Geotechnical Report Dec 2013 Revision 1

                              55 LAKE MACDONALD DRIVE, COOROY




Executive Summary
This report details the results of a geotechnical investigation carried out for a proposed 31 lot residential
subdivision at 55 Lake MacDonald Drive, Cooroy. The geotechnical investigation was undertaken by
Tectonic Geotechnical Pty Ltd (Tectonic) for Kalkev Pty Ltd, at the request of Callaghan & Toth Consulting
Engineers (C&T). The geotechnical investigation comprised excavation/drilling of test pits and boreholes,
and subsequent laboratory testing. This report summarises the results of the investigation and provides
recommendations regarding site preparation, earthworks, and pavement design parameters.

The proposed development will comprise the subdivision of existing Lot 136 on MCH978 into 32 new
residential allotments. Construction has commenced on the initial four lots fronting Lake MacDonald Drive.
The next stage comprises three lots fronting Wilgee Court. This current investigation addresses site
conditions on Stages 3 and 4 of the development.

The site investigation comprised excavation of thirteen test pits across the site to depths of up to 2.2m below
ground level (BGL). Representative soil samples were obtained from the test pits and forwarded to a
geotechnical testing laboratory for soil classification analysis. An additional two hand auger boreholes and
dynamic cone penetrometer (DCP) tests were undertaken in the western drainage gully.

The subsurface conditions encountered in the test pits generally comprised about 0.2m of loose to medium
dense silty sand topsoil over about 0.1m to 0.2m of loose to medium silty sand (similar material as the topsoil
but no vegetation), then loose to medium dense clayey sand (clay fines of low to medium plasticity) over high
plasticity, stiff, sandy/silty clay.

The main exception to the above profile was test pit TP8, which was located within the drainage gully near
the western boundary of the site. TP8 was positioned on the outer edge of the proposed pavement, and
encountered wet, very loose silty sand and sand over stiff clay. The boreholes located in the drainage gully
encountered very loose silty sand topsoil over soft saturated silty clay to about 0.5m BGL, then firm silty clay
to about 0.8m BGL, then stiff (or stiffer) silty clay.

Groundwater was encountered in two test pits during the investigation, being TP8 at 0.3m BGL and TP10 at
1.4m BGL.

Topsoil stripping depths are expected to be in the order of 150mm to 200mm across the site. If earthworks
are conducted during or following wet weather, the silty sand is expected to lose significant strength upon
wetting up. Deeper stripping to remove the 100mm to 150mm thick silty sand layer below the topsoil may be
required.

Following topsoil stripping, we expect that the exposed subgrade will comprise the silty sand layer or
underlying clayey sand. A preliminary CBRE of 10% may be adopted for the clayey sand. For sandy clay
subgrades, a presumptive CBR of 5% may be adopted, provided appropriate drainage measures are
included in the design. If silty clay subgrade is exposed, CBR values less than 3% may be possible, in which
case, additional overexcavation and replacement may be required.

At the location of test pit TP8, the wet, very loose silty sand and sand must be removed prior to filling. The
exposed silty clay may also be wet and should be treated by oveexcavation and replacement, or be tyned
and dried.

Excavations to the depths of the test pits (generally 1.5m BGL, and TP10 at 2.2m BGL) are expected to be
within the limits of medium to large excavators and dozers.




2 December 2013
Report No. 137632019-001-R-Rev0                        ii