Two new 10 Ml reservoirs will significantly strengthen water supply to rapidly-expanding areas of Mpumalanga.

These are the first two reservoirs in the country to be built using a new South African precast-concrete water-retaining wall system in combination with a tried-and-tested modular roof technology.

The first reservoir was built in Kwa-Mahlangu and the second is being constructed in Bundu on behalf of the Thembisile Hani Local Municipality.

Monde Consulting Engineers & Project Managers is supervising the construction teams and worked closely with Corestruc in refining the designs of the two reservoir structures.

The leading firm of consulting engineers is known for its focus on innovation to assist municipalities significantly accelerate service delivery.

This project is certainly no exception, with both construction sites serving as an important testing ground ahead of the imminent commercial launch of the system by Corestruc.

Sefiso Mdingi, who is directly overseeing the construction works on behalf of Monde Consulting Engineers, says that municipalities will have to embrace new technologies and thinking around construction to attend to the growing backlog in services infrastructure.

“While Corestruc’s roof system has been successfully deployed on many other reservoir construction projects, this is the very first time that its water-retaining wall system has been used by any local municipality. The client has demonstrated a lot of faith in the skills and capabilities of its professional team through its willingness to be the first to test new innovation in the construction sector,” Monde Consulting’s civil-engineering technician says.

Monde Consulting Engineers & Project Managers was especially impressed with the extent of innovation that went into ensuring a water-tight structure.

Top-level management of Corestruc, including technical director, Tian de Jager, visited many other countries to garner best international practice in the field and adapted this learning for unique local conditions.

Members of the engineering team also visited CoreSlab’s factory where the system is manufactured to see for themselves the extensive procedures in place to ensure a consistently high quality level.

In Kwa-Mahlangu, Monde Consulting Engineers & Project Managers and Corestruc worked alongside main contractor, Gaby Construction.

This Mpumalanga-based Grade 7 contractor built the eight kilometre pipeline and floor of the structure, while Corestruc’s own installation team undertook the construction of the walls and the roof.

The initial design of the reservoir at Kwa-Mahlangu was based on traditional in-situ construction technologies and later modified to incorporate precast-concrete technologies to deliver the reservoir in an extremely short timeframe.

Corestruc, therefore, only mobilised to the Kwa-Mahlangu site once the floors and bases had already been completed.

At the construction site in Bundu, Corestruc was involved in the project right from the early design phases.

This also provided the company the opportunity to assist in determining the most optimal construction sequence.

Work started with the construction of the foundation and bases by the main contractor, Mbako Projects & Trading, to accommodate the precast-concrete columns that support the beams and hollow-core slabs that make up the roof of the structure.

The roof structure was completed by Corestruc’s team in just under a week in September, and Mbako Projects & Trading then commenced with the precise construction of the ring-beam, ahead of the arrival and installation of the precast-concrete wall slabs.

They will then be post-tensioned to keep the joints compressed and the work will end with the construction of the floor and grouting of the precast-concrete wall slabs to create a single monolithic slab structure.

At the Bundu reservoir construction site, a total of 60 wall panels, each weighing about eight tons, and about 10 m long, two metres wide and 170 mm thick, were lifted and placed to complete the wall structure.

The most time consuming aspect of the reservoir construction programme is the preparation for the grouting of the joints between the walls.

About 6,6 km of PVC post-tensioning ducts and cables are installed by hand between the joints of the wall panels, before the grout is pumped around the circumference of the reservoir.

It takes just more than a full shift to fill the joints with a specially-designed medium, which reaches a compressive strength of 100 MPa in as little as four days.

The team then inspects the internal and external walls, and fills any voids by hand to further safeguard against leakages.

As a further measure, Corestruc even brought its own water to site to ensure the same reaction it achieved during the testing phases of the grouting material.

We are proud to be associated with Monde Consulting Engineers & Project Managers, which continues to unlock new opportunities for precast-concrete technologies in municipal infrastructure delivery programmes.