Colditz said filling the cracks with resin from the underside of the bridge will strengthen the span at the same time as minimising disruption for drivers.
“The bridge is structurally sound and safe to use but filling cracks, which have developed over many years, is essential for the life of the bridge,” he said.
“While we understand the lower speed will be an inconvenience for road users, it is critical everyone complies with the temporary 30km/h speed limit. This is important to keep vibrations to a minimum to reduce the impact on the bridge structure while the work takes place and to allow the resin to cure.
The work is expected to be finished towards the end of the first week of December, weather permitting.
In August last year, the agency imposed a speed restriction on the bridge to limit the risk of deterioration pending further assessment and likely restrengthening after cracks were revealed in an in-depth assessment of the bridge earlier in 2022.
It revealed “a number” of cracks on the spans, triggering fast-track design and a high priority for repairs.
The bridge replaced another which was swept away in the 1938 Eskdale flood, and Waka Kotahi has conceded it wasn’t designed for the heavy-vehicle use now prevalent with logging trucks.