M&D Construction Group forges ahead at complex WWTW project
Leading South African construction company, M&D Construction Group, is helping Dr Ruth Segomotsi Mompati District Municipality strengthen wastewater-treatment capacity in Vryburg, Free State.

The group’s civil arm commenced construction of the new 16 ML wastewater-treatment works (WWTW) in April 2016.

M&D Construction Group’s 30 month contract is valued at more than R200-million, and the work scope includes a four kilometre outfall sewer, inlet, 100 m x 48 m bio-reactor, anaerobic digester, thickener, raise pump station and chlorine contact channel, as well as two 100 m x 40 m dry beds and two circular secondary settling tanks. In addition to all inter-connecting pipework, the contractor is constructing an administration building and warehouse and has already completed the 2,4 km of access roads, including a railway crossing.

Dr Ruth Segomotsi Mompati District Municipality’s decision to entrust M&D Construction Group with this complex greenfields project was based on the company’s 10 years of successful participation in many of government’s water-infrastructure programmes. 

Work is progressing according to schedule and much of the success achieved over the past 18 months can be attributed to the extensive planning that took place ahead of construction. Importantly, emphasis was placed on establishing a robust working relationship between the main contractor and the various consulting engineering teams on site.

M&D Construction Group hosted a one day workshop where construction legal experts provided important contractual advice, paving the way forward for a professional working environment. In addition, realistic timeframes and programmes were established, complementing other initiatives, not least of which was establishing a direct and open communication channel to chief-executive officer, Rukesh Raghubir, for swift trouble-shooting.

Ian van der Walt, M&D Construction Group’s contract manager, says that the sheer extent of the work involved has made this an extremely complex project.

“There are about 200 people on site, spanning supervision through to the workers. The enormous quantities of building material involved also mirror the immense task at hand.

In just over a year, our bulk earthworks team had already moved 500 000 m³ of material as part of the total works programme. In addition, we have placed 12 000 m³ of concrete and handled about 1 000 tons of reinforcing bar,” says Van de Walt.

The most complex aspect of the entire work programme has been the outfall sewer. 

To accommodate the shortest possible route and river flood line, the 1,2 m-diameter pipeline crosses extremely flat terrain – a percentage fall for every four metres – and an old mine waste dump. Extensive earthworks had to be undertaken to first remove and spoil about 45 000 m³ before excavating the deep trench to depths varying between seven metres to 14 m.

Moreover, the pipe-laying teams have had to carefully handle many sections of high-density polyethylene (HDPE) pipeline that expand and warp in hot weather conditions. Temperatures in Vryburg reach extremes of more than 40 degrees Celsius.

They are strung along the trenches in 12 m lengths and then lowered onto the carefully placed bedding, comprising selected material and fill, using excavators and mobile cranes, before being welded, strapped, tied and levelled.

Nothing is left to chance to ensure the highest quality in this component of the works programme. The outfall-sewer has been designed to have a life of more than 100 years to also facilitate future upgrade as the plant.

“We appointed a specialist to undertake the butt-welding, which undergoes constant testing by a third party. Laser-surveying technology is being used to ensure accurate levels of the pipe before backfilling. In addition to tensile-destructive testing, the pipeline will be air-tested between each manhole using special imported bladders,” he says.

M&D Construction Group is now working at four construction faces, and will commence work on the inlet, drying bed and thickener next year.

Raghubir is also very proud of the fact that as much as 56% of the project is supported by local businesses.

“Significant emphasis has also been placed on small-medium and micro enterprise development, complementing the extensive training still under way on this project. More than 100 members from the local community are currently working alongside M&D Construction Group’s own team. Murray & Dickson Construction Group has also excelled in other critical areas, including health and safety, as well as environmental,” the chief-executive officer concludes.