Attachment 5 - Geotechnical Assessment · MCU18/0015

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below the colluvium in test pit TP6 at 1.2 m depth. It is possible that the cobbles and
boulders are residual materials.

Borehole BH7A intersected very loose sand to 2.2 m depth, then medium dense sand to 2.5 m,

‘below which hard, medium to high plasticity sandy clay was encountered to hand auger

refusal at 2.8 m depth. From the DCP results, it is inferred that very stiff to hard clay extends
to about 5.8 m depth, where practical DCP refusal (35 blows/100 mm) was encountered.

Borehole BH8 and test pit TP8 encountered very loose to loose sand to 2.2 m depth, then
medium dense sand to 2.6 m, below which dense or hard materials were intersected to the
depth of investigation.

Test pits TP9 and TP10 located on the eastern side of the creek encountered stiff sandy clay
and mostly dense silty sand colluvium, respectively, to depths/of 0.4 m and “1,4 m. These
materials overlay very stiff to hard, inferred residual clay to-bueketrefusal om probable ‘core
stones’ of diorite at depths of 1.2 m and 1.7 m, respectively» Boreholes GAland GABH21
drilled on the Viridian site to the east encountered ‘sandstone’ below.2.9.m and 6.2 m depth,
respectively.

Only a trace of groundwater seepage was‘noted at 1.7 m, depth in test pit TPS during the
investigation. Groundwater was not ericountered in the other boreholes or test pits. Our
experience at similar sites indicates that groundwater ‘may develop in the sandy materials
overlying the less permeable clays arid soil / rock colluvium, particularly following periods of
heavy or prolonged rainfall.

4 Laboratory Testing

CBR values of 1 % and 14% were respectively recorded by testing carried out on silty clay
and silty sand samples recovered from test pits TP9 (1.0-1.2 m) and TP10 (0.5-0.7 m). The
CBR testing was conducted foliowing 100% Standard compaction and four days of soaking.

Atterberg Limits and-Percent Fines testing was undertaken on samples of sandy clay and silty
clay recoyered from 0.2 m and 0.9 m depth in test pit TP9. The results indicate a medium
plasticity clay with 57% material finer than 0.075 mm at 0.2 m depth, and a high plasticity
clay with 88% fines at 0.9 m depth.

Four PSD tests were conducted on sand samples recovered from the dune area and these
indicate that the material is fine to medium grained with a trace of silt. A PSD conducted on a
sand sample recovered from 0.5-0.7 m depth in test pit TP10, east of the creek, indicates a
fine to medium grained silty sand.

Golder Associates