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Strengthening work on the Alexandra bridge is now complete. New Zealand Transport Agency Otago senior network manager John Jarvis said work on the bridge was completed at the end of last month and scaffolding was being removed.
''We also took the opportunity to clean up all the pigeon droppings,'' he said.
The $770,000 project went as planned and stayed within budget and had ''pretty minimal disruption''.
The work included fixing steel plates to increase the depth and thickness of 21 beams, which would allow the bridge to carry large trucks with loads between 45 and 61 tonnes.
It was part of bridge-strengthening work that was being carried out between Alexandra and Queenstown, which would cost a total of $1.6 million.
The Roaring Meg Bridge, Gentle Annie Bridge and Kawarau River bridge on State Highway 6 between Cromwell and Queenstown were also part of the programme.
Cleaning up after the pigeons was necessary because of the surface damage it caused, which, if left for a long time, could damage the steel, he said.
The bridge's ''nooks and crannies'' had also been cleaned, painted and primed to protect the steel.
Pigeons were culled regularly, the operation being carried out at night using night-vision goggles and air rifles with silencers, after unsuccessful attempts using poisoned bait.
''It's the most effective way of dealing with them.''
The agency had also looked at using bird control spikes but the the surface of the bridge made it difficult to attach them, Mr Jarvis said.