4.3.15. On-Site Stormwater Mitigation
On-site stormwater mitigation devices may be required to reduce the impact of stormwater runoff (quantity) on receiving systems.
The installation of stormwater storage devices as part of a site’s private drainage system can ensure that the rate of stormwater discharge does not increase when the site is developed.
All stormwater mitigation devices are subject to specific design and approval by the council, and shall be designed in accordance with the relevant Auckland Council technical guidelines.
The council requires devices to be provided in the following situations:
- Where required by either planning rules or conditions of resource consent
- All new developments in all combined sewer areas
- Instances of kerb discharge
- In catchments where there are known capacity issues with the downstream stormwater system
- Where soakage systems require reduced flow rates in order to match the available infiltration rate.
At the council’s discretion, some developments matching the above criteria may be exempt from the requirement to install a stormwater mitigation device where this is of wider benefit to the overall catchment.