Reference Document - OPW23 0189

                                                                                        ADG Consulting Pty Ltd



        Laboratory analysis of samples recovered from   Initially, then as                     Environmental
                                                                             ADG Consulting
        extracted groundwater (pre‐treated)                 required                             Consultant

6.6   Maintenance
      The groundwater treatment systems must be regularly maintained. Maintenance must include:
           Regular cleaning and or replacement of the filters within the filtration unit, where required to be
            installed.
           Regular removal of sediment from the sedimentation tank. The sediment must be either returned
            to the excavation pit for dewatering and bulking out with excavated material, or removed from the
            site by a licensed liquid waste contractor.
           Regular check of the dosing system and top‐up of buffering solutions and flocculants.
6.7   Reporting
      Dewatering management procedures and monitoring results will be reviewed by ADG Consulting weekly
      to ensure that the treatment procedures are effective, and that the receiving waters are not being
      impacted by the extracted groundwater being discharged.

      The following reporting procedures will be adopted:
           A summary report will be prepared upon completion of the initial pre‐discharge monitoring. The
            report will be submitted to the Site Manager, Dewatering Contractor, and NSC upon request.
           Weekly interim reports will be prepared upon receipt of laboratory data for each round of ongoing
            compliance monitoring. The interim reports will display all data obtained during the previous
            monitoring event, and provide comments and recommendations based on the results.
           A dewatering compliance report will be prepared on completion of the project (upon request).
      The above reports will be prepared by ADG Consulting and provided to the Site Manager and Dewatering
      Contractor as they become available. The reports will include all water quality results and comparison to
      the WQOs, corrective actions and recommendations made to the Site Manager and Dewatering
      Contractor during the monitoring period.

      The Site Manager must keep records of complaints, volumes of chemicals used and treatment methods
      employed. These records must be available on‐site at all times and submitted to NSC by the Site Manager
      upon request.
6.8   Contingencies
      If water quality monitoring indicates ongoing exceedances of the performance criteria, and the water
      quality objectives for the receiving waters cannot be met, then corrective actions will be adopted as
      necessary. Possible contingencies may include one or more of the following:
           Installation of additional sedimentation tanks to provide increased residence time and assist with
            the retention of precipitated iron hydroxides, other heavy metals and/or suspended sediments.
           Installation of additional flocculant and/or coagulant dosing systems to assist in precipitation of
            suspended sediments and/or heavy metals.
           Installation of activated carbon filtration or other fine media filtration to retain suspended
            sediments and/or heavy metals.
           Install a floating sediment curtain/s around the stormwater termination point in the receiving
            waterway to prevent unsightly plumes and contain sediment and/or heavy metals for periodic
            removal (subject to approval by Noose Shire Council).
           Preventive and corrective actions shall be taken in the event that groundwater monitoring
            observations indicate that unexpected groundwater contamination has been encountered during



 ADG1580.23 Dewatering Management Plan_Rev0_28.09.23                                                    Page 15