"The slip site has a high number of underground services, including water mains, which NZTA needs to work around."
Whanganui Mayor Hamish McDouall said the road was important and it needed to be sorted as soon as possible.
He feared what would happened if another washout in the same spot cut off SH4.
"It's too vital," he said.
"Imagine entering 2018. That'd be two and half years since the flood, and nothing.
"We don't want to enter another winter like that."
NZTA is currently providing more information for Horizons Regional Council to assess the consent application.
There were over 120 sites damaged as a result of the June 2015 storm event across both the Manawatu and Taranaki regions with an estimated total repair cost of $47 million.