Taranaki Regional Council is investigating whether one of the anchors used in the Waipipi Iron Sand operation has been removed from the South Taranaki seabed.
It was notified of the possible removal by Jeremy Penrice, an electrical engineer who has worked with subsea infrastructure in the oil and gas industry.
He lived in Patea as a child and remembers the huge ships anchored off Waverley from 1971-87 to be filled with iron sand pumped from an onshore mine.
Mr Penrice had talked to someone about the anchor system, and was later phoned by the person to say he had removed one of the anchors on January 9.
The removal was an illegal act by a "sophisticated Steptoe", Mr Penrice said, and he made a complaint to the council.
Taranaki Regional Council resource management director Fred McLay said the anchor system left behind after the Waipipi Iron Sand operation finished is "orphaned equipment dating back to pre-Resource Management Act days".
The council does not own it and is only investigating the possible environmental effects of a removal.
A staff member was at Waipipi on Thursday.
He talked to the landowners, who had seen and heard nothing. He found no evidence of any removal.
Mr McLay was aware of one unsuccessful attempt to remove the anchors about 20 years ago. He said the council will be monitoring the situation.
The anchor system for the huge iron ore tankers consisted of an enormous revolving buoy, held in place by 14 huge anchors, all 3 kilometres out to sea.
Each anchor could weigh as much as 25 tonnes, Mr Penrice said, and would fetch a good price if sold to a harbour authority or barge owner.
Since 1987 the anchors may have sunk into the sand. Removing them would need a diver and a sizeable vessel, he said.
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