20220109 - 21236-002-Rev0 Maher Tce · OPW23/0182

GV Emanuel Constructions                                                                         21236-002-Rev0
                                                                                                 1 February 2023

Borehole and DCP locations are shown in Figure 1 attached at the end of this report, with borehole and
DCP logs presented in Appendix A, together with explanatory notes. Borehole coordinates were recorded
using a handheld global positioning system (GPS).

The subsurface conditions encountered in boreholes BH3 and BH4 were relatively consistent summarised as
follows:
        Fill (presumably uncontrolled) – comprising stiff sandy clay of medium plasticity to 0.2 m BGL,
         then or from the ground surface
        Residual Soils – stiff sandy clay of medium plasticity (borehole BH3 only) to 0.2 m BGL, then very
         stiff (or stiffer) sandy clay of medium plasticity to depths between 1.7 m and 2.5 m BGL; overlying
        XW Materials – mostly hard sandy clay of medium plasticity to the borehole termination depths.

Groundwater seepage was not encountered whilst solid flight augering, nor was any groundwater observed
emanating through the excavation face.

Subsurface conditions inferred from standalone DCP4, were generally consistent with the boreholes
comprising inferred stiff clays to 0.1 m BGL, then very stiff (or stiffer) clays with practical DCP refusal on
inferred hard clays or XW materials at 0.8 m BGL.
In general accordance with the original geotechnical report (Tectonic Ref. 21236-001-Rev0, dated 16 July
2021), we provide the following advice.

All footings must penetrate through any fill (existing or future) and unsuitable natural materials to found at
least 0.3 m into stiff (or stiffer) residual soils. Depending on the design loads, high level strip and pad
footings, or a stiffened raft slab, may be adopted for the proposed basement and development. An allowable
bearing pressure (ABP) of 100 kPa may be adopted for high level footing design where footings are founded
at least 0.3 m into stiff/medium dense (or stronger) residual soils.

Based on the subsurface conditions encountered in both boreholes and inferred from the central DCP, very
stiff (or stiffer) residual clays were encountered or inferred at depths of about 0.2 m BGL (levels at the time of
the investigation). Pocket penetrometer readings exceeded 300 kPa below these depths with DCP values
> 7 blows per 100 mm intervals. Therefore, high level footings founded at least 0.3 m into very stiff (or
stronger) residual soils, could be designed using an ABP of 300 kPa.

Should excessive column loads preclude the use high level footings, or in areas where unsuitable materials
(e.g. fill) are exposed at the design level, deeper piled footings would be required. Piles could be designed
based on the following ABPs:

        0.5 m into very stiff to hard residual soils – ABP 400 kPa.
        0.3 m into XW materials or very low strength sandstone – ABP 600 kPa.

It is recommended that all footings are inspected and assessed by a structural/geotechnical RPEQ prior to
pouring concrete. Resultant settlements from footings founded as described above should be within
serviceability limits, estimated to be less than 25 mm or 1% of footing width. It should be noted that over
dimensioned strip/pad footings may result in excessive settlements, which should be considered.

Footing design should also account for potential soil reactivity to be equivalent to Class M. It should be noted
that placement of reactive clay may result in a more severe equivalent site classification, such as H1 or
greater.

All footings should found such that they are not adversely affected by any adjacent excavations, trenches, or
retaining walls that are not designed to support building loads. Footings adjacent to any fill batter crests
should be deepened to found below the toe of the batter. Footings should found at least below a plane
extending 1 m horizontally from the base of trenches/excavations/retaining walls, then rising up at 1V:1H, as
illustrated in Text Figure 2 overleaf.




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