The fix-it job for a SH4 dropout near Upokongaro is "rubbish" and a waste of time and money, Whanganui River Rd farmer Donald Wickham says.
He's been driving the riverside highway for about 50 years and said designers of the dropout repair should have used the same method that has held some Anzac Pde banks in place for 15 years.
"It was to dig the soft stuff at the bottom out, and put in rocks as a base. When they had the base solid they filled it up similarly to what these people have just done. But they had no solid base and it just oozed out."
Mr Wickham knows the river near Upokongaro from waterskiing there in the past. He said the east side was very deep, with a strong current, and there were underground streams running out from under a covering of soft pumice.
"That system had been proven, and yet they are able to put all of that spoil into the river without even looking back at what had been done previously. It's a waste of time and money," he said.
He intends to speak to Whanganui MP Chester Borrows about it.
Something similar is happening with repairs to slips and dropouts on the upriver side of
Gentle Annie on Whanganui River Rd. The only method that works on the sandy slopes there is to plant silver poplars both above and below the road, he said.
Instead a different fix is being tried, using piles with concrete poured around their base.
Mr Wickham is not the only person with opinions about how to fix the highway. Several others have weighed in on Facebook.
Ted Hagenaars said the same kind of slumping has happened at the Somme Pde repair near Roberts Ave, where work is at a standstill.
David Parker agreed the dropout needed to be excavated until hard ground was reached, before fill was put in. Others said the road should be moved farther away from the river, or too much bush has been removed.
Aaron Doyle said he was a roading supervisor for the contractor doing the job and the work was designed by the New Zealand Transport Agency (NZTA). He said the land was made of pumice and there were streams flowing into the river from under the road and that had caused the disaster - with a bit of help from the June 2015 flood.
Carol Webb asked what was happening with the slip just upriver from the City Bridge in Whanganui East. It happened in June 2015, with more ground giving way about six weeks later.
The complex repair job will cost $2 million to $5 million, the Chronicle has been told. It has been put off several times, with the latest NZTA spokesman saying it's due to start in September or October.