Reference Document - Acid Sulfate Soil Management Plan (For Stamping) MCU25/0053 & OPW25/0074

       In accordance with the ‘Queensland Acid Sulfate Soil Technical Manual – Soil Management Guidelines Version 5.1’ (Qld
       Government, 2024), a “Very High Level of Treatment” is required at this site based on:

       »      Approximately 800 tonnes of soil to be disturbed below RL 5 m AHD; and
       »      Highest recorded net acidity value of 90 mol H+/t in the ground surface to 3.5 m depth range.

       As a “Very High Level of Treatment” is required, an Environmental Management Plan and closure report are also required in
       accordance with the information presented in the ‘Queensland Acid Sulfate Soil Technical Manual – Soil Management
       Guidelines Version 5.1’.

       An experienced, competent and suitably qualified soil scientist or engineer must be present onsite to ensure that the lime
       treatment activities including validation testing, and groundwater monitoring (where required), described in this ASSMP are
       followed onsite.

       5.3.1 Background
       It should be noted that Acid Sulfate Soils are typically observed in the field as a grey, or dark grey brown to black soil in colour,
       sometimes with a yellow mottle. Acid Sulfate Soils may also emit a hydrogen sulfide (‘rotten egg smell’) gas/odour, especially
       when the soil is disturbed such as during earthworks and excavation operations.

       The aims of the ASSMP are as follows:

       »      Analysis of the data from the investigation and assess the severity of Acid Sulfate Soil within the project area and formulate
              a suitable lime treatment regime for the soils to be disturbed by earthworks, and reduce the potential for acid generation
              due to the site earthworks; and
       »      Monitor groundwater (where encountered) during earthworks.

       In order to reduce the potential for acid generation due to the proposed earthworks, soil treatment and groundwater
       monitoring (where required) should be carried out in accordance with the information presented in Section 5.3.2 of this
       ASSMP as follows.

       5.3.2 Recommended Management of Acid Sulfate Soils & Groundwater
       The proposal to manage Acid Sulfate Soil and groundwater (as required) as part of the planned site earthworks below
       RL 5 m AHD covers the following issues, which are detailed further in Table 1.

       Table 1: Acid Sulfate Soil Management for Proposed Site Earthworks
           Issue:                 Acid Sulfate Management and Treatment, Groundwater Monitoring and Potential Treatment

           Operational Policy:    To effectively manage the Acid Sulfate Soils and groundwater at the site and avoid any adverse
                                  environmental impacts before, during and after site earthworks.
           Performance            »    Validation sampling indicates that the appropriate treatment procedures have been employed
           Criteria:                   such that results of these tests do not exceed the Action Criteria levels of 18 mol H+/tonne,
                                       assuming that more than 1000 tonnes of soils are disturbed below RL 5 m AHD.
                                  »    Groundwater should be monitored for depth/level, pH, Electrical Conductivity, aluminium
                                       content and iron content, before, during and after the earthworks period. On site performance
                                       criteria for water monitoring should be based on the Queensland Water Quality Guidelines 2009
                                       (revised in 2013), herein referred to as the ‘QLD DEHP Guidelines’ (DEHP, 2013). For any
                                       parameter values not covered in the QLD DEHP Guidelines, refer to the Australian and New
                                       Zealand Guidelines for Fresh and Marine Water Quality (ANZECC and ARMCANZ, 2000).
           Soils:                 Based on the soil test results, it is recommended that:

                                  »    The earthworks are managed by a reputable and suitably qualified consultant experienced in the
                                       field of Acid Sulfate Soils and treatment.
                                  »    Soils excavated below RL 5 m AHD in the existing fill profile will require lime treatment. The lime
                                       treatment rate for soils excavated in the existing fill profile is 4 kg/tonne (6.8 kg/m3). The values
                                       presented as kg/m3 assume a bulk density conversion factor 1.7 t/m3.
                                  »    A bulk density factor will be required to convert from kg/tonne to kg/m3. A bulk density
                                       conversion factor of 1.7t/m3 has been used in the absence of soil test results, however it is

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Document Set ID: 24149759
Version: 1, Version Date: 26/09/2025