A temporary rock platform being built in the Shoalhaven River as part of work on the new $342 million Nowra Bridge will contain around 22,000 tonnes of materials.
The platform, affectionately named by some locals as 'Fulton Hogan Island' will eventually extend about halfway across the Shoalhaven River.
It will provide a working area for bridge piling and foundation work in the southern half of the river where the water is shallow and barges can't be used.
In the northern half of the river, where the water is deeper, piling and bridge work will be carried out from barges and boats.
A spokesperson for Transport for NSW said the new bridge will require 39 steel piles driven into the river bed, with nine piers across the river to match the existing concrete bridge.
"Four piers on the southern side will be built off the temporary rock platform while the other five piers on the northern side will be built off barges," the spokesperson said.
"When the bridge is complete, the temporary platform will be removed and some of the material will be reused elsewhere on the project."
One day alone last week 2000 tonnes, equating to 65 truck and dog loads of material, was transported to the site from a quarry in Albion Park.
Regular river users have told the South Coast Register, last month's floods have significantly changed the river's depth and channel positions, with a "large amount of silt" being deposited in some areas.
It is understood the channel on the northern side of the river has grown deeper and wider.
Transport for NSW said the project has not carried out any further studies in the river since the flooding in August, however monitoring of the riverbed has revealed no unexpected or abnormal changes in water depth.