A controversial Shropshire sculpture, commissioned for the 200th anniversary of Charles Darwin's birth, will cost up to £100,000 more than expected.
Quantum Leap in Shrewsbury which is made of 31 stone "ribs", could now cost up to £483,000 to finish.
Project manager George Candler said ground work and tree preservation were among unexpected issues faced.
The sculpture has caused controversy across the county over its cost and design.
A decision by Shropshire Council's cabinet to pay the extra money will go before the full council on Thursday.
A spokesman for the council said it would be exploring opportunities to raise the additional cash.
'Make it work'
Mr Candler added that each end of Quantum Leap had been covered in concrete to prevent people climbing on it.
Jon King, from Shropshire Council, said the concrete was also part of the "anchoring process".
Mr King said: "You need to make it secure, make it safe, make it work and be as close as it possibly can to the artist's original concept."
Mr Candler described it as "iconic" and a piece of public art that Shropshire people would be proud of.
Shropshire Council said the overall project was due to be finished by 10 November.