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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: Results of AGS Qualitative Risk Assessment
               Hazard                          Likelihood      Consequence                Risk Level
            Global Failure                   Barely Credible   Catastrophic                    Low
     Shallow slumping or slide of               Unlikely          Minor                        Low
             surface 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 addition to other items highlighted within this
document. These points are considered to be typical good hillside construction practice as
explained in attached documentation:

•   Foundations should be founded into stiff (or stronger) residual clay.
•   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 collected and 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
    and services must also not be allowed to leak and regular maintenance and inspections
    should be undertaken.

09 Dec 2021                                                    Proposed Subdivision and Residence