ADG1673.24 Dewatering Management Plan_Rev0_12.07.24

                                                                                        ADG Consulting Pty Ltd


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
           dewatering. The most appropriate action(s) shall be dependent on the stage of construction and
           risk of adverse impacts to groundwater users and the receiving environment.
          Any modification to the dewatering system and pumping rates shall be in consultation with a
           suitably qualified scientist/geotechnical/engineer.
          Following heavy rainfall all ponded surfaces waters are to meet discharge criteria (Table 3) prior to
           offsite discharge. Where discharge criteria not met, Site Manager to obtain approval from
           Dewatering Contractor regarding treating surface waters with treatment gear before offsite
           discharge.
          Pumping systems and shoring works to be maintained in fit for purpose state by Dewatering
           Contractor and/or shoring contractor. In the event that dewatering equipment has failed and is
           likely to cause a significant impact on the environment, or surrounding properties (i.e. flooding) the
           Dewatering Contractor is to be contacted immediately. The Principal Contractor, in consultation
           with the Dewatering Contractor shall be responsible in rectifying the failure in a practicable time
           frame to minimise potential impacts. Equipment, spare parts, materials and tools necessary to
           manage aspects of the system/s which present a high risk of significant impacts in the event of
           failure (if any) shall be readily available.
          Construction vibrations could potentially cause settlement in the loose upper level sands, thereby
           damaging nearby structures founded in these strata. Prior to commencement of construction on
           site (including staged works), it is recommended that a detailed dilapidation survey be undertaken
           to establish the condition of all existing adjacent structures, roads and services.




ADG1673.24 Dewatering Management Plan_Rev0_12.07.24                                                       Page 17