WOOLWORTHS DISTRIBUTION CENTRE

A small budget and 29 ha landscape area rendered the issue of irrigation cost and water consumption one of the main concerns for the Woolworths Midrand Distribution Centre. With a borehole system already rejected by the geo-technical report and the total water expense for an already automated and water saving irrigation system in excess of a million Rand per year, options were restricted.

As a solution and in answer to a requirement of the Johannesburg Road Agency, a series of three retention ponds (overflowing into each other) was designed to collect excess storm water. Grey water was also harvested into the first and second ponds respectively and filtered through a vertical wetland into the third pond. From here irrigation water it is pumped out at night to minimize evaporation and prevent interference with pick-up and delivery activities.

To contain costs, the irrigation design also ensures a larger surface area was covered per sprinkler head. And by specifying larger valves and standpipes the total amount of equipment needed was minimized.  In addition, the landscape design and plant selection was carefully evaluated for their specific irrigation needs resulting in the installation of a weather station, which contributed to greater water savings.

Through this judicious design process, NLA succeeded in reducing the need for potable water to 25 per cent of the total irrigation demand. This volume is now being made up by borehole water after a viable borehole position was found.  The end result is an irrigated site with a 100 per cent reduction in potable water expenditure.