Att 1 - Engineering - RFI Reponse · MCU21/0117.01

                                                                                             23098 - SBSMP/4
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                                            Table of Contents
1     INTRODUCTION ............................................................................................ 3
2     EXISTING SITE.............................................................................................. 4
  2.1    The Site ................................................................................................ 4
  2.2    Surrounding Area ...................................................................................... 4
3     PROPOSED DEVELOPMENT ............................................................................... 5
4     EXISTING DRAINAGE PATTERNS ......................................................................... 6
  4.1    Existing Infrastructure ............................................................................... 6
  4.2    Existing Drainage Patterns ........................................................................... 7
  4.3    Lawful Point of Discharge............................................................................ 7
5     STORMWATER QUANTITY................................................................................. 8
  5.1    Rational Method Assessment ........................................................................ 8
    5.1.1     Design Storms ....................................................................................8
    5.1.2     Rainfall Intensity ................................................................................8
    5.1.3     Times of Concentration .........................................................................8
    5.1.4     Runoff Coefficients ..............................................................................8
    5.1.5     Peak Flows ........................................................................................9
  5.2    Proposed Development Drainage ................................................................... 9
  5.3    DRAINS Modelling Assessment ....................................................................... 9
    5.3.1     Hydraulic Model Parameters ................................................................. 10
    5.3.2     Design Storms .................................................................................. 10
    5.3.3     Intensity Frequency Distribution ............................................................ 10
    5.3.4     Pre-Development Model ...................................................................... 10
    5.3.5     Post-Development Model ..................................................................... 11
    5.3.6     Post-Development Mitigated Model – On-site Detention Tank .......................... 11
    5.3.7     Comparison of Peak Flows at Lawful Point of Discharge ................................. 13
6     STORMWATER QUALITY ................................................................................ 15
  6.1    State Planning Policy Assessment ................................................................ 15
  6.2    Construction Phase ................................................................................. 15
  6.3    Operational Phase .................................................................................. 17
    6.3.1     Sources of Contaminants ..................................................................... 17
    6.3.2     Proposed Treatment Train ................................................................... 18
    6.3.3     Pollutant Export Modelling ................................................................... 18
    6.3.4     MUSIC Modelling Parameters ................................................................. 18
    6.3.5     MUSIC Modelling Results ...................................................................... 19
7     FLOODING ................................................................................................ 21
8     CONCLUSION ............................................................................................. 22
Appendix A DETAILED SITE SURVEY ........................................................................ 23
Appendix B PROPOSED DEVELOPMENT PLANS ............................................................ 24
Appendix C NSC INTERACTIVE MAPPING PLANS .......................................................... 25
Appendix D NSC WATER QUALITY AND DRAINAGE CODE ................................................ 26
Appendix E RATIONAL METHOD CALCULATIONS ......................................................... 27
Appendix F CONCEPT SITE LEVELS AND DRAINAGE PLAN ............................................... 28
Appendix G BOM IFD ......................................................................................... 29
Appendix H DRAINS PRE & POST DEVELOPMENT RESULTS .............................................. 30
Appendix I DRAINS POST DEVELOPMENT MITIGATED RESULTS ........................................ 31
Appendix J STORMWATER QUALITY OPERATION AND MAINTENANCE GUIDELINES .................. 32
Appendix K NSC FLOOD HAZARD OVERLAY MAP .......................................................... 33




Site Based Stormwater Management Plan
Proposed Townhouse Development at 5 Pearl Street, Cooroy