Rail workers say they will not set foot on a rail yard in Melbourne's west if it becomes a dangerous dump site for the West Gate Tunnel's toxic soil, potentially leading to mass train cancellations on the strained V/Line network.

The Age has revealed a controversial state government proposal to dump the toll road's soil — contaminated with potential carcinogens PFAS and asbestos — at a Wyndham Vale rail yard, just metres away from housing and four planned schools.

The Wyndham Vale rail stabling yard now under construction is just north of housing estates. Credit:Joe Armao

The government has said it plans to use the 82-hectare government-owned site in Treasurer Tim Pallas' Werribee electorate as a "back-up, temporary" dumping ground, but the move has triggered a fierce backlash among local residents.

The West Gate Tunnel builders have threatened to leave the project amid an impasse with Transurban and the state government over how to deal with PFAS soil. The builders are expected to release tender documents for the dumping of 2.3 million tonnes of soil by the end of this week.