ADG1304.21 Dewatering Management Plan_Rev1.1_17.12.24

                                                                                                          ADG Consulting Pty Ltd


     Table notes:
     1. DES (2022). Noosa River environmental values and water quality objectives (canal, harbour or marina).
     2. ANZG (2018). Supersedes ANZECC/ARMCANZ (2000) ‐ Marine water trigger values for 95% species protection.
     3. Criteria subject to expected condition in Development Application (DA) notice by Noosa Shire Council.
     * = Insufficient data to derive a reliable trigger value. Low reliability value adopted (refer ANZECC/ARMCANZ (2000) Section
     8.3.7.

     Although ADG has not been provided a copy of the DA notice and conditions for the proposed
     development, based on previous dewatering projects in the Sunshine/Noosa Coast Region it is expected
     that total iron and aluminium concentrations as listed in Table 3 (above) are likely to be conditioned by
     Noosa Shire Council for compliance. It should be noted, that these concentrations are considered to be
     onerous with respect to the risk‐based (worst‐case) bioavailable trigger value criteria contained in ANZG
     2018 & ANZECC/ARMCANZ (2000) for marine water (moderately disturbed) 95% species protection, and
     are likely to be difficult to achieve given the groundwater conditions encountered in the locality on
     previous dewatering projects on the Sunshine/Noosa Coast.

     Prior to discharge to the stormwater system or any waterway, discharges are to be tested to meet the
     requirements of the ANZG 2018 & ANZECC/ARMCANZ (2000) Guidelines for Fresh and Marine Water
     Quality. There is currently no chemical toxicant trigger value criteria available for total or dissolved (i.e.
     bioavailable) concentrations of aluminium or iron for marine or estuarine waters under the Australian
     and New Zealand Guidelines for Fresh and Marine Water Quality Guidelines (ANZG 2018 &
     ANZECC/ARMCANZ 2000 – i.e. ANZECC Guidelines) or the Guidelines for Managing Risks in Recreational
     Waters (NHMRC 2008), with regards to managing environmental impacts to the waterway.

     In addition, Section 5 (Guidelines for recreational water quality and aesthetics) of the ANZECC/ARMCANZ
     (2000) Guidelines (per section 5.2 thereof) was superseded by the Guidelines for Managing Risks in
     Recreational Water in 2008 (NHMRC, 2008). Therefore, a reference to the ANZECC/ARMCANZ (2000)
     Guidelines is by association and extension a reference to the current 2008 NHMRC Guidelines. The 2008
     NHMRC Guidelines contain no criteria for aluminium, and only includes an aesthetic criterion for iron –
     noting this is an aesthetic criterion derived from the Australian Drinking Water Guidelines on the basis of
     ingesting 2L of the recreational water solution per day. ANZECC/ARMCANZ (2000) Section 5.2.3.3, notes
     that as a general guideline, under Toxic Chemicals, ‘Higher concentrations of toxicants may be tolerated
     occasionally if it assumed that no person will ingest more than a maximum of 100 mL water during a
     normal swimming session (NHMRC 1990) compared with 2L/d for potable water’, and Section 3.1.1.3,
     under Risk based approach of the guidelines, ‘The guideline trigger values are based on bioavailable
     concentrations, and hence are relatively conservative when compared with total concentrations in the
     field, so the use of the decision frameworks will increase guideline concentrations in most cases’.
     Therefore, any chemical toxicant trigger values would require reassessment and likely increase upwards
     of any ANZG 2018 &/or ANZECC/ARMCANZ (2000) Guideline trigger values due to the slightly to
     moderately disturbed nature (and thereby reduced sensitivity) of the receiving waters.

     In conditioning more onerous criteria, rather than the available marine chemical toxicant trigger value
     criteria contained within the ANZG/ANZECC Guidelines, an unachievable constraint may be placed on the
     development. This DMP has allowed for contingency measures to be incorporated into the treatment
     and discharge system if required, including silt curtains to be installed within the receiving waterway
     surrounding the discharge location, or further onsite treatment measures such as filtration, to prevent
     and/or minimise as far as reasonably practicable the potential for release of suspended solid loads into
     the broader receiving waterway.




ADG1304.21 Dewatering Management Plan_Rev1.1_17.12.24                                                                               Page 8