Urgent slumps in the rock retaining wall of the Patea moles have cost the South Taranaki District Council $38,000 to repair.
But the council has saved itself a further $10,000 by working with energy company Vector on the project.
The council was able to do a "contracting job share" with Vector and has saved the contractor's initial establishment fee.
Council Group Manager Engineering Services Brent Manning said because there had been some major erosion upstream of the rock wall of Vector's pipe gas line the company had brought in contractors Whitaker Civil Engineering.
"While Vector was carrying out repair works to an upstream section of the rock wall to protect their high-pressure underground gas pipeline, we realised it was ideal to get the work we needed on the rock wall at the same time" Mr Manning said. "And it's saved us money."
One large and two smaller slumps had been discovered in the Patea moles rock walls after an inspection in December last year, he said.
The retaining wall was integral to keeping the water from the Patea River tracking behind the moles.
"If there is a breakthrough in the wall the river will change direction and eventually make the river mouth impassable to boaties."
Mr Manning said the maintenance of the Patea moles - or breakwaters - was of prime economic benefit to the Patea and South Taranaki Community.
The moles in the harbour entrance were also of great historical and spiritual value to the Ngati Ruanui, he said.
With the council maintaining the moles, it decreased the risk of gradual reduction of the rock wall or possibly a catastrophic failure if the river flooded or there was major storm surge, he said.
The council planned to bring in an expert consultant in coastal erosion this year to look at the moles.