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Stormwater Detention: Council Requirements for Residential and Property Development

Stormwater Detention: Council Requirements for Residential and Property Development

Local councils require stormwater detention for residential development throughout many built-up areas in Australia. This article will look at why this is necessary in developed areas, general requirements you might need to meet, and how you can comply with water detention requirements.

What is Stormwater Detention?

As the number of residential homes increase and areas are increasingly developed, hard surfaces also increase such as roads, driveways, pavements, rooftops and the like. These surfaces, unlike the ground and vegetation that existed prior to them, are impenetrable by water and can cause a lot of rainwater runoff.

Councils attempt to draw water away through stormwater drains, however, in downpours even these can fill up and spill out onto the street flooding roads and residential areas.

To help share the burden of responsible stormwater runoff, your council might require you to take some responsibility over your own property’s water runoff by temporarily detaining some stormwater on your property when it rains.

General Council Requirements

While one council differs from another, council requirements normally detail:

  • Type of development, property sizes and specific areas required to detain stormwater (for example, dwellings proposed on allotments under 500 square metres)
  • Amount of stormwater your property needs to capture and store (a minimum of 2000 litres of rainwater from the roof is about typical)
  • Minimum percentage of roof area that must be directed to your detention system and/or maximum outflow (for example, a minimum of 60% of your roof area is directed to your stormwater detention system with a maximum outflow rate of 3 litres per second)
  • Additional detention requirements for developments that have many hard surfaces such as shared driveways and large parking areas.

It is important to know your local council’s specific stormwater detention requirements so that whoever is doing your structural drawings can account for it.

Achieving Stormwater Detention Requirements

Your builder will have a qualified hydraulic engineer to consult to design an appropriate stormwater detention system for your property. If you aren’t building, but adding in a stormwater detention system, then you may need to consult a qualified engineer yourself.

Several common solutions for onsite stormwater detention which councils normally approve of include:

  • Stormwater detention tanks: specially designed tanks that have split storage inside, one compartment for storing rainwater, the other for detaining stormwater.
  • Underground storage tanks: for storing stormwater runoff, normally designed with your rainwater harvesting system to receive excess water overflowing from a rainwater tank.
  • Rainwater tanks: large water storage tanks may satisfy some councils.
  • Surface holding areas: basin, soakage pits, trenches, or swimming pools.

Since requirements vary from one council to the next, it is important that you discuss with them any stormwater detention requirements before choosing your solution.

What is a Stormwater Detention Tank?

Traditional rainwater tanks are used to store rainwater for domestic use. Stormwater detention tanks on the other hand are intended to remain empty, except during periods of rainfall and a small period thereafter.

Unlike rainwater tanks, stormwater detention tanks are generally based upon a two or three module tank system and modified with a special valve that slowly releases water over time. During heavy downpours, the detained water helps to prevent flooding on roads, creeks, your property and its surrounding area.

Optionally, stormwater detention systems can also be setup with two separate tanks, one that harvests and stores rainwater, and the other used as a water retention or detention system.

If you need tanks for a suitable stormwater detention system for your new home, talk to the expert team at Team Poly. We have manufactured and distributed over 1 million water tanks throughout Australia since 1990, providing us with a wealth of experience and ability to understand and service your needs. Talk to us today about your needs, request a free quote through our site or call us.