Response to Information Request 20220004 -Tunba Court

            It was found that run-off stormwater peak and low rate storm flows resulting from the
            earthworks are altered by less than 5%, which is considered an insignificant increase in
            potential to increase bed or bank erosion or sedimentation in receiving waterways. The
            provision of energy dissipating outlets to reduce flow velocity and disperse concentrated
            flows will further reduce the potential of this increase having negative impacts to the
            downstream waterways.
                    PO13
                    Development is designed and constructed to maintain surface and ground water
                    balances that sustain the environmental values of water dependent ecosystems,
                    including downstream aquatic, riparian, wetland and terrestrial ecosystems.


            No attenuation or capture surface run-off is proposed, with all run-off from upstream
            catchments and the proposed development areas discharge into the drainage gully to
            which they would fall in the absence of the development. A geotechnical investigation
            carried out by Morrison Geotechnics of the proposed development area did not identify
            evidence of groundwater within boreholes taken from the development area, so it is not
            considered likely that the proposed development will impact upon the surface and
            ground water balances in a way that would negatively impact environmental values of
            downstream ecosystems.


                    4. If the survey plan indicates that the works extend beyond the property
                       boundary provide plans for the works to be undertaken to relocate the
                       earthworks to be within the subject site.

            A note on the design plan has been added indicating that earthworks extending across
            the boundary are to be removed and reinstated to pre-development conditions. The run-
            off that was being channelled to this area requiring a table drain at the base of the batter
            slope is now conveyed to the north to ensure it is discharged clear of the boundary so
            there are no issues with the removal of this small section of earthworks.


                        5. Provide comment on which is the preferred construction alternative and
                        provide amended plans prepared by a suitably qualified person which clearly
                        indicate the full extent of works required.

            The batters for the development will be altered in line with the geotechnical
            recommendations consisting of:

                    •   Benching the cut batter where batter height exceeds 4m with maximum slope of
                        38º
                    •   Flattening the fill batter to a maximum of 2.5H:1V

            Please refer to the attached plan which provides the updated earthwork extents required
            to comply with these design constraints.




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