Rfi - Scg 32167(S)

3     SITE DESCRIPTION

The construction area has a gradient in the order of 6 – 16%.

Vegetation on the construction area (and nearby surrounds) consists of grasses and scattered trees.

The trees are located in the neighbouring allotment on and adjacent the proposed construction site.

The trees are of a height and proximity that could affect the moisture conditions within the proposed construction
site. Refer to the appendices to the rear of this report for guidance on Trees and Construction.

The existing surface drainage is good and sub-surface drainage is good.


4     FINDINGS

The soil profiles encountered are shown on the attached borelog sections.

No water table was encountered during our testing program.

The sandy soils encountered are susceptible to collapse when unconfined. This may effect excavations and
result in additional earthworks and increased concrete volumes. Temporary shoring or Forma-Tube may be
required to retain the sands prior to concreting.

The samples classified on-site were assessed as having negligible plasticity, therefore laboratory testing was
considered unnecessary.

We have assessed the expected differential movement of the soil profiles encountered to be the equivalent of a
site with a Ys of less than 20mm.

Fill, which we have described as uncontrolled was encountered to the following depths.

                                Test Site 1 – 300 mm             Test Site 2 – 400 mm

At the time of writing this report we were unable to describe the fill as controlled. This can be revised if
documentation is available indicating that this fill has been compacted and certified in accordance with AS 3798-
2007.

The following foundation material will provide a safe bearing capacity (100 kPa) for buildings within the scope of
AS 2870-2011 and is shown shaded on the attached logs;

           FOUNDATION MATERIAL - NATURAL MEDIUM DENSE SILTY SAND

5     SITE PREPARATION DETAILS

We recommend the structure be supported on steel screw piers designed and installed by a specialist contractor
to achieve the loads nominated on the structural plans.

We recommend scraping this site free of all organic material and debris, then cutting and filling the construction
area to form a level pad. The fill should be clean material from the cut, laid out in 150mm (maximum) layers and
tracked rolled with the excavator (six passes in each direction) and extended out 2.0m (minimum) from the
building footprint. The fill is to be placed and compacted in accordance with AS3798-2007 to a level sufficient to
achieve a Level 1 certification with a minimum relative field density of 98%. Cut batters of 1 to 2 (vertical to
horizontal) and fill batters of 1 to 3 will be stable providing all fill is compacted as above and exposed banks are
protected against erosion. The earthworks must incorporate surface spoon drains at the base and on the high
side of the cut. Both drains must have an efficient outflow downslope and clear of the dwelling.

Where a retaining wall is required, a cut batter of 1 to 2 (vertical to horizontal) in the sand profile taken from the
base of the proposed wall should be excavated. Backpropping to retaining walls should be provided throughout
the backfilling and compaction process. These earthworks must incorporate shallow surface spoon drains at the
base and along the high side of the cut. Drains must have an efficient outflow down-slope and clear of the
construction area. The exposed face should also be protected against the potential for stormwater erosion.
Should these recommendations be un-achievable the builder should seek guidance from this office on temporary
shoring, benching or other suitable techniques.

     SCG Consulting Engineers                                2                                     SCG Ref: 32167(S)