Compiled Reference Document - MCU25/0020 (As Published)

ADG Consulting Pty Ltd

 

3. Previous investigations
This DMP is based on site and locality specific information sourced from the following information
provided to ADG by SCG Consulting Engineers and/or otherwise sourced by ADG:
=  Geo-environmental Investigation, Proposed Residence, 11 Ravenwood Drive, Noosa Heads. Tectonic.
June 2025. Ref. 25040-001-Rev1.
— Site Classification Report, Proposed Residence 11 Ravenwood Drive, Noosa Heads. Global Testing,
August 2016, Ref: 16/0686.
— Foundation Design Report, Lot 1 9 Ravenwood Drive, Noose Heads. STA Consulting Engineers,
September 2016, Ref: ES137382-B.
— River Oasis, DA Issue C, design plan set. Chris Clout Design. 3 October 2025 (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 Tectonic Geotech 2025
A Geotechnical and Acid Sulfate Soils (ASS) Investigation was undertaken at the site in February 2025 by
Tectonic to assess ground conditions for the currently proposed development.
3.1.1 Soils

A total of two boreholes (BH1 and BH2) were drilled to 15 and 16.5 m in depth. Shallow fill material
encountered comprised loose to medium dense silty sand fill containing gravel and deleterious materials
(cobbles, building materials) to depths of 2.3 to 3.0 mbgl, overlying medium dense to very dense sands
overlying stiff clays at depth. A firm sandy/silty clay layer was encountered between 4.8 and 5.5 mbgl in
both boreholes, with some loose sands above.

A total of 32 samples were obtained and laboratory analysed for field screening of ASS, with six of these
selected for further analysis using the Chromium Reducible Sulfur (CRS) suite. Results reported by
Tectonic indicate that some degree of ASS is present within the existing fill and natural sand materials to
4 mbgl (noting some acid neutralising capacity is present within this part of the soil profile), with an
unquantified acid generating potential for deeper soils, noting the ASSMP included by Tectonic indicates
further testing for liming rates is required during construction, as no assessment of ASS beyond 4 mbgl
was undertaken by Tectonic.

3.1.2 Groundwater

3.2

Groundwater seepage was encountered in both boreholes (BH1 to BH2) at approximately 1.8 — 2.0m
below the ground surface at the time of the investigation, with standing groundwater measured in a
standpipe in BH1 at 1.8 mbgl. No analysis of ground water was conducted as part of the investigation.
However, groundwater levels are anticipated to be directly influenced by tidal variation in the canal
(adjacent to site). A groundwater sample obtained by Tectonic was lab analysed and reported to contain
high levels of total and dissolved aluminium and iron, and strongly alkaline (pH 10) which may affect
water quality during dewatering, and/or worsen as dewatering progresses in acid sulfate soil conditions.

Global Testing 2016

A Site Classification Investigation was undertaken at the site in August 2016 by Global Testing (Global) to
assess the soil suitability for slab and footing establishment associated with a previously proposed
development. ADG notes the relevance of this report is limited due to the age of the report, and fact that
the site was developed with a residential premises including basement carparking in 2018, which has
since been demolished as of October 2024.

 

ADG1786.25 Dewatering Management Plan_Rev1_07.10.25 Page 4