KiwiRail chief operating officer for construction delivery Robert Gibbes said consents had been lodged and preparation was under way for the next stage of the project.
Staged demolition was starting this year, and the new site was expected to be operational by mid-late 2023.
Detailed design work for the redevelopment was being carried out at present.
Around 70 people were working on the project and those numbers were expected to grow as the work progressed, Mr Gibbes said.
A new wagon assembly facility would complete two wagons a day, with an expectation that at least 1500 wagons would be built over three years.
There would be a new traverser, cranes and jacks, and electric shunt engines, as well as new shared offices and workshops.
When the work was complete more than 100 KiwiRail staff would work from the site, Mr Gibbes said.