Compiled Reference Document - MCU25/0020 (As Published)

ADG Consulting Pty Ltd

 

3.2.1 Soils

A total of two boreholes (BH1 and BH2) were drilled to 3.5m in depth. Shallow fill material encountered
comprised brown, fine to coarse grained medium-dense sands to between 0.0m and 2.0m in depth.
Underlying fill materials comprised similar material with increasing moisture (saturated) from 2.1m to
the termination depths of 3.5m in both boreholes. Global makes mention that the encountered fill was
likely placed a significant number of years prior and that the site may be underlain with deep settling
marine clays.

3.2.2 Groundwater

3.3

3.4

Groundwater was intercepted in both boreholes (BH1 to BH2) at approximately 2.1m below the ground
surface at the time of the investigation (July 2016). No analysis of ground water was conducted as part
of the investigation. No steady groundwater levels were obtained, however given the site location and
highly permeable soils, groundwater levels are anticipated to be directly influenced by tidal variation in
the canal (adjacent to site). 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. It is also noted that no acid sulfate soil (ASS)
investigation was undertaken alongside the soil classification investigation for the site.

Therefore, as part of the groundwater monitoring program, untreated groundwater will be sampled as
part of the pre-discharge monitoring (and then as required) to detect any potential in-situ oxidation of
potential ASS, and potential contingencies such as reinjection of groundwater to minimise oxidation will
be recommended if required.

STA Consulting Engineers 2016

A Site Investigation was undertaken on the adjacent site at 9 Ravenwood Drive by STA Consulting
Engineers (STA) in September 2016. A total of two boreholes (BH1 and BH2) were drilled to between 2.0m
and 2.6 m in depth. Subsurface material encountered comprised brown, orange-brown, medium-dense
to dense silty sands to between surface level and termination depths in all boreholes.

No groundwater seepage was indicated on the bore log sheets provided however the subsurface material
was logged as being wet from approximately 1.6m in depth in both boreholes.

No additional relevant information can be summarised from this report in relation to the dewatering
operations for the project.

Groundwater quality

No site-specific groundwater quality data was provided to ADG to assist with the preparation of this DMP,
however 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:

— 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 yS/cm to
48,000 uS/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) provided in 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.

 

ADG1786.25 Dewatering Management Plan_Rev1_07.10.25 Page 5