Attachment C - Soil Survey Report · MCU18/0013

Project No. 1-20119                                                                                                        Page | 10
March, 2018
Ref: 1-20119, 2018-03-02, BR VER 2
Sam Hopper – Slope Stability Assessment and Geotechnical Report - Proposed Residence, 24 Arakon Crescent, Sunshine Beach




5.0 RISK ASSESSMENT

    5.1 General
For the purposes of this study, the assessment of Risk for the site has been based on risk to
property and risk to persons, where Risk is the product of Likelihood and Consequence.

This method is based on the method outlined in the “Practice Note Guidelines for Landslide
Risk Management 2007” (PNGLRM), produced by the Australian Geomechanics Society, 2007
and is based upon the Risk Matrix in Appendix H.

    5.2 Review of Stability Data
The stability of the natural slopes at this site was assessed based on observations from the site
walkover, as well as a review of the published information and results of our drilling program.

Following a review of the above information, the subject area of the site was able to be divided
into two separate areas (refer drawing 1-20119-01, Appendix I). The areas include:-

          Area I – Existing slopes
                      a – Area above the house to the west (Arakon Cres).
                      b – Area below the house to the east (includes proposed back yard, stormwater
                       management area) and extends to adjacent dunes.
          Area II – Proposed building footprint at the front and centre of the lot where cuts will be
           required to excavate the ground floor level, understood to be temporarily retained by
           existing and additional sheet piles.

    5.3 Identification of Potential Hazards on Site
Based on the site walkover, a review of the site information and experience on similar sites, the
following potential hazards have been identified for assessment at the location of the proposed
residence (subject site):-

     A. Shallow landslides on the existing slopes – applies to Area I (both).
     B. Proposed Cuts – applies to Area II.
     C. Surface scour on the site during construction – applies to overall subject site.

    5.4 Likelihood Estimation

           5.4.1       Methods of Assessment

The site was assessed and zoned using the method as outlined in MacGregor and Taylor
(2001). The method has been adopted as a slope stability assessment tool and used in both the
Gold Coast and Redlands Shire regional stability assessments.

           5.4.2       Evaluation of Likelihood Rating for Existing Overall Site

Once the relative frequency of slope instability for the site is calculated, MacGregor and Taylor
(2001) suggests a likelihood rating as outlined in Table 2 below.

This rating has then been compared to the Likelihood Descriptor from Appendix C of “Practice
Note Guidelines for Landslides Risk Management (PNGLRM) (2007c)”.