Tamworth MP Kevin Anderson said new culverts were now being installed as part of the $5 million upgrade of the Hoss Causeway between Gunnedah and Tamworth.
"The causeway work is expected to be completed in December, weather-permitting," Mr Anderson said.
"In addition to the culvert installation, a 1.2km section of highway to the east of Hoss Causeway will be rebuilt to provide a safer and smoother surface with better alignment.
"Work will start following the installation of the culverts."
The project was set back months after cracks were found in concrete culverts supplied by a manufacturer late last year.
Gunnedah Shire Council decided all the culverts should be replaced so there was a delay as new culverts were manufactured and frustrated drivers were forced to use a side-track while work was at a standstill.
The schedule of works includes raising the road level and installing new drainage.
Levee work has also been carried out west of Gunnembene Lane, and the road level of Gunnembene Lane is being raised.