Photo: SUPPLIED / DUNEDIN CITY COUNCIL
Work to dismantle part of the country's only gasworks will begin soon in Dunedin after an imminent risk to public safety was discovered.
The Dunedin Gasworks Museum was closed earlier this month while the safety of its 25-metre high chimney stack was being assessed following possible earthquake damage.
The Dunedin City Council, which owns the Category 1 historic place, said drone footage showed that the structure had changed and it received advice about the "imminent risk".
The footage showed evidence of new cracks, movement within the structure and further deterioration of a large crack which appeared to pre-date last month's earthquake.
A safety barrier was put in place to keep people away from the chimney, and a neighbouring supermarket was issued an Affected Building Notice and had made changes to mitigate any potential risks if the chimney collapsed.
The council's property services group manager Anna Nilsen said they had received advice on different options to eliminate the risk of collapse and the current risks to public safety including temporarily securing the chimney.
An engineer's report found the chimney's lower sections had not been significantly altered, despite concerning cracks higher up.
Council staff and the Dunedin Gasworks Museum Trust, which operates the museum, decided to deconstruct the chimney above a crack line, with work expected to start next week.
That would remove about 6-8 metres of the chimney stack.
Dunedin Gasworks in a photo taken about 1880. Photo: Dunedin Gasworks Museum
"Temporarily securing the structure may reduce the risk of collapse, but deconstruction would still be required at some point in the future," Nilsen said.
"We know this is not the outcome the trust or heritage lovers want, but public safety needs to come first."
Naylor Love would undertake the urgent deconstruction work over the coming weeks in a way "that is sympathetic to heritage values and protects the possibility of reconstruction using the same materials at a future date", she said.
The council wasn't ruling out rebuilding the chimney in the future, but said public safety came first and any reconstruction would depend on funding and feasibility assessments, she said.
The council had carried out periodic visual inspections of the site.
"Until recently, cracks in the chimney structure were not considered a major issue and the chimney was not at risk of immediate failure, despite some maintenance needs which are to be expected for a structure of its age," Nilsen said.
Last year, an engineering review recommended a more detailed seismic assessment of the chimney was carried out, which was being considered as part of the council's wider work to address seismic issues across its properties.
The drone footage was sought after staff noticed changes to the chimney structure.
The Gasworks Museum has been reopened, but the area immediately surrounding the chimney remained cordoned off.
