RESPONSE TO FURTHER ADVICE - ADG1808.25 Dewatering Management Plan_Rev0_07.05.25 · MCU25/0054

                                                                                            ADG Consulting Pty Ltd


1        Introduction
         ADG Consulting Pty Ltd (ADG) was engaged by Ross Palazzesi care of SCG Consulting Engineers to prepare
         a Dewatering Management Plan (DMP) for the proposed residential duplex development within property
         described as Lot 3 on RP3813, situated at 20 William Street, Noosaville, Queensland.
1.1      Proposed development
         It is understood the proposed development will comprise of a three‐storey residential duplex building
         over a single level in‐ground basement car park with car turntable.

         Based on information provided by SCG Consulting Engineers, existing ground levels across the proposed
         basement footprint are approximately RL 1.35 m Australian Height Datum (AHD). Excavations to facilitate
         the basement construction are proposed to extend to an approximate depth of 2.05 m below existing
         ground level (bgl), corresponding to an approximate elevation of ‐0.7 mAHD (allowing for up to 325 mm
         raft slab and 75 mm blinding layer for basement finished floor level of ‐0.3 mAHD). Localised deeper
         excavations will be required to facilitate other structural elements (i.e. car turntable, pile caps and
         footings), where required.

         During a geotechnical and acid sulfate soil investigation on the site in March 2025, no groundwater was
         recorded in the drilling of boreholes to depths of up to 3.0 mbgl (PTG Consulting, 2025). However, ADG
         notes that groundwater levels can be perched and fluctuate seasonally and during heavy rainfall events.
         Due to the site’s close proximity to the tidal Noosa River and the permeable nature of the silty sand soils
         encountered, this increases the likelihood of groundwater fluctuations. In addition, ADGs recent previous
         experience in the locality has generally identified standing groundwater at or around RL 0.5 to 1.0 mAHD,
         and given the 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. Dewatering will therefore be necessary to allow the basement and other
         structural elements to be constructed in dry conditions.
1.2      Relevant guidelines
         The DMP was prepared with reference to the following documents:

              Australian and New Zealand Guidelines for Fresh and Marine Water Quality 2018. Australian and
               New Zealand Governments and Australian state and territory governments, Canberra ACT, Australia
               (ANZG, 2018), which supersedes Australian and New Zealand Guidelines for Fresh and Marine Water
               Quality, Australian and New Zealand Environment and Conservation Council and Agriculture and
               Resource Management Council of Australia and New Zealand (ANZECC/ARMCANZ). 2000.

              Environmental Protection (Water & Wetland Biodiversity) Policy 2019. Queensland Government.
               2019.

              Guidelines for Managing Risks in Recreational Water. Australian Government, National Health and
               Medical Research Council (NHMRC). 2008.

              Monitoring and Sampling Manual 2018, Version 2 June 2018. Department of Environment and
               Science (DES). 2018.

              Noosa River environmental values and water quality objectives. Department of Environment and
               Science (DES). 2022.

              National Environment Protection (Assessment of Site Contamination) Measure 1999, (as amended
               May 2013). National Environment Protection Council (NEPC). 2013.

              Queensland Water Quality Guidelines 2009, Version 3. The Department of Environment and
               Heritage Protection (DEHP). 2013.


    ADG1808.25 Dewatering Management Plan_Rev0_07.05.25                                                       Page 1