Draft Stormwater Bylaw 2022

The purpose of the bylaw is to allow the Council to manage activities that could compromise our infrastructure, cause a nuisance to the public or pollute the environment.

Regulatory requirements

Environment Canterbury requires the Ashburton District Council to reduce the contaminants in stormwater through a stormwater discharge resource consent (CRC 186263). The consent requires Council to reduce contaminants in stormwater discharges to protect and improve the health and water quality of local streams, rivers and groundwater.

The consent also requires Council to introduce a bylaw (or other alternative) to support the effective operation of the consent.
Council is currently seeking stormwater discharge consents for the stormwater networks serving Methven and Rakaia.  The Bylaw will support the effective operation of those consents, when they are granted.

Stormwater network

The stormwater network collects and carries stormwater through a system of pipelines, open drains, channels and overland flow paths where it discharges the untreated stormwater to local waterways or land via soak pits and infiltration basins.

It’s important to note that stormwater is different from wastewater, which is the water that goes down the drain after we do our washing, flush the toilet or have a shower. Wastewater is carefully treated before being discharged to the environment, while stormwater treatment varies. Recent, modern subdivisions treat stormwater to a high standard, however older, existing disharges may only have partial treatment.

While stormwater drains to a piped network, this network is completely separate to the wastewater network. It's important to keep stormwater out of the wastewater network to prevent overflows to waterways during high rainfall events.

Why manage stormwater?

Stormwater can collect contaminants as it travels from its source to the stormwater network and then discharges to the receiving environment. In Ashburton, stormwater discharges untreated to Wakanui, Laghmor and Carters Creek and a number of soak pits and infiltration basins around the township.

Contaminated stormwater entering these streams can have negative impacts on water quality, aquatic life, public health and recreational use of waterways.

Additionally fats, debris and oils can build up causing blockages and damaging the stormwater network. Even small blockages in the network can significantly increase the flood risk during rainfall events.

For most residential properties there will be little change. Acceptance of discharge is covered as part of the building and consenting process and is considered low risk. Should additional treatment be required on existing properties, we'll work with owners to ensure this can be done in practical ways. New developments are already required to submit sediment and erosion control plans, which are implemented during the construction phase.

While everyone has a responsibility to help reduce contaminants entering our stormwater system, the focus of this bylaw is primarily on industrial and commercial sites, whose activity can pose the greatest risk to the network.

We will work alongside industrial and commercial businesses to make sure they are aware of their responsibilities. A staged approach will allow businesses to carry out their daily activities while helping us to gradually improve the quality of stormwater entering the network.

The biggest proposed changes from the bylaw are:

• Setting conditions for new and continued acceptances of discharge into the stormwater network
• Setting stormwater quality standards that stormwater discharge will need to meet
• Develop a register of industrial sites and risk classification system
• Implementation of stormwater protection plans if and when required