The state of the moles that keep the Whanganui River mouth navigable is a worry for Horizons Regional Council's river manager, who hopes to start repairing them this summer.
"They're falling apart. I think anyone can see that they're falling apart," Ramon Strong said.
He hopes the $15 million job of fixing them can start later this summer.
It depends on a lot of things: money from the Government through the Provincial Growth Fund (PGF), resource consents and collaboration with local iwi, and sourcing large pieces of durable rock.
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"Over the last 12 months this has occupied a fair chunk of my time," Strong said.
He's confident work can begin soon. If the moles continue to deteriorate, they will become much more expensive to fix.
Transporting freight by sea on "the blue highway" is one of Government's transport priorities because it produces fewer greenhouse gas emissions. The port is needed for that.
It was no one's fault the moles had deteriorated, Strong said. Some of the damage happened while River City Port owned the port.
Former mayor Michael Laws "arm wrestled" it back into council ownership in 2010.
Preparing it for more coastal shipping is the subject of another application to the PGF.
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Horizons Regional Council agreed to take responsibility for lower river infrastructure from July 2018.
During the 2017 election campaign, Labour leader Jacinda Ardern made a "firm commitment" to $3 million toward repairing the moles. Asked about that this month, she said it was one of several campaign promises going through the PGF process.
Horizons has applied to the fund for $7.5 million - half the cost of repairing the moles. The other half would be paid by ratepayers, Strong said, with 80 per cent from Whanganui and 20 per cent from the rest of the region.
Whanganui District Council is to provide 25 per cent of that half share.
If the PGF turns down the application, Strong can go to Treasury's infrastructure unit for help.
The repair work will be "heavy civil engineering". Rocks the size of cars need to be transported, one per truck. Nobody in their right mind would take it on as a commercial enterprise, Strong said.
Horizons has been working with Tupoho and the Ngā Tāngata Tiaki o Whanganui Trust (NTT) around resource consent and procurement.
"The intent is to ensure an appropriate governance and partnership model for the proposed lower river infrastructure work of Horizons and the port development work of Whanganui District Council, [and that it] is completed in line with the values of Te Awa Tupua," NTT chief executive Ray Hall said.
The first job will be to replace the outer covering of North Mole with huge pieces of rock. The Kaikoura earthquake and Transmission Gully construction have made big rocks a scarce commodity - and 50,000 to 60,000 tonnes will be needed.
They may have to be sourced from Ruapehu, Taranaki or Golden Bay. That would be costly, slow, and the heavy trucks carrying them would damage roads and emit carbon.
"What's good for the economy and environment is sources as close to the river mouth as possible," Strong said.
Nearby Waitahinga Quarry is a possible source of shellrock but it's opposed by some Wanganui Tramping Club members because mining it could affect trails the club has established.
Neither Whanganui District Council nor Strong has confirmed whether that quarry will be used.
Before North Mole can be reclad, demolition rubble dumped there will have to be removed, and dumping will have to stop.
"[North Mole] has been used as a tip," Strong said.
"The iwi are understandably unhappy about that. It's a health and safety issue and an eyesore."
Horizons will move to stop further dumping, and may use enforcement to do so.