Appendix B - SWMP, Flood Cert & Form 15

            5. CONCLUSION
            This Stormwater Management Report has outlined how the stormwater run-off from the site
            is to be managed to comply with the relevant requirements and minimise any adverse
            impacts to the downstream catchments.

                    •   The existing site and upstream catchments’ drainage patterns currently discharge
                        from the site as overland flows into towards Lake Doonella to the south of the site.

                    •   The proposed legal point of discharge for the site will continue to be Lake Doonella.

                    •   The existing and proposed development site have been modelled for the critical
                        design storm events for the site, which found attenuation would be required. Further
                        modelling for the mitigated developed site was able to demonstrate that there will
                        be no increase to total existing discharge conditions from the site for any of the storm
                        events.

                    •   During construction, erosion and sediment control measures shall be implemented
                        to minimise potential contaminants impacting the downstream receiving
                        environment. An erosion and sediment control plan shall be developed as part of a
                        submission for Operational Works approvals.

                    •   In the operational phase of the development, a stormwater treatment train will
                        provide quality improvements as required by the Noosa Council Planning Scheme
                        Policy. Roof run-off is to be directed towards 4 x 3,000L rainwater reuse and
                        attenuation tanks that will be fitted with first-flush divertors to will divert initial roof
                        run-off to on site irrigation of vegetated areas. The tanks are to be plumbed for reuse
                        for internal (laundry and toilets) purposes that will serve to provide both treatment
                        and reduce the volume of run-off leaving the site. Overflows from the tanks, as well
                        as the piped drainage will be directed toward the 6.5m2 bioretention areas at the
                        south of each site that will treat the majority of run-off from the site while also
                        attenuating run-off volumes. Ocean Protect Ocean Guard litter baskets will be
                        provided to the pits within the driveway areas to provide at source primary
                        treatment. Outflows from the bioretention area will be via a surcharged drainage line
                        from each area, using a one-way flap gate outlet to prevent backflows.

                        By implementing the proposed stormwater treatments, the development will reduce
                        the quantity of stormwater pollutants by more than 90% of gross pollutants, 80% of
                        total suspended solids, 60% total phosphorous and 45% total nitrogen, exceeding
                        the pollutant reduction targets required for the site.

                    •   By implementing the proposed stormwater solution, it is considered that stormwater
                        layout proposed will minimise any adverse impacts to the downstream environment
                        arising from the stormwater run-off while also meeting the stormwater quality targets
                        required for the development.




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