However, Dunedin City Council staff remain confident it will eventually emerge from tanks of treatment solution to be displayed at two separate locations - inside the Wall Street mall and Otago Settlers Museum - while a third piece is kept in storage.
The historic manuka and kanuka causeway, believed to date back to the 1850s, was described as a find of national significance when unearthed at the Wall St construction site in June 2008.
About 60% of it was deemed too rotten to save, but council staff had hoped the remains might be ready to display inside the mall - where a photograph of the real thing lies under a glass display space - by mid-2010.
However, it had remained in its chemical bath since then, with preservation efforts being overseen by wet-wood conservation expert Dilys Johns, of the University of Auckland.
The timber was submerged in polyethylene glycol, a water-soluble wax, which soaked into the timber's cell structure and provided support when water was removed by drying, the experts said at the time.
Museum director Linda Wigley said yesterday the causeway's remains were not expected to emerge from the tanks until the middle of next year.
Asked about the shifting timeline, she said it was her understanding the causeway was always intended to be ready next year.
And, after 150 years in the waterlogged ground, it was important not to rush the process, she said.
"If you just dry the wood out everything will just fall apart and disintegrate. You don't want to rush it. It's got to be robust for the future."
