The first bridge is on the south branch and is part of a $20 million project by the New Zealand Transport Agency.
Work on both bridges was progressing well and once the smaller one was completed in March it would be opened for traffic, agency Canterbury/West Coast highway manager Colin Knaggs said.
Work would then begin on demolishing the old timber bridge.
With the structural steel completed, work was scheduled to begin soon on installing the bridge's precast concrete deck.
Meanwhile, work was continuing on the piling, pier and pier head construction for the second and longer of the two bridges on the Hakataramea side. This was expected to be completed mid-March for work to begin installing the structural steel.
The second bridge was scheduled to open before September 2014.
Mr Knaggs said the second of the 132-year-old timber bridges would then be demolished, but two sections would be permanently displayed on Kurow Island.
The remainder of the material would be given to the Waitaki and Waimate District Councils and the Department of Conservation for disposal for historic and community projects.
Construction of the new bridges has provided up to 20 jobs in the Kurow area and boosted the local economy.
