The old bridge had been deteriorating rapidly and had reached the end of its economic life, Allingham said.
The replacement project was fast-tracked last year, with funding reallocated from Wakefield St Bridge in Whanganui East.
He said forestry trucks had to take a 40-minute detour during construction.
“With heavy truck use and wet winter weather, damage inevitably occurred along the detour route while the bridge was out of action.
“I’m pleased to say repairs to the detour route will be funded by Waka Kotahi New Zealand Transport Agency [NZTA], with the council recently receiving an extra $250,000 for drainage, resurfacing and repairs along the affected route.”
NZTA also provided 60% of the funding for the bridge replacement.
Allingham said now it had reopened, pressure would come off other roads in the area and “we can get on with repairing small slips that occurred along sections of the detour route”.
“This gives us a great final outcome – an upgraded bridge and a more resilient transportation network to benefit both residents and industry in the Kauarapaoa area.”
Work on a culvert replacement 13km below Erni’s Bridge was expected to begin early next year but the road would remain open.