The project came in close to budget, a report for the Dunedin City Council showed.
The three-year budget envelope was about $105m, which included $10m of contingency funding, and, essentially, the full complement was required.
"Where the project was earlier tracking more favourably against the design and construction budget, construction costs increased over the course of the project, with materials inflation, unexpected ground conditions and more challenging infrastructure issues, meaning the project contingency was also spent," the report said.
"To address these escalations, staff accelerated the programme, removed some areas of scope and worked closely with the contractor to find any efficiencies or alternative solutions possible."
In June last year, councillors celebrated a reduction of $7.2m from the estimated completion cost.
By May this year, when the revamp was essentially completed, the situation had shifted to costs running close to target.
The report was prepared after Dunedin deputy mayor Cherry Lucas called for it and it will be discussed at the council’s infrastructure services committee meeting next week.
Its key finding was the cost of the project was $110.3m.
However, part of the total cost related to financial years earlier than the three-year budget.
The upgrade included replacement of pipes and creation of a more pedestrian-friendly environment in George St.
It started in October 2021 and was "substantively completed" in May this year, the council said.
The programme was originally expected to be completed last month, but a significant component of the work was able to be brought forward, leading to the early finish.
The report highlighted an update for the committee in February last year, when the project was estimated to cost $105.1m, including the contingency component.
This figure became the budget for the design and construction cost of the project for the three-year period from July 1, 2021, to June 30, 2024, the council said.
The actual cost for design and construction was $104.8m.
"Actual cost for design and construction of the retail quarter upgrade project was within the budget envelope of $105.1m," the report said.
Preparatory and investigative work cost $2.6m and other professional services $2.9m, bringing total capital expenditure to $110.3m.
The preparatory and investigative work happened in the 2019-20 and 2020-21 financial years, which were outside the three-year budget window.
Other professional services included detailed business case development, health and safety and traffic auditors, quantity surveyors, project managers, contract administrators and artists.
The council expected to incur some costs over the defect liability period, to deal with any minor design and construction issues and to implement any recommended changes stemming from an independent safety review and final subcontractor costs.
Early indications were that these would be about $360,000, when $60,000 had been budgeted.
"As with any project of this size, minor defects will continue to be addressed over the coming year."
NZ Transport Agency Waka Kotahi contributed $23.4m to the project.
The council provided a series of numbers about the upgrade.
There was 5.2km of new kerb and channel and 25,000sqm of new paved and asphalt surfacing, 126 new street light poles, 61 seats, 48 cycle stands, about 7330 new plants and more than 90 "semi-mature trees".
Below ground, 4.3km of historical egg-shaped brick barrel stormwater pipes first constructed in the 1870s had been rehabilitated, strengthened and lined.
The project delivered a total of 15.5km of stormwater, wastewater and drinking water pipe rehabilitation and renewal.
At least 29 wastewater to stormwater cross-connections were identified and repaired during the works, preventing untreated wastewater from entering the stormwater system and harbour.
