Stormwater Management Plan

              4.1.1 Emergency Overflow (>100year ARI events)

              Emergency overflow, for events (>Q100) which cannot be
              wholly infiltrated by RIPs, would surcharge from the RIPs and
              be collected by an emergency overflow pit within the swale and
              stormwater line realigned beneath the building and sized to
              convey flows up to 100 year ARI to the existing headwall at the
              constructed wetland to the south whilst maintaining a minimum
              freeboard of 0.5m to the proposed hotel building.

              Refer to Engineering Drawings at Appendix A for details.

              Consequently, the combined capacity of the emergency overflow
              system and RIPs would equate to two (2) times the 100 year ARI
              storm which is considered to be the Probable Maximum
              Precipitation (PMP) event.

              Calculations of RIP infiltration capacities and emergency inlet
              pit capacities (50% blockage) are included at Appendix D.

              Whilst a volumetric easement in favour of Council is proposed
              over the emergency overflow system, inspection and
              maintenance of the swale, RIPs and overflow pits and pipes
              would fall to the owners of the site with the site owner accepting
              all risk associated with such a role and the consequences of
              system failure.

              Refer Maintenance Schedule at Appendix B.




              4.2    HOTEL CATCHMENTS             RAPID INFILTRATION
                     SWALES B AND C

       Runoff from impervious areas of the proposed hotel development will
       be collected and piped to Rapid Infiltration Swales B and C with events
       up to 100-year ARI infiltrated into the natural sands via a series of
       Rapid Infiltration Pits (RIPs) in order to achieve no net reduction in
       rainwater infiltration.

       Driveway and carpark areas will be passed through a GPT/oil arrester
       to remove oils and hydrocarbons prior to infiltration.



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A6769/22/SWMP/RevA      October 2022                                         Page 4 of 6
SH/PL
                         Brah101 Pty Ltd t/as ALTA PROJECTS