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

        Soils (continued):             recommended that density testing of the soil is carried out to provide a better estimate of the in-
                                       situ soil density.
                                  »    As an alternative to lime treatment of excavated soils, the excavated soils may be transported
                                       offsite untreated, where disposed of at a suitably licenced landfill facility which is able to accept
                                       untreated Acid Sulfate Soil. The Acid Sulfate Soil may still require lime treatment once placed at
                                       the landfill facility, to be checked with the site owner.
                                  »    If onsite materials won from cuts below RL 5 m AHD are to be used as fill, these soils will be
                                       required to be lime treated and validated to ensure that the soil acidity has been neutralised prior
                                       to placement as fill.
                                  »    Note that higher Acid Sulfate Soil contents and soil lime treatment rates may be encountered
                                       within the untested soils between the small diameter boreholes tested. This must be understood
                                       by the contractor before excavations are carried out.
                                  »    If soil is to be disturbed below the depths tested, or outside the areas tested as indicated in this
                                       report, further soil testing will be required prior to earthworks to confirm treatment requirements.
                                  »    Soils excavated below RL 5 m AHD are to be adequately treated with lime at the recommended
                                       rates on a lime pad constructed either at the site or offsite so as to achieve neutralisation. All
                                       materials to be treated must be thoroughly mixed in thin layers typically less than 300 mm
                                       thickness with a rotary hoe or similar device. The lime pad is to be prepared by compacting a clay
                                       layer typically 300 mm thick, then constructing earth bunds around the perimeter using soils
                                       known to be free of Acid Sulfate Soils. Finally, a ‘lime guard layer’ is to be placed at a rate of
                                       5 kg/m2/300 mm layer of stockpile. The treatment area must be located away from surface water
                                       flow paths. Refer to Figure 1 found later in this ASSMP to observe an example treatment pad
                                       section.
                                  »    The contractor responsible for soil lime treatment needs to ensure the soils are adequately and
                                       properly treated with lime to ensure neutralisation.
                                  »    Once the soils are treated with lime, audit/validation testing must be carried out to ensure that
                                       the soils have been neutralised. Acid Sulfate Soils which are not neutralised during the first round
                                       of soil lime mixing will require a second round of treatment by adding lime to the soils at rates
                                       based on the results of the validation testing. Refer to the ‘Validation Testing’ section of this
                                       ASSMP for further information. Validation testing must be carried out prior to removal of the soils
                                       from the site, or replacement at the site.
                                  »    Provide earth bunds constructed using materials known to be free of Acid Sulfate Soil at locations
                                       surrounding the earthworks/development area so as to reduce the potential of surface water
                                       running off the site.
                                  »    0.5 kg of lime/m2 will be applied to the base of all excavated areas to ensure ‘hotspots’ or isolated
                                       areas not tested are neutralised.
                                  »    A lime spray will be used on excavation faces using a nominal lime:water ratio.
                                  »    500 kg of agricultural lime must be kept on site at all times in case of emergency treatment.
                                  »    The pH of any water collected within bunds or sumps is to be monitored. A pH value of between
                                       6 and 8 is to be maintained before release or reuse onsite. Note that the results of the pre-
                                       excavation groundwater pH testing may indicate a pH value outside this range which may be
                                       deemed as a ‘natural’ value based on the assessment of a suitably qualified and competent
                                       groundwater consultant. Further water criteria may apply based on Noosa Shire Council
                                       requirements and this should be checked.
                                  »    It is noted that construction materials may need to be suitably protected from the acidic soil
                                       environment. A suitably qualified and competent corrosion engineer should be contacted for
                                       further advice.
        Groundwater:              Although groundwater was not encountered in the boreholes drilled as part of the PTG Geotechnical
                                  Investigation Report, information is provided regarding groundwater monitoring as a precaution.

                                  Depending on the earthworks duration and timeline, earthworks may be carried out during wet
                                  weather periods and groundwater may rise and develop further within the soil profile. The
                                  groundwater level may also be affected by the water level in Noosa River adjacent to the site.

                                  Groundwater monitoring is recommended to check that the earthworks do not adversely affect
                                  groundwater.

                                  Where guideline values are provided, on site performance criteria for groundwater monitoring should
                                  be based on the QLD DEHP Guidelines. For any parameter values not covered in the QLD DEHP
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Document Set ID: 24149759
Version: 1, Version Date: 26/09/2025