Slope Stability Report (4) · EXE22/0020

Specialists in transport geotechnics

5.4 Foundations
No structural details have been provided at this stage of assessment besides to architectural
plans. It is noted that surface loose sands have been identified as having poor bearing capacity
and as such it is assumed the foundations would extend to the underlying medium dense (or
denser) sand. Excess and/or differential settlement may result if foundations are constructed on
very loose/loose sands. As a minimum, good hillside design practices as defined in AGS (Refer
to Appendix 3) are recommended for this site.

5.5 Surface drainage
Surface details for the proposed development, levels are currently only available on approximate
architectural drawings. It is recommended that swale drains be constructed to direct flow around
the foundation area to slow and dissipate flow down the slope keeping concentrated flow away
from the house and associate structures.

5.6 Overall effect of development on stability
It is considered that the proposed development has the potential to have a Low impact on the site
given its current condition. Implementation of engineering controls outlined in Section 6 should be
incorporated to reduce the long term and short-term risk. Inspection, monitoring and maintenance
should be undertaken at a minimum to ensure the site stability into the future.

6 CONSTRAINTS/ PRECAUTIONS/ RECOMMENDATIONS

6.1 General
Good hillside engineering construction practice is considered mandatory during development of
the site. The notes and illustrations attached in Appendix 3 of this report outline some typical
hillside construction guidelines including, earthworks, erosion control and drainage practices for
hillside areas, which should be applied to this site.

6.2 Foundations
It is recommended that the foundations for the shed and spa be designed and constructed in
accordance with AS2870 Residential Slabs and Footings. As a minimum, foundations should
extend to found at depth in the underlying medium dense sands to meet bearing capacity
requirements.

6.3 Drainage
The control of drainage is important to the stability of the proposed development. The following
recommendations are made with respect to drainage for the site:
   •   Well designed and engineered surface water controls should be used to reduce the
       infiltration potential of the site during and following rainfall. Surface water from the site and
       from areas upslope of the site must be diverted away from footing systems, cut and fill
       batters and retaining walls. The use of appropriate self-flushing spoon drains is
       recommended.




9 August 2022                     CGC-SR-2022-012-R01-Rev01                                   Page 14