08/0169 - Response to Information Request [As Published] · 132008.169

4.0 MORPHOLOGY

The allotment is situated within a massive aeolian sand bed of Quaternary age. As a general
observation dunal horizons such as these are stable where;

- The natural slope is tess than the angle of repose for sand (32°)
- Vegetation exists to protect from wind generated scour
: The drainage pattern is such that there is no risk of fluvial scour.

These horizons are unstable during and after any major tectonic event (earthquake) and can become
unstable when aeolian or fluvial scour erode slopes to angles greater than 30°, particularly when
coincident with vegetation removal.

5.0 FINDINGS
The soil profiles encountered are shown on the attached log sections.
No water table was encountered during our testing program.

We have classified the site in accordance with Section 2 of the Residential Slabs and Footings Code
(AS2870-1996) code as Glass P due to the uncontrolled fill encountered, adjacent the access point to
the allotment. However a less severe classification of Ciass S could be adopted where the natural soils
occur away from the filled area.

At the entrance to the allotment we encountered uncontrolled fill 900mm in depth.

6.0 SLOPE STABILITY:

The sloping sand profiles in these sand dune areas typically have a safety factor against sliding of 1
(one) where the slope is 32° and where the consistency of the sands is at least medium dense. A slope
angle of 27° would produce a safety factor of 1.2 against sliding, provided the consistency of the sands
is at least medium dense. The factor of safety is enhanced in the presence of ground covering
vegetation.

Where the consistency of the sand is loose, a lesser angle of 28° would provide safety factor of 1 (one)
against sliding.

The factor of safety is enhanced in the presence of ground covering vegetation.

The survey data supplied indicates the slope within the allotment generally sits at an angle of between
16° - 26°.

Borehole and DCP results indicate the sands are generally loose to a depth of around 2000mm from
where they increase in density to Medium Dense. This suggests the slope stability within the upper
profile of the allotment in the steeper grades in above one. The presence of vegetation is increasing
stability of the slope.

7.0 | RECOMMENDATIONS: a

7.1 Bearing Loads

Any proposed structural loads should be founded into the NATURAL MEDIUM DENSE SAND profiles :

where a safe bearing capacity of 100kN/m? can be expected. Where this layer is deep or covered by fill ‘

we recommend the foundations be supported on normal bored, grout injected or steel screw piers 4
4
)

founded into medium dense sand profiles or deeper as required to achieve the loads required. Non 4
vibratory techniques must be adopted for all work, including pier installation on the site. :

SCG Consulting Engineers 2 SCG Ref: 19064(S) .