He said the market�s competitive nature resulted in the saving after announcing construction company Georgiou had been awarded the building contract.
The $29.5 million facility will increase parking at Edgewater train station by 560 bays.
Mr Nalder said the carpark would help ease growing demand in the northern suburbs.
�Edgewater, Joondalup and surrounding suburbs have experienced incredible residential growth in recent years thanks in part to the accessibility afforded by the Joondalup line,� he said.
The carpark has been designed to maximise security, natural lighting and ventilation while providing shading and weather protection where possible.
It will feature a lift, open staircase and open roof to fit in with surrounding buildings.
Construction will start early next year for use by the end of the year.