Haast residents fear a slip on a sheer cliff face nears Knights Point is threatening State Highway 6, and they have appealed to the New Zealand Transport Agency to act now before the road collapses.
The slip has worsened in the past couple of months, and is now nearing the edge of the cliff where the highway skirts around an old rockfall. The detour around the rockfall has been in place for possibly 10 years, pushing the road closer to the edge.
Locals say that most motorists are oblivious to the new slip, but Haast fisherman, Cr Kerry Eggeling, said he got a good look at it from out at sea: "It's huge, absolutely huge".
He believed the cliffside had slipped in two movements, the first in November. When he returned a month later it had tripled in size and he estimated that thousands of cubic metres of material had come down.
"If that drops away the road will be out for months," Cr Eggeling said.
The consequences of that would be akin to the flood that washed out the Wanganui River bridge, near Harihari, earlier this month as SH6 was the only route and a lifeline for South Westland.
"We've had two roads out through Christmas and it absolutely devastated businesses in Franz, Fox and Haast," he said.
The NZTA needed to start work now.
"This (collapse) is going to happen."
The slip was currently about 4m from the edge of the road, with a "virtually vertical" drop of 40m.
Jackson Bay fisherman Geoff Robson spotted the slip a couple of weeks ago.
"It looks like a lot of material has gone from it."
Haast supermarket owner Helen Rasmussen was concerned at the prospect of another prolonged road closure.
"It is concerning. We realise how fragile the infrastructure is for our community and businesses."
She hoped authorities were working now on a contingency plan should the road be lost.
Another Haast resident brought the concern to the attention of West Coast-Tasman MP Damien O'Connor, saying the danger could only be spotted from sea or from a helicopter, hence the possible lack of appreciation.
Mr O'Connor told the Greymouth Star the NZTA needed to heed local knowledge.
He applauded the response to the Harihari washout but said in this case the agency needed to look towards prevention rather than cure.
Meeting in Hokitika today, the Westland District Council said it would meet with NZTA to address the issue.
NZTA West Coast area manager Mark Pinner said the slip just north of the detour occurred in October.
The detour had been necessary to move away from the rockfall above the road some years ago.
Mr Pinner said they were regularly monitoring the site and would take immediate action to ensure the road was safeguarded.
"Safety is our utmost concern."
The agency was well aware of the impact of a sudden road closure.
"(NZTA) are doing everything we practically can to keep the road open while always being very aware that the safety of road users comes first."
- The Greymouth Star