It has also alleged minor breaches of resource management rules by three neighbouring operators.
The report by planner Russell Butchers was obtained by the Otago Daily Times yesterday.
It was requested by the Queenstown Lakes District Council following complaints about the landfill by other Ballantyne Rd residents and took in the activities of the three other businesses in a waste management hub.
The report states the unauthorised landfill activities relate to the depositing of non-cleanfill items, in breach of the Queenstown Lakes District Council district plan and the Otago Regional Council regional plan.
It recommends Wanaka Landfill Ltd cease non-cleanfill activities or face enforcement proceedings in the Environment Court.
The operator, Robert Duncan, has advised the council non-cleanfill dumping has ceased.
But he has declined to stop all activities voluntarily so the council can conduct an environmental risk assessment.
Queenstown Lakes District Council chief executive Duncan Field said yesterday he was not doing anything to implement any further legal action as it would be easier for the ORC to do it.
Otago Regional Council resource management director Selva Selvarajah said yesterday Lakes Environmental had agreed to supply additional material this week.
The additional material and the report would be referred to ORC's lawyers this week and he hoped for an opinion on the regional council's legal action options would be available by the end of the month.
Mr Selvarajah said it was important not to alarm the public into thinking there were hazardous substances in the landfill.
There was no evidence before him or in Mr Butcher's report of any hazardous substance on the Wanaka Landfill site, he said.
"In this case we got information on wires, pipes, wet concrete, bitumen, which is a different case... In this case, we have to assess the real risk to environment, what materials are there and what effects are likely on ground water," Mr Selvarajah said.
"If the answer is that the material is unlikely to give harmful contamination, one would take a pragmatic approach and contain the material rather than take it out."
The site was a historical landfill site and was now closed.
It was reasonable for cleanfill and other waste management activities to operate there.
Mr Selvarajah distinguished the landfill issue from a recent Hawea Flat case where former timber millers Allan and Evelyn Gray, landowner F.
Urquhart Farmlands Ltd and others settled with the ORC for $25,000 and removed hazardous substances from a paddock at ORC's request.
That case involved traces of arsenic, copper and chromium in dumped material.
Mr Selvarajah said Wanaka Landfill Ltd had been fully co-operative with the regional council and its directions regarding non-cleanfill material.
He believed if Mr Duncan was asked for further co-operation, he would likely give it.
However, the council had legal processes it could use to enter the site and obtain samples, if co-operation stopped.
The important steps now were to obtain the further information, seek legal advice, obtain a clear understanding of any plan breaches and find out what was in the landfill, he said.
Wanaka Community Board chairman Lyal Cocks said yesterday he was pleased with Mr Butchers' report and he understood no further wet concrete would be be dumped in the landfill.
"I think it was a good report, a good audit, a full and thorough report. It was needed. It was overdue," he said.
