Virginia Triangle - feeding Adelaide’s garden

The significance and scale of South Australia’s Virginia Irrigation Scheme is evident in its project history. Taking 20 years to initiate and 2.5 years in planning negotiations, the scheme has now been completed, following an 18 month construction programme. The result is a technologically advanced water recycling system that is the largest, not just in Australia, but in the whole of the southern hemisphere.

Known as the Virginia Triangle, the focus of the scheme is a key agricultural area on Adelaide’s Northern Plain, which provides the food bowl for Adelaide’s fresh vegetable supply. This vast market garden has grown to meet demand over 100 years of operation, placing an increasing strain on the area’s freshwater resources. The crop farming community had suffered from a receding and increasingly saline water table, until the new irrigation system came on stream.

Some 230 individual properties are now served with a continuous and secure supply of ‘A’ grade (Californian Standard) water from the new Bolivar treatment plant near the Adelaide conurbation. A network of ABS plastic pipes, totalling 186 km, currently delivers the water at a rate of 110 Ml/day, which makes a large reduction to the treated wastewater outflow into coastal waters, while providing crop irrigation.

The pipe network is record breaking in its own right, incorporating the world’s largest ABS pipe diame ters, up to 826 mm on the two trunk mains. Manufactured and supplied by Tyco Water Plastic Pipeline Systems (Eurapipe), the pipe system used two joining methods.

Together with conventional solvent cement welding, used over much of the network, Eurapipe elsewhere employed their more recently introduced rubber ring joint system. Using these joining methods, trained teams of contractors achieved pipe laying rates of 300 metres per day on the large diameter sections. The ABS pipe system is widely used in the Australian water industry and is now available in Europe from the UK distributor, EPCO.

The rapid installation and success of the Virginia Irrigation Scheme overall mean that it is soon likely to be replicated. Tyco, with its joint venture partners Multiplex and Gutteridge, Haskins and Davey, are working on a similar proposal for Melbourne Water’s Eastern Treatment Plant. Large diameter sections were laid at a rate of 300 metres per day.