Rangitata SH1 bridge pile repair underway

From early next week, NZ Transport Agency Waka Kotahi (NZTA) will be repairing a bridge pile at the northern end of the Rangitata River Bridge, SH1.

Most drivers and traffic will continue to cross the double-lane bridge as per normal, says Mark Pinner, System Manager for NZTA in the Central South Island.

“Only the heaviest overweight permitted vehicles and all overweights heading south, will need to take an alternative inland route while this work is underway over three or so weeks,” he says.

There are no signs of any weakness in the bridge deck, reports NZTA’s structural engineering team, with the restrictions on heaviest vehicles a precautionary measure.

The broken bridge pile was only visible after dewatering/ draining the river water around the pile’s base just over a week ago.

“We were carrying out our own repairs and maintenance under the Rangitata River bridge at the same time KiwiRail was carrying out emergency repairs to their rail bridge nearby,” says Mr Pinner. “It made sense to inspect the way the river had been cutting into the northern bank while KiwiRail had an access road in place and water channelled away from the north side.

“While we are not concerned about the bridge’s strength or stability, we need to restore it to close to 100% of its design as soon as we can. It is a relatively straightforward repair and road users will be largely unaffected by this work.”

NZTA has already repaired and restored a number of concrete piles under the road bridge where the concrete had been worn away by the river flow. One final pile which was showing signs of wear was further investigated on Friday, 21 June. After draining the river at that point, the extent of damage was obvious.

Over the next three weeks, a piling rig and structural repair team will reinstate a temporary pile and restore the bridge’s full weight-bearing capacity. A full, permanent pile replacement is planned, likely to take around eight weeks to install.

Some overweight vehicles will be affected for the next few weeks

To minimise the impact on the bridge while this work is underway, two restrictions will be placed on overweight permit holders, as a precautionary measure:

• Overweight traffic will not be permitted for vehicles travelling in the southbound lane – towards Orari/Timaru. These vehicles will have to take an alternative inland route.
• Overweight traffic will not be permitted for vehicles required to travel along the centre of the bridge in either direction, (eg heavy plant like bulldozers, transformers on trailers with a pilot vehicle). These vehicles will have to take an alternative inland route also.
• These drivers and operators need to check with the Timaru and Ashburton District councils to get their permits altered for the inland routes. NZTA has contacted permit holders so they are aware of these changes.

Overweight traffic remains accessible for vehicles travelling in the northbound lane, towards Hinds/ Ashburton – no change required.  

All other traffic on the bridge including HPMV will be unaffected by the repairs.