25289-001-Rev0 - The Esplanade (1)-compressed

control and testing of fill are given in Australian Standard AS 3798-2007 Guidelines on Earthworks for
Commercial and Residential Developments.


6.2         Building Foundations
6.2.1       Indicative Site Classification
Site classification for footing design is determined in accordance with AS 2870-2011 Residential Slabs and
Footings, and depend on the depth of cut / fill undertaken at a site, variations in the natural soil profile,
and the reactivity of the in situ soil and any imported fill materials.
Based on the results of the investigation, it is recommended that a site classification equivalent to Class
M is used in relation to the assessment of flexibility requirements for ground slabs, footing and plumbing
design. The footing design recommendations given below must also be considered.

6.2.2       Footing Design
No design loadings were available at the time of reporting. Footings for the proposed residence and any
ancillary structures (e.g. retaining walls, pool etc.) must penetrate through any fill materials and
unsuitable natural soils (i.e. very loose to loose sands) to found at least 1 m into medium dense (or
denser) natural sands. High-level footings may be possible in areas of deeper excavation where medium
dense to dense (or denser) sands are exposed at or near the subgrade. This would be subject to an
assessment by a suitably qualified and experienced geotechnical RPEQ (including verification testing).
High-level footings, so founded, could be designed using a maximum allowable bearing pressure of
100 kPa.
Elsewhere (excluding the shear pile wall), based on the results of the investigation, pile founding depths
for the building of up to 3.5 m BGL (existing ground levels) are anticipated. Deeper piles may be
necessary subject to an assessment of building loads at the detailed design stage.
Excluding the shear pile wall, steel screw piles would be an appropriate footing option, where required.
Piles may be designed using a maximum allowable end bearing pressure of 600 kPa in medium dense
sands, or at least 1 MPa in the deeper dense sands. Due to the presence of very loose to loose upper
sands, together with the restricted site conditions and close proximity of adjacent houses, open bored
piers or driven piles are not recommended for this site. A possible alternative to screw piles could be
grout-injected, CFA piles, provided that construction water loss is carefully monitored and controlled.
Steel reinforced concrete bored piles may be possible; however, the use of sacrificial liners (e.g.
‘Formatube’) would be required.
If steel screw piles are adopted, it will be important to ensure close supervision of installation, as piling
may not encounter sufficient drilling resistance (from torque measurement) in sands at the suggested
founding depth, and piles could extend to much greater depth than necessary.
It is therefore recommended that site specific dynamic load testing be conducted on screw piles, if
adopted, at a minimum.
Where tension or compression capacity developed in the footings is critical for the future structure (e.g.
resistance to uplift forces from high winds), then cyclic load tests (including measurement of deflections
under tension and compression cycles) should also be undertaken prior to construction. Kentledge for
static testing, or simulated cyclic loads, should prove the piles to a minimum of two times the expected
working load within tolerable deflections.



Geotechnical investigation
19 November 2025 | 25289-001-Rev0                                                                               19