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

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4.     Laboratory Testing

Soil samples were recovered from the bores at regular intervals to 4 m depth, and were screened by
measurement of pH after the addition of distilled water (pHf) and peroxide (pHfox). The pHf test
provides a preliminary indication of past oxidation of sulfides resulting in the presence of actual acid
sulfate soils (AASS). The pHfox test provides a preliminary indication of the presence of unoxidised
sulfides and therefore, potential acid sulfate soils (PASS).

Based on the results of the screening tests and visual inspection of the samples, selected samples
were subjected to more rigorous Chromium Suite analytical testing. The results of this testing are
discussed further below with detailed report sheets attached.

Preliminary field screening and chemical laboratory tests for ASS were carried out with reference to
the QASSIT Guidelines (Ahern, C R; Ahern, M R; Powell, B, 1998), the Soil Management Guidelines
(Dear, et al., 2014) and the Laboratory Methods Guidelines (Ahern, McElnea, & Sullivan, 2004).

In addition, a groundwater sample was recovered from the PVC standpipe and also submitted to
laboratory testing. The results of the groundwater testing are attached.


5.     Comments

5.1    Criteria for Evaluation of Acid Sulfate Soils

The criteria on which the results (including previous testing) of screening tests (pHf and pHfox) were
assessed as indicative of possible actual acid sulfate soils (AASS) or potential acid sulfate soils
(PASS) were based on the QASSIT Guidelines as follows:
•     pHf of less than 4 indicates oxidation of sulfides has probably occurred in the past, indicating the
      presence of actual acidity (AASS). None of the samples tested returned a pHf value of less than
      4.
•     pHf between 4 and 5.5 indicates the soils are acidic. This may be as a result of limited oxidation
      of sulfides, but may also be as a consequence of the presence of organic acids.
•     pHf of greater than 5.5 indicates the soil has little or no actual acidity; however, this can be
      common with PASS materials or marine-influenced samples. The majority of samples tested
      returned pHf values of greater than 5.5.

The pHf test method does not detect acidity bound within sulfides; however, the pHfox test gives an
indication of any potential acid release. Results of the pHfox are summarised as follows:
•     pHfox of less than 3, plus a pHfox reading at least one pH unit below pHf, plus a strong reaction
      with peroxide, strongly indicates the presence of PASS. The only samples which returned a pHfox
      values of less than 3 were of the natural sands, and generally with a moderate reaction to
      peroxide.
•     pHfox between 3 and 4 indicates the possibility of PASS material and a pH fox between 4 and 5
      may indicate the presence of small amounts of sulfide or fine carbonates.




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