Source: Radio New Zealand
Queenstown’s historic Skippers Bridge. Google Maps
Popular Queenstown tourist attraction Skippers Bridge could be abandoned, according to an engineer’s report the council released on Thursday.
A Queenstown Lakes District Council spokesperson said the council had yet to consider the contents of the report and would be assessing the proposed options as part of the annual plan process.
First closed following a safety inspection in October last year, the Queenstown Lakes District Council announced last week the 124-year-old bridge would stay closed indefinitely due to safety risks.
The report, completed by engineering firm Stantec in mid-December, warned the bridge should not be reopened to either pedestrians or vehicles until damaged cables could be repaired or replaced, which it said would be “difficult and neither cheap nor quick to implement”.
It noted the “extensive brittle failure” of wires in the bridge’s cables made it impossible to test load capacity, but that testing would not necessarily prove the bridge’s capacity because of the risk of the cables failing unpredictably, and that testing itself could cause a sudden, catastrophic collapse.
Excavation of the portion of cables buried underground in December had revealed “severe brittle failure” of wires on the left of the bridge.
Engineers had found around one-fifth of cable cross sections were lost in some spots, while the initial report from October found between 30 and 60 percent of sections lost cables. Both reports said there was no visible damage to the cables above ground.
It was thought that the damage was caused by stress corrosion cracking and exacerbated by the bend of sections of cable over a ‘roll over’ plate.
Stress corrosion cracking can result in “a disastrous failure” occurring unexpectedly, the report said.
A photo from a report by engineering consultancy Stantec showing snapped wires making up some of the cables on the historic Skippers Canyon suspension bridge. Stantec
Three options were presented to maintain access: reaffixing the existing above-ground cables into new or extended anchor blocks on both sides of the bridge, replacing the cables or abandoning the existing bridge and constructing a new, shorter, lower pedestrian bridge about 300m downstream.
Plant and materials, including concrete, excavators and drill rigs, would have to be flown to the site by helicopter. Though consultants suggested it could be possible to construct a temporary flying fox to transport some construction materials across the river.
Either of the repair bids would be likely to cost more than a million dollars, the report said.
No cost was given for the new pedestrian bridge option, but the report noted it would make access “very challenging” and “possible only to a few people”.
The report noted a number of issues relating to the rest of the bridge that would have to be taken into account when considering whether to attempt to repair the worn cables.
These included that the 120-year-old towers at either end were unlikely to be earthquake safe, that the timber trusses and deck planks showed signs of decay, and concerns about the suitability of the site.
It was considered unlikely a replacement bridge in the same location would get a building consent or meet the Building Code.
A Stantec report from May noted there would need to be a significant increase in maintenance and upgrades to keep the bridge open going forward.
“Recent average annual maintenance expenditure on the bridge has been approximately $62,000 (+ GST) per year. We anticipate that considerably more maintenance effort will be required immediately and within the next 20 years a variety of significant upgrades are likely to be required to maintain the bridge in a trafficable state.”
In a statement, the QLDC said the report contained “a number of high-level options for the future of the structure” that would require further investigation and development before they could be properly costed and presented for a decision by the council.
The 96m long single lane bridge is the country’s highest suspension bridge, suspended on wire cables 91 metres above the Shotover River.
The bridge is the only route from Queenstown to Skippers Canyon and the Mount Aurum Recreation Reserve.
It forms part of theHeritage New Zealand category 1 historic places listing for Skippers Road. It is “one of the most outstanding of New Zealand’s surviving nineteenth century roads,” and one of the country’s “most enduring tourist attractions”, according to the Heritage New Zealand listing.
It also features on Engineering New Zealand’s Engineering Heritage Register.
It provides the only access to the 9100 hectare Mount Aurum Recreation Reserve and the historic Skippers Point School – the only significant building which remains from the settlement established in Skippers Canyon following the 1862 gold rush. The school, which opened in 1879, closed in 1927, and after a period as the Mount Aurum Station woolshed, fell into disrepair before before being restored by the Department of Conservation in the 1980 and 90s.
The neighbouring Mount Aurum Homestead was burnt to the ground in 2018.
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– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
