Work on a major repair to State Highway 5 at Tumunui, south of Rotorua, began 15 August and motorists are advised to expect lengthy delays and consider using an alternative route.

NZ Transport Agency contractors will be digging out and replacing a 12-metre wide, four-metre deep stretch of the highway, which has been damaged by a natural process called tunnel erosion.

Tunnel erosion starts at depth and gradually migrates to the surface, in this case causing cracks to appear in the road.

The Transport Agency‘s Bay of Plenty highway manager, Niclas Johansson, said work to repair the road was weather dependent but expected to take approximately six weeks.

“The damaged section of road will be dug out and replaced with layers of rocks wrapped in geo-textile to act as a bridge across the underlying weak area,” he said.

“The excavation will be four metres deep and extend for most of the width of the road. One lane of the road will be worked on at a time to allow traffic to pass through.”

A 30km/h speed restriction and stop/go traffic management has been in place since the damage to the road first occurred in late July, and this will remain in place until the work is completed.

Motorists should be prepared for delays of up to 15 minutes during work hours and are urged to consider using an alternative route, such as State Highway 1 and State Highway 30.