Appendix D - Geotechnical Report

Placement of heavy ‘builders plastic’ or filter ‘cloth’, pinned to batters may be required if heavy of
prolonged rainfall occurs during construction. Exposure of temporary batters should be minimised in
order to limit shrinkage cracking in clayey soils and potential development of temporary instability.
Ground surfaces 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.
The above recommendations do not supersede any existing safety regulations or legislation applicable to
excavations (e.g. limits on personnel entry into trenches).
The residual soils and weathered rock where broken down to <100 mm particles, as encountered in the
test pits would be suitable for use as structural fill, subject to appropriate moisture conditioning and
compaction. It is noted that placement of any site won materials as fill would have an effect on the site
classification (Ref. Section 7.3.1 below).
All fill must be ‘benched’ into the natural slope, over-filled by at least half-width of the compaction plant
(horizontally), and then trimmed back to the well compacted material.
It is recommended that any imported fill should comply with the following:
▪   Minimum CBR of 10 %
▪   Maximum plasticity index of 15 %
▪   Shrink-swell index ≤ 1 %
▪   Maximum particle size of 100 mm
Fill should be compacted at moisture contents within the range of ±2 % of optimum moisture content
for Standard Compaction. Select fill should have a maximum particle size of 100 mm for an
uncompacted layer thickness of 200 mm and shall be compacted by repeated rolling with a small
compactor to achieve a dry density ratio of at least 95 % of the Standard Maximum Dry Density for
cohesive soils, or 70 % Dry Density Index for any imported cohesionless soils.
Confirmatory compaction testing should be carried out at regular intervals. A minimum of two tests per
vertical lift is recommended where structural fill heights are to exceed 300 mm. Further details for
control and testing of fill are given in Australian Standard AS 3798-2007 Guidelines on Earthworks for
Commercial and Residential Developments.


7.3          Building Foundations
7.3.1        Preliminary Site Classification
Based on the results of the investigation, the site classification for the proposed new lots is estimated to
be Class M in accordance with AS 2870-2011 Residential Slabs and Footings. It should be noted that the
predicted order of movement is based on the existing natural soil profiles, and moisture content changes
within soils due to normal seasonal moisture variations only. Where up to 1 m of fill was placed as part of
an earthworks building pad, for example, the site classification would extend to Class H1.
Reactive soil movements and site classification should be assessed by the footing design engineer at
Building Works stage to consider the extent of earthworks proposed, together with any
removed/retained trees (yt factor).




Geotechnical Investigation
10 June 2026 | 26073-001-Rev0                                                                              18