210408 - 72 Podargus Parade, PEREGIAN BEACH - Slope Stability Report

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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: Results of AGS Qualitative Risk Assessment
                  Hazard                  Likelihood         Consequence                 Risk Level
               Global Failure           Barely Credible       Catastrophic                    Low
    Shallow creep/slumping of surface      Unlikely              Minor                        Low
                  soils
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 “Low”.

7.0 Hillside Construction
The following works should be implemented in additional to other items highlighted within
this document. These points are considered to be typical good hillside construction practice
as explained in attached documentation:

•     Foundations for lightly loaded or non-liveable structures should be founded on and keyed
      into medium dense (or stronger) sands. Heavy structures should be supported on either
      piles founded into medium dense (or stronger) sands or high level footings founding into
      the same material. The footings should dound a depths which ensure the zone of influence
      from the footings does not intersect the ground surface
•     Where slopes are not supported by an engineer designed support system, natural slopes
      within or near building envelope or movement sensitive areas should be no steeper than
      2H:1V.
•     Building platform fill should be limited to a maximum height of 1 m. The filling should be
      step keyed into the natural slope and battered no steeper than 3H:1V unless an engineer
      designed retention system is in place.
•     Unsupported cuts steeper than 2.5H:1V will require engineer designed retention systems.
•     All stormwater and surface water is to be discharged by an approved stormwater drainage
      system. The use of subsurface drainage systems are not suitable unless greater than 50
      m downslope from the envelope at this site.
•     Ongoing maintenance of the effluent wastewater area is also considered mandatory. The
      location of the application area should be located below the proposed building. Plumbing


12 Oct 2021                                                                     Proposed Extensions