Further information re Request to Change Approval MCU 132003.221132.8

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                    Results
                    The results of the analysis indicate that the new and reconfigured detention basins and outlet structures
                    achieve the non-worsening objective. There is now a decrease in peak flows for an 100 Year ARI event
                    of 5%.Peak flow results are shown in Table 3 below.


                                                     Table 3: Existing and Mitigated (Option3) Peak Flows




                    The Water Surface Levels (WSL’s)for each basin have also been considered (refer to Table 4
                                                                                                                                                            below).
                    Basin B1A, B1C and the Twigrush Basin are consistent with freeboard
                                                                                                                                        requirements. Depth of flow
                    across the overflow weirs are also             less than 300mm during the Peak 100
                                                                                                                                      year ARI event.


                                                                      Table 4: Option 3 Basin WSL’s




                    For tlle Dodonaea Basin results indicate that there is a decrease in peak WSL’s compared to that

                    specified in the previous report. Results are presented in the Table 4 above. Significant reductions in
                    the detention volume and the WSL between the previous strategy and Option 3 have been provided.
                    The resulting changes in volume in the Dodonaea basin are presented in Table 5 below.




                    The peak 100 year ARI WSL in the Dodonaea Basin (11.21m. AHD)will also ensure the fauna
                                                                                                                   passage
                    will remain flood free during this event. A reduction in the time for the basin to drain has also been
                    demonstrated. It takes Dodonaea Basin 30 minutes less to empty. during a 100
                                                                                                                                                  year ARI event then
                    previously determined.

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