SUPERSEDED Approved Plans & Document OPW25-0042 · OPW25/0042

                     Infiltration Rate (mm/s) = 13mm/sec + 33 x head (m)

                     Refer to Appendix D for 2024 prototype test results.

                     Video of prototype testing being carried out are included at Appendix K.




                     6.2.3 PROTOTYPE              RIP    TEST     RESULT       COMPARISON         AND
                     APPLICATION

                     It is not entirely clear as to the factors contributing to differing infiltration
                     rates observed in 2003 and 2024.

                     2003 testing was carried out at a relatively elevated northern area of the site
                     compared to 2024 rates observed at a lower southern area of the site.

                     Both locations saw the prototype founded on clean white sands although
                     possibly insitu sand density may have differed between the two locations.

                     Inclusion of a rock base may have contributed to higher infiltration rates
                     observed in 2024 although the arrangement better replicates actual RIP/RIC
                     construction.

                     Regardless of contributing factors both 2003 and 2024 prototype test results
                     returned very high infiltration rates.


                     7.0 RIP/RIC DESIGN AND MODELLING

                     In order to ensure a conservative approach is adopted for infiltration of
                     stormwater and to minimise risk of RIP/RIC surcharge the following
                     approach has been adopted: -

                          •    Size proposed RIPs/RICs to infiltrate associated catchment flows based
                               on the Excel model mentioned in Section 5.1

                          •    Conservatively adopt the lower 2003 algorithm for all RIP and RIC
                               infiltration rates modelled in eXcel.

                          •    Apply a Factor of Safety of 2.0 to infiltration rates modelled.



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