Silver Fern Farms has been fined $337,000 over an ammonia leak at its Hāwera plant that was potentially lethal to its staff, emergency services personnel and nearby residents.
The February 2020 leak is also being described as likely the worst single-point freshwater pollution event in terms of fish killed in New Zealand history.
In a departure from conventional practice, proceedings began today with a karakia from a Ngāti Ruanui kaumātua.
The iwi is manu whenua of the Tawhiti Stream, which bore the brunt of the ammonia spill.
Its policy and strategy manager, Graham Young, told the court the awa was central to the iwi's identity.
"The Tawhiti Stream is about Ngāti Ruanui's past, its present and its future. It's about Ngāti Ruanui's wellbeing, it's about Ngāti Ruanui's cultural identity.
"The tuna within the stream that has been lost is significant to Ngāti Ruanui. The tuna is a god, it is a taniwha and it's gone."
He said the impact on the iwi had been profound.
"It's been devastating to Ngāti Ruanui in the last 12 months that this stream and the wider catchment has in fact suffered so greatly at the hands of a spill that probably should not have happened had accurate systems had been in place to ensure ammonia did not enter the Tawhiti Stream."
The court heard that on February 19 last year, a Silver Fern Farms' engineer accidentally opened a damaged ammonia valve while trying to adjust the temperature of a blast chiller.
The onsite Emergency Response team initially sprayed water onto the gas cloud before Fire and Emergency set up a water curtain.
More than 4000kg of ammonia gas was released over six hours.
Judge Brian Dwyer said the potential health effects on staff, emergency services and nearby residents could not be ignored.
He went on to list them.
"Severe damage to eyes including blindness, skin irritation, burning and blistering, burning of the digestive and respiratory tracts, and difficulty in breathing, choking and headaches, dizziness and weakness, and in cases of severe exposure, death."
Dwyer said it was fortunate only one engineer had needed treatment.
The liquified ammonia had a more lasting effect.
Judge Dwyer said it overwhelmed Silver Fern Farms' stormwater system, polluting more than 13km of the Tawhiti Stream and more than 6km of the Tāngāhoe River.
"A low estimate of thousands and possibly tens of thousands of fish in the stream would have died as well as any larvae and eggs in the water that simply cannot be quantified. This was a devastating kill."
He then read from the environmental impact report.
"This, and I quote, 'this fish kill incident was undoubtedly significant being likely one of the worst recorded single-point discharge freshwater events in New Zealand's history, in terms of the number of fish killed."
In sentencing, Judge Dwyer said ammonia management at the plant was "careless in the extreme, an accident waiting to happen and reckless".
He said Silver Fern Farms had little capacity to contain stormwater on-site and its culpability for the offending was at the highest level.
Outside court, Hāwera plant manager Scott Lamplough said Silver Fern Farms regretted the incident and was doing everything it could to make sure it did not happen again.
"We're putting in a full containment water system, so that will test water before it's released into any stormwater moving forward and it's going to have the ability to maintain enough water for firefighting, and also rainwater."
Lamplough said the company wanted to work with Ngāti Ruanui.
"We are deeply disappointed about what happened and we're fully committed to making things right for the future and fixing the stream and the mistakes that we've made."
Ngāti Ruanui's Graham Young said the fine was less than hoped for.
"Obviously, the fine of three hundred-odd thousand dollars is not as great as we expected, but we think it is an acknowledgement of the magnitude of the devastation caused to the Tawhiti Stream."
Young said he looked forward to working with Silver Fern Farms on restoring life back to the affected waterways.