Drivers of heavy vehicles will have to keep driving the long way into St Bathans after the Central Otago District Council this week decided the five-tonne weight restriction on the St Bathans Downs Rd bridge would remain while options to repair or remove the damaged bridge were investigated.
The restriction has been in place since December last year after it was found the bridge had slumped due to degradation of its piles following floods.
However, it could be up to three years before its fate is decided. That is how long it will take for the council to develop and consult on a bridge strategy.
Council roading manager Julie Muir said the council owned 176 bridges and many would need significant work in the next 10 to 20 years. However, many were also located on roads with few ratepayers, meaning it would be hard to get the work subsidised by the New Zealand Transport Agency.
"In order to be able to make informed decisions, council and the community need to know what bridges will require significant work in the future, what this will cost the community and what the level of service options and costs are," she said in a report to council.
At a meeting this week, the council roading committee recommended that remedial or removal options and an investigation of alternative routes be included in the development and consultation on the council's bridge strategy.
The concrete piles of the 65-year old St Bathans Downs Road bridge, which crosses the Manuherikia River, were damaged after various floods, causing the structure to settle and affecting its stability.
Council archives show settlement may have been occurring for some time. Cracking was first noted in 1985, but the bridge has become much worse since flooding last October.
In December, the bridge was measured and the deck was found to have slumped 100mm.
Another factor affecting the stability of the bridge is the river bed, which council roading manager Julie Muir said might have been "degraded" by up to 3m in depth around the piles.
In a report to the council, she said that as well as affecting the weight-bearing capacity of the piles, it had made the bridge more susceptible to damage from floods and earthquakes.
The alternative route available for heavy traffic, such as stock trucks, is along State Highway 85, St Bathans Loop Rd and Beattie Rd, but that adds about 18km to the trip.
The options
• Options for the St Bathans Downs Rd bridge and estimated costs:
• Remedial work: $350,000
• Replacement: $1.37 million
• Ford construction: $426,000
• Posting and monitoring: $4000 per year
• Closure: $30,000
