Eastgate Shopping Centre harvests rainwater to boost sustainability

IN a step that sets an example for South Africa as a water-scarce country, Eastgate Shopping Centre has contracted Concor to install a rain harvesting and water treatment facility. 

This will also make use of groundwater, ensuring optimal use of available water and reducing the centre’s reliance on municipal supply.

The new facility comprises two segmented steel tanks capable of storing about 200 000ℓ of water. Rainwater runoff from the roof top parking area – which currently runs into the city’s stormwater drains – will be piped into these tanks.

This will be supplemented by groundwater resources under the centre which will be pumped up and stored. These tanks are linked by a 300m water line to the centre’s existing buffer tank. Working in a live shopping centre environment, the water pipe has to be run through a busy parking area and across a public road, requiring careful planning and traffic management.

The tanks will hold over 200 000ℓ, demanding a firm foundation. In preparation for this work, test pits were excavated to ascertain the presence of services, piping or ducting – as accurate as-built plans were not available. 

Concor considers these kinds of processes as vital to risk mitigation at every step of a project. In addition to uncovering various services, the test pits also revealed a concrete crane base some 500 mm in depth, which had to be removed before foundation works could begin.

In this case, geological conditions called for the use of twelve 130 mm micro-piles to ensure the stability of the tanks, following which raft foundations were cast over a 5m by 10m area. Construction of the foundations and the tanks is in close proximity to an existing LPG gas chamber that serves tenants such as restaurants in the centre. This requires special attention to health and safety procedures, including regulated permissions and certain restrictions on the use of electrical equipment in the area.

The project includes the installation of filtration and treatment facilities, ensuring that the water is potable for use throughout the centre.