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Tim Hanna and Dipton farmer Murray Johns had a good look at the Benmore bridge which is currently closed and in danger of remaining closed for good.
It is one of a number of bridges facing this outcome and one of a large number of similar aged wooden bridges that may also be at risk of closure. Tim reports that “The bridge had clearly taken a substantial
hit from a heavy object, probably a big willow tree washed out while the
river was in spate, and one structure of piles has been nudged slightly
out of line“.
Some sections of the railings on the bridge seemed less than ideal, although much of it had been obviously properly repaired in recent times, and the deck, although somewhat beaten up had also had a significant amount of planking replaced relatively recently. Below the bridge massive steel beams, put in place about 30 years ago, that run the length of the section of bridge spanning the river seemed to be in first rate condition. The heavy timbers beneath the bridge also seemed to be in very good condition with no obvious signs of deterioration other than the single set of slightly askew piles.
Dipton farmer Murray Johns and Tim Hanna at the recently closed
For many years a dragline reportedly took shingle from the river immediately down-river of the bridge which assisted the flow of the river and possibly assisted in the prevention of the kind of hit the bridge has taken from floating debris. After the local council banned the operation, shingle built up beneath the bridge and very possibly exacerbated problems during times of high water flow.
Some locals have expressed the idea that reopening the bridge for light traffic and ensuring for example that trucks could not use it by installing a steel beam at the required height across the access from both sides would be at least better than a complete closure. It would seem that what is urgently needed is a proper engineering assessment of all the available options including straitening the affected piles and perhaps driving another set into the river bed beside them. Repairs to the top side of the bridge would seem to be relatively straight forward, especially if heavy traffic was permanently blocked from using the bridge.
When the Pyramid Bridge near Riversdale was blown apart by debris washing down the Mataura River, Gore Mayor Tracey Hicks expressed extreme surprise; and similarly, Southland’s mayor is professing shock at the status of the older bridges on our road network. It is hard to see how this seeming ignorance of such an essential service as our road network came to be. In the case of the Pyramid Bridge, the congestion of the river by dangerous amounts of debris caused by the collapse of willow branches into the river following a heavy snowstorm was well appreciated. In fact, a digger was hard at work clearing the worst of it when a complaint by a fisherman caused the council to stop all work. The rest, as they say, is history.
The question of our ageing bridges is thorny and obviously, the first objective must be to ensure that they are safe. However, we must also ensure our rural communities are not isolated by routine closures by councils so afraid of their liability exposure that sensible, safe options are not even explored. Closing old bridges in times of flood, installing sensing equipment to measure vibration and deflection and perhaps putting a 4-inch layer of re-enforced concrete over existing essentially sound decking when pile supports are sound, are the kinds of options we need to explore.
We need to extend the life of these bridges if it is possible to do it safely before replacement structures can be built.
We need a properly assessed timetable for bridge replacements and we then need to work out how we prioritize such work and mitigate against the possibility that we might not be able to replace all of them to ensure our rural community is not unreasonably disadvantaged. One thing we don’t need is political leadership that is suddenly surprised that we have a problem.