Reference Document - Dewatering Management Plan (For Stamping) MCU25/0053 & OPW25/0074

                                                                                                                 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




Document Set ID: 23735664
Version: 1, Version Date: 12/05/2025