Attachment B Geotechnical report

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                                                                                  Job No. DE14/231


For the swimming pool where settlements of less than 5mm are desirable, the allowable end
bearing pressures should be restricted to 750 kPa and 1000 kPa in medium dense sand and
sandstone rock, respectively. Allowable shaft adhesion in the sands should be reduced to 15
kPa.


3.3.3 Screw Piles

Screw piles offer a satisfactory alternative for loads up to 50 tonnes. Specialist contractors
will offer a pile type and spiral dimensions for the loadings required.

All piles should be hot dipped galvanized and should be drilled to a minimum depth of 7
metres on the lower slopes and 5 metres in the northern part of the site represented by DP4
and DP6.

Allowable base resistance may be taken as that applicable for drilled concrete piles as 1000
kPa.

Ultimate tension or pull out resistance is the mass of a 30 degree tapered cone of sand above
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the pile spiral base plate based on an average sand density of 17.5kN/m .



4.0    SLOPE STABILITY

The natural cleared slope at 20 to 25 degrees has a Factor of Safety of 1.2 to1.6 and below
the house site with trees remaining of 1.4 to 1.7. Heavy rainfall however may cause local
over steepening if runoff is concentrated on the slope as all of the sand (dune sand and
Teewah sand) is highly erodible.

Preferably all storm water runoff should be taken to the natural drainage below the site.


5.0    GROUNDWATER

Seepage in the sand will occur after heavy rain but there is no shallow groundwater table as
such. In the northern part of the site seepage can be expected at the sand/clay interface
represented by test pit TP2 at about RL42.5m,

All retaining walls should be well drained with a gravel filter and pipe protected by a geofabric
surround.


6.0    LIMITATIONS

The use of drilled piles will require inspections at construction to confirm the base and shaft
friction and the working load capacity as the dynamic probes did not allow adequate soil
identification.

Screw piles on the other hand may be approved by meeting the contractor’s torque capacity
correlation appropriate at the pile working load.

Recommendations given in this report are based on information supplied regarding the
proposed construction in conjunction with the findings of the investigation. Any change in
construction type may require additional testing and/or make recommendations invalid.

Every reasonable effort has been made to locate test sites so that bores are representative of
the soil conditions within the area to be investigated. The client should be made aware
however, that this assessment has been based on limited site data using small diameter
boreholes.



Ref 19195B – Markus Hasler                                                MORRISON GEOTECHNIC
71 Seaview Terrace Sunshine Beach