An independent review into mining tests at Karangahake, south of Paeroa, has found the activities would pose minimal pollution to waterways, a fear held by some local iwi descendants.
Some members of Ngāti Tamaterā are worried that the mining work by New Talisman Gold Mining could contaminate their tribal waterways including the Waitawheta River.
They were among members of the environment group Protect Karangahake which lobbied the Waikato Regional Council last week because of concerns acid could leach into the rivers, based on an affidavit by an internationally acclaimed expert in the formation of caves Dr Chris Hendy.
He reported that acid and other heavy metals could contaminate waterways because of drilling, blasting and bulk sampling.
Waikato Regional Council said it commissioned a review to be done by Dr James Pope, who has 20 years experience in minerals sector.
His report suggested that, based on New Talisman's water management plan, the volume of what would be sampled and the recirculation of water in the mine there would be little affect on contaminating waterways.
It said the walls of the mine should be washed down to ensure fine material from bulk sampling was removed and also suggested that some of the water that was reused could escape the site - however Dr Pope was certain the small amount would not pose a threat to the waterways.
New Talisman welcomed the findings of the review.
Chief executive Matthew Hill said Dr Pope's review should help to allay concerns by local groups.
Based on the latest report, the Waikato Regional Council said it confirmed its previous advice that no discharge permit is needed for exploratory drilling.
Since it received the independent review the council said Dr Pope had been in talks with Dr Chris Hendy.
Meanwhile, the Ngāti Tamaterā Treaty Settlement Trust is negotiating with the Crown about co-governance and redress as part of a treaty package which would include the area where New Talisman was working.
It said its aim was to seek a long term solution, and said it was not against mining but wanted to ensure that the environment was protected.
Protect Karangahake will legally challenge the resource consent issued by the Hauraki District Council to New Talisman, and said a judicial review was to be held later in the year.