Additional Geotech Investigation 22.02.01 From Douglas Partners - 95120.01.R.001 · OPW21/0315

                                                                                                             Page 4 of 6




To provide confirmation of the above qualitative testing, quantitative analytical testing was carried out
on selected samples, generally with the greatest difference in pHf and pHfox readings and strongest
reaction using the Chromium Suite method.
•     The chromium reducible sulfur values (SCR) where greater than 0.01 %S indicates a significant
      level of sulfide, and where greater than 0.03 %S then the soil has a potential acidity level
      exceeding the QASSIT guideline value. Samples of both the fill and natural sands tested returned
      SCR values greater than 0.03 %S indicating levels of potential sulfur.
•     Where the total actual acidity (TAA) value exceeds 18 mol/t then the soil has an acidity level
      exceeding the QASSIT guideline value. Three of the samples tested returned TAA values greater
      than 18 mol/t (or 0.02 %S) indicating the presence of acidity.

Generally, the action criterion from the chromium suite of tests, which triggers a requirement for ASS
disturbance to be managed, derived from the Soil Management Guidelines is as follows:
•     Net Acidity (TAA + SCR + SNAS) of greater than or equal to 0.03 %S for disturbances of greater
      than 1000 tonnes

Based on the laboratory test results, both the existing sand fill and natural silty sand are considered to
contain PASS, having the potential to generate sulfuric acid when disturbed and exposed to oxygen.


5.2    Management and Treatment of ASS

As the disturbance of the ASS material cannot be avoided, these soils when disturbed will require
treatment to reduce the risk of oxidation and consequent reduction of pH to produce acidic conditions
potentially damaging to the environment and to buried steel and concrete.

‘Ag lime’ should be used as the preferred neutralisation material for the management of ASS as it is
usually the cheapest and most readily available product for soil neutralisation. This material is mildly
alkaline (pH of 8.5 to 9), of low solubility, and does not present any handling problems. The ‘ag lime’
comprises calcium carbonate typically made from limestone that has been finely grounded and sieved
to a fine powder.

Table 1 provides indicative liming rates for neutralisation of the different ASS material likely to be
disturbed.

Table 1: Indicative Liming Rates
                        Material                                       Lime Application Rate for Treatment (kg/m 3)
                   Existing Sand Fill                                                      3.0
                     Natural Sands                                                         4.0
                                                                   3
Notes: Assumes a bulking up factor of approximately 1.5 tonnes/m


A guard layer of ‘ag lime’ should also be applied over the base of the basement excavation. This
guard layer of lime should be applied at a rate of 2.5 kg/m2.




Proposed Residence                                                                                  95120.01.R.001.docx
33 Wyuna Drive, Noosaville                                                                                February 2022