Dewatering Management Plan · OPW24/0032

                                                                                          ADG Consulting Pty Ltd


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.
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 2 and Table 3.
     4. The extracted groundwater will be directed into the stormwater 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
     groundwater, treated discharge water and off‐site monitoring in the receiving waters (in the mixing zone
     within a 20 m radius of the discharge point). The exact location within the receiving waterway (Noosa
     River) is to be confirmed, however it is anticipated to be directly south/adjacent of the site. Background
     water quality monitoring of field parameters will also be conducted during each sampling event, if
     applicable. Background samples will be recovered from the river, either upstream or downstream from
     the receiving water location (tide dependant).

     The proposed monitoring locations are shown in Figure 1, Appendix A are a subject to confirmation
     following mobilisation of dewatering gear to site.

     Monitoring will be undertaken at the following frequencies:


          Daily monitoring of field parameters (pH, electrical conductivity, dissolved oxygen, temperature and
           turbidity) in the treated discharge water and pH of the untreated extracted groundwater (to
           determine potential acidification). Daily monitoring will be undertaken by a suitably trained site
           employee under the supervision of the Site Manager.




ADG1304.21 Dewatering Management Plan_Rev0_08.10.21                                                          Page 13