When the stack toppled over, the dye spilled into the catchpit and then into the Oruarangi Stream and estuary.
Eventually, the dye travelled throughout 900m of freshwater and inter-tidal zone, approximately 3.5km of estuarine environment, and was still visible several hundred metres into the harbour.
Court documents stated the spill had a "calamitous" effect on the awa, which had previously supported a "healthy and abundant" freshwater fish and eel population, dominated by short-fin eels and inanga as well as some long-fin eel and banded kokopu.
Up to 400 eels may have been killed, along with just under half of the mud snails and other species in the estuary.
Images taken by council officers showed dead eels that had been turned purple, and creek water that had also been heavily coloured.
It also drastically affected various oysters beds in the area with many oysters being killed, while fishing was banned in the area for months.
The company was today fined $103,000, and ordered to pay in $25,000 costs after being found guilty in the Auckland District Court.
"It is a fundamental responsibility of any person in any management position to understand and appreciate the workplace risks and the wider risks associated with any activities that are conducted within the business which they manage," Judge Melanie Harland said in sentencing.
"The failure by management to even appreciate that there was a relevant rule in a plan that applied to them was also remarkable."
Auckland Council resource consents compliance manager Stefan Naude said this prosecution and the level of the fine made it clear to business owners and managers that they must find out what their obligations are under the Resource Management Act and other relevant regulations, and comply with those obligations.
"In this case, if the container had been stored in a secondary containment device, at minimal cost, as required by the regulations, the discharge of the dye could have been prevented."
The fine took into account the defendant's previous good record, guilty plea and remorse.
Environmental Defence Society chairman Gary Taylor called the spill a "high-end offence" that caused long-term ecological harm.
"The size of the penalty reflects the lack of care to avoid a spill," he said.
"It is a reminder that if people cause environmental harm there is a price to pay."