The 40-year-old Roxburgh Bridge, spanning the Clutha River on the outskirts of the town, needs repairs because of structural damage. A speed restriction of 20kmh has been imposed.
''It's not serious enough damage for us to close the bridge but it is concerning that this has happened on one of our more modern bridges. It's 40 years old and it shouldn't be getting this sort of problem,'' roading engineer Scott Graham said. One abutment had ''relaxed'', meaning there was no gap between the abutment and deck, Mr Graham said. The two parts should not be in contact. That has caused problems on the opposite side of the bridge as well. Continued use by heavy vehicles would cause more damage and a speed restriction has been imposed, instead of a weight restriction.
''If a weight restriction was imposed, this would require heavy vehicles to detour around the Roxburgh Dam,'' council roading manager Julie Muir said.
''A temporary speed restriction therefore has a lesser impact on the bridge users and was our preferred option.''
A speed hump has also been installed at the town side of the bridge to slow traffic. Mr Graham said he was aware of some adverse comments about the design of the speed hump and would take another look at its height.
Options for repairing the abutment will be investigated but it was too soon to estimate the cost of repairs, he said. The damage must have been caused by a combination of factors as no single factor had been highlighted. A landslip had been ruled out as the cause, Mr Graham said. The council was responsible for 175 bridges and the damage was discovered during a review of the district's bridges.
''We weren't expecting this one to have any problems, so it wasn't included in our budget for the coming financial year and we'll have to do some re-juggling of the budget to finance the repairs.''
Ms Muir said the speed limit on the bridge was likely to remain in force for about six months.
