A total of 28 charges are expected to be heard over the diesel spill at the Turoa ski area last September.
Up to 19,000 litres of diesel is believed to have leaked from a tank at the ski area into the ground and the Makotuku Stream on September 26-27.
The stream is a source of water for Raetihi, and the town's supply had to be shut down for several weeks.
Raetihi survived on water delivered by tankers and then from the Makara Stream until residents were finally able to draw drinking water from the Makotuku again in March.
Ruapehu Alpine Lifts and Petroleum Services (2001) are expected to lodge pleas to the 28 charges at their next appearance in the Taihape District Court, sitting in Ohakune, on July 11, the Ruapehu Bulletin reports.
Under two breaches of the 1991 Resource Management Act, the Horizons Regional Council claim the companies allowed the discharge of a contaminant, up to 19,000 litres of diesel, from an industrial trade premises at the Turoa ski field, which entered the Makotuku Stream between September 25 and 28, 2013 the Bulletin said.
The maximum fine that can be imposed by the court on each of these charges is $600,000.
WorkSafe New Zealand has also lodged 16 charges against Petroleum Services and eight against Ruapehu Alpine Lifts.
Most of those charges attract a maximum fine of $500,000.
The prosecution is claiming that in August 2006 the company responsible for the installation of the tank which was used to hold the diesel failed to ensure the container system and associated pipe-work was designed, constructed, installed, tested and inspected so it was fit-for-purpose.
Additional charges have also been laid pertaining to the tank's manufacture.
WorkSafe NZ also claims that Petroleum Services obstructed, hindered or delayed an inspector following the September spill.
The eight charges laid against Ruapehu Alpine Lifts by the Government health and safety watchdog vary in date and pertain to the maintenance and repair of the system and pipework from as early as April 2008.
It is also alleged that between October 2011 and October 2013 the company failed to ensure an emergency response plan which identified every person with responsibilities; that this plan was tested every 12 months; and that between May 25, 2013, and October 21, 2013 the plan was available to the relevant people.
Ruapehu Alpine Lifts is also charged that between September 27 and October 11 the company failed to take all practicable steps to notify WorkSafe New Zealand of the diesel spill as soon as possible.