"Given the overall circumstances surrounding the spill, including that the environmental impact of the sulphur spill was very minor, the council does not consider that formal enforcement action against either Ballance Agri-Nutrients or the transport contractor is warranted," NRC group manager regulatory services Colin Dall said.
He said the spill was not a deliberate act and was caused by a failed tank weld.
After becoming aware of the spill, Dall said both Ballance Agri-Nutrients and the transport contractor worked proactively to ensure police, fire brigade and clean-up crews attended the affected areas immediately.
He said the companies are taking steps to prevent a similar spill happening again, including inspection of the other tank used to transport the sulphur.
Mark Adams, Ballance site manager in Whangarei, said the spill was really disappointing as it was the first time it has happened in the 32 years the company has been transporting pure sulphur from the refinery.
Liquid sulphur is a byproduct of the refinery and is used by Ballance in fertiliser mixes.
Adams assured the public the bright yellow product was pretty benign and that motorists should simply wash it off if the sulphur came into contact with their vehicles.
NZ Transport Agency Northland system manager Jacqui Hori-Hoult said the sulphur was non-toxic.