People fishing off Whanganui's South Beach are again being reminded to keep their lines well clear of the outfall pipe from the city's wastewater treatment plant.

The pipe runs for about 1.8km offshore, and a large triangular sign marks the point where it goes under the beach dunes and into the sea.

But recently Coastguard Wanganui contacted a commercial dive company warning that it had received reports that a number of recreational fishers had lost kontiki long lines which had snagged on parts of the undersea pipeline.

Commercial Dive Services is contracted to the Whanganui District Council to carry out regular maintenance on the outfall, a job it has done for about 20 years.


Shane McDonnell, supervisor and project manager for the company, told the Chronicle the information from Coastguard "pushed alarm buttons for us".

Mr McDonnell said it was after getting the warning from Coastguard that his divers started finding the snagged gear. He said any kontikis found had been handed in to Whanganui Police.

"The problem is the line these kontikis take offshore can have a breaking strain of more than 300 pounds and will carry more than 20 hooks. Worst of all it's transparent so our guys can't see it underwater."

He said his crews carried knives and worked in pairs so if they did become entangled they could cut the line.

"But if any surfers were out there and got entangled in the line they'd go straight under. They don't carry knives," he said.

Kontikis can take up to 2km of line out to sea.

As well as the triangular sign onshore, a series of buoys mark the pipeline's path to keep boat owners and recreational users well clear of the area.

It's not only the pipeline itself. With the wastewater treatment plant currently out of action, the waste being dumped out to sea is barely treated and poses a potential health risk as well.

Councillor Ray Stevens, who holds council's infrastructure portfolio, said people fishing the area needed to use common sense.

"We're not wanting to stop anyone fishing there but they must observe the rules and keep well clear of the pipeline. And they have to be aware of the drift along the coastline," Mr Stevens said.

"But the council has obligations under health and safety legislation so we must be doing all we can to alert people to the pipeline and potential dangers."

From time to time council publishes notices reminding people about the prohibited fishing area around the outfall and will do that again.