Appendix 5. Geotechnical Engineering Report [As Published] · 132007.2399

October 2007                                    -5-                           077682076(AB)


RESIDENTIAL DEVELOPMENT AREA

Across the proposed residential development area, five boreholes (BH1 to BH4 & BH6) were
drilled to depths of 3 m and one borehole (BH5) was drilled to 6 m. The 3 m deep boreholes
encountered mostly medium dense to dense natural silty sand and sand to the depth of the
investigation. Loose sand was encountered from the ground surface to 0.2 m depth in most of
these boreholes, however was recorded to 0.7 m depth in borehole BH6. Boreholes BH1 to
BH4 encountered dense to very dense indurated sand (‘coffee rock’) in layers of various
thickness, commencing at depths of between 0.9 m and 2.6 m.

Borehole BH5 was drilled in the low-lying south-western part of the residential development
area and encountered a different profile comprising silty sand and firm sandy/silty clay fill to
1.1 m depth. Given our understanding of the history of placement of fill within the subject
site, any fill materials would likely be classified as “uncontrolled” in accordance with
Australian Standard AS3798. With uncontrolled fill, between test locations, there is
significant uncertainty regarding the composition and degree of compaction of the fill,
together with the proficiency of site preparation (eg. topsoil stripping and subgrade
compaction).

The fill materials in borehole BH5 overlie inferred natural swamp deposits of loose to
medium dense clayey sand or soft sandy clay to 2.4 m depth then soft to firm silty ‘marine’
clay to 3.2 m depth. Below 3.2 m depth the silty clay becomes stiff to very stiff (inferred
residual) and extends to the depth of investigation (6 m).

GOLF TEE REALIGNMENT AREA

Two boreholes (BH7 and BH8) were drilled to depths of 3 m and 6 m, respectively, across the
proposed 18th hole golf tee realignment area. Borehole BH7 encountered mostly medium
dense (or denser) natural silty sand or sand to 2.8 m depth with a band of indurated sand from
2.2 m to 2.8 m depth, then stiff sandy clay to 3 m. Borehole BH8 was drilled in the low-lying
south-western area near BH5 and encountered a similar profile, being very loose natural
clayey sand from the ground surface to 0.9 m depth overlying soft sandy and silty clay
becoming stiff (or stiffer) below 2.6 m depth.

4.3     Groundwater

Groundwater seepage was generally encountered at depths of between 1 m and 1.5 m in the
boreholes during the investigation, except for boreholes BH6 and BH7 where seepage was
encountered at depths of 2.4 m and 2.2 m respectively. The groundwater level across the site
will be subject to variations dependent upon the intensity and duration of preceding rainfall
events and may rise close to the ground surface in places.




                                     Golder Associates