RFI - SWMP.pdf

6.3.3     Configuration



To mitigate the peak flow increase from the developed site, it is proposed to include an inground open
bio retention/detention basin for catchment B, located within the north eastern corner of the site. We
propose for the detention basin to cater for flows up to the Q100 storm event and a limited capacity to the
existing stormwater infrastructure located in Lot 101 RP 106085, refer to section 6.4 for further
discussion. The proposed on-site detention will have the following properties: -



          •      Base Area                                  =     140m2
          •      Internal Depth                             =     1.1m
          •      Low Flow Orifice                           =     0.18m diameter
          •      Overflow Pit Elevation from base           =     1.1m
          •      Required Volume                            =     150m3
          •      Provided Volume                            =     180m3



The site was divided into sub-catchments to mirror the Stormwater Management Plan drawing no: SCG
31131- SW1.1 - SW1.5 detention basin was also included for catchment B as discussed above.



6.3.4     Results



The pre development and post development peak median flow rates were compared for the catchments
and are displayed in Table 6.5 below:



                                        Table 6.5 – Comparison of peak Flows

              Condition            Q1          Q2         Q5       Q10          Q20      Q50      Q100
                                  (m3/s)     (m3/s)      (m3/s)      3         (m3/s)   (m3/s)   (m3/s)
                                                                  (m /s)

        Drains Catchment B        0.048      0.065       0.095    0.119        0.141    0.167     0.187
         Pre Development




SCG Consulting Engineers                       Page 20                                  SCG Ref: 31131(SWMP)