Attachment 6 - Stormwater Management Plan

R1767: NOOSA LANDFILL: CLEAN WATER DRAIN AND HES BASIN (SW5) – DESIGN REPORT & MAINTENANCE AND INSPECTION PLAN



Desilting is not a requirement from a compliance point, with the forebay acting as a mixing mechanism rather than a
storage or treatment volume.

6.3.2.           MAIN CELL
The main cell has a defined sediment storage volume between RL 18.30 and RL 18.60. A sump has been located in the
northern corner of the main cell to assist in desilting. Desilting is recommended to be undertaken once accumulation is
50% of the sediment storage zone. A marker post is to be installed to monitor the depth of sediment accumulation.

6.3.3.           EQUIPMENT FOR CLEAN-OUT
The concrete specification has been designed based on access via a rubber wheel/tracked Posi-track. The concrete ramps
and floor of the basin are not to be accessed by larger equipment which may exceed the design loadings.

6.4.                DESIGN EVENT & COMPLIANCE

The sediment basin has been sized as a Type A sediment basin with a design event of a 1 year ARI 24 hour storm event
equating to 136mm in 24 hours. If this event is exceeded, it is expected that outflows may exceed the EA requirements.
For events under the nominated design event, outflows are to be in accordance with the EA requirements. Where the
sediment basin is not adhering to the water quality requirements, interrogation of dosing and monitoring data should
be undertaken or advice sought from a specialist.

Table 5 – WT2 EA water quality requirements for controlled releases


               PARAMETER                          RELEASE LIMIT                                       COMMENTS


                       pH                             6.5 -9 .0                     Real-Time included on Monitoring Station

         Specific Conductance                      < 1500 uS/cm                     Real-Time included on Monitoring Station

           Dissolved Oxygen                          > 6 mg/L                       Real-Time included on Monitoring Station

   Total & Dissolved Aluminium                           N/A                               Sampling to be manual by NSC

            Suspended Solids                            < 50                       Cannot measure in the field. Correlation with
                                                                                  Turbidity to be gained by > 5 sampling events
                                                                                        during initial releases from basin.

                  Turbidity                         Correlation                    Correlation to be undertaken if not currently
                                                                                                       used




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