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

                                                                                        ADG Consulting Pty Ltd

     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.




ADG1808.25 Dewatering Management Plan_Rev0_07.05.25                                                       Page 9