In August 2014, Roads and Freight Minister Duncan Gay announced the government would be looking to the private sector to build the 35-kilometre line.

This was in part because the cost – estimated in 2013 to be $667 million – was too much for the state government to fund.

A spokeswoman from Transport for NSW (TfNSW) said the expression of interest period was so the government could gauge the level of interest from the private sector to ‘‘construct, operate and maintain the proposed Maldon to Dombarton railway on a commercially sustainable basis without any NSW government funding.’’

Two groups have registered an interest in building the line – one a single entity and the other  a consortium.

The single entity is Australian-based ATEC Rail Group, which has developed and managed freight rail lines in NSW and Queensland.

Multinational engineering firm Aurecon, which has handled numerous infrastructure projects in Australia, and funds management group Centurion Custodian have put in a joint submission.

Aurecon had also tendered to enhance the Maldon-Dombarton tunnel design in 2012.

The TfNSW spokeswoman said they were evaluating the two responses against the criteria.

‘‘The outcome will determine the next steps forward for the proposed Maldon to Dombarton railway,’’ she said.

The rail line has long been seen as one of the missing links in the NSW rail network.

It would offer a new route between Port Kembla and coal-mining districts, as well as direct freight access to western Sydney.

In addition it would provide a viable alternative to Mount Ousley Road for freight transportation.