The scheme will cost £29.5 million.
Glasgow MSP Paul Sweeney has said he is “astounded” that the cost to deliver “this fairly basic pedestrian swing bridge” has risen to £30m.
However, a council spokesman said the bridge will bring “significant economic, environmental and social benefits” and requires “very complex” engineering.
Councillors are being asked to back awarding a £29.5m contract to construction firm Farrans next week — but the original estimated project budget was £17.5m.
Price “volatility” in the construction market, including the cost of steel, and the ongoing impact of Covid-19 and Brexit have been listed as reasons for the increase.
The report also states the original budget was based on an “early version” of the scope and “did not reflect the final scope of works which was tendered”.
It confirms the extra funding has been secured through the City Deal programme.
The new pedestrian/cycle bridge over the River Clyde, connecting Water Row with Pointhouse Quay, is part of the Glasgow City Region City Deal, where the Scottish Government and the UK Government have provided £500m each for infrastructure projects.
Reacting to the rise on social media, Glasgow MSP Paul Sweeney said the cost is £10m more “than the much larger four-lane Clyde Arc road bridge cost in 2006. How can it be justified?”
The Clyde Arc, known as the Squinty Bridge, cost just over £20m, but does not open like the Govan-Partick bridge will.
The council spokesman said the proposed bridge “undoubtedly complements a number of major regeneration projects taking place on both sides of the Clyde close to the new crossing”.
“The reasons for the increase in cost from the projected figure include the well-documented price increases facing all construction projects at this time and increased scope for the project.
“It should be noted this swing bridge actually requires very complex engineering — the requirement to provide navigational clearance over a 50 metres navigational channel means the main span of the bridge is approximately 70 metres long, making it one of the longest opening footbridges in the UK.
“A significant proportion of the cost is associated with the mechanical and electrical elements required to allow the bridge to open.”
Final approval of the contract isn’t expected until next month, when it will go before the City Region cabinet.
Work on the bridge is expected to start in January and be completed towards the end of 2023.
The £29.5m includes the operation and maintenance costs of the bridge for two years and the upkeep of bridge lighting for a period of five years.
It also includes the cost of the extension of the quay wall at Pointhouse Quay, which is needed to provide a landing point for the bridge on the north bank.
In the council report, it states there has been an “extensive” review of the contractor’s submission which identified a “number of factors which have contributed” to the difference between the contract value and the original estimated budget.
A planned Renfrew-Yoker opening road bridge has an estimated construction cost of around £80m.