The project, which would see the memorial expanded with new gallery spaces while tearing down others, has been given the green light by parliament and the Environment Department and now requires its final approval from the National Capital Authority before work can begin.

Memorial director Matt Anderson told a Senate estimates committee on Wednesday he believed final approval could be achieved with the memorial working through any necessary revisions deemed by the authority in order to get the tick.

"Of course, the decision is ultimately [the NCA's] to make but just like every other process that we've gone through ... were [the NCA] to come back to us with revisions, then we go away and we make those revisions," Mr Anderson said on Wednesday evening.

"I'm just confident that, you know, having been in conversation with them for such a long time ... we will follow their direction.

"This is another step that we need to adhere to."

While approval had not yet been granted, some work had been done to make preparations for the project's early works, he said.

This included closing down Anzac Hall to the public in March and relocating exhibition items to its storage facility in Mitchell - a move he said was entirely reversible if the plans are rejected.

Mr Anderson said he would continue to work with the authority to address any issues public submissions raised, acknowledging more public consultation would be needed before the main works could begin.

"We are bound by whatever directions the National Capital Authority place upon us. We look forward to working with them. We look forward to continuing to engage [with them]," Mr Anderson said.

"This is just for the early works program, this isn't for the main design package and I imagine there'll be just as many submissions when we - if we - get through this stage."

Program director Wayne Hitches added four tenders had gone to market for the larger project with three suppliers being identified as the preferred contractor if authority approval is given.

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The national authority has uploaded nearly half of the 599 public submissions it received during its consultation period with the overwhelming majority of the submissions arguing against the plans.

Common themes among the dissenters included opposition of the Anzac Hall's destruction, noting its heritage value, and the planned felling of more than a hundred trees around the grounds.

Mr Anderson earlier told The Canberra Times the planned demolition and replacement of Anzac Hall would grow the institution's heritage value by creating more space to tell Australia's military history.

"The heritage value of Anzac Hall is the stories that are told within it, not the blade wall, and the roof line," he said in April, referring to the building's signature design features.

"If we're doubling the space available to tell the stories, we're doubling the heritage value of that building, and of the memorial's power to tell the story of continuing service and sacrifice.

"We're just not doing that, we're not meeting that obligation to be fair to contemporary veterans, modern veterans, in the same way we've told the stories of their forebears."

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