Water, Sewage & Effluent September October 2018 | Page 20

Afriline Civils, discusses some of those encountered. Challenges With a large section of the site bound between Macassar Road and existing residential areas, the working width of the site was very limited, with some of the pipes being installed at depths of between seven and eight metres deep, so ensuring adherence to Health & Safety compliance posed a challenge, says Reed. “The depth of the excavations required that they be battered, and staff had to work within a ‘drag box’ at invert level to create a safe working environment for our staff.” As the project took place in a residential area, the local community, children specifically, entered the construction area unauthorised. “With all the pipes and mounds of sand, for the children, it’s a playground,” Kleynhans noted. Coupled with this challenge, the project experienced continuous theft and vandalism of safety barriers, traffic signs, plant, equipment, and materials, Reed describes. “We put up fences to prevent entry, but in the morning, they were gone,” Reed adds, necessitating full-time security on the site for the duration of the contract, as well as enlisting safety marshals from the local community, “which was more effective as they know the people,” he points out. Reed says that during the excavations, while minor quantities of rock were encountered, it was the subsurface water that was a major obstacle and challenge in the pipe installation and chamber construction, with the need to deal with water in the trenches and structures (groundwater and surface run-off). “That the gradient of the pipeline to be constructed was 0.76mm per metre, made precision surveying and installation of utmost importance,” he adds. “Dealing with the crossing of existing services such as high-voltage overhead power lines, fibre optic cables, water and sewer pipelines, and constructing adjacent to these services, also posed challenges,” he observes. While the project started during the peak of the Cape drought, in November 2016, imposing water restrictions on the project that also required dust control in the Cape winds, Kleynhans believes that the drier conditions made it easier for pipe installation. He explains that the groundwater is relatively high in the area of the sewer installation, but because of the drought, this was less problematic during the installation. The recent rains have since changed the scenario, but the majority of pipe laying has been completed. Technical scope of work Reed explains that as the main contractor on the project, Afriline Construction of DN 900 diameter pipeline, 8–9 metres deep, along the City of Cape Town waste yard in Macassar. 18 Water Sewage & Effluent September/October 2018