Appendix B - SWMP, Flood Cert & Form 15

            “All stormwater runoff is treated to achieve maximum removal of nutrients, gross pollutants
            and suspended solids as determined by cost to efficiency ratios. (e.g., bioretention basins
            must be sized to achieve at least 80% reduction in total suspended solids, 60% reduction in
            total phosphorous, 45% reduction in total nitrogen and 90% reduction in gross pollutants
            >5mm).”

            It is proposed that the following measures to be implemented will provide the required
            level of stormwater quality improvement to minimise impacts to the downstream network:

                    •   First-flush divertors will be installed for roof-water drainage to divert initial run-off
                        capture to irrigation of the vegetated areas on site.
                    •   4 x 3,000L Slimline Rainwater tanks will be used to capture roof run-off, with 50% of
                        the tank volume allocated to reuse, and 50% to attenuation storage.
                    •   Ocean Protect Ocean Guard Litter baskets (or similar) to be provided to the
                        driveway inlet pits minimise sediment and gross pollutants from entering the
                        drainage line. Refer to Appendix B Ocean Protect Ocean Guard Litter Basket for
                        details.
                    •   2 x 6m² Bioretention areas will be used to treat and detain stormwater run-off from
                        prior to discharge from the site.

            4.2.1 MUSIC Modelling

            The proposed development and the above treatment train have been modelled in MUSIC
            (Model for Urban Stormwater Improvement Conceptualisation) software in accordance
            with the Water by Design MUSIC Guidelines 2018.

            The climatic data has been modelled using the rainfall and PET data at station 40059
            (Cooroy Composite) in 6-minute timesteps. The rainfall run-off parameters have been set
            as defined for the Southeast Queensland region, shown below in Figure 4.2 - Rainfall run-
            off parameters for SEQ.




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