Swmp

                                                 Table 3.1 - Rational Method calculations

                                                                                                   Storage
             A.E.P               Qy_pre (m3/s)        Qy_post (m3/s)        Qincrease (m3/s)       Estimate (m3)
                        4 EY              0.0058                   0.0059              0.0001              0.0367
                        1 EY              0.0116                   0.0118              0.0002              0.0735
                      0.5 EY              0.0155                   0.0158              0.0002              0.0980
                    20% AEP               0.0212                   0.0216              0.0003              0.1340
                    10% AEP               0.0263                   0.0267              0.0004              0.1660
                     5% AEP               0.0315                   0.0320              0.0005              0.1990
                     2% AEP               0.0401                   0.0408              0.0006              0.2534
                     1% AEP               0.0463                   0.0471              0.0007              0.2927



            A 3,000L trafficable underground detention tank, nominally a Graf Platin system or similar
            (refer to Appendix C - Graf Platin Detention Tank Brochure for details), is proposed to
            attenuate flows to pre-development levels. All roof water will be collected in the detention
            tank before discharging (via low flow and overflow outlets) into the site internal drainage
            network.

            The internal drainage network will collect run-off along the western boundary of the site
            discharging to the proposed point of discharge in Bottlebrush Avenue. Two new kerb
            connection outlets to Bottlebrush Avenue are proposed as the legal point of discharge to
            the road collection system.

            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.

            The site is below the 2,500m² development area that would trigger the State Planning Policy
            (SPP, July 2017) stormwater quality requirements, as set out by the Department of
            Environment and Resource Management (DERM), so no stormwater quality treatment
            targets are required by the development. It is expected that the upgrade of the paved
            driveway areas which are currently failing and likely generating sediment and loose material
            pollutants, will improve the post-development quality of stormwater discharged from the
            site.

            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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