Reference Document - Dewatering Management Plan (For Stamping) MCU25/0053 & OPW25/0074

                                                                                                               ADG Consulting Pty Ltd

                              sandy subsurface profile and proximity to the tidal canal network associated with Noosa Inlet these
                              relative groundwater levels should be expected, with higher levels during or following periods of intense
                              or extended rainfall.
                      3.2     Groundwater quality
                              No site specific groundwater investigation was undertaken as part of the Geotechnical and ASS
                              Investigations undertaken by PTG Consulting. However, ADG is of the opinion that localised monitoring
                              well data can often be misleading and does not always accurately represent the properties of the
                              groundwater that will be extracted and treated from the entire site and local surrounds during
                              dewatering. Therefore, based on numerous groundwater investigations and dewatering monitoring
                              projects that have been undertaken by ADG throughout the Noosa Coast and nearby sites in recent years.
                              Our understanding of the groundwater quality in the region is provided below:
                                  Groundwater is generally mildly acidic to neutral, with pH levels ranging from approximately 5.5 to
                                   6.5 and electrical conductivity ranging from brackish to saline between 2,000 µS/cm to
                                   48,000 µS/cm. Groundwater pH has the potential to reduce (become more acidic) following
                                   oxidisation of PASS as dewatering progresses, particularly if re‐wetting of the soils occurs.

                                  Dissolved oxygen levels in static groundwater typically range from approximately 35 – 40 %
                                   saturation.

                                  The groundwater associated with indurated sand strata is moderately to highly turbid as a result of
                                   staining and organic content.

                                  Concentrations of dissolved metals are typically below the available marine water trigger values
                                   (MWTV’s) in ANZG (2018) which supersedes ANZECC/ARMCANZ (2000) for the receiving waters,
                                   however elevated levels of aluminium and particularly iron are expected in the untreated
                                   groundwater and have the potential to increase following oxidisation of PASS as dewatering
                                   progresses or as a result of existing acidic groundwater conditions.

                                  Given the location and previous use of the site, groundwater impacts resulting from site
                                   contamination are not anticipated.

                              A groundwater investigation will be undertaken at the commencement of dewatering as described in
                              Section 6.5.2 of this report. This assessment will be representative of the groundwater being extracted
                              and treated from the entire site, as opposed to localised monitoring well data which is often misleading.
                              Based on previous experience with dewatering in the area, ADG expects the groundwater to require
                              treatment to increase pH and dissolved oxygen levels, as well as reduce turbidity, suspended sediments
                              and dissolved metal concentrations prior to being discharged to the stormwater system.




                        ADG1777.25 Dewatering Management Plan_Rev0_01.05.25                                                      Page 5




Document Set ID: 23735664
Version: 1, Version Date: 12/05/2025