AS PUBLISHED Negotiated Decision Notice MCU23 0094 · MCU23/0094

                              i.       Implement drainage and erosion control measures (including contingency
                                       measures), prior to rainfall, which prevent or minimise rill erosion and gully
                                       erosion.
                              ii.      Ensure clean stormwater is diverted/managed around or through the site without
                                       increasing the concentration of total suspended solids or other contaminants in
                                       the flow and without causing erosion (on-site or off-site). If it is not feasible to
                                       divert all areas discharging clean stormwater around or through the site, the clean
                                       stormwater runoff is managed in the same manner as contaminated stormwater
                                       runoff and ensures that sediment basins are sized to accommodate the additional
                                       volume of runoff.
                              iii.     Prior to each rainfall event ensure concentrated stormwater flow paths are
                                       provided with capacity in accordance with IECA (2008) Table 4.3.1 and do not
                                       cause water contamination, rill or gully erosion, sedimentation or damage to
                                       structures or property
                      c.      Minimise sediment released from the site
                              i.       All site sub-catchments greater than 2,500m2 in area, are to be provided with
                                       sediment controls which are designed, implemented and maintained to a
                                       standard which would achieve at least 80% of the average annual runoff volume
                                       of the contributing catchment treated (i.e. 80% hydrological effectiveness) to
                                       50mg/L Total Suspended Solids (TSS) or less, and pH in the range 6.5–8.5.
                                       Where this is proposed to be achieved through the use of sediment basins, the
                                       following applies:
                                       A.    each basin is sized and operated in accordance with either a Type-A or
                                             Type-B sediment basin as documented in IECA (2008) Appendix B (June
                                             2018), based on the contributing catchment area including undisturbed
                                             catchments which cannot be diverted;
                                       B.    each basin is to be provided with an automated system of flocculant dosing
                                             and a suitable supply of flocculant/coagulant, with the type of
                                             flocculant/coagulant determined based on Chemical Coagulants and
                                             Flocculants Fact Sheet (IECA, 2018);
                                       C.    markers are provided within each basin indicating the maximum sediment
                                             storage level and any additional water storage capacity for water reuse
                                       D.    during discharge from the primary outlet system, the concentration of total
                                             suspended solids (TSS) discharged does not exceed 50mg/L and that pH
                                             is within the range of 6.5-8.54. These discharge standards apply equally to
                                             any intentional release of any water captured or stored within the site;
                                       E.    The hydraulic structures such as inlets, outlets, spillways must be
                                             structurally sound for the design events as specified in IECA (2008); and
                                       F.    The sediment basin is to be constructed and operational before any
                                             disturbance occurs in the catchment upslope of the basin. Accumulated
                                             sediment from basins and other controls is to be removed and disposed of
                                             appropriately without causing water contamination.
                              ii.      For site sub-catchments less than 2,500m2 in area and where it is not feasible to
                                       divert runoff from these small disturbed areas of the site to a sediment basin,
                                       compensatory erosion and sediment controls are implemented prior to rainfall to
                                       ensure that erosion of those of areas is minimised and Type 2 or Type 3 sediment
                                       controls are provided in accordance with IECA (2008).
                              iii.     Controls are to be installed to minimise the tracking of dirt from the site onto
                                       roadways. Any dirt on roadways caused by vehicles leaving the site is to be
                                       removed without causing water contamination, prior to rainfall and at least at the
                                       end of each work day.

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Document Set ID: 23011984
Version: 3, Version Date: 13/05/2024