The first stage of a project to boost Perth's drinking water supplies with treated sewage will be twice as big as expected after claims the cost of developing it is lower than expected.
Water Minister Mia Davies will confirm today that stage one of a plan to inject highly treated wastewater into aquifers in Perth's north will have a capacity of 14 billion litres a year - rather than seven billion litres as first planned.
With an estimated construction cost of $124.6 million, the plant will be the first sewage recycling project of its type in Australia when commissioning starts in October 2016.
Work is due to begin next month.
Ms Davies, who will announce a joint venture between engineering firms Thiess and CH2M Hill has won the contract to design, build and commission the plant, said the bigger first stage was something of a surprise.
She said it was made possible by the intensity of the competition for the contract, and had even resulted in the expected cost of the project being revised down.
"It was originally planned that stage one of the plant would have a capacity of seven (billion litres) per year, which would then be expanded to 14 billion litres and 28 billion litres over several years as demand increased," Ms Davies said.
"However, due to a comprehensive and competitive tendering process and strong competition for the contract, the State Government has been able to effectively get the first two planned stages built for less than the price of one - saving $24 million in the process."
The winning tender comes after the Government last year expanded a trial that pumped about 3.5 billion litres of treated effluent from the Beenyup wastewater treatment plant into an aquifer beneath the project.
Under the Government's long-term plans, more than 100 billion litres of drinking water could eventually be sourced from such technology - about one-third of current usage in Perth, Mandurah and the Goldfields each year.