Geotech Report · OPW19/0205

Gympie Terrace Noosaville Pty Ltd



The field pH result (pH 5.4) indicates that the groundwater is slightly acidic. The measured electrical
conductivity (EC) value of 1.5 mS/cm indicates that the groundwater is brackish.
Dissolved iron and aluminium concentrations are low. Total iron and aluminium concentrations recorded
were consistent with other sites located along the coastal areas of Southeast Queensland.

C1.3       Preliminary Screening
Results of preliminary screening are summarised in Table C1. Soil pH (represented by pHF results) was
found to range between pH 5.1 and pH 6.9 (moderately acidic to slightly acidic). The pHFOX ranged from
pH 2.2 to pH 4.6, suggesting a generally moderate to high potential for the presence of PASS.

C1.4 Quantitative Soils Analysis
Table C3 below shows the ASS action levels adopted in Queensland. These categories are used to identify
whether action / management of ASS spoil is required, based on ‘net acidity’. Action criterion of 0.03% S
equivalents (18 moles/tonne) was adopted for this investigation.

Results of the 12 samples analysed are summarised as follows:

        No samples returned Titratable Actual Acidity (TAA) results above the action criteria of 18 mol H+/
         tonne (0.03% S).

        Nine samples returned Oxidisable Sulfur as SCR at levels above the action criteria of 0.03% S.

        No samples returned a pH-KCl value exceeding pH 6.5, therefore were not tested for acid
         neutralising capacity (ANC).

        No samples returned pH-KCl values of less than or equal to pH 4.5, therefore were not tested for
         retained acidity (SNAS).
Table C3: ASS Action Criteria.
                                                                                       Action Criteria
                                                  Action Criteria
                                                                                  > 1000 tonnes disturbed
            Type of Material                 1-1000 tonnes disturbed
                                                                                  (and major fill projects)
                                           Existing + Potential Acidity          Existing + Potential Acidity
                                                                             Equivalent sulfur Equivalent acid
Texture range              Approx. clay Equivalent sulfur Equivalent acid
                                                                             %S oxidisable     mol H+/ tonne
McDonald et al. (1990)     content (%) %S oxidisable      mol H+/ tonne
                                                                             (oven-dry basis) (oven-dry basis)
Coarse Texture
                                ≤5             0.03               18                0.03                  18
Sands to loamy sands
Medium Texture
Sandy loams to light           5 – 40          0.06               36                0.03                  18
clays
Fine Texture
Medium to heavy clays           ≥40            0.10               62                0.03                  18
and silty clays




J000799-002-R-Rev0                                                                                  Page 16