Scg 25335(S) · OPW16/0105

3      SITE DESCRIPTION

The construction area has a gradient in the order of 8%.

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

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

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.

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 SANDS

5      SITE PREPARATION DETAILS

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. 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. 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. Backpropping to retaining walls should be provided
throughout the backfilling and compaction process. 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 95%.
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.

Areas where existing structures or trees are removed shall be backfilled with engineer approved fill material
compacted to achieve a minimum relative field density of 95% and be in accordance with AS2870-2011.
Where trees are removed prior to construction the moisture conditions of the soils must be allowed to normalise
across the site prior to commencing foundation preparations.

Any loose or soft material uncovered in the site preparation shall be removed and replaced with approved fill
material compacted in accordance with AS2870-2011, or alternative measures to be provided by the engineer.




    SCG Consulting Engineers                                  2                                        SCG Ref: 25335(S)