Work on the Beaumont Bridge seems to have been going on forever. What's going on? Why hasn't NZTA simply replaced the bridge? How much has been spent and when is the work going to end? Hamish MacLean finds out.
Fewer trucks on the road: that goal is behind the work that has the New Zealand Transport Agency (NZTA) rerouting traffic away from the Beaumont Bridge yet again.
The latest closure of the bridge on State Highway 8 is part of a programme to strengthen bridges across the South Island.
NZTA project team manager Simon Underwood says the work on trucking routes from Picton to Bluff, Christchurch to Queenstown, and Dunedin to Queenstown will allow ''high-productivity motor vehicle use'' - bigger trucks.
And heavier trucks carrying larger loads needed stronger bridges.
''The purpose [of the current work] is so we can make the route between Dunedin and Queenstown more efficient for freight traffic,'' Mr Underwood says.
''The general theory is that the highway is then able to carry the same amount of freight on these trucks - that's what it's all about.
''For the freight operators, it makes their business more efficient, for the consumer, freighting costs come down per unit and for the motorists there's fewer trucks for the same amount of freight carried.''
Since Monday, the Beaumont Bridge has been closed to traffic, with detours in place, from 7pm-6am on weekdays.
The bridge will be opened briefly on the hour every hour to clear any traffic waiting.
Last month, at a cost of $50,000, the bridge was closed as the strengthening work began: a truss damaged in a car crash was removed, Mr Underwood says.
In the latest work, steel is being added to to provide more structural integrity.
When finished, the gross weight that trucks on SH8 can carry without specific permits will rise from 44 tonnes to 62 tonnes.
But it will need another round of strengthening in six to nine months.
However, even then the scaffolding will remain on the bridge permanently as as monitoring of the historic structure continues, Mr Underwood says.
The annual maintenance bill for the bridge is about $250,000.
In 2008-09, work on the Beaumont Bridge cost $800,000, because rather than the regular maintenance programme, work was undertaken to extend its life.
Maintenance done to stem fatigue is ''working quite well'', he says.
The latest work is only to ensure the bridge can carry high-productivity motor vehicles.
The NZTA originally planned to begin investigating options for a new bridge at Beaumont this year, says Ian Duncan, the NZTA acting southern business unit manager for highway network operations.
''For the past two years, the transport agency has been actively monitoring the Beaumont Bridge deck and beams, and managing the bridge by traffic signals. The monitoring has shown us that our original concerns the structure was beginning to reach the end of its serviceable life are unfounded.
''The structure is stable and can effectively be maintained for longer than we previously anticipated.''
NZTA plans to have a business case in 2018-19 to replace the bridge, construction is tentatively expected in 2020-21, he says.
''There's a big difference in scale and cost and preparation between adding steel to an existing bridge and building a whole new bridge,'' Mr Underwood says.
The cost to replace the bridge is likely to be $20million, about the same as for the new Kawarau Falls bridge, which is out for tender, he says.
About 1800 vehicles cross the Beaumont Bridge each day, a figure Mr Underwood describes as ''modest'' for bridges in the area.
At the Kawarau Falls bridge, traffic volumes topped 6000 vehicles per day.
It is important Beaumont's bridge is not replaced earlier than is necessary.
''There's a big difference in scale and cost and preparation between adding steel to an existing bridge and building a whole new bridge,'' Mr Underwood says.
''It is still an old bridge and we are looking ahead. It's still on the horizon for replacement.''
Bridge work
• Detours at Beaumont Bridge from June 22-July 11, on Monday to Friday nights 7pm-6am.
• Traffic queues at the bridge cleared on the hour, every hour for local traffic.
• The latest work is the second of three phases of bridge strengthening.
• The strengthening will allow vehicles with up to 62-tonne loads to use the bridge.
• From 2008-16 up to $3 million could be spent on the Beaumont Bridge.
• Annual maintenance costs $200,000.
• The bridge could be replaced by 2021 and could cost $20 million.
Source: NZTA
