20210041 27 Bottlebrush Ave Stormwater

            process, it was determined that an attenuation portion of 5kL with a low flow outlet orifice
            of 60mm, and 150mm overflow outlet will be suitable for the development.

            Using this mitigated development model, the proposed developed flows were again
            compared to the existing state as shown below in Table 3.2 Existing and proposed
            mitigated site peak discharge rates.

                           Table 3.2 Existing and proposed mitigated site peak discharge rates

                                                           27 Bottlebrush Avenue                 Total
                                     A.E.P            Qexisting   Qproposed      Qchange         Qchange
                                                      (m³/s)      (m³/s)         (m³/s)           (%)

                                 1EY               0.011          0.008        -0.003          -27%
                                 50%               0.013          0.010        -0.003          -23%
                                 20%               0.019          0.017        -0.002          -11%
                                 10%               0.023          0.021        -0.002          -9%
                                 5%                0.029          0.025        -0.004          -14%
                                 2%                0.033          0.031        -0.002          -6%
                                 1%                0.036          0.034        -0.002          -6%


            As the total peak flows are equal to or below the existing site conditions, the proposed on-
            site detention will suitably control the peak flow storm events from the development.

            To minimise impacts of any overland flows upon the proposed development, surface run-
            off from the upstream property will be captured along the northern boundary in a turfed
            catch drain graded towards an inlet pit of the internal drainage network.

            Due to the small scale of the development and the residential nature of the proposed use,
            the impacts to stormwater quality during the operational life of the development are
            expected to be minimal, therefore stormwater treatment is not proposed for the
            development.

            The attached Roads and Drainage Layout Plan (refer Appendix A - Proposed Development
            Plans) provides further details on the proposed stormwater layout. The drainage system for
            the proposed site is to 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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