The work is focused on Bath St, but also has traffic implications for lower Stuart St, George St and the Octagon and will extend well into 2025.
The Dunedin City Council released more information about the $17 million project this week.
What the council calls water "enabling" work is to start on Sunday night.
The lower Stuart St end of Bath St would initially be closed to vehicles for a few days at a time and the street would become two-way during this period.
There would also be temporary one-lane closures in George St, from Moray Pl to the Octagon, and in lower Stuart St, from the Octagon to Moray Pl, to make adjustments to the footpaths to allow two-way traffic in Bath St.
Construction work would follow in lower Stuart St from next month, focused on the intersection with Bath St.
Council infrastructure services committee chairman Jim O’Malley said replacing old underground pipes, some dating back to the 1880s, was the main reason for the work.
Cr O’Malley said contractor Downer was beginning to relocate pipes and telecommunications cables in the road and footpath in Bath and lower Stuart Sts to make way for sheet piles.
These would retain the walls of a 5m-6m hole to be excavated from mid-May at the intersection of Bath and lower Stuart Sts.
A collapsed watercourse pipe under Bath St needed to be replaced and the council said it was taking the opportunity to upgrade other pipes at the same time.
The hole at the intersection would allow critical connections to be made to existing pipes, the council said.
"This next stage of work means we will need to close off three-quarters of the first block of lower Stuart St from the Octagon to vehicles for six months", Cr O’Malley said.
"Foot traffic access to all businesses and residences will be maintained."
The council said the carpark at 414 Moray Pl would reopen in time for the lower Stuart St closure, and the first 15 minutes of parking there would be free of charge.
"We’re also temporarily changing parallel parking to angle parking in lower Stuart St to create more spaces", the council said in a newsletter.
Hoardings would be put up around the work area in Stuart St next month.
This would be extended into Bath St in late June.
A project overview timeline refers to night work in Bath St from December to March next year.
This is understood to relate to road surfacing.
The council has said contractors would work closely with retailers and building owners to ensure access was maintained.
