Workers abseil to repair State Highway 4 slip in Whanganui

Nailing rock into place and spraying concrete onto a cliff face make for precarious work on Anzac Pde/SH4 in Whanganui. Photo / Bevan Conley

A business contracted to repair a slip on State Highway 4 through Whanganui has needed abseiling skills for the job.

Ground Stabilisation International (GSI), a geotechnical company with expertise in abseiling, was doing the job, Waka Kotahi NZ Transport Agency regional transport systems manager Ross I'Anson said.

Rock and soil came down onto the highway near Georgetti Rd twice this year - on March 9 and April 5.

The repair entails soil nailing and shotcreting - which is spraying concrete on to the slip face. Above the concrete, plants will be hydroseeded and, above that, a safety fence will be installed above the drop from the Wairere Rd section.

Contracting GSI meant cranes were not needed, I'Anson said. A crane would have reduced the available width of the highway.

The cost of the repair is estimated at $800,000. He would not say how much of that would be paid by Waka Kotahi and how much by the owner of the private property affected.

While the repair is taking place, shipping containers are being used to prevent debris from falling on to the highway, and speed on that section of road is reduced to 30km/h.

While work is taking place, drivers are restricted to one lane by stop/go traffic management.

The repair is expected to be finished by Christmas.