospech points out that, during the winter months of 2024, there were occasions when the entire seven hectare site was submerged – although an efficient pumping regime allowed work to resume on the higher levels. Temporary berms were also constructed to mitigate the regular
31 CONSTRUCTION WORLD MARCH 2026
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