A Waiuku dairy farmer could face criminal charges after he was found pumping cow effluent directly into a waterway.
Waikato Regional Council discovered the alleged discharges this week after a tip off from the public.
Council inspectors visited the dairy farm on Tuesday and found a number of effluent discharges into the environment.
Council's investigations and complaints manager Patrick Lynch said most concerning was a pump set up to channel effluent directly into a nearby tributary of the Waikato River.
''We regularly come across discharges that result from negligence or carelessness but deliberate discharges into the environment are rare,'' Mr Lynch said.
''Quite frankly, this is appalling.''
The council has not named the farmer because its investigation is ongoing.
Mr Lynch said ''Joe Public'' as well as the farming community would be equally upset by the farmer's actions.
''I would think that this is very upsetting for the wider dairy industry and all of those farmers who manage their effluent responsibly. Clear direction has been given to the farmer to halt these discharges immediately.''
Mr Lynch said there was a ''high likelihood'' criminal charges would follow the council's investigation.
Last month the council announced it would trial a new way of monitoring effluent breaches, with fewer helicopter checks and a greater focus on ground-based visits and ''high risk soils''.
The Waiuku farm was not visited as part of the new inspection regime.
The council plans to target up to 500 farms in areas with soils that are seen as having a greater risk of allowing effluent to get into waterways.
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