Further information re Request to Change Approval MCU 132003.221132.8

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                                  Table 8: Options 4 Existing Peak Flows


                                                  Existing WBNM (Peak Flow mj/s)
ARI
                                   BlA                           BlC                  Twigrush
2                                  0.15                          0.20                   0.21
5                                  0.24                          0.32                   0.34
10                                 0.29                          0.38                   0.41
20                                 0.35                          0.47                   0.50
50                                 0.41                          0.53                   0.57
100                                0.48                          0.62                   0.65


For the developed scenario, identical basin configuration as previous options have been used for BIC

and BIA, and the original sized Twigrush Basin configuration from (OPTION 2) have been adopted.


With the objective being to mitigate developed peak flows to existing conditions with the smallest

basins   possible, factors were input into the model to optimize basin sizes to achieve the non-
worsening objectives. For BIA, BIC and Twigrush size factors of 40%, 55% and 65% were used
respectively. Table 9 shows the resultant peak flows and Table 10 shows the changes in Peak Flows.

                              Table 9: Options 4 Developed WBNM Peak Flows



                                                Developed WBNM (Peak Flow mj/s)
ARI
                                   BlA                           BlC                  Twigrush
2                                  0.08                          0.18                   0.20

5                                  0.20.                         0.24                   0.25

10                                 0.25                          0.30                   0.27

20                                 0.36                          0.42                   0.32

50                                 0.43                          0.53                   0.52

100                                0.49                          0.63                   0.66




                           Table 10: Options 4 Percentage Increase in Peak Flows


                                                 Increase (%)from Existing Scenario
ARI
                                   BlA                           BlC                  Twigrush
2                                 -51.3%                        -8.1%                  -5.3%

5                                 -19.3%                        -24.1%                 -27.4%

10                                -13.1%                        -21.4%                 -33.3%

20                                 2.8%                         -11.1%                 -37.1%

50                                 3.9%                         -1.5%                   -8.8%
100                                1.4%                          1.3%                   1.7%



It should be noted that the analysis for Option 4 does not take into account the timing of peak flows

from the upstream external catchment. Council may not accept this option as it is not a full

catchment analysis (which has previously been provided) and does not account for peak flows from

the site and upstream catchment coinciding.




B09182.W _Options_2_3_ 40N LV _130314.docx                                                       Page 4