MCU14/0056 - Attachment G - Engineering Report & Stormwater Management Plan

                                                                                                                Preliminary Detention Calculations
                                                                                        Date:      17/04/2014                Document No.:                14012-Detention
                                                                                            By:       AvT                        Revision No.:                    A


                                                                                                                                                 Project No: 14012

                                              PROJECT: PROPOSED MIXED USE DEVELOPMENT
                                              ADDRESS: CORNER MYALL STREET & FERRELLS ROAD COOROY QLD
                                           CATCHMENT: TOTAL SITE

   Runoff Coefficient (C10) - Undeveloped:                     0.70           (QUDM Table 4.05.3 (b))                     tc =              6 min.
   Runoff Coefficient (C10) - Developed:                       0.82           (QUDM Table 4.05.3 (a))                     tc =              6 min.
   Catchment Area - Undeveloped:                              50354     m2
                                                                         2
   Catchment Area - Developed:                                50354     m

                                                                Parameters
   ARI                                                                  2yr              5yr         10yr          20yr             50yr         100yr
   Rainfall Intensity                                         mm/hr    150.0            184.0        204.0         232.0            268.0        296.0
   Frequency Factor            fy=                                      0.85            0.95         1.00          1.05             1.15          1.20
   Undeveloped C              Cu=                                             0.60          0.67     0.70           0.74             0.81        0.84
   Developed C                Cd=                                             0.70          0.78     0.82           0.86             0.94        0.98

                                                                      Flows
   Undeveloped Flow           Qu=              C*I*A           l/s            1248      1711         1997          2385             3018         3478
   Developed Flow            Qd=Qi=            C*I*A           l/s            1462      2005         2340          2794             3535         4074
   Difference                                                  l/s            214       293          342           409              517          596

   Outlet Flow              Qo=        Max. Qu (or Q2)         l/s            1248    1711        1997             2385             3018         3478
                                                                                     Multiple Outlet Pipes

                                                               Initial Volume
   Reduction ratio             r=            (Qi-Qo)/Qi                   0.146         0.146        0.146         0.146            0.146        0.146
   Inflow Volume               Vi=            4tc*Qi/3         l/s            702           962      1123          1341             1697         1956    QUDM Equation

                              Culp      Vs=(r(1+2r)/3)*Vi      m3             44            61        71             85              107         123     QUDM Equation 5.01

                              Boyd             Vs=r*Vi         m3             103           141       164           196              248         286     QUDM Equation 5.02
   Volume to Retain
                             Carroll    Vs=(r(3+5r)/8)*Vi      m3             48            66        77             92              116         133     QUDM Equation 5.03

                             Basha         Vs=(r(2+r)/3)*Vi    m3             73            101       118           140              178         205     QUDM Equation 5.04



                            Volume to Retain =                 m3             67            92       107           128              162          187
                                                                                                                                    3
                                                                        Total Volume to Retain = 186.93 m




vT Consulting Engineers
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