Appendix H - Dewatering Management Plan · MCU25/0053

                                                                                          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.

           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 additional fine media filtration to retain
            suspended sediments and/or other specific target contaminants.

           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 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 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. In the event that dewatering equipment has failed and is likely to cause a significant
            impact on the environment, or surrounding properties (E.g. 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.

           Accumulated sediments and heavy metals within the treatment system can be emptied to available
            area onsite and bulked out during earthworks or alternatively removed from site by a licenced waste
            removal contractor (sucker truck).

           Acid sulfate soils on site are to be managed in accordance with a site based ASSMP.




 ADG1777.25 Dewatering Management Plan_Rev0_01.05.25                                                        Page 17