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

J000154-001-R-Rev0                                                                                November 2015


6.7       Extent and Severity
The results from this investigation indicate that the fill materials across the site have a low likelihood of
containing existing, actual or potential acidity. However, based on the testing carried out to date soils with
actionable levels of potential acidity appear to be limited to the natural soils below 2 m.
The SPP14 Guidelines require that the level of treatment for management of ASS is based on treatment of
all existing and potential acidity. The results of the laboratory testing have been accumulated in an Acid-
Base Account to give the Net Acidity for each sample in units of mol H+/tonne as presented in Table B1.
This value has been calculated from sulfur trail potential acidity (SCr) plus actual acidity (TAA).
Liming rates have been calculated in kg CaCO3/t and kg CaCO3/m³ using a factor of safety (fineness factor)
of 1.5 and an assumed bulk density of 1.8 tonne/m3. Calculation of liming rates required for full
neutralisation of combined actual and potential acidity are presented in Table 4, below.
Table 3: Preliminary Liming Rates
 Location                        Soil Type                            Depth                Treatment Rate

 Fill material across the site   Sand, yellow and pale grey           0.0 m – 2.0 m bgl    No Treatment
                                                                      (approx.)            Required

 Natural material across the     Sand, pale grey to dark grey         2.0 m – 3.5 m bgl    31 kg CaCO3/m³
 site                            with silt


6.8       Risk Assessment
As excavations for the proposed basement will intersect soils with potential acidity, there will be a
requirement for management of that acidity.
Information provided to Core indicates that a majority of the basement excavation will be within the fill
material with approximately 0.5 m of excavation within the natural material. It is expected that approximately
200 m3 of excavated material will be natural and require treatment. The likely volume of disturbance
indicates that management of potential acidity at this site would be classified as Very High (VH) treatment
(5 to 25 tonnes of aglime) in accordance with Queensland Soil Management Guidelines V4.0 - Table 4.2
The SPP14 Guidelines require that for Category VH treatment a stand-alone Acid Sulfate Soil Management
Plan (ASS MP) must be provided. Recommendations on strategies to be included in the ASS MP are
outlined below in Section 7.0.
Based on the results of the investigation and the proposed earthwork, the risk of impact to the surrounding
environment is considered low to moderate. Provided that the management measures outlined in Section 7.0
of this report are adhered to and an ASS MP is prepared for the project and implemented, the environmental
risk will be reduced further.

7.0      RECOMMENDATIONS
The results of this investigation indicate there is the likelihood of disturbance of soils with high levels of
potential acidity associated with the basement excavations. It is recommended that an ASS MP be
developed and implemented. Recommendations on strategies to be included (as a minimum) in any such
ASS MP should include:

     Excavated soil must be managed by neutralisation of potential acidity. Good quality agricultural lime
      should be thoroughly mixed with the spoil. Any lime treatment should be carried out in accordance with
      Queensland Acid Sulfate Soil Technical Manual, Soil Management Guidelines (Ver. 4.0. 2014).

     Lime neutralisation treatment rates and methodologies should take into account the acid tolerant nature
      of some species in the immediate receiving environment.




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