Att 1 - Engineering - RFI Reponse · MCU21/0117.01

                                                                                             23098 - SBSMP/4
                                                                                                   Page 11




5.3.5 Post-Development Model
The post-development catchment model utilises the following values in Table 5-5. The sub
catchment area taken into account for the post-development catchment is 0.2275ha. Refer to
Figure 5.2 below for a screenshot of the pre-development model.

              Table 5-5 – Post-Development Catchment Characteristics for Catchment
                                                            Effective         Remaining
                                                                                                Pervious Area
              IL-CL Hydrological Model                     Impervious       Impervious Area
                                                                                                    (PA)
                                                            Area (EIA)           (RIA)

 Post-Development
                           Percentage of area (%)                51               25                 24
    Catchment
                       Time of Concentration (mins)              5                 5                  5




                                  Figure 5.2 – Post-Development Model

5.3.6 Post-Development Mitigated Model – On-site Detention Tank
The post-development mitigated catchment model utilises the following values in Table 5-6. The
sub catchment area taken into account for the post-development mitigated roof catchments are
0.0335ha, 0.0214ha, and 0.0258ha, respectively. The sub catchment area taken into account for
the post-development mitigated ground catchment bypassing to the lawful point of discharge is
0.0258ha.

        Table 5-6 – Post-Development Mitigated Catchment Characteristics for Catchment
                                                                               Remaining
                                                Effective Impervious Area                       Pervious Area
          IL-CL Hydrological Model                                             Impervious
                                                           (EIA)                                    (PA)
                                                                                Area (RIA)
Post-Development Percentage of area (%)                    100                      0                 0
Mitigated – Building
                     Time of Concentration
   1 Catchment
                             (mins)
                                                            5                       0                 0

Post-Development Percentage of area (%)                    100                      0                 0
Mitigated – Building
                     Time of Concentration
   2 Catchment
                             (mins)
                                                            5                       0                 0

Post-Development Percentage of area (%)                    100                      0                 0
Mitigated – Building
                     Time of Concentration
   3 Catchment
                             (mins)
                                                            5                       1                 1

 Post-Development     Percentage of area (%)                0                      56                44
   Bypass Ground
                      Time of Concentration
    Catchment
                              (mins)
                                                            0                       5                 5


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