A $1.6 million project to repair slips triggered by a monster storm on State Highway 1 near Moerewa will be finished within the next few weeks - two and a half years after Northland's road network suffered some of its worst damage on record.

The passing lane and shoulder on Turntable Hill have been closed since July 2014 because of a series of slips and slumps.

The same storm caused major slips on SH1 near Kawakawa and SH14 at Kaihu, cutting the Far North off from the rest of New Zealand for days.

One of the two Turntable Hill slips worsened in another bout of heavy rain in August this year.

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The road cones and closed passing lane had become part of the Mid North landscape but should be gone by mid-December, with the slip stabilised and re-sealing near Hautapu Rd completed this week.

Further work will be required to install a new guardrail and finish drainage work next to the downhill lane.

The NZ Transport Agency's Northland highway manager, Brett Gliddon, said reopening of the 1km-long northbound passing lane before the busy summer holiday season would ease delays for motorists heading up the hill.

The time taken to carry out repairs was caused by the difficult location, complex soil and ground conditions, and the challenge of coming up with a suitable engineering solution.

However, the NZTA had been able to maintain two-way traffic during the bulk of the construction process, minimising delays to motorists, he said.

Slips and slumps on Turntable Hill, Moerewa.
Slips and slumps on Turntable Hill, Moerewa.

The total cost of repairs and re-surfacing for both slips was $1.6m.

When the Advocate first reported on the Turntable Hill slip, repairs were expected to take six weeks.

A bypass around the worst slip of the 2014 storm, on SH1 south of Kawakawa, was opened within days but permanent repairs took until August 2015 and cost $3.25m.