Response to Information Request 20220004 -Tunba Court

                    PO5
                    Stormwater drainage infrastructure is aligned to avoid crossing waterways,
                    wetlands, drainage lines and ecological important areas, or where it is
                    demonstrated this is unavoidable, disturbed areas are reinstated and revegetated
                    upon completion of works.

                    PO6
                    Development is located, designed, constructed and operated to protect and
                    enhance environmental values and water quality of waterways, wetlands, lakes,
                    ground waters and drainage systems.

            The drainage infrastructure proposed for the development does not cross waters ways,
            wetlands, drainage lines and ecologically important areas. Drainage characteristics
            downstream of the proposed development will be sufficiently similar to pre-development
            conditions as described above, with the proposed outlet for the development into a gully
            to which existing flows currently are collected. Additionally, disturbed areas arising from
            the earthworks are to be stabilised with grass seeding after construction to minimise
            sediment losses from the proposed development and maintain the water quality of the
            downstream receiving water.

            The environmental values and water quality of the receiving waters will be maintained
            through the provision of erosion and sediment controls during construction in accordance
            with the Erosion and Sediment Control Plan submitted with the application. Post
            construction, stabilising of disturbed areas to minimise any risk of ongoing water quality
            impacts from the earthworks.


                    PO10
                    Development prevents increased bed and bank erosion and sedimentation in
                    receiving waterways by avoiding changes in low rate, peak flow run-off and flow
                    duration.

            An assessment of the estimated peak flows from the pre-development area and from the
            earthworks pad was carried out to determine the impacts arising to peak flows for
            different storm events using the rational method to provide an indication of the scale of
            the change. A summary of the comparison is provided below – refer to the attached
            calculations for further detail.

              Qy (m3/s) - Pre-developed    Qy (m3/s) - Earthworks       Change (L/s)     % Change
                                    0.0331                       0.0346           1.5889      0.0481
                                    0.0399                       0.0416           1.7136      0.0430
                                    0.0602                       0.0628           2.5536      0.0424
                                    0.0740                       0.0777           3.6587      0.0494
                                    0.0891                       0.0929           3.8416      0.0431
                                    0.1129                       0.1176           4.7227      0.0418
                                    0.1301                       0.1353           5.1968      0.0399




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