An anchored piled wall is to be designed by the NZ Transport Agency to be built along the seaward side of State Highway 6 to support the highway at Knight's Point if there is any further deterioration at the site of the slip.
The Transport Agency's State Highway Operations Manager Pete Connors says they will continue to monitor the slip on a weekly basis and the remedial work will be undertaken only if any deterioration at the site places at risk of the loss of access along the stretch of road.
This week's decision follows the receipt late last month of the full assessment and review of the on-site geotechnical and engineering investigations which are currently being peer reviewed.
"Since the slip happened in October last year during heavy rain, we have been monitoring the site and there has been no further movement, despite the area experiencing some of the worst winter weather in recent years.
"The slip remains five metres from the road and it is anticipated that in even the worst case scenario of rapid deterioration at the site, single lane access will be able to be maintained," he says.
In making its decision, the Transport Agency considered four main options:
Mr Connors says with any of the last three options, it would take one to three months to complete the work, and as a conservative estimate, cost up to $2 million.
"Following the peer review, work will get underway designing the preferred option in case the worst does happens. Once this is completed, we will also complete contract negotiations to ensure we are ready to proceed with the work if needed.
"We will continue our weekly on-site monitoring and if there is any further movement, we will reassess the situation and advise you accordingly."