Slope Stability Report-21190-001-Rev0 Pomona Kin Kin Rd

Phil Brierley                                                                                                21190-001-Rev0
C/- NDD Constructions Pty Ltd                                                                                   21 June 2021

 Table 2: Details of Qualitative Risk Assessment for Property (AGS 2007)

                                                                 Assessed
 Hazard                               Likelihood   Consequence     Risk     Comments

                                                                            The likelihood of a failure through the fill or natural
                                                                            residual soil materials is assessed as Unlikely due
                                                                            to the low to moderate ground slopes immediate to
                                                                            the proposed structures, apparent lack of
 1: Shallow failure through fill or
                                                                            groundwater and no signs of previous instability.
natural soils above the                Unlikely       Minor          Low
                                                                            The consequence of such a failure would be Minor
foundation depth
                                                                            considering the anticipated confined extent of
                                                                            instability, and the depth of foundations
                                                                            recommended, with the resultant risk being Low as
                                                                            per AGS 2007.

                                                                            The likelihood of a deep failure through XW materials or
                                                                            weathered rock below the foundation depth is assessed
 2: Deep failure through XW
                                                                            as Rare due to the strength of these materials, gentle to
materials or weathered rock             Rare          Major          Low
                                                                            moderate ground slopes and lack of groundwater.
below the foundation depth.
                                                                            Although the consequence of such a failure could be
                                                                            Major, the resultant risk is Low as per AGS 2007.



The potential impacts on slope stability of the development components have been assessed, and the
measures recommended below in Section 4 have been designed to mitigate those impacts.


4.0      RECOMMENDATIONS
General recommendations to help maintain the stability of the site are given in the document Some
Guidelines for Hillside Construction, which is attached.

4.1    Site Layout
Should the proposed shed and workshop locations be amended from that shown in Text Figure 1, Tectonic
must re-assess slope stability prior to construction. The proposed shed must be setback at least 3 m
horizontally from the crest of the fill platform.

4.2    Earthworks
Based on the proposed development and the existing site conditions it is anticipated minimal cut and fill
earthworks will be required (i.e. less than 0.5 m depth/height). Should proposed cut/fill exceed 0.5 m
depth/height, the impacts on slope stability must be reviewed by Tectonic before construction.

4.2.1 Site Preparation and Trafficability
Prior to construction, organic rich topsoil (e.g. placed post bulk earthworks for erosion control) or any water
softened materials (e.g. ponded water collected on the finished surface) must be stripped and removed from
the construction area. The platform subgrades should be proof rolled using a fully laden water cart (or
similar) to identify any ‘soft spots’. Any such soft spots should be excavated and replaced with select fill
material, constructed as recommended in Section 4.2.3.

The subgrade materials exposed after site stripping and excavations are expected to comprise mostly firm to
stiff clay materials and weathered argillite (in areas of existing cut). Such soils could be subject to strength
loss from repetitive vehicle loading (particularly from rubber tyred plant) or if they become wet. Due to the
potential for poor trafficability during and after wet periods, placement of a minimum 150 mm thick granular
working platform may be required, particularly along access ways and any laydown areas.

The site should be graded to shed surface water runoff away from construction areas. It should be noted
that during wet weather, the natural soils may cause turbid stormwater run-off. Appropriate erosion and
sediment control measures must be installed prior to commencement of earthworks at this site.




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