From tomorrow (18 April), work will begin to shore up a collapsing quarry face in the Vale.
Building the barrier at L'Epine will allow the minor lane next to it to reopen.
The road was closed without warning last June because it was considered dangerous.
The Vale Constables were told by Guernsey Water that the barrier, or 'bund' is a sizeable structure.
The stone will be brought in by tractor, so parking in the access road will be suspended on weekdays.

Gift to private schools could save Guernsey taxpayers £2.2m a year
Beau Sejour closed after legionella detected
Scorecard for people in Guernsey to monitor their alcohol intake
Plans to sell Guernsey rectory
Thousands of new species discovered in Guernsey’s freshwater habitats
Guernsey Post to end air deliveries
Channel Islands Pride: What's on where?
18 months before work can begin on resurfacing Alderney's runway