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.