20220218 22 Grant SWMP · MCU22/0172

The results of the modelling against the range of design storms for the development under the existing and
proposed development conditions are shown in Table 3.1 Existing and proposed unmitigated site peak discharge
rates.


                              Table 3.1 Existing and proposed unmitigated site peak discharge rates

                                                                      Delorme Street
                                                                                                      Qchange
                                           A.E.P               Qexisting   Qproposed     Qchange       (%)
                                                               (m³/s)      (m³/s)        (m³/s)
                                             1EY                0.016       0.018         0.002        13%
                                            50%                0.018         0.020       0.002         11%
                                           0.2 EY              0.027         0.030       0.003         11%
                                            10%                0.035         0.036       0.001          3%
                                             5%                0.040         0.041       0.001          3%
                                             2%                0.047         0.047       0.000          0%
                                             1%                0.051         0.051       0.000          0%



As expected, the site has increased the total peak flows from the site, however the overall increase is minor with a
maximum of 3L/s increase under 2100 climate conditions. This level of increase is unlikely to result in significant
impact or nuisance to the downstream network and is therefore negligible. No attenuation is proposed for the
development.




Project number 20220218                                                                                           Page 8 of 14
File 20220218 22 Grant SWMP.docx, 2022-09-15 Revision 1

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