ADG1290.21 Dewatering Management Plan_Rev1_02.02.22 · OPW21/0315

                                                                                          ADG Consulting Pty Ltd




     Tertiary treatment – may be required following initial testing of extracted groundwater.
     A filtration treatment system with specialised fine filtration media and chlorine dosing will be utilised to
     provide the required heavy metal removal (specifically for total and dissolved iron) where not
     precipitated and retained within the sedimentation tank/s (secondary treatment). This treatment system
     will provide tertiary treatment of the groundwater prior to offsite discharge. This type of fine media
     filtration treatment system is a forced‐flow system under pressure, and generally capable of treating flow
     rates of up to 20 L/sec per filtration unit (therefore residence time is inconsequential to treatment quality
     achieved).

     Tertiary treatment will only be required if the required water quality is unable to be achieved following
     primary and secondary stages of treatment. Subject to the results of field and laboratory testing during
     the pre‐discharge monitoring event.


6.4.2 Dewatering strategy
     The Site Manager, Dewatering Contractor and ADG Consulting must formulate a dewatering strategy to
     ensure that the dewatering treatment system is sufficient to meet the requirements of the project and
     that the necessary equipment can be accommodated within the site prior to the commencement of
     dewatering. Where the construction of the proposed development requires occupation of the road
     reserve (verge area and/or road formation) for either short term or long term, a road reserve permit must
     be obtained from Council prior to any occupation of the road reserve, in accordance with RAP21/0020
     Part 5 Condition 9.
6.4.3 Initial pump‐out
     Prior to discharge of any extracted groundwater to the canal system, the following pre‐dewatering
     procedure will be undertaken:

     1. The basement area will be excavated down to the standing groundwater level.
     2. The initial dewatering discharge will be directed (via the treatment systems) into the excavation and
        allowed to infiltrate/recharge the aquifer. This process will provide initial clarification of the extracted
        groundwater as disturbed sediment loads are typically reduced following the initial pump‐out.
     3. Samples of the treated groundwater will be recovered and analysed for the parameters detailed in
        Table 3 and Table 4.
     4. The extracted groundwater will be directed into the canal system following confirmation that the
        water quality complies with the discharge criteria.
6.5 Monitoring
6.5.1 Visual monitoring
     Visual inspections of the site and dewatering equipment shall be undertaken daily by the Site Manager
     to identify the following:
              Quantity of chemical product within the dosing system
              Effective operation of all dewatering treatment equipment
              Short circuiting of water around baffles and filter media in sediment tanks, where required to
               be installed.
              Visible hydrocarbon sheens and odours
              Green blue or extremely clear water indicating high levels of dissolved aluminium.
6.5.2 Water quality monitoring
     Water quality monitoring will be undertaken for the duration of dewatering activities at the site by a
     suitably qualified and independent person. The monitoring will include analysis of the extracted



ADG1290.21 Dewatering Management Plan_Rev1_02.02.22                                                          Page 14