Geotechnical Report

                             PROPOSED UNIT DEVELOPMENT
                             31 BOTTLEBRUSH AVENUE, NOOSA HEADS



Executive Summary
This report details a geotechnical investigation undertaken for a proposed unit development at 31
Bottlebrush Avenue, Noosa Heads. The investigation was carried out by Tectonic for Camtegan Pty Ltd.
This report presents the results of our geotechnical investigation, incorporating a slope stability
assessment, together with geotechnical advice for the project.

The proposed development comprises a three storey unit block constructed with masonry blockwork, and a
partially inground semi-basement level for carparking and storage. No earthworks plans were provided but
based on the layout details provided it is anticipated earthworks will include cuts for the basement level of up
to about 3 m deep in in the rear, northern part with the excavation daylighting in the central/southern part.
Only minor filling is expected to be required up to say 1 m in height to form finished surface levels.

Site investigation works comprised desktop review, a walk-over survey combined with drilling of two
boreholes to depths of 3 m and 5 m below ground level (BGL) with insitu strength testing.

The site presents as a south-west facing sand dune slope dipping at an overall angle of about 10° to 12°.
Subsurface conditions encountered in the boreholes comprised, very loose to loose silty sand fill to 0.6 m
BGL (in borehole BH1 only), overlying natural loose sand becoming medium dense below depths of 1.2 m
to 1.4 m BGL and grading to dense below 3.6 m to 4.3 m BGL.

Groundwater was not encountered in any test pits at the time of investigation.

Based upon the existing site conditions, and subject to the implementation of recommendations given within
this report, it is our assessment that there would be a Low (L) Risk of global slope instability affecting the
proposed unit development.

Excavations through the existing soils should be achievable using conventional earthmoving plant (e.g. small
or larger excavators with toothed buckets). Temporary cuts in the very loose to loose sands could be formed
at 1V:2H and at 1V:1 in medium dense or dense sand, for batters up to 3 m in height, provided groundwater
seepage is not encountered and sands do not slough from the batter face as they dry out. If space
restrictions limit battering of temporary cuts on the site, some form of retention will be required such as sheet
piles.
Based on the results of the investigation, the natural soil profile is non-reactive and so would be estimated to
have characteristic surface movements (‘ys’) of less than 20 mm (equivalent to Class S based on the reactivity
of the foundations assessed in accordance with AS 2870-2011 Residential Slabs and Footings). It should be
noted that the predicted order of movement is based on the existing soil profiles (i.e. no additional cutting or
filling), and moisture content changes within soils due to normal seasonal moisture variations only.

Footings for the proposed development and any ancillary structures (e.g. retaining walls, pool, etc.) must
penetrate through any fill materials and unsuitable natural soils (i.e. very loose to loose sands) to found at
least 0.5 m into medium dense (or denser) natural sands. Such materials were encountered below depths of
1.2 m to 1.4 m BGL. Thus, piled footings will be required unless excavations expose such materials at or near
foundation subgrade level. Given the sandy soil profile and depths of footings required, steel screw piles are
considered to be a suitable foundation type. Due to the presence of loose sands, together with the close
proximity of adjacent residences, open bored piers or driven piles are not considered to be suitable for this
site.




17 December 2020
Report No. 20384-001-Rev0                               ii