Construction World December 2017

Category A1: Civil Engineering Contractors


30 000 m 2 and due to the soil condition at the Three Rivers site, an engineered platform had to be constructed to accommodate it. Lime was used to stabilise the material, and the engineered platform was constructed creating a 1 000 mm-thick soil mattress. The 30 000 m 2 area had to be covered with a 100 mm-thick layer of no-fines concrete acting as a drainage system. The concrete structure was constructed on top of the ‘drainage system’, and consists of floor panels and 180 walls dividing the sedimentation tank into four bays. A total of 60 floor panels, measuring 25 m-by-25 m each were constructed. The 180 walls, each 25-metres long, were constructed by using timber and steel support frames as formwork. Around 50% of the walls have launders constructed on top of them. Out of the 84 walls, 24 walls are in-situ launders and the remaining 60 walls are precast launders. The precast launders are also the first time this specific precast methodology was implemented on a Rand Water project. The sludge pump station was constructed six metres below the natural ground level and has heavily reinforced walls. The building that will supply power and house the instrumentation for the pump station will be constructed on top of the pump station, within a steel structure that will create the roof of the pump station and building.

A civil joint venture between Stefanutti Stocks Civils, its strategic enterprise development partner Axsys Projects and Mdzili Enterprise was awarded the first phase of the design, build and commissioning of Rand Water’s new 600-M ℓ /day System 5 Water Treatment Plant.

The water treatment plant in Vereeniging is one of Rand Water’s flagship projects and after the completion of Phase 1, will see a 12,5% increase in the current Rand Water water-supply network. This will ultimately result in potable water being supplied to an additional 1,5 million people, as well as to associated industrial and business activities. The joint venture employed WorleyParsons as a consultant to complete the designs for the project. The construction programme started at the beginning of August 2015, and the 36-month long contract period will see the completion of the flocculation, sedimentation and carbonation plants, as well as the sludge pump station that includes all the MEIP Related Works for Zuikerbosch Pumping Station’s new water treatment and pumping system. This is where coagulants (chemicals) are added to the water to start the process of coagulation and flocculation. Flocculation is the process whereby particles (or colloids) in the water come together to form bigger particles, otherwise known as Flocks. To ensure the water tightness of the three flocculation tanks, the outer walls and one internal wall will be constructed in-situ and the remainder of the internal walls will be precast panels. The precast panels were manufactured off site. This is the first time that this precast methodology has been

implemented on a Rand Water project. By adding coagulants to the water, during the flocculation process, the pH in the water is increased to an unstable level of between 10.5 and 11.0. The purpose of the Bay is to reduce the level of the pH. The pH is reduced and stabilised by bubbling carbon dioxide gas through the water. This reduces the pH to between 8 and 8.4. As the carbonation area only consists of bases and straight walls, a timber walling systems with steel support frames was chosen as formwork. The use of timber walling systems achieves an exceptionally high quality concrete finish, as well as facilitating a higher production output. The carbonation plant walls are four- metres high and the longest single section of wall poured was 75-metres long. The Sedimentation Tank is indicative of its name, and this is where the larger particles in the water, once dense enough, will settle on the floor as sediment. As the separation of particles continues, and the Sedimentation Tank fills, the less turbid water flows into the clear-water launders and is fed into the Carbonation Bay. The sediment which is left behind is then pumped into the Sludge Pump House, firstly to clean the Sedimentation Tank, and secondly to be used as a by-product of the water treatment process. The Sedimentation tank covers over


• Company entering: SAM JV (Stefanutti Stocks, Axsys Projects and Mdzili Enterprise) • Client: Randwater • Contract value: R235-million • Start date: June 2016 • End date: August 2018 • Main contractor: Stefanutti Stocks

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