Further information re Request to Change Approval MCU 132003.221132.8

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                                Table 5: Options 3 Dodonaea Basin WSl Results


                                                         Dodonaea Basin
                   ARI          Previous Peak WSL          OPTION 3 Peak           Change in WSL (m)
                                     (m.AHD)               WSL(m.AHD)
          2                            10.81                    10.03                       -0.78
          5                            11.32                    10.42                        -0.9
          10                           11.59                    10.62                       -0.97
          20                           11.90                    10.89                       -1.01
          50                           12.04                    11.12                       -0.92
          100                          12.11                    1l.33                       -0.78




                            Table 6: Options 3 Dodonaea Basin Change in Volume   1m3)

                                                         Dodonaea Basin
                   ARI        Previous Peak Volume         OPTION 3 Peak           Change in Volume
                                       (m3)                 Volume (m3)                     (m3)
          2                             479                      99                         -380
          5                             950                      250                        -700
          10                           1304                      360                        -944
          20                           1808                      538                        -1,270
          50                           2073                      739                        -1,334
          100                          2202                      962                        -1,240




Significant changes are seen in the detention volume and the WSL between the previous model and
Option 3.       A reduction in the time for the basin to drain has also been determined.                 It takes

Dodonaea Basin 30 minutes less to empty during a 100 year ARI event then previously determined.

The times for Dodonaea Basin to empty are present in Table 7 below.


                               Table 7: Options 3 Dodonaea Basin Emptying Time


                                 Previous Emptying       OPTION 3 Emptying              Change in Time
                   ARI
                                     Time (min)               Time (mi.n)                   (min)
           2                            120                      100                         -20
           5                            165                      150                         -15
           10                           175                      155                         -20
           20                           185                      155                         -30
           50                           195                      165                         -30
           100                          175                      145                         -30
                 Times given for storm durations producing the peak WSL’s with the basin.


OPTION 4: This strategy analyses the developable areas of Stage C only. The upstream catchment

and drainage reserve (environmental corridor) are not considered in the model. Basins B1A, B1B

and Twigrush have been optimized to mitigate their upstream catchments only.


OPTION 4 applies a strategy where the analysis is only made in the development areas, and basins

are   sized to mitigate those areas.    Therefore, mitigation effectiveness is analysed by a per basin
basis.


An existing scenario has been modelled for the three developable catchments. Results of Peak Flows

are shown in Table 8 below.




B09182.w_Options_2_3_40NLY_130314.doex                                                                    Page 3