New Zealand Transport Agency Otago-Southland state highway manager Ian Duncan said the work was expected to take contractors at least two months.
It involved drilling and inserting drain pipes into the bank along 200m of Pine Hill Rd, north of the George St overbridge.
''Most of the work will be undertaken between 7am and 7pm, Monday to Saturday. The whole job, including landscaping, is scheduled for completion by late May,'' he said.
The drainage infrastructure would strengthen the road and reduce the risk of further land movement. About $600,000 had been budgeted for the work, Mr Duncan said.
''This area does have a history of land movement, but our expectation is that these pipes will remove enough water to reduce any major risk of land movement that may have an impact on the stability of the road.''
During construction, the north-bound section of SH1 will be reduced to one lane, with no access to Bank St for right-turning traffic off Pine Hill Rd.
Vehicle access to properties will be maintained, but some alternative routes might be required, Mr Duncan said.
When contractors were on site, access to Bank St will be via the Opoho Rd end only.
At the end of each day, contractors will reinstate both uphill lanes of the highway.
