SUPERSEDED Approved Plans & Document OPW25-0042 · OPW25/0042

                     Individual sub-catchments are applied to corresponding RIPs/RICs.

                     Existing vegetated areas where no significant works are proposed are
                     excluded from modelling on the basis that they will continue to infiltrate
                     incident rainfall as per the existing pre-development case.

                     Largely soft landscaped catchments 4/1, 4A/1 and 4B/1 are to be directed to
                     RIPs constructed along the external catchment drainage line discussed in
                     Section 6. This arrangement is consistent with the existing stormwater line.

                     The above RIPs are not modelled via spreadsheet in recognition of the fact
                     that they will accept commingled runoff from both internal and external
                     catchments. They are however addressed in the overall development site
                     Quantitative MUSIC model.

                     Spreadsheet model results for all proposed RIPs and the RIC appear below in
                     Table 5.1.1


                     Table 7.1.1 Summary of Excel Spreadsheet Modelling




                     By inspection criteria of infiltrating all flows up to the 10% AEP over the
                     developed site has been demonstrated.

                     Excel model files are attached at Appendix H with catchment drawings
                     appearing at Appendix A.


                     Emergency Overland Flow Weir calculations model the unlikely case of
                     complete RIC failure with full 100 Year ARI flows conveyed toward existing
                     vegetated swale areas and appear on engineering drawings at Appendix A.
                     __________________________________________________________________________

                     A6769/25/SWMP/Rev OpW(A) – Feb 2025
                                                                                                  Page 11 of 9
                     SH/PL
                                              Brah101 Pty Ltd t/as ALTA PROJECTS
Document Set ID: 23646596
Version: 1, Version Date: 21/03/2025