RESPONSE TO FURTHER ADVICE -Geotechnical Report · MCU25/0054

                                                                                                      PTG/02023 – 0001 – Rev1


Based on an understanding of the preliminary ground conditions, it is likely that the most suitable foundation system
for the buildings would comprise of screw piles into competent strata.


         SITE CLASSIFICATION AND SITE MOVEMENTS
In accordance with ‘AS2870-2011: Residential Slabs and Footings’, the site is classified as ‘P’ due to:
» The bearing strength is less than that specified in Clause 2.4.5 as per Section 2.1.3(a);
» The site may be subject to moisture changes due to site conditions more severe than the normal site conditions
     described in Clause 1.3.2:
     o Removal of an existing building or structure likely to have significantly modified the soil moisture conditions
         under the footprint of the footing system of the building as per section 1.3.3 (a);
     o Removal of trees prior to construction as per section 1.3.3(b); and
     o Presence of trees on the building site or adjacent site as per section 1.3.3(c).

The site is in a Wet Coastal climatic region with a depth of suction (Hs) of 1.5 m. The encountered soil material is sand
to the depth of the soil suction profile. Applying the empirical methods described in Section 2.3 of AS 2870:2011, the
characteristic ground surface movement will most likely be negligible, consistent with a site class ‘A’.

This classification is relevant to sites subject to normal moisture conditions. Abnormal moisture conditions, such as
from the removal or planting of trees (including on adjacent sites), poor site drainage, and development of gardens
adjacent to the footings, may cause higher movements to occur, possibly resulting in damage, which may or may not
be within acceptable limits.


         FOUNDATIONS & RETENTION OPTIONS
Based on an interpretation of the typical structural loads anticipated, and subsurface conditions encountered during
the investigation, screw or piled foundations could be considered suitable for the development. Due to limited
information available on the underlying strata foundation, design parameters cannot be accurately provided at the
time of writing this report. Additional work will need to be completed to provide commentary on foundations and
retention options.



9 PRELIMINARY ACID SULFATE SOILS (ASS) COMMENTS
No Acid Sulfate Soil Management Plan (ASSMP) has been prepared at the time of writing and therefore these
comments are limited to commenting on the test results obtained and information referenced from the National ASS
Guidelines.

Possible Actual Acid Sulfate Soils (AASS) are typically indicated by pHF results below 4.0. None of the samples
recorded these test results. The lowest pHF result was 5.9 as recorded in the sample from borehole BH3 at a depth of
2.0 m.

Possible Potential Acid Sulfate Soils (PASS) are typically indicated by pHF results above 4.0 along with pHFOX results
below 3.0 and showing a reaction to added peroxide. Most of the tested samples met these criteria, apart from two
samples in borehole BH2 that had a pHFOX of just over 3.0. The following samples indicated possible PASS:
» BH2 – 0.50 m, 0.75 m to 1.50 m inclusive and 2.75 m to 3.00 m inclusive; and
» BH3 – 0.25 m to 3.0 m inclusive.

Based on the pH screening test results (pHF and pHFOX), possible PASS were indicated by the test results and on this
basis, Chromium Reducible Sulfur (CRS) testing has been arranged to confirm the presence or absence of ASS.

The texture of the soil sediment influences soil behaviour and therefore treatment if excavated. The equivalent sulfur
and equivalent acidity action criteria thresholds for different soil textures are shown in Table 3. The following table is
from Table 2 of the ‘Queensland Acid Sulfate Soil Technical Manual, Soil Management Guidelines V5.1’.




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