RFI - Stormwater Management Plan

       RIPs have been installed on all of the Cape Bouvard Developments
       within Settlers Cove and have proven to work very well.

       Refer engineering drawings at Appendix A for RIP details.



       4.2    RIP Infiltration Capacities (100 Year ARI events)

       Alta Projects Engineers (formally TATE) were involved in formulation
       of the over-arching development approval document and EMP1.

       Such involvement included construction of a prototype RIP on the
       Settlers Cove site and field testing to determine infiltration rates.

       Results were consistent indicating a liner relationship between driving
       head and infiltration rate such that:

       Infiltration Rate (mm/s) = 4mm/sec + 13.6 x head (m)

       Refer to Appendix C for prototype test results.

       In order to model the operation of the RIP’s, a spreadsheet has been
       developed and utilised for all previous stages of Settlers Cove.

       Temporal patterns for Zone 3 from the Australian Rainfall and Runoff,
       Volume 2 were applied. These temporal patterns were used in
       conjunction with the average rainfall intensities for the Noosa region to
       create a series of design storms of varying duration for a 100-year
       average return interval (ARI).

       Temporal patterns were converted to flow rates by breaking each
       storm event into a series of short duration storms. A triangular flow
       verses time approximation was used for each sub storm with sub storm
       flows then added to produce flow Vs time for RIP inflow.

       Outflow and water depth were then calculated through iterations for
       the duration of the storm based on the infiltration rate / head
       relationship discussed above. A factor of safety of 2.0 was applied to
       the observed prototype infiltration rate. Each RIP was then sized to
       prevent overtopping in a 100-year ARI storm event of any duration.

       Spreadsheet model results for the proposed hotel buildings are
       attached at Appendix E.

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A6769/22/SWMP/RevB – June
2023                                                                         Page 5 of 9
SH/PL
                       Brah101 Pty Ltd t/as ALTA PROJECTS