geotech report · 132003.220660.5

• A new grass covered area constructed immediately to the east of the existing house with a surface level
  equivalent to the floor level for the proposed additions (i.e. the lower floor level of the exiting house).
  The eastern (downslope) side of the grass covered area will be supported by a concrete block retaining
  wall (maximum height about 1m).

The existing house has been constructed on a terraced building platform cut back (to the west) into the
hillside with cuts supported by retaining walls and the existing ground floor slab and pool suspended over
the slope. The structural design drawings indicate that the footings comprise high level (strip and pad)
footings and localised piers. The provided architectural drawings and structural design drawings for the
existing house indicate that an existing sewer line extends north-south through the site below the existing
pool.



3    ASSESSMENT PROCEDURE
This stability assessment was carried out on 18 September 2024 and was based upon:
• An inspection of the topographic, surface drainage and geological conditions of the site and its immediate
  environs by our geotechnical engineer, Cody Surawski. These features were compared to those of other
  similar lots in neighbouring locations to provide a comparative basis for assessing the risk of instability
  affecting the proposed development. The attached Appendix A defines the terminology adopted for the
  risk assessment together with a flowchart illustrating the Risk Management Process based on the
  guidelines given in AGS 2007c (Reference 1);
• A review of the subsurface conditions presented in the provided ASI report; and
• Completion of two Dynamic Cone Penetration (DCP) tests (DCP101 and 102) which extended to a 8m
  depth within the footprint of the proposed additions to the north and north-east of the existing building.

The attached Figure 2 presents a geotechnical site plan showing the principle geotechnical features observed
at the site and our DCP test locations. The DCP test were set out using tape measurements from existing
surface features. Figure 2 is based on aerial imagery sourced from Nearmap with the approximate outline of
the proposed alterations and additions, as well as the previous ASI test locations superimposed. Additional
features on Figure 2 have been measured by hand held clinometer and tape measure techniques and hence
are only approximate. Should any of the features be critical to the proposed development, we recommend
they be located more accurately using instrument survey techniques. Figure 3 presents an explanation of the
geotechnical mapping symbols used on Figure 2.

The relative compaction of the inferred fill and the relative density of the inferred natural sands was assessed
from the DCP blow counts. We note that due to friction between the DCP rods and the sands, particularly at
depth, this can result in artificially higher blow counts.

No long term groundwater level monitoring has been carried out.

Further details of the methods and procedures employed in the investigation are present in the attached
Report Explanation Notes.

32032URrpt                                         2