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

              as controlled sheet flow at velocities/depths which will not
              induce significant scouring.

              In order to achieve this outcome RIP’s are to be aggregated in
              discrete basins adjacent the POSCWP areas and behind existing
              boulder retaining walls. Stone pitched weirs 3m long and at a
              constant height 0.2m below surrounding bunded area will
              control emergency overflow into the POSCW. The rough nature
              of the stone pitching will also provide an “energy dissipation”
              effect.

              The following calculations demonstrate adequacy for lot 9: -

              Running the RIP spreadsheet for 100year ARI storm of 5-minute
              duration we note the following (refer Appendix D)

              Qi (max)      =      355 L/s at 5-minutes.

              We also note that this corresponds with an available head of
              3.2m (weir height above base of RIP’s) and an infiltration rate
              through the RIP’s of: -

              Maximum discharge outflow Qo (2.77m) = 245 L/s

              Hence emergency overflow via the weir will not engage for
              events <Q100 and will be contained within the designated RIP
              system.




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A6107/L9/SMP/RevB/Jun 2022                                                   Page 6 of 7
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