Muddy water was still running off the hillside as dawn broke today and contractors and Grey District Council staff inspected the scene.
A second slip came down at noon, halting work to clear the road, which is not expected to reopen today. People were urged to keep away.
Two calls in rapid succession to Arnott Heights had the Greymouth and Cobden volunteer fire brigades scrambling - literally.
The pile of earth that slid down Milton Rd at 1am prompted the first 111 call, and just one minute later a kitchen fire at an Arnott Heights property - beyond the slip - was called in.
With the road buried in dirt, a police officer was able to reach the scene of the kitchen fire on foot, and ascertain that the fire was out.
Greymouth Volunteer Fire Brigade chief fire officer Lee Swinburn said an excavator left on site after starting remedial work on an earlier slip, was used to clear a rough path through the debris and the fire crew's 4WD emergency response vehicle was then sent through the muck to ensure the house was not under any further threat.
The kitchen fire was caused by unattended cooking.
Meanwhile, volunteers from the Cobden brigade assisted at the slip site.
One Milton Rd resident was woken by the car alarm and quickly moved the vehicle out of the way; another car was left unscathed - by just centimetres.
The Niwa weather station in Greymouth recorded 20mm between 10pm and 1am, on top of already sodden ground.
Arnott Heights resident Leigh Sullivan was still without electricity just before 9am. He said the slip happened at the same time as the thunder and lightning.
"We didn't know anything until about 6am - we noticed the power off. One lady messaged me at 6 to say the road was actually closed."
Mr Sullivan said the council was erecting a whole new retaining wall system after last year's slip.
"All we can do is carry on."
"It has undone our planned work, however preparation for this had just begun," transport and infrastructure manager Patrick Blanchfield said.
The slip was substantial, but the council had not received any reports of damage to nearby properties and the debris had mainly been confined to the Milton Rd carriageway.
"Today our aim is to restore access and install bunds to stabilise the slip. Our contractors are working hard to clear the debris and, all going to plan, expect to have the road open to one lane today."
The slip needed to settle before a full assessment could be carried out to confirm the extent of the damage, and what would be required to restore the site, Mr Blanchfield said.
Westpower general manager network Mark Blandford said the power outage in Greymouth in the early hours was caused by the same slip.
A total of 1319 consumers were initially affected. Supply was restored to most within an hour. Fifty-five customers were still without power just before 9am as a safety precaution while the road and power-lines was inspected.
An outage in South Westland yesterday afternoon was caused by a lightning strike near Mahinapua, affecting 1174 consumers as far south to Paringa. Power was off for 90 minutes.
- By Laura Mills and Meg Fulford
