13. Existing DMP (2006)

7.2 Risk Assessment & Soil management Guidelines

It is unlikely that acid sulphate soils will be an issue with this project because:
       There will be only shallow dredging of recent sand banks (<2.5 metres AHD)
       Only small volumes of sand are to be dredged per year (<5000 tons)
       Although re-suspension of deposited fines may occur, absence of pyritic fines
       at this site, reduce the likelihood of contamination of the water column (Soil
       Survey 2006).
       The areas concerned have a high tidal exchange and any acidity will be
       quickly neutralised by seawater and/or the self-buffering capacity present
       within the substrate that is high in calcium carbonate (CaCO3) mater (Soil
       Survey 2006).
       Dredge operations will be water quality monitored daily and if pH levels
       exceed WQO s then operations will cease.


Risks of ASS are identified in table 6 below.
Soil                   Method                  Issues                   ASS Risk
Dredged Sand from      Hydraulic               None                     Low
site                   separation of fines
Imported sand          Truck                   Cost, access and low     Low
                                               sand quality
Imported sand from Sand barged from            Navigation, public       Low
lower estuary      areas with no Acid          concerns, expense
                   Sulphates e.g. use
                   existing ERA at
                   river entrance or
                   sand banks off
                   Munna Point


7.3 Specific Quantities

Of the <5000 tonnes of dredged material that has been stipulated on the ERA, it is
estimated that <2000 tonnes (approximately) will need to be dredged for
replenishment purposes of stated areas that have been defined in 1.51 of this
document.




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