Mr Alsop is hoping to find items in the bags which could identify the culprits.
Mr Alsop said the council were aware of it, and would be following it up.
Mr Alsop estimates the pile is about 25 to 30cu m in size but it is impossible to tell for sure due to the steep terrain.
Mr Alsop said the site is 500m on the Whangarei side of the boundary.
He took samples from upstream, in the middle of the rubbish and downstream to test for water pollution.
The results indicate the rubbish is polluting the stream.
Mr Alsop said work to clear the site will likely start the week beginning on July 17, dependent on the weather.
He estimates the clean up will cost between $10,000 and $20,000, with it depending largely on what contractors find once they get started.
According to the draft Waste Minimisation and Management Plan, illegal dumping costs the Whangarei District Council around $9,000 per month.
Mr Alsop said the council serve infringements of up to $400 for fly-tipping.