What are the legal consequences of polluting a waterway?

It can be serious. The Resource Management Act 1991 makes it an offence to discharge a contaminant into water or onto land where it may enter water unless the discharge is permitted by a rule or a consent. Penalties can include prosecution, large fines for companies and individuals and possible imprisonment for serious offending, as well as abatement notices, enforcement orders requiring remediation and orders for reparation. Cooperation, prompt clean-up, notifying the council early and preventing recurrence are relevant mitigating factors. Engage a lawyer before giving any formal interview, since councils can use statements as evidence. Preserve records of the incident and clean-up, review your spill response procedures and check your insurance policy, as some policies exclude fines but cover clean-up costs.