The Rangitata River rail bridge has been temporarily repaired and KiwiRail is looking at a permanent fix.

KiwiRail’s chief infrastructure officer André Lovatt said the temporary repairs to the 610-metre rail bridge were completed on Thursday after one of the concrete piers was washed away in flood waters on April 12.

The temporary fix has been a “significant undertaking” to restore the rail link between Ashburton and Timaru, he said.

The repairs involved changing the flow of the river, and building caissons - watertight boxes to enable construction – to install a new structure beneath the bridge.

“With the line reopened, we will now begin work to permanently replace the pier.

“The design is underway and initial works will begin next week.

The work will include driving new casings deeper into the riverbed and building a steel and concrete pier structure, he said.

“We expect the permanent repairs will take around 10 – 12 weeks.”

During the bridge closure, the new Fairfield Freight Hub played an important role with road-bridging operations, Lovatt said.

The return of normal rail services “will make freight movements more efficient and reduce the number of heavy trucks moving between Timaru, Ashburton and Christchurch”.

The search for the missing pier, which could be buried in the riverbed, also continues.