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Two road bridges blamed for exacerbating floods on the Thames coast are to be replaced over the next two years at a cost to Transit NZ of more than $7 million.
The agency announced yesterday that it had funds available to award a construction contract by the end of this year for new bridges across the flood-prone Tararu and Te Puru creeks on State Highway 25 north of Thames.
Single-lane Bailey bridges will be installed to keep the coastal highway to Coromandel township open during a construction period of about 18 months, although Transit does not expect these will be needed over the coming summer.
Transit's Waikato manager, Chris Allen, said the existing bridges were too low and short to handle more than about half the volume of water shooting downstream in big storms such as the 2002 "weather bomb" which caused millions of dollars of damage and claimed the life of a woman in a caravan washed away at nearby Waiomu.
Debris squashed against the bridges in storms has caused widespread flooding to homes upstream, particularly at Tararu, where Environment Waikato has installed a marine wall to protect about 35 properties.
Mr Allen said Transit would also build large river "training" walls to direct water flow to a widened channel under the new Tararu bridge, which would be about 20m long and 10m wide to carry two lanes of traffic and ample shoulders and footpaths for cyclists and pedestrians.
Te Puru's new bridge would be a 36m single-span structure, without need of the existing bridge's piers, which have caused scouring in heavy floods.
Environment Waikato, which has overseen a $10 million Government flood protection package with Thames-Coromandel District Council and other agencies, intends building stop-banks below and above the new bridge once it is completed.
Both bridges will be built higher than their predecessors. Mr Allen said there would be enough room for flows from floods of a severity not expected to hit the area more than once in every 100 years
As for the one-lane Kopu bridge south of Thames, notorious for holding up holiday traffic, Mr Allen said design work for a $32 million two-lane replacement structure was almost complete, although construction was unlikely to start until 2010-11.
