ADG1673.24 Dewatering Management Plan_Rev0_12.07.24

                                                                                         ADG Consulting Pty Ltd


3    Previous investigations
     This DMP is based on site specific information sourced from the following, provided to ADG by
     SCG Consulting Engineers:
             (Preliminary) Geotechnical Investigation, Proposed Residential Development, 25 Wyuna Drive,
              Noosaville. June 2024. PTG Consulting. Ref: PTG/00259 – 0001 – Rev0.
             Operational Works for Residential Development: Earthworks Plan – 25 Wyuna Dr, Noosaville, QLD.
              Drawing set May 2024, SCG 0282‐CD Issue 1, (particularly Drawing 0282 ‐OW3.1). SCG Consulting
              Engineers Pty Ltd (Refer Appendix C).
     It is noted that dilapidation reports for surrounding structures and services are proposed to be
     undertaken prior to commencement of construction and dewatering, however are to be provided to
     Council separately from this DMP.

     A brief discussion of relevant soil and groundwater conditions is provided below.
3.1 PTG Consulting 2024
     A preliminary Geotechnical Investigation and concurrent Acid Sulfate Soils Investigation was undertaken
     at the site in May 2024 (reported June 2024) by PTG Consulting.
3.1.1 Soils
     A total of one (1) borehole (BH1) was drilled on the proposed development footprint to 6.0 mbgl.

     The subsurface profile encountered is generally described as silty sand fill material at the ground surface,
     extending to the depth of 2.6 m. Fill material is underlain by natural sand and silty sand which is initially
     loose, becoming denser with depth, extending to depths ranging between 2.6 m to the 6.0 m termination
     depth.

     Alongside the Geotechnical Investigation (2024), Acid Sulfate Soil (ASS) samples were collected at 0.5 m
     intervals in BH1 to 6.0 m depth. A total of twenty‐four (24) samples were collected for ASS screening and
     four (4) samples were selected for further analysis by the Chromium Reducible Sulfur suite (CRS).

     ADG notes that the testing was limited to one borehole with ASS testing to 6.0 m depth, and PTG reports
     that within part of this depth profile the natural sands are considered to contain potential ASS requiring
     liming at rates of up to 12 kg/tonne. Additionally, on‐site fill material is considered to contain potential
     ASS requiring limiting rates of to 3.6 kg/tonne. All excavated spoil from depths below RL 5 m AHD within
     the excavation footprint will be appropriately neutralised with lime and validated in accordance with
     recommendations by PG in the ASS Investigation Report (PTG, 2024).
3.1.2 Groundwater
     During drilling activities for the Preliminary Geotechnical Investigation, groundwater seepage/inflow was
     encountered at 2.4 m depth below the ground surface (PTG, 2024) (inferred approx. 0.3 m AHD from SCG
     OPW civil drawings).

     It should be noted however, that groundwater depths and ground moisture conditions are affected by
     weather and climatic conditions, tidal variations, surface and subsurface drainage/permeability
     conditions, and human influence and will therefore vary with time. Groundwater levels are expected to
     be similar to the water level in the river to the north, albeit somewhat a dampened response to tidal
     variations.
3.2 Groundwater quality
     No groundwater quality data was obtained by PTG as part of the preliminary geotechnical investigation.
     However, based on numerous groundwater investigations and dewatering monitoring projects that have
     been undertaken by ADG throughout the Noosa Coast Region in recent years, our understanding of the
     groundwater quality in the region is provided below:


ADG1673.24 Dewatering Management Plan_Rev0_12.07.24                                                         Page 4