RFI - Attachment E - Acid Sulfate Soil Management Plan · MCU25/0053

Groundwater    guidelines, refer to the Australian and New Zealand Guidelines for Fresh and Marine Water Quality
(continued):   (ANZECC and ARMCANZ, 2000).

               The groundwater should be monitored before, during, and after earthworks have been completed,
               based on the following test criteria:-

               »   Groundwater testing should be carried out before the earthworks begin to establish baseline
                   testing values for groundwater level, pH, Electrical Conductivity, aluminium content and iron
                   content. Pre-development ‘baseline’ values should be recorded by a suitably qualified and
                   competent consultant as close as possible to, and before the first day of earthworks.
               »   Groundwater will be required to be monitored for groundwater level, pH, Electrical Conductivity,
                   aluminium content and iron content during the earthworks period, and prior to discharge from the
                   site.
               »   A groundwater sample should be obtained by a suitably qualified and competent groundwater
                   consultant as soon as possible after the earthworks period has been completed to monitor any
                   change in the groundwater level, pH, Electrical Conductivity, aluminium content and iron content.
               »   Groundwater pH should be monitored on daily basis and prior to discharge, and range between
                   pH 6 and pH 8 (‘National Acid Sulfate Soils Guidance – National acid sulfate soils sampling and
                   identification methods manual, June, 2018’, Australian Government, 2018), unless an assessment
                   by a suitably qualified and competent groundwater consultant deems there to be an alternative
                   ‘natural/baseline’ range which can be used.
               »   Electrical Conductivity (EC) should be monitored on a daily basis and prior to discharge, and
                   should be less than 520 µS/cm (QLD DEHP, 2013).
               »   Dissolved and Total Aluminium (Al) content monitored on a weekly basis and prior to discharge,
                   and should be less than 0.055 mg/L (ANZECC and ARMCANZ, 2000).
               »   Dissolved and Total Iron (Fe) content monitored on a weekly basis and prior to discharge, and
                   should be less than 0.3 mg/L (ANZECC and ARMCANZ, 2000).
               »   It is recommended that a suitably qualified and competent groundwater consultant be contacted
                   for further information on groundwater testing, monitoring and any treatment requirements
                   before earthworks are carried out on the site, and where the groundwater test results do not meet
                   the required test criteria.
               »   Specific groundwater monitoring criteria may need to be achieved to satisfy Noosa Shire Council
                   before water is discharged offsite and this should be checked.
               »   Specialist, competent and suitably qualified groundwater consultants should be contacted prior
                   to the proposed earthworks and any dewatering.
               »   As a precaution, excess agricultural lime should always be kept as a standby measure to treat any
                   acidic groundwater produced during earthworks. Hydrated lime is not recommended for
                   groundwater treatment, as this material can have adverse effects on water such as producing
                   highly alkaline groundwater with pH levels greater than pH 9 or pH 10. A suitably qualified and
                   competent groundwater consultant should be contacted should groundwater pH or other
                   groundwater monitoring test results suggest that groundwater treatment is required.
Monitoring:    Three phases of Acid Sulfate Soil testing will be undertaken:

               »   Phase 1 – In-situ testing (completed).
               »   Phase 2 – Groundwater level and pH monitoring before, during and after earthworks (where
                   required), and
               »   Phase 3 – Validation testing of lime-treated material.

               Areas exposed during the development shall be monitored daily for evidence of iron staining of soils
               and water, yellow efflorescence on soil surface, sulfurous odours (“rotten egg gas”) and low soil pH.

               Once the soil excavated as part of the proposed earthworks below RL 5 m AHD is lime treated at the
               required rates, a suitably qualified and competent environmental or geotechnical consultant is to be
               contacted to ensure validation sampling and testing of the lime treated soil is carried out. This process
               ensures that the lime has been thoroughly mixed through the Acid Sulfate Soil and that the acidity has
               been neutralised. Once the lime treated soil is validated, it may be transported or used offsite, subject
               to further contamination, geotechnical or other quality testing as required.

               Refer to the ‘Validation’ section of this ASSMP for further information on validation testing.

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