A6107 Lot9 Stormwater Management Plan (RevB) June 2022 · OPW22/0166

              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 each building are attached in
              Appendix D.




       6.2    Emergency Overflow (>100year ARI events)

              Emergency overflow, for events (>Q100) which cannot be
              wholly infiltrated by RIPs, is to be directed to the POSCWP area
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A6107/L9/SMP/RevB/Jun 2022                                                   Page 5 of 7
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