Attachment 7- Site Based Stormwater Management Plan

Appendix 2 — Stormwater management
design objectives

Table A: Construction phase — stormwater management design objectives

Application:
© Applies to all climatic regions.

Part 1 Construction phase — stormwater management design objectives

Issue Desired outcomes

Drainage control 1, Manage stormwater flows around or through areas of exposed soil to avoid contamination.
2. Manage sheet flows in order to avoid or minimise the generation of rill or gully erosion.

3. Provide stable concentrated flow paths to achieve the construction phase stormwater
management design objectives for temporary drainage works (part 2).

4. Provide emergency spillways for sediment basins to achieve the construction phase
stormwater management design objectives for emergency spillways on temporary
sediment basins (part 3).

 

Erosion control 1, Stage clearing and construction works to minimise the area of exposed soil at any
one time.

2. Effectively cover or stabilise exposed soils prior to predicted rainfall.

3. Prior to completion of works for the development, and prior to removal of sediment
controls, all site surfaces must be effectively stabilised* using methods which will
achieve effective short-term stabilisation.

 

Sediment control 1. Direct runoff from exposed site soils to sediment controls that are appropriate to the
extent of disturbance and level of erosion risk.

2. Allexposed areas greater than 2500 metres? must be provided with sediment controls
which are designed, implemented and maintained to a standard which would achieve
at least 80% of the average annual runoff volume of the contributing catchment
treated (i.e. 80% hydrological effectiveness) to 50mg/L Total Suspended Solids (TSS)
or less, and pH in the range (6.5-8.5).

 

Litter, hydrocarbons and other 1. Remove gross pollutants and litter.
contaminants 2. Avoid the release of oil or visible sheen to released waters.

3. Dispose of waste containing contaminants at authorised facilities.

 

Waterway stability and flood 1. Where measures are required to meet post-construction waterway stability objectives

flow management (specified in table B), these are either installed prior to land disturbance and are
integrated with erosion and sediment controls, or equivalent alternative measures
are implemented during construction.

2. Earthworks and the implementation of erosion and sediment controls are
undertaken in ways which ensure flooding characteristics (including stormwater
quantity characteristics) external to the development site are not worsened during
construction for all events up to and including the 1 in 100 year ARI (1% AEP).

 

® Note: Drainage, erosion and sediment controls should be appropriate to the risk posed by the activity for the relevant climatic region e.g. considering the
potential soil loss rate, monthly erosivity or average monthly rainfall.

© Note: An effectively stabilised surface is defined as one that does not, oris not likely to result in visible evidence of soil loss caused by sheet, rill or gully erosion
or lead to sedimentation water contamination.

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