RFI -Attachment 6 - Geotechnical Investigation Report CORE.pdf

Walsh Consulting Engineers




Executive Summary
As requested by Walsh Consulting Engineers, Core Consultants Pty Ltd (Core) has carried out a
geotechnical investigation for a proposed boutique hotel at Noosa Springs.
Proposed bulk earthworks are anticipated to comprise mainly cutting up to about 3 m below ground level
(BGL), with localised filling up to about 2 m to 3 m in height.
The proposed hotel footprint is on the west-facing slope of an approximately north-south trending ridge/dune
line. The ground surface slopes down to the west at about 8 degrees overall, with localised steeper slopes of
about 15 to 20 degrees.
The investigation fieldwork comprised eight boreholes drilled to depths ranging between 0.8 m and 5 m
below ground level (BGL), under engineering supervision. BH1 to BH6 were drilled using a 4WD-mounted
auger rig. HA1 and HA2 were hand-augered where vehicle access was not available. Dynamic cone
penetrometer (DCP) tests were carried out adjacent to/within the boreholes to assess soil density.
Subsurface conditions encountered in the boreholes generally comprise loose/medium dense to very dense
aeolian (dune) sand. Shallow sand fill (re-worked natural soil) was encountered in some boreholes. The fill is
deemed ‘uncontrolled’ as defined in Australian Standard AS 3798-2007 Guidelines on earthworks for
commercial and residential developments (AS 3798-2007).
Groundwater was not encountered in the boreholes during drilling. Due to the relatively permeable nature of
the sands, and the sloping nature of the site, prolonged high groundwater levels or periods of waterlogged
soil are not anticipated.
High-level footings may be founded in medium dense (or denser) alluvial sand (or future ‘Level 1’ controlled
fill) and can be designed using an allowable bearing pressure of 100 kPa. Footings in uncontrolled fill or
loose sand are not recommended.
Further recommendations are mare in this report regarding earthworks, foundations, retaining walls, soil
dispersion, aggressivity of soils and drainage.
A qualitative slope stability risk assessment for this project has been carried out following the Australian
Geomechanics Society (AGS) Guidelines for Landslide Risk Management (March 2007). Based on the
available information and the results of our investigation, it is our opinion that there is a Low Risk of slope
instability for the proposed development, subject to implementation of the recommendations in this report.
From a geotechnical viewpoint, our assessment is that the site is suitable for the proposed development.




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