4.5.7 On-site Disposal
This refers to the discharge of stormwater on site as opposed to "on-site mitigation" which refers to various on-site measures used to mitigate effects such as the volume and rate of stormwater runoff from the site. When on-site mitigation is implemented an approved stormwater outfall is still required for the final discharge of the stormwater.
On-site disposal of stormwater is generally not an acceptable method for stormwater disposal due to the underlying clay soils, typically steep terrain and thin layer of topsoil as it may result in excessive overland flow onto neighbouring properties. There are, however, some situations in which on-site disposal may be permitted:
Under exceptional circumstances, situations not meeting one or more of the above criteria may be considered, subject to approval by the Council. In such situations, as a minimum, the stormwater runoff from the site shall be reduced to pre-development levels through the use of measures such as rainwater harvesting, detention and bioretention (rain gardens).
Overland flow paths shall be provided in accordance with Section 4.3.2 to cater for events exceeding the capacity of the primary system and occasions when the primary drainage system fails.