PTG_00259 - 0001 - Rev0 - Geotechnical Investigation Report (1)

                                                                                                        PTG Consulting
                                                                                                   ABN: 89 668 880 448
                                                                                             www.ptgconsulting.com.au


Table 3: Summary of Chromium Suite Testing
                                                 Actual        Potential       Acid              Existing plus
 Borehole
               Depth (m)        Material         Acidity        Acidity     Neutralising       Potential Acidity
    ID
                                                (% pyrite S)     (%S)      Capacity (%S)             (%S)
    BH1        1.75 – 2.0         SAND            0.007         0.070          N/A                   0.08
    BH1        2.75 – 3.0         SAND            0.011         0.240          N/A                   0.25
    BH1        2.75 – 4.0         SAND            0.006         0.050          N/A                   0.06
    BH1        4.75 – 5.0         SAND            0.006         0.063          N/A                   0.07


8. PRELIMINARY ACID SULFATE SOILS COMMENTS
The pH and Chromium Reducible Sulfur test results indicate the presence of Potential Acid Sulfate Soils. This
section outlines preliminary treatment advice however the following further work will be required to comply
with the National Acid Sulfate Soils Guidance – National acid sulfate soils sampling and identification methods
manual (June, 2018) as referenced by the Noosa Shire Council Acid Sulfate Soil overlay code:

For excavations between 501 m3 and 1000 m3 below RL 5 m AHD – drill an additional three boreholes to 1 m
below the lowest cut depth/level, sample and test.

An Acid Sulfate Soil Management Plan will be required as the preliminary testing has indicated test results which
breach the ‘action criteria’ in accordance with the information set out in the Queensland Acid Sulfate Soil
Technical Manual – Soil Management Guidelines Version 5.1, noting that less than 1000 t of sand based soils will
be excavated below RL 5 m AHD.

Due to the likely disturbance of Acid Sulfate Soils (ASS), it is imperative to treat the soils to mitigate the risk of
oxidation. This prevents pH reduction that could lead to acidic conditions, potentially harming the environment,
as well as buried steel and concrete.

For the management of ASS, 'Ag' Lime is recommended as the optimal neutralizing agent. It maintains a mildly
alkaline pH range of 8.5 to 9 and has low solubility, making it easy to handle without any significant operational
issues. 'Ag Lime' is essentially calcium carbonate derived from finely ground and sieved limestone.

The indicative/preliminary recommended liming rates are as follows:

    •     3.6 kg of lime per ton for on-site fill treatment; and
    •     12 kg of lime per ton for natural sandy soils.

It is advisable to use 'Ag Lime' with a purity of 95% or higher whenever possible. All lime treatment rates to be
confirmed/finalised by further testing once carried out.



9. GEOTECHNICAL COMMENTS
The geotechnical comments in this report are based on factual information collected during the fieldwork,
common practice, local experience and published literature however are fundamentally opinions.

Based on the ground conditions, it is likely that the most suitable foundation system for the buildings would
comprise bored and screw piers.




PTG/00259 – 25 Wyuna Drive, Noosaville              Page 10 of 15                                       28 June 2024