Explosives to be used on Milford boulders

This large slip blocked the road to Milford Sound in Fiordland. Photo / Supplied

Engineers will today pack explosives into huge boulders that have closed Milford Rd in Fiordland, as residents face their fifth day cut off.

A series of slips closed the only road to the area on Friday during bad weather, bringing 200-tonne boulders crashing onto the road.

New Zealand Transport Authority Southland area manager Peter Robinson said engineers were today blowing up the bigger rocks.

"They've got machines that drill into the rock leaving about a 20mm diameter hole into which they pack explosives, then they get back to a safe distance and pop it," he said.

It was hoped one lane would be open to traffic tomorrow but the weather could still get in the way of their plans.

"The issue is we still have some rock which in heavy rain may be an issue. It's meant to rain hard later and if it becomes too heavy we'll have to withdraw from the site because of the risk of further landslides," Mr Robinson said.

Fortunately, the road had been closed because of an avalanche risk when the slips happened so tourists had already been asked to leave the area.

Mr Robinson said Milford residents were well set up to live without the road.

Milford Sound Lodge manager Japke Doodeman said yesterday the closure meant the lodge was losing about 30 people a day.

"But considering all the boat companies and kayak companies that have buses coming in on a daily basis as well, it's quite a lot more than that."

There were 26 people staying at the lodge when the road was closed. Most had been flown out of the area.

Milford was "regularly" cut off, and the business was prepared when it happened, but this weekend's slip was "massive", she said.

"Over winter it does happen a bit more often, definitely towards the spring season because that's when the avalanche risk gets higher."