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State highways and the design and management of state highway assets can potentially affect natural waterways and drainage patterns.

If you are designing, constructing or maintaining stormwater assets find out more about our requirements.

Our goals for stormwater management include:

  • For new projects, avoiding, to the extent reasonable in the circumstances, adverse effects on sensitive receiving environments by implementing and developing project specific water quality and quantity measures.
  • Comply with regional plan and discharge permit conditions when managing adverse effects on water resources
  • On the existing network, identify sensitive receiving environments that are adversely affected by state highway runoff. As appropriate, treat the identified sites, based on a prioritisation approach
  • Ensure stormwater treatment devices in the network are effective

Standards, guidance and specifications provide an opportunity to clearly specify the NZ Transport Agency’s expectations around how to achieve these goals, what the minimum levels of service required are, consolidate practical experience gained by the organisation and disseminate specific specialist knowledge relating to highway construction operation and maintenance so this knowledge can be applied efficiently and consistently across the organisation.

This page contains key documents relating to the Agency's expectations relating to water resources and encompasses stormwater water quality and quantity, erosion and sediment control, and provision of fish passage.

P46 NZ Transport Agency state highway stormwater specification

The scope of the specification is intended to set out the design and construction stormwater requirements for all state highway improvement projects. It provides sufficient detail for design and construction purposes, while allowing flexibility to cater for different types of projects

It is expected that this stormwater specification will be used as the starting point for the development of project specific requirements and will need to be adapted as appropriate to address local issues and the scope of any given project.

Stormwater treatment guidelines for state highway infrastructure

This document has been prepared to assist roading practitioners with the selection and design of roading stormwater management practices. It should be used as a reference for any state highway project which will discharge stormwater. It provides guidance on:

  • Choosing stormwater management devices for roads
  • Stormwater management practice design
  • Financial considerations
  • Principles of retrofitting stormwater treatment
  • Construction guidance
  • Maintenance issues
  • Costing issues

It also provides background information on sources of contaminants from roads, and stormwater management concepts.

Fish passage guidelines

Use this guideline if your project or work involves construction or alteration of structures in streams, channels or rivers or the creation or modification any water diversion structure. The guideline contains details of legal requirements as well as best practice design considerations.

Erosion and sediment control


There are  stormwater management and erosion and sediment control eLearning modules are available at link).

Note: Please ensure that popups are not blocked to load the eLearning module.

For further information contact