Compiled Reference Documents - MCU20/0084.01 (As Published)

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                 Instability issues for the two batters would likely involve slumping and erosion. Larger scale movements of soil
                 are less likely but still possible, particularly if any erosion is left untreated or following heavy rainfall. The
                 consequences of this instability for the upslope batter is assessed as minor, however, instability of the
                 downslope batter may affect the foundation of the dwelling and is therefore more significant. On this basis, this
                 instability has been assessed as a ‘Moderate’ hazard.

                 Requirements to achieve and maintain a ‘Low’ hazard rating for the batters are given in the next section.
                 Requirements that must be carried out or implemented in order to maintain the ‘Low’ rating for the global
                 landslide hazard rating are given in the subsequent section.



                 Batter Treatment Requirements

                 To achieve a ‘Low’ instability hazard rating for the batters, the following is required:

                     •    Trim the batters back to no steeper than 2:1 (horizontal to vertical);
                     •    Mulch and vegetate the batters as soon as possible to reduce the potential for surface scouring and
                          erosion.

                 The dwelling should be located no closer than 1m from the crest of the downslope batter.

                 As an alternative to flattening the batters, engineer designed retaining walls can be considered.



                 Slope Maintenance Requirements

                 The following comments and recommendations are required for the proposed development works to ensure
                 long-term stability of any proposed infrastructure and batters within the BLE.

                     •    Ensure all stormwater drains are free of blockage to allow surficial and subsurface water flow to freely
                          flow into piped road drainage and/or stormwater storage tanks;
                     •    Any proposed earthworks should be undertaken in accordance with relevant Council guidelines and
                          Australian Standards;
                     •    The Australian Geomechanics Society extract ‘Australian Geoguide LR8 (Hillside Construction)’
                          (attached) must be strictly followed for good hillside construction practices.
                     •    Engineering design and global stability analysis should be undertaken on all proposed retaining walls
                          and batters within or adjacent the BLE.

                 Uncontrolled surface runoff and discharges can cause an ingress of surface water into the sloping terrain and
                 fill material if adequate drainage is not implemented and maintained. Providing adequately designed,
                 constructed and maintained surface and subsurface drainage is important to the long-term performance of the
                 Site in terms of slope stability and erosion. This includes the following:

                     •    A suitably lined surface drain must be constructed upslope of the building area to intercept and divert
                          water runoff away from the building area.
                     •    Drainage outlets and water discharge areas must be located downslope from the building area.
                     •    All surface runoff and collected roof water should be piped into the road drainage system or into
                          storage tanks. Any tank water overflow must be piped downslope of the building and road areas.
                     •    Uncontrolled water discharges onto the existing ground and hill slope in the building area or adjacent
                          area must be avoided.
                     •    All stormwater and drainage systems must be approved by Council.



                                                    Gold Coast | Sunshine Coast | Melbourne | Emerald


                 PTP/12376 328 Upper Pinbarren Creek Road, Pinbarren                                                 11 August 2023

Document Set ID: 22574699
Version: 1, Version Date: 07/09/2023