Amended Stormwater Management Report

 Temporary Drainage Works                        Anticipated Operation Design Life and Minimum
                                                              Design Storm Event


                                                 <12 Months        12-24 Months         >24 Months

 Where located immediately up-slope of an                     1 in 10 year ARI/10% AEP
 occupied property that would be adversely
 affected by the failure or overtopping of the
 structure

 Culvert Crossing                                             1 in 1 year ARI/63% AEP


Table 4 – SPP Appendix 2: Part 3 Construction Phase – Stormwater Management Design Objectives
for Emergency Spillways on Temporary Sediment Basins

            Drainage Structure                   Anticipated Operation Design Life and Minimum
                                                              Design Storm Event


                                                  <3 Months         3-12 Months         >12 Months

 Emergency spillways         on    temporary      1 in 10 year      1 in 20 year        1 in 50 year
 sediment basins                                 ARI/10% AEP        ARI/5% AEP          ARI/2% AEP

Best practice erosion and sediment controls must be installed to minimise the discharge of sediment
laden runoff during construction and to achieve the objectives outlined in Tables 2-4. This is discussed
in the following section.
4.2.2 E ro sio n and Se dim en t Co ntr ol

Management of stormwater runoff during construction is necessary to avoid pollution of downstream
waterways from sediment and gross pollutant loading. Impacts of inadequate erosion and sediment
control downstream from the site include:

    •   traffic safety problems;

    •   blocked drains;

    •   local flooding problems;
    •   aesthetic pollution of drainage paths; and

    •   damage to local ecosystems.

Best practice erosion and sediment controls must be installed to minimise the discharge of sediment
laden runoff during construction. Erosion and sediment control plans shall be developed during detailed
design phase and must be continually maintained and amended as required to minimise environmental
harm.
Erosion and sediment control plans are based on three sets of control measures:

    •   drainage control;

    •   erosion control; and

    •   sediment control.


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