The 200m long Australian hardwood wharf, with is distinguishing cross-bracing and curved base, has been closed to the public for years because of its dangerous state. In 2008, a report was prepared on its restoration but nothing has happened since then, the structure continuing to deteriorate.
Now the wharf has been inspected again and a report for the Waitaki District Council indicates it is approaching the point of no return. It could cost up to $900,000 to repair piles and $1.5 million to restore bracing and decking for it to reopen to pedestrians and vehicles. Even demolishing it could cost $400,000.
"Ongoing deterioration is reaching tipping point," the council's corporate services group manager Carolyn Carter says in a report to Monday's harbour sub-committee meeting.
"Partial collapse of the structure can be expected," she said.
The wharf was opened in 1884, built for the start of New Zealand's frozen meat industry to take ships transporting the carcasses, and named after former Oamaru Mayor and chairman of the Oamaru Harbour Board, George Sumpter.
In May, the wharf was inspected again, with a principal focus on the condition of the piles supporting the structure.
Previous plans looked at preserving and partially restoring the wharf to make it safe for pedestrians. In 2008, the Sumpter Wharf Action Group was formed to pursue funding for the work, but without success.
The wharf is a major part of the Oamaru Harbour, designated a historic area by the New Zealand Historic Places Trust in 2004.
Both the council and trust want to preserve the wharf for its historic importance and a potential tourist attraction, but face the difficulty of the cost.
Options and opportunities to preserve the wharf will be discussed with interested heritage groups and potential funding bodies to find a way forward, Mrs Carter said.
The latest inspection by a diver showed about 67% of the 150 piles were no longer taking any significant load because they had deteriorated at low water level.
About 10% of the piles were either broken or had disappeared, leaving only stumps.
The cross-bracing holding the deck was not in a good condition.
Deck support timbers had also deteriorated, but much of it was salvageable.
"While volunteer labour and materials recovered from the demolition of other hardwood structures can be used to reduce the cost of the reinstatement, the cost of the piling repairs cannot because of the need for specialist plant and equipment," Mrs Carter said.
The wharf was beyond the stage of "a patch-up" and deterioration now affected the entire structure.
