Adelaide City Council’s debt is forecast to approach a quarter of a billion dollars as it prepares to borrow $64.5m to rehabilitate three ageing CBD landmarks.

City ratepayers are poised to spend $27.7m on the Torrens Weir structure, $20.3m on Adelaide Bridge and $16.5m on Rundle UPark to extend their “useful lives” before structural failure.

A draft long-term financial plan, tabled ahead of a council meeting on Tuesday, revealed the works would significantly increase the council’s debt, which would peak at $215.9m in the 2034-35 financial year.

The council is seeking state or federal funding for the weir and bridge, but has assumed in its financial forecast it will need to borrow the funds, placing “substantial pressure on the existing ratepayer base”.

A council report said the Torrens Weir – constructed in 1881 with sluice gates added in 1929 – was mostly in a “fair to poor condition” as it approached “the end of its useful life”.

It said failing to renew the weir could lead to “increased safety and property damage risks from stormwater flooding” and a “reduction in amenity”.

The 1931-built Adelaide Bridge – which carries traffic over the River Torrens on King William Rd – is also projected to soon “reach end of life”.

The council plans to rehabilitate the bridge and increase its load limit, with both the bridge and weir renewals described as “once-in-a-generation” projects.

The works would not include the construction of a tramline along the Adelaide Bridge – a project the council has previously asked the state government to fund.

Works are also planned for Rundle UPark – the council’s Rundle St carpark built in 1975 – to “extend its useful life” before it reaches a structural expiry date.

Funding the renewals would push the council to 98 per cent of its self-imposed prudential borrowing limit in the 2032-33 financial year.

The project spending depends on council members voting on Tuesday to accept the draft long-term financial plan, which would become the subject of community feedback before being approved.

A council spokesman said it was “important not to confuse 98 per cent of the prudential limit with having no remaining capacity”.

“At the forecast peak, council would still have approximately $36.1m (including a $17m ‘allowance’ for uncommitted projects) in borrowing headroom, which is equivalent to around 16.6 per cent of annual rates income for that year,” he said.

“This provides for a prudent and manageable buffer while delivering several major renewal projects within a relatively short period.’

The Lord Mayor was unavailable for comment.