strong>Omoto slip/ landslide near Greymouth, SH7 - what we know and the way forward

A landslide at Omoto, between Greymouth and Stillwater, on State Highway 7 is showing no signs of slowing down.

Accelerated movement at the historic slip site closed the highway on Wednesday night and with more rain forecast it will remain closed through the weekend and be reassessed Monday afternoon, says NZ Transport Agency Maintenance Contract Manager Moira Whinham.

The detour is on the north side of the Grey River via Taylorville. Traffic is being diverted at each end at the Stillwater and Cobden bridges. The detour adds a few minutes to the overall journey, Greymouth to Reefton.

Meanwhile the rail line at Omoto is also closed. The TranzAlpine is still running to Arthur’s Pass. Freight services are also affected, says KiwiRail South Island General Manager Operations Jeanine Benson.

Background
Wet weather and subsequent land saturation at the slip site in recent weeks has contributed to the landslide’s movement from mid-August. At that stage and until this week, Transport Agency crews were able to maintain a single lane of traffic between Greymouth and Kaiata and keep SH7 open.

“Ground investigations have now been completed,” says Ms Whinham. “We are considering a number of medium and long-term remedial options, working closely with KiwiRail and our geotechnical advisors on a solution for both the rail and the road. But, we need the ground to stop moving before these can be put in place.

“At this stage the best thing we can do is to continue to monitor the rate of slip movement, keep the highway closed and the detour in place, for everyone’s safety,” says Ms Whinham.

“We thank local people who are inconvenienced by this closure for their patience and we will be doing whatever short-term measures we can to manage ground movements and saturation at the site.”

These include reinstating the swale/ depression at the road to prevent additional stormwater entering the slip and the head of the slope. The Transport Agency will also investigate whether any changes can be made to the culvert east of the slip site to better cut off stormwater at this point.

• Web link for Omoto landslide ie open/ closed SH7 east of Greymouth: https://www.journeys.nzta.govt.nz/traffic/roadclosures/270371

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