Appendix B - SWMP, Flood Cert & Form 15

            2. 3. P R O P O S E D D E V E L O P M E N T D R A I N A G E P A T T E R N

            2.3.1 Stormwater Concept

            Under existing conditions, the stormwater is discharged from the property as overland
            surface flows towards Lake Doonella to the south of the sites. It is proposed that this will
            remain the lawful point of discharge for the proposed development with the design
            required to demonstrate no worsening of the peak discharges for the design storms for the
            proposed development compared to the existing state.

            Roof run-off for each unit will be collected and flow via downpipes into a single 3kL slim-line
            rainwater tank. The tanks will be plumbed for internal reuse in toilets and laundry areas, with
            1.5kL of the tank allocated for reuse, and the remaining 1.5kL per tank dedicated to
            attenuating site run-off. To minimise pollutants entering the tank, first flush diverters will be
            installed to divert the initial capture of roof water to irrigation of the vegetated areas on site.

            The driveway run-off will be collected via grated trench drains that will filter through Ocean
            Protect Ocean Guard litter basket (or approved equivalent) to provide primary treatment of
            gross pollutants and larger particulates from the run-off.

            Run-off from the upstream footpath catchments will be intercepted at the driveway access
            to the site with a grated trench drain to control its flow through the site within the internal
            drainage network.

            Run-off from the rainwater tank overflows, driveway and upstream footpath areas will be
            discharged through a lined bioretention area at the south of each site to provide secondary
            treatment targeting the removal of phosphorus and nitrogen, ensuring the maximum run-
            off from the development will receive treatment prior to discharge.

            Outflows from the bioretention area will be via a surcharged pipe outlet with a one-way flap
            gate to prevent backflows entering the pipe. The outflows will be dispersed through a rock
            apron dissipator to break up the concentrated outflow and minimise the possibility of scour
            from the outlet.

            The roof and allotment drainage system for the proposed site shall be designed to comply
            with:

                    1. Noosa Shire Council Planning Scheme Policy (PSP) - Engineering Design Standards
                       – Roads, drainage and earthworks;

                    2. The Queensland Urban Drainage Manual (QUDM); and

                    3. AS/NZS 3500.3:2015 - Plumbing and Drainage Part 3: Stormwater Drainage.




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