Slip blocking Ngaio Gorge Rd route into Wellington won't be cleared before Sunday

Ngaio Gorge Road is likely to be closed till Sunday due to a large slip. Photo / Supplied

A landslide that's blocked a major Wellington access road will not be cleared until Sunday at the earliest, authorities say.

The steep bluff above Ngaio Gorge Rd first began crumbling on Saturday morning, and collapsed further on Sunday. The road is now completely covered in boulders and rubble, blocking access to Wellington from Khandallah.

A helicopter was expected to arrive in the gorge around 4.30pm to begin sluicing down the slip, a Wellington City Council spokesman said.

The sluicing aims to bring down loose rock so a 20-tonne excavator can then operate safely.

Tomorrow morning the stability of the slip will be reassessed.

Saw the slip on Ngaio Gorge this afternoon. As you can see, it is a big job and we need people to be patient and stay clear of the area pic.twitter.com/nwus7HZEk6

— Justin Lester (@justin_lester) July 31, 2017

Motorists are advised that Old Porirua Rd above the slip is closed to all through traffic. Residents of the road are still allowed downhill access to the narrow road, as are cyclists.

Drivers taking detours are being asked to drive slowly and carefully as the routes have become busy due to the closure of Ngaio Gorge Rd.

This includes Onslow Rd and Wadestown Rd - where there have been complaints vehicles are travelling too fast through the shopping area.