Attachment 4 - Geotech Report · MCU23/0030

                             50 NOOSA PARADE, NOOSA HEADS
                             PROPOSED RESIDENCE

The combined actual and potential acidity exceeded the adopted action criteria for 5 of the 8 quantitative
samples tested, confirming the presence of acidic soil within the underlying soil profile. The strength of
recorded (net) acidity ranged from 7 to 145 mol H+ per tonne.
ASS laboratory test results are summarised in Table C1 in Appendix C along with laboratory certificates.

7.4      ASS Risk Characterisation
Based on the site investigation and soil test results, fill materials encountered to a depth of 1 m BGL (approx.
RL 1.4 m) are characterised as non-ASS, and will require no specific treatment or management where
disturbed. Materials encountered below a depth of 1 m BGL were found to contain levels of PASS which
exceed the action criteria. It is noted that proposed bulk excavation for basement construction will extend to
a depth of about 3 m BGL (approx. RL -0.6 m) and will therefore involve disturbance of material containing
PASS. Where disturbed, these materials will require treatment to neutralise the ASS hazard.
Proposed basement construction is also expected to involve excavation extending below the observed
groundwater table. Design and construction of a temporary retention system will be required to effectively
mitigate the risk of ground settlement and/or oxidation of possible in situ ASS in areas adjacent to the subject
site. The use of a suitably designed and constructed perimeter cut off wall should also help reduce volumes
of groundwater inflow, which will aid in managing onsite construction water prior to discharge.
Recommended site management measures are described in Section 8.


8.0      ACID SULFATE SOIL MANAGEMENT PLAN
The primary objective of this management plan is to provide a framework to allow the proposed works to
proceed without adverse environmental impacts related to the disturbance of ASS. To successfully achieve
this objective, the following issues shall be addressed:
       Mitigation of risk associated with ASS present in disturbed soil (via neutralisation of disturbed soil
        and successful verification testing);
       Containment, testing and treatment (where necessary) of any water collected during the excavation
        and/or during the treatment processes; and
       Limitation of any alteration to the existing groundwater conditions and appropriate treatment of any
        collected groundwater before re-use, offsite discharge or disposal.

8.1      Training and Orientation
Appropriate training should be provided to all Contractors staff involved in earthworks on the site, to be
delivered as part of site induction. Sessions should be conducted prior to the commencement of earthworks
and at other such regular intervals as required to ensure staff are fully aware of the requirement for field
management of ASS and associated waters, the management strategies to be implemented, and their roles
and responsibilities in achieving the desired management outcomes.

8.2      Management of Disturbed Material
Material encountered from the existing ground surface level to a depth of 1.0 m BGL presents no net
ASS risk and may be excavated and removed from site without need for specific ASS management
measures.
Material excavated or otherwise disturbed below a depth of 1 m BGL will be treated to neutralise the levels of
potential acidity present including a factor of safety of 1.5.
Neutralisation of disturbed soil will generally be undertaken within the basement excavation where erosion
and sediment control measures will be in place to prevent any uncontrolled spills or releases. This is
consistent with general site control requirements for erosion and sediment control during construction and
should not pose any additional effort on the part of the Contractor to implement.


2 February 2023
Report No. 22500-001-Rev0                              15