Slope Analysis 18 Hay St

                                                                                                         ABN 51 640 311 842
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                                                                                        Sunshine Coast | Brisbane | Gold Coast




6         AGS ASSESSMENT
Landslides are caused where a soil or rock mass has a decrease in strength, usually attributed to groundwater,
resulting in the material not being able to maintain its own self-weight resulting in a slope failure.
The Australian Geomechanics Society (AGS) developed a set of tools and procedures for assessing the stability of
a slope. The tools and procedures presented with the AGS documentation form the basis of the assessment
undertaken herein and their documentation is attached for reference.
The guidelines also identify that the regulator typically sets the standard for levels of tolerable risk. AGS defines
tolerable risk as “risks within a range that society can live with so as to secure certain benefits. It is a range of risk
regarded as non-negligible and needing to be kept under review and reduced further if practicable”.
The guides suggest that areas of moderate or greater risk should not be developed unless a rigorous remediation
plan be implemented to reduce the area to a level of Acceptable Risk. AGS defines acceptable risk as “risk which
everyone affected is prepared to accept. Action to further reduce such risk is usually not required unless reasonably
practicable measures are available at low cost in terms of money, time and effort.”.
AGS suggest that regulators generally accept risk levels of “low” or lower as a level of acceptable risk.
AGS prepared a semi-quantitative assessment tool for determining the level of risk for a site. The tool separates the
potential hazards for a site, from a stability context, and rates them with a level of risk frequency. The multiplication
of these individual risk frequency summates as the risk frequency rating which is then measured against the levels
of risk nominated by AGS.
The results of this analysis are shown in Table 1.
TABLE 1: AGS ASSESSMENT

                Hazard                         Likelihood                Consequence                   Risk Level
             Global Failure                   Barely Credible                 Major                      Very Low
     Shallow Soil Slumping or Creep                Rare                       Minor                      Very Low


Based on the results of the AGS assessment, the perceived risk based on the conditions encountered and information
available at the time of the assessment is “Very Low”.

7         HILLSIDE CONSTRUCTION
The following works should be implemented in addition to other items highlighted within this document. These
points are considered to be typical good hillside construction practice as explained in attached documentation:
 All footings should be founded into very stiff natural clays.
 Attention should be given to erosion protection. Where possible, drainage channels should divert surface water
  flow away from the proposed residence.
 It is important that the stormwater management system be designed and maintained so that it will not adversely
  affect or compromise the overall slope stability. Do not allow areas of the site to become saturated from seepage
  or surface water, and regularly check and clean all drainage lines so that they do not become blocked.
 Avoid leakage from underground services and drains. Any leaking services or blocked drains should be remedied
  promptly.

8         GEOTECHNICAL RECOMMENCDATIONS
The following sections details specific geotechnical constraints or recommendations in addition to general hillside
construction notes.

Sunshine Coast | Brisbane | Gold Coast