Approvals Application Supporting Material · MCU26/0084

                                                  Noosa Harbour & Las Rias Foreshore Management Works
                                                    OFFICIAL




3 Receiving Environment and Potential Impacts

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This section presents an overview of environmental context for the site and anticipated environmental
impacts and management considerations for the works.

3.1 Water and Sediment Quality
Dredging and placement works present a risk of impacting water quality through suspension of
sediment in the water column (at the dredging site) and runoff of sediment-laden water (at the
placement site). Additionally, where dredged material contains acid sulphate soils (ASS) or
contaminants, mobilisation and exposure of this can lead to impacts in receiving environment water
quality. The waters of the dredging footprint and immediately downstream of the placement footprint are
mapped as high ecological value (HEV) lower estuary waters under WQ1401 and therefore has a
management intent of maintain indicators for all environmental values (EVs) of water. This includes
meeting the relevant water quality objectives (WQOs) for these EVs.

Sediment sampling across the Noosa River has been undertaken historically on behalf of Noosa Shire
Council, inclusive of the shoals through to the Noosa River mouth. The most recent testing was
undertaken by BMT in 2022 in accordance with the National Assessment Guidelines for Dredging 2009
(NAGD) and the National Environment Protection (Assessment of Site Contamination) Measure 2013
(NEPM). This identified the following:

•       Shoals within the Noosa River are comprised principally of sand (up to 98% of shallow sediment
        present)
•       Sediment had no concentrations of metals, metalloids or organic compounds above NAGD
        screening levels or NEPM guideline values
•       Nutrients occur at depth but mostly absent from surface material
•       Potential ASS is present in pockets/hot spots but generally at low levels and with self-neutralising
        capacity.
Based on these findings, it will be possible to undertake dredging without disturbance of ASS or
contamination but site-specific sediment sampling will be required prior to dredging to inform the exact
dredging locations. Where it is not possible to avoid ASS, material can be treated with low level
application of lime.

Similarly, it will be possible to avoid dredging of silts, clays and other material that would otherwise
create a persistent dredge and/or tailwater plume.

On this basis, the dredging and placement works are anticipated to cause only highly localised sand
plumes at the dredging and placement locations. Sand naturally falls out of suspension rapidly, with
plumes likely <100m. This may lead to temporary and isolated increases in turbidity above the
scheduled water WQO for aquatic ecosystem EV of 8 NTU but no broader changes in water quality for
the lower Noosa River.

3.2 Coastal Processes
Coastal processes within the Noosa River estuary have been extensively investigated through historical
studies and recent site‑specific assessments, including the options assessments. These investigations
confirm that shoreline behaviour at the site is governed by estuarine processes, primarily tidal currents,
channel alignment, and episodic high‑flow events, rather than open‑coast wave‑driven longshore
transport.
© BMT 2026
004024 | 001 | 00                                       13                                       10 August 2026