Any hopes of Saturday's planned re-opening of Graham Valley Rd were washed away in last Tuesday's heavy rainstorm which brought down another cascade of boulders.
The popular access into Kahurangi National Park could remain shut until Christmas if all the recently fallen rock has to be removed.
It's the fourth time the road has been closed in the last 16 months. The latest slip came days before the road was again due to be re-opened since the last major slip in June.
The road's maintenance is shared between the Department of Conservation, Tasman District Council and the New Zealand Transport Agency.
Clearing the active slip face has so far cost around $750,000. It's estimated it could cost a further $300,000 if all of the latest fallen debris has to be removed.
DOC Motueka field base community services manager Mark Townsend said around 150 millimetres of rain was recorded in Brooklyn during the rainstorm - but much more fell in the valley.
He said the rain brought down the remaining rock at the top of the slip face. "We have managed to put a track through to provide access for residents and the Friends of Flora but the rock has fallen the full length of the face."
Mr Townsend said geo-technical engineers would look at the face early this week. "Their advice will dictate the options we can look at."
He said the road was ready to re-open this Saturday. "We had it all ready and had spread the gravel and then we had another horrible rainstorm."
The council's transportation maintenance engineer, Selwyn Steedman, said today's predicted heavy rain would indicate if the remaining face was stable or not.
"We have to wait and see if we have to take all the rock away. It could be eight to 10 weeks' work if we have to remove it all."
Trying to keep the road open had so far cost parties around $750,000 and removing the latest slip could cost a further $300,000, he said.
Other replacement roading routes to access the park had been considered but the nature of the country meant they were very difficult, he said.
In late June last year the unstable face first collapsed, bringing down around 30,000 cubic metres of debris and closing the road for five months.
Smaller slips earlier this year had twice closed the road, and work clearing the rockfall had been almost complete until another major slump in mid- June.
In Motueka's West Bank, Brooklyn, Dovedale, Rosedale and Riwaka, the rain also caused slips, had spread debris across roads and caused scouring to creeks.
- © Fairfax NZ News