8. APP G. Engineering RFI Response

                Table 5.1: Stormwater Detention Basin Summary
                                      Parameter

                                  Base Dimensions                                                12m x 18m

                                         Depth                                                    1.25m

                                  Storage Volume                                                  245 m3

                                  Outlet Arrangement

                                  Low Flow Outlet                             150mm diameter orifice at the base of the Tank

                                                                            225mm diameter orifice at 800mm above the base
                                  High Flow Outlet
                                                                                             of the Tank
                The detention tank parameters listed in Table 5.1 were calculated using XPRafts. An iterative
                method was used to adjust the parameters until the catchment flows were reduced to the
                predevelopment flows. Hydrographs relating to the detention tanks, including basin storage
                volume, have been included in Appendix F.

5.1.3           MODEL RESULTS
                The discharge rate at each discharge point is tabulated below for the existing, developed and
                mitigated scenarios. This table shows that the proposed detention tank is successful in
                mitigating the developed discharge back to existing rate for all of the ARI storm events.

                Table 5.2: Stormwater Discharge Rates
                                         Existing             Developed             Mitigated       Impact
                        ARI              Scenario              Scenario             Scenario
                                                                                                      (%)


                    Q1 (m3/s)               0.039                 0.161                  0.039        0%

                    Q2 (m3/s)               0.054                 0.206                  0.046       -15%
                    Q5 (m3/s)               0.076                 0.239                  0.056       -26%
                              3
                   Q10 (m /s)               0.094                 0.269                  0.073       -22%
                   Q20 (m3/s)               0.117                 0.311                  0.110       -6%
                   Q50 (m3/s)               0.135                 0.342                  0.131       -3%

                  Q100 (m3/s)               0.155                 0.408                  0.150       -3%




139 Eumundi Noosa Road & 30 Lionel Donovan Drive, Noosaville Service Station and Retail Site—Stormwater
Management Plans
Hyder Consulting Pty Ltd-ABN 76 104 485 289                                                                                    9
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