Reference Document - MCU24/0002 [As Published]

                                                                                                         Job No: 23-458
                                                                                                                 Page 8

                       •    No tension cracks were observed within the site;
                       •    Hummocky or bulging soils were not identified on the site slopes. There were sections of uneven
                            ground downslope of the house, which is attributed to previous earthworks and the removal of
                            trees.
                       •    Physical observations made on existing structures such as Trees and Crib retaining walls
                            indicate signs of soil creep;

                  Evaluation of these features in a Landslide Frequency Assessment Form provided an indication of their
                  relative importance to slope failure. The assessment of the features included the allocation of a weighted
                  factor for each feature based on site observations, judgment, and experience. This allows a Relative
                  Frequency to be calculated by multiplying the selected factors together for each of the above site
                  conditions highlighted in blue and green.

                  From the assessment of results from their study (Hargreaves and Kidd 2012) and other studies in similar
                  terrain, a correlation between Relative Frequency and Hazard Rating has been established, as shown
                  in Table 2.

                  Table 2: Correlation between Relative Frequency and Hazard Rating

                           Relative Frequency (Output)                         Hazard Rating (Susceptibility)

                                         < 0.2                                         Very Low (VL)

                                       0.2 – 0.6                                           Low (L)

                                       > 0.6 – 2.0                                      Moderate (M)

                                       > 2.0 – 6.0                                        High (H)

                                         > 6.0                                         Very High (VH)


                  The above major site features listed in Section 2.4 have been considered in determining a likelihood
                  estimate of landslides in this property. The features relevant to this site under consideration, as
                  recommended by Hargreaves and Kidd (2012), apply to Case 1 (1 - 7) and Case 4 (1 – 22).

                  With knowledge of the proposed development (earthworks, retention systems, fill, etc.), the assessment
                  has been carried out for the pre and post-development stages. The assessment indicates that the
                  relative frequency (Output) pre-development is 1.09 for Case 1 (items 1 to 7), which implies that the
                  landslide risk on the site is "Moderate", which may be tolerated by regulators; however, requires
                  investigation and implementation of treatment options to reduce the risk to Low or better.

                  To reduce the potential landslide risk level from “Moderate” to "Low" or better, the recommendations
                  presented in Section 2.5 should be implemented during and after construction.

                  2.5 Landslide Risk Mitigation Strategy

                  #399 Sunrise Road, Tinbeerwah, was identified as a "Moderate” landslide risk site per current site
                  conditions. The following recommendations are therefore provided to improve the landslide risk level
                  onsite during and post earthworks.

                  2.5.1 Fill
                  The borehole logs have not disclosed any fill at the drilled locations onsite. However, given the landform,
                  it is expected that some areas of fill would be present. Any material identified as fill is deemed unsuitable
                  to support structural loads. In areas subject to structural loads, these materials must be removed and
                  replaced with fill that is engineered and certified.
                  2.5.2 Cut and Fill Batter Support
                  Cut/fill batters must be cut to a grade no greater than 14 degrees (1V:4H). Batters steeper than this
                  must be appropriately retained. An engineered post and concrete sleeper or block retaining wall is
                  deemed appropriate for the site conditions.


                                                                                                                  Ref: 4602
                                                                                             399 Sunrise Road, Tinbeerwah
Document Set ID: 22750694
Version: 1, Version Date: 03/01/2024