Wall Street project manager Dave McKenzie said the wooden remains - described as a find of national significance when unearthed last year - were still in the hands of conservators.
About 60% of the pedestrian causeway, made from manuka and kanuka, had been found to be too rotten to be saved following its discovery in June last year. The remaining 40% of material had been emersed in a skip of glycol solution off-site to preserve it.
Another set of tests - including core samples - would be taken in three months to check on progress, Mr McKenzie said.
"Really, we are in their [conservators'] hands as to their process. My guess is it will be more than a year away.
"It's slowly seeping in, but the parts we have saved are pretty dense and solid, so it's going to take a while."
A 3m-diameter circular image of the causeway's remains had been installed under 40mm-thick glass inside the mall, he said. The image would be unveiled by Mayor Peter Chin during the official opening of the development on Friday night, he said.
