J000154-001-R-Rev0_ASS Investigation Report · RAP15/0034

J000154-001-R-Rev0                                                                              November 2015



 Cl:SO4 Ratio

 Total Dissolved Solids (mg/L)                     470

 Dissolved Aluminium (mg/L)                        0.10

 Dissolved Iron (mg/L)                             0.16

 Total Aluminium (mg/L)                             1.5

 Total Iron (mg/L)                                  1.6

 Dissolved Manganese (mg/L)                       0.030

 Calcium (mg/L)                                     45

 Magnesium (mg/L)                                   11

 Potassium (mg/L)                                   <5

 Sodium (mg/L)                                      86


The groundwater pH (6.2) indicates that the groundwater is slightly acidic. The electrical conductivity (EC)
value (437 us/cm) and salinity (0.15 ppt) indicate that the groundwater is fresh, however this may be a result
of the sample being collected on a low tide and may not represent the groundwater conditions during a full
tidal cycle.
The Chloride:Sulfate (Cl-:SO42-) ratio provides an indication of whether the environment is influenced by ASS.
A Cl-:SO42- ratio of sea water is approximately 7, a Cl-:SO42- ratio below this value can indicate that excess
sulfur may be present as sulfides. However, in this case the sulfate concentration recorded was considered
too low to provide reliable information from which any conclusions could be drawn.
The groundwater was generally recorded being net alkaline with results of alkalinity testing indicating
moderate to high alkalinity levels, and with a pH value of pH 6.2 the buffering capacity of the groundwater
would be considered adequate to maintain acceptable pH levels in the future under current conditions.
Total iron (Fe) concentration in the groundwater is indicative of an iron rich environment, common along
coastal Southeast Queensland. The dissolved Fe concentration also indicates possible past influence by
lower pH groundwater.
Total and dissolved aluminium (Al) concentrations recorded were consistent with other sites located along
the coastline of Southeast Queensland.

6.5      Preliminary Screening
Results of preliminary screening are summarised in Table B1 (Appendix B).
Soil pH (represented by pHF results) was found to range between pH 3.6 and pH 6.6 (slightly to highly
acidic), with the majority of the samples being between pH 5.5 and pH 6.5, indicating a low probability of the
presence of actual ASS at the borehole locations.
A mixture of low to high level reactions to addition of hydrogen peroxide was observed in all samples. There
was a noted difference in the pHF and pHFOX test results for the majority of samples tested below 2 m (natural
soils). The pHFOX in the samples collected from the natural soils ranged from pH 1.3 to pH 2.8 indicating a
high potential for the presence of PASS. However, the pHFOX ranged from pH 2.9 to pH 6.1 in the fill material
suggesting a low to moderate potential for the presence of PASS.




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