The wheels have been put in motion for the $518 million upgrade of the Ballarat train line.

The state government is seeking proposals to deliver the long-awaited rail project that – once completed – will create more space for trains to operate on the rail corridor between Deer Park and Rockbank.

The project will mean 17 kilometres of rail line being duplicated between Deer Park and Melton. An additional three kilometres of single track will be built west of Warrenheip.

The project is under the auspices of the Melbourne Metro Rail Authority, which has released a “request for proposal”, with applicants being given a May 1 deadline.

About 200 geotechnical investigations will be carried out before works begin, starting this month between Caroline Springs and Rockbank.

Kororoit MP Marlene Kairouz said the investigations would provide critical information about ground conditions that would inform how the project was designed and built.

“Early works are under way and the project is out to market – we’re getting on with it,” she said.

Construction is expected to start early next year, with a completion tipped for late 2019. Funding was allocated for the project in the 2016-17 state budget to address congestion and cater for growing patronage.