Innovative new circular reservoir to relieve East Rand water demand pressure
Construction at Vlakfontein in Standerton, Mpumalanga, of a 210 Ml concrete reservoir – the largest reservoir structure designed by Bosch Projects to date – is well under way and is due for completion in the first half of 2023.
This concrete reservoir, which was commissioned last year by Rand Water, is under construction through a joint venture between WBHO Construction, ANZI Plant and Mining Services and the Motheo Construction Group. Construction administration and monitoring is being undertaken by Rand Water in collaboration with the Bosch Projects team, which includes the design APP (Approved Professional Person) in terms of Dam Safety Legislation. The size of the reservoir is such that it has been classified as a dam with a significant hazard rating, which requires stringent monitoring during the construction phase.
“The purpose of the project is to provide additional balancing and emergency storage to Rand Water’s domestic and industrial bulk water supply system, supplying the eastern areas of Johannesburg and Ekurhuleni,” explains Andy Knox, Sector Director: Water, Bosch Projects – a member of the Bosch Holdings group of multidisciplinary engineering companies.
“This system has been under severe strain over the last few years due to increased demand from urban expansion in the eastern areas.
“During the concept and viability stage, three concepts were considered for the preferred shape of the new reservoir. Of the three concepts, there were two main shapes, either rectangular or circular. Initially, a circular reservoir was not considered an option since Rand Water has traditionally preferred rectangular shaped reservoirs for the size required for Vlakfontein. From the onset, the design team was challenged to be more creative and to optimise the reservoir design.
“The design team conducted extensive research into possible innovative concepts, of which one was a circular reservoir. Through research and discussions on constructability and the economics of construction with a reputable contractor, it was decided that a circular post-tensioned reservoir should be included under the preferred options.
“After reviewing all the risks, pros and cons, as well as the financial considerations, it was concluded that the circular structure was the most viable option for the specific requirements and site conditions at Vlakfontein.”
In attempt to limit leakage, the reservoir has been designed as jointless, with only one sliding joint between the reservoir wall and the wall footing to take-up thermal and dynamic movements as the reservoir fills and empties. A high level of research and detail has gone into to providing adequate water proofing to withstand anticipated movement in this joint.
The reservoir, which will store 213.4 million litres of potable water, is circular in shape, with post-tensioned outer concrete walls that are 11.8 m high, similar to a three-storey building. These walls are tapered from a thickness of 1 100 mm at the base to 300 mm at the top. It has an internal diameter of 154 m – the length of one and half football fields – with 256 round reinforced concrete columns, 600 mm diameter, to support the roof slab.
Construction has reached an interesting stage. Bulk excavations are substantially complete and work has started on the 2.5 m diameter pipe jacks for the incoming and outgoing supply mains. Casting of the underfloor drainage system, foundations for the ring beam for the outer wall panels and installation of the inlet, outlet, overflow and scour pipe, plus interconnecting pipework are also underway. Work has also commenced on the foundations for the four tower cranes, which will used during construction.
Bosch Projects offers solutions throughout Africa, in diverse sectors, including energy and industrial plants, water and wastewater, dams, roads, land and building developments, as well as sugar and agriculture (including irrigation), ports and terminals.
These services include detail engineering design, project and construction management; programme management – management of multiple linked projects; procurement and contract services; risk management; quality assurance and projects control, including cost and schedule management.
Melanie Elsworth, Marketing Co-Ordinator, Bosch Holdings (Pty) Ltd
Contact:
Tel (Direct): +27 (0) 31 535 6192
Tel (Switchboard): +27 (0) 31 535 6000
E-mail elsworthm@boschholdings.co.za
