The Waikato Regional Council says its formal warning to Fonterra for illegally dumping millions of litres of buttermilk should be enough to prevent it happening again.
The council issued a formal warning to the company for discharging five million litres of the waste onto land at Atiamuri last October - an act the council initially thought to be a relatively serious environmental incident.
It has also issued warnings for breaching the Resource Management Act to the owner of the land and the person managing it.
Investigations manager Patrick Lynch says a formal warning is the least punitive of the responses it could have taken and it was appropriate the council did not prosecute. He says that's because there was no apparent contamination of ground or surface water.
Mr Lynch says Fonterra has since told him that it has changed its procedures.
"We've got a very high level of assurance that that won't be happening again," he says.