Geotech Report · OPW19/0205

Gympie Terrace Noosaville Pty Ltd



C1.0 ACID SULFATE SOILS INVESTIGATION METHOD AND RESULTS
C1.1 Laboratory testing
A total of 48 samples were screened to assess field pH (pHF) and pH after oxidation (pHFOX) using 30%
hydrogen solution.
The pHF/pHFOX screening method consists of two steps. In the first step, the field pH of a 1:5 soil/water
suspension is measured (pHF). In the second step, a 30% Hydrogen Peroxide solution is added to a second
sample of the same material which is then heated to accelerate the oxidation of the sample. The pH after
oxidation (pHFOX) is then measured. A significant difference between the pHF and pHFOX results is indicative
of PASS; however, test results may be affected by other inclusions such as shell material and organics.
Based upon the results of these screening tests, 12 samples were selected and dispatched to Eurofins/MGT
to undergo quantitative analysis by the Chromium Reducible Sulfur (Scr) suite in accordance with ASS
Method 23F and 22B laboratory procedures of Ahern et al (2004).
This method includes analysis of ‘inherent buffering capacity’ from naturally occurring alkaline materials (i.e.
calcite, coral debris, fine shell fragments) and 'retained acidity' which includes sulfur held in stable oxidation
minerals such as 'jarosite' and allows for calculation of 'net acidity'.
An overall acid-base accounting method was used to calculate a ‘net acidity’ value which is used to qualify
analytical test results and calculate liming rates. This equation is:

  Net Acidity = Actual Acidity (as TAA) + Retained Acidity (as SNAS) + Potential Acidity (as SCR) - insitu Acid
               Neutralising Capacity (ANC).

The laboratory certificates of analysis, chain of custody documents and laboratory quality control documents
are attached, and the results are summarised in Table C1, attached.

C1.2 Groundwater Quality Analysis
A groundwater sample was collected from BH1 on 14 November 2018 to provide a ‘snapshot’ of the
groundwater conditions. The results of groundwater analysis are summarised in Table C2.
Table C2: Results of Groundwater Analysis
 Parameter                                                                            BH1

 Field Results
 Groundwater level (m below ground surface)                                            2.0
 Field pH                                                                              5.4
 Electrical Conductivity (mS/cm)                                                       1.5
 Observations                                                                        Brown
 Laboratory Results
 Acidity as CaCO3 (mg/L)                                                               140
 Sulfate as S (mg/L)                                                                    42
 Chloride (mg/L)                                                                       290
 Cl:SO4 Ratio                                                                          6.9
 Dissolved Aluminium (mg/L)                                                           < 0.05
 Dissolved Iron (mg/L)                                                                  15
 Total Aluminium (mg/L)                                                                310
 Total Iron (mg/L)                                                                     440



J000799-002-R-Rev0                                                                                     Page 15