A programme of works is being finalised ahead of construction work beginning on the Union Terrace Gardens project.
It was revealed in April that contractor Balfour Beatty has been chosen to carry out the £25.7 million work to create an “inclusive 21st-Century space”.
Work has begun “off-site” on the project, according to council bosses, including finalising the programme of works.
Although the revamp is due to begin during summer, a specific date has yet to be announced for when construction will begin at the site.
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Aberdeen City Council co-leader Douglas Lumsden said while construction has not started, work has been carried out on the designs.
He said: “The contract was signed with Balfour Beatty last week. Work is happening on the designs. It’s really pleasing to hear.”
LDA Design, the firm behind London’s Olympic Park, has developed the plans which will see shops and cafes created in the arches along with new water features and community gardens.
Other proposals include an accessible walkway and reinstating the grand staircase from Rosemount Viaduct.
Work on the project, which has been hit by years of delays and setbacks, is expected to take between 18 and 21 months to complete.
Opposition councillors have been critical of the project, which will be delivered two years behind schedule.
Both the SNP and Liberal Democrat groups put forward proposals in their budget in March to make £25.7m by throwing out the scheme and instead committing £3.1m to carry out safety works at the Victorian park.
SNP group leader Stephen Flynn said: “UTG is over budget and massively behind schedule – the administration should have scrapped the plans and agreed with the SNP proposal to improve access. It is farcicial that the administration can’t give a definite start date.”