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Updated 13 July 2020 12:15pm

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The effects of stormwater discharges on the environment 

Stormwater affects water quality as it contains contaminants that are carried by rainfall runoff. Wastewater can also enter the stormwater network during heavy rainfall if the wastewater drains become overloaded.

These contaminants then enter waterways and the coastal environment. Contaminants in stormwater can cause negative effects on aquatic ecosystems, human health, mauri, people's enjoyment of the area, the suitability of water for recreation and shellfish gathering.


The framework for managing stormwater discharges from local authority networks 

The proposed Natural Resources Plan aims to achieve a progressive reduction in the negative effects of stormwater discharges from local authority networks to fresh and coastal water.

This is to be achieved through two stages: stage one is to gather information about the effects of stormwater discharges over five years, and stage two is implementing a longer term action plan to achieve progressive improvements.

The framework includes a ‘global’ approach to managing stormwater discharges, meaning that discharges are considered and managed in a holistic way (ie, across a city or district).

Two-stage global stormwater consent framework 
Years 1-5

Stage 1

  • Monitoring to identify the negative effects from the stormwater network
  • Review and update of a Stormwater Monitoring Plan annually
  • Management of acute effects on human health
  • Development of a Stormwater Management Strategy to prioritise progressive improvements under stage 2
From year 6

Stage 2

  • Implementation of a Stormwater Management Strategy to meet water quality objectives
  • Reducing impacts of untreated wastewater on fresh and coastal water
  • Improving existing stormwater and wastewater infrastructure

pNRP water quality objectives, including whaitua specific objectives, also feed into stage 2

Current stormwater consents held by city/district councils 

There are currently two stage-one stormwater consents for discharges from local authority networks.

Wellington Water (on behalf of Wellington City Council, Porirua City Council, Hutt City Council and Upper Hutt City Council) and Kapiti Coast District Council have resource consents for discharges from their stormwater networks to fresh and coastal water.

These discharges include stormwater that is occasionally contaminated with wastewater. The officers’ reports and resource consent certificates (conditions) for these consents are available on this page.

The stage one consents include two key documents: a Stormwater Monitoring Plan and a Wastewater Overflows into Network Procedures Plan. The monitoring plan guides the collection of information over the five-year duration of the consent.

The consent holder (Wellington Water and Kapiti Coast District Council) are responsible for undertaking monitoring in accordance with the monitoring plan.

The Network Procedures plan sets out how the acute effects on human health will be communicated and managed, for example through signage. The actions required under these plans are illustrated below.

View the full monitoring framework

In addition to monitoring the effects of stormwater discharges, the stage-one consents require the acute effects on human health to be managed, specifically where there are discharges that contain wastewater.

The stormwater consents include microbiological trigger values that, if exceeded, require investigation into the cause of the contamination and communication procedures to be put in place. These triggers are set out in the consent conditions.

Where the cause of the contamination is identified, immediate remedial actions must be taken to address the cause of the contamination. If an investigation is undertaken and the cause of the contamination is not identified and there are risks to human health, a human health project in the catchment must be undertaken.

After five years of monitoring the monitoring data will be used to develop a Stormwater Management Strategy.

The Stormwater Management Strategy will set out how stormwater quality will be progressively improved to meet water quality objectives set out in the Proposed Natural Resources Plan, including the whaitua-specific freshwater objectives that will be incorporated in the plan.

The strategy will form the basis of the stage-two consents and could include goals and timeframes in relation to the progressive elimination of wastewater overflows to the stormwater network.

 Wellington Water stage-one stormwater consent

Kapiti Coast District Council’s stage-one stormwater consent