After 134 years’ service, the single-lane bridge was at the end of its economic life, NZ Transport Agency projects team manager Simon Underwood said.
Traffic is controlled by lights and long queues can build up at peak times, as traffic stops to let vehicles travelling the other way through.
Connecting Milton and Roxburgh on State Highway 8, the bridge was a vital transport link but one in need of replacement, Mr Underwood said.
The new bridge will be immediately downstream of the existing one, on an alignment which enables the highway to remain in front of the Beaumont Hotel.
"That was something strongly favoured by the local community," Mr Underwood said.
"The community also made it clear they wanted to see the existing bridge remain where it is, to provide a heritage link over the river to the Clutha Gold walking and cycle trail."
Consultation with Beaumont residents began in 2016, and that provided a good understanding of local history and an appreciation of the role the current bridge played in shaping the area,Mr Underwood said.
However, its replacement would still be some time away.
"Depending on the timing and outcome of this design phase, and subject to construction funding approval, this $20 million project could be under way by the second half of 2020," Mr Underwood said.
"The design and supervision of construction contract is worth $1.8 million."
WSP-Opus was awarded the design contract, which will begin with geotechnical testing to survey ground conditions.
"WSP-Opus will initially be approaching landowners concerned, ahead of wider community engagement on the new bridge design," Mr Underwood said.
