Compiled Reference Documents - MCU25/0091 (As Published)

            Wingara Hills Pty Ltd

            Based on our slope stability assessment, it is our opinion that there is a Low Risk for the proposed
            development, provided that the recommendations in this report are implemented. This level of risk is
            normally acceptable to regulators (i.e. Council).
            The recommendations provided in this report are provided to enable an inferred factor of safety against
            landslide of over 1.5. The above recommendations must be reviewed when earthworks and building designs
            are finalised, to confirm an acceptable factor of safety is achieved.

            7.0       DEVELOPMENT IMPACTS & MITIGATION MEASURES
            It is our opinion that this site is suitable for the proposed development, from a geotechnical viewpoint, subject
            to implementation of the recommendations provided in this report. The potential impacts on slope stability of
            the proposed development have been considered, and the measures recommended below have been
            designed to mitigate those impacts. Building development should follow normal slope maintenance
            procedures and the document ‘General Guidelines for Hillside Construction’, which is attached in Appendix
            D.

            7.1 Earthworks
            Earthworks should be carried out in accordance with Australian Standard AS 3798-2007 ‘Guidelines on
            Earthworks for Commercial and Residential Developments’. Filling should not exceed 1 m in depth.

            7.1.1 Site Preparation & Trafficability
            Site preparation in building and pavement areas should include the following:

                  Strip the surface of vegetation, organic matter, organic rich soils (topsoils) and severely root affected
                      soils.
                  ‘Proof roll’ the stripped surface by several passes of a minimum 10 tonne roller to identify loose or
                      soft areas.
            An experienced geotechnical engineer from Core should carry out an inspection of the subgrade 'proof roll'.
            Loose/soft areas identified by proof rolling and/or inspection will require treatment by either of the following
            methods:

                  Over-excavation and replacement with suitable fill compacted in layers (refer Section 7.1.4); or
                  Re-compaction of the loose or soft material provided that it does not contain substantial organic
                      matter or deleterious substances.
            At the time of the investigation the site was trafficable with a tracked excavator with caution. Following
            stripping of topsoil materials, trafficability issues should be anticipated following rainfall. Due to the potential
            for poor trafficability across the site, it would be prudent to allow for the placement of a compacted granular
            fill layer particularly in access road and laydown areas. A geotextile separation layer between the natural
            ground and granular fill may also be required.

            7.1.2 Excavations
            Excavations into the residual soil, and extremely weathered materials/rock should be achievable using
            conventional small to large earthmoving equipment (i.e. 6 to 20 tonne excavators).
            Bands of higher strength mudstone may be encountered requiring ripper tyne excavation (e.g. as found in
            test pit TP1).

            7.1.3 Batter Slopes
            For short-term construction periods, excavated un-surcharged faces could be battered at 1V:1H in the
            residual stiff to hard clayey soils, and weathered material and underlying mudstone. Shoring will be required
            to enable personnel entry into near vertical sided trenches deeper than 1 m.
            Flatter batters may be required if significant groundwater seepage is encountered or if exposed faces are not
            protected from erosion by rainfall.


            J002915-001-R-Rev0                                  8


Document Set ID: 24031832
Version: 1, Version Date: 14/08/2025