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Stormwater-Picture

The stormwater system exists in our urban towns to manage run off from rainfall events.

The council is responsible for the stormwater system, which consists of drains, swales, pipes, soakholes and treatment devices (wetlands, basins and proprietary devices) that manage run off from roof and hard-stand areas. Stormwater is discharged either to ground or to surface water including open drains or streams depending on the ground conditions in the area. Details of the stormwater schemes are provided in the Activity Management Plan.

Stormwater Network

Council maintains the stormwater network within the 22 townships in the District. For new areas of subdivision the primary stormwater network (pipes etc) are sized to carry a 10 year or 10% AEP (Annual Exceedance Probability) event. The secondary stormwater network (roads and overland flow paths) are sized to carry a 50 year or 2% AEP event. This means that in a large storm event the roads are intended to carry stormwater. Older parts of the network have a smaller capacity and are likely to be able to carry a 2 year event.

In newer parts of the District, where stormwater is discharged to surface water or near shallow groundwater, Environment Canterbury require stormwater to be treated. In the Selwyn district this is typically done using basins, wetlands and swales. In industrial areas or where there is less space, proprietary treatment devices can be used.

Council will maintain the existing stormwater network to provide the best service possible. If you see water ponding on the side of the road, please contact Council and let us know. Better still, take a photo and send it in to us.

Swales

Mowing of roadside berms including swales is the responsibility of adjacent property owners. Council maintains berms adjacent to all property which Council owns. Council’s resource consents require grass in swales be between 50mm and 150mm in length to provide adequate treatment of stormwater.

Pipes on Your Property

Council are responsible for maintaining the stormwater pipes up to the boundary of your property. If you have a problem with the stormwater lateral on your own property, you should call a drain layer or drain cleaning company for assistance.

Soakpits

Parts of our District have well-draining soils that are suitable for receiving and soaking stormwater. Where this is the case, water from the roof of your property will be disposed of to the ground via a soakpit on your property, and your property will not have a connection to the stormwater system. Property owners are responsible installing and maintaining their soakpits. Roof soakpits must be installed in line with section E1 of the building code. If you have any queries regarding installing and sizing a soakpit on your property please contact Council and ask for the Building Department.

Council’s roading contractors maintain roadside soakpits that dispose of water from the road.

Consents

Council currently hold a number of stormwater consents that govern the discharge of stormwater. These typically consent the discharge of stormwater from roads and individual residential properties.

Council resource consents exclude some high risk industrial and trade activities and property owners are required to obtain their own resource consent from Environment Canterbury.

Global consents provides further information on our global stormwater consents.

Dewatering to the Stormwater/Drainage Network

Any construction dewatering to the Selwyn District Council stormwater or drainage network requires pre-approval. Please use the Water Discharge Application Form and return to the Stormwater Engineer via waterservices@selwyn.govt.nz

Open Drain Culverts

All culverts over open stormwater drains and swales are the responsibility of the landowner whose access is over the drain/swale. When they need to be replaced or maintained, it is the landowner's responsibility. Approval is required from the Council for all new and replacement culverts.

You can apply for an entranceway crossing online. Council's standard drawings for culverts over Council drains and swales.

For more information please contact Council.

Pollution

Stormwater drains in some parts of the District (e.g. Tai Tapu, Lincoln, Springston, Doyleston and Leeston) discharge into Council’s Land Drainage network and drain to Te Waihora (Lake Ellesmere). It’s easy to forget that anything that gets spilt on the road or your driveway can be washed into the drain, and will have an impact on the environment. Our drains are home to tuna, inanga and Canterbury mudfish.

Water from washing your paint brushes, spilt oil, or your car could be going directly into our waterways.

Here are some tips to help protect our drains, our environment and local fish species:

  • Use a car wash or wash your car on grassed areas
  • Fix oil leaks in vehicles as soon as you can
  • Don’t tip any waste paint, oil, antifreeze or chemicals go down the drain – take them to the transfer station for recycling or safe disposal. Household volumes of hazardous waste are accepted free of charge.
  • Don’t let rubbish get into your drains, it could cause a blockage
  • Sweep up garden waste from your driveway rather than washing it down the drain

Dispose of all pet waste in your red bin

Stormwater Design

Information for designers of stormwater systems.