Three bodies are investigating the September 26-27 diesel spill on Mt Ruapehu and penalties could be as severe as prosecution and fines of up to $500,000.
About 19,000 litres of diesel from ski company Ruapehu Alpine Lifts' Turoa ski area leached into the Makotuku Stream, polluting Raetihi's water supply. The town had to rely on drinking water brought in by Ruapehu District Council and Ruapehu Alpine Lifts from October 2 to 22, causing inconvenience and financial loss.
Horizons Regional Council is investigating the spill under the Resource Management Act.
The formal investigation process is in two stages, strategy and regulatory manager Nic Peet said. First it would look at what happened and why, and then it would decide how to deal with it. At present, Dr Peet and regulatory manager Richard Munneke are the main people involved, with legal advice coming from outside the council.
The investigation would take until around Christmas, Dr Peet said, and the outcome could be prosecution or another penalty such as a fine. "We don't want to say whether any of those things will happen because we aren't predetermining the result of the investigation."