RFI - Attachment 1 - Amended Stormwater Management Plan

                                                          Therefore, a further assessment is undertaken below.

Common Law: Principles of nuisance                        If the existing discharge point is maintained, and
                                                          discharge quantities and velocities are maintained as
Alterations to the natural flow regime will be lawful     per the pre-developed state, then no third-party
if all necessary statutory approvals have been            damage is occurring, and this gives no rise to
obtained and complied with, and:                          actionable nuisance claims.

       There is no nuisance or interference to the       Therefore, if the development can maintain these
        use or enjoyment of affected land; or             pre-development attributes when discharging from
       The affected land owner has consented to the      the Site in the post-developed state, the alterations
        change in drainage                                will be lawful.

   TABLE 1 LPOD ASSESSMENT AGAINST PROPOSED DEVELOPMENT




   3. STORMWATER CHARACTERISTCS

   3.1. Comparison of Pre/Post Development and Quantity
   The development proposes to increase the impervious area of the site by 229m2 for the additional
   dwelling and allowance for the driveway surface – note this is an approximation to provide allowance
   for siting the actual driveway layout.

   In the previous version of this report, the post-development was modelled as having an impervious
   catchment of 31% to reflect these characteristics. In response to Council’s IR, the post-development
   has been updated to account for a conservative scenario consisting of dwelling, paved and
   landscaping areas over a 400 m2 pad resulting in an overall imperviousness of 45%. The developed
   catchment increases from the 31% to 57% and the modelling has been updated to account for this
   change in Table 2.

                                                    Pre-Development        Post-Development

                           Catchment                       Pre-01                Post-01

                            Area (Ha)                      0.153                  0.153

                        Fraction Imp (%)                     20                     57


                  Time of Concentration (mins)             10.13                  10.13




   TABLE 2 MODELLING PARAMETERS




   Pre and post discharge rates have been calculated using DRAINS software to evaluate the effect of
   the development. Attenuation of post-development flows have achieved by modelling each dwelling
   having a 3kL rainwater tank.