Decision Notice OPW20 145 06 (As Published) · OPW20/0145.06

                      Erosion and Sediment Control
               55.    Prescribed Water Contaminants (as defined in Schedule 9 of Environmental Protection
                      Regulation 2008) must not be released from the site or to waters within the site, or be likely
                      to be released should rainfall occur, unless all reasonable and practicable measures are
                      taken to prevent or minimise the release and concentration of contamination. These
                      measures must be designed, implemented and maintained in accordance with “Best Practice
                      Erosion and Sediment Control” published by the International Erosion Control Association
                      (Australasian Chapter) (IECA, 2008), to the extent that such measures and practices are also
                      consistent with the following:
                      a.      Minimise Erosion
                              i.       For areas of the site which drain to a sediment basin, implement drainage and
                                       erosion control measures prior to rainfall which prevent or minimise rill erosion
                                       and gully erosion
                              ii.      For areas of the site which do not drain to a sediment basin, implement drainage
                                       and erosion control measures prior to rainfall (including contingency measures)
                                       which prevent or minimise erosion, including rain drop erosion, chemical erosion,
                                       rill erosion and gully erosion
                              iii.     Prior to the sealing of the plan of survey for the development, all site surfaces
                                       must be effectively stabilised using methods which have achieved effective short-
                                       term stabilisation and which will continue to achieve effective stabilisation in the
                                       medium to long-term. For the purpose of this condition, an effectively stabilised
                                       surface is defined as one that does not, or is not likely to result in visible evidence
                                       of soil loss caused by sheet, rill or gully erosion or lead to sedimentation, or lead
                                       to water contamination.
                      b.      Manage concentrated stormwater flows
                              iv.      Prior to each rainfall event ensure concentrated stormwater flow paths are
                                       provided with capacity in accordance with IECA (2008) Table 4.3.1 and are
                                       structurally stable in all rainfall events for the following sources:
                                       (a)        From stormwater catchments upslope of the area of disturbance
                                             which are either stable or external to the site, ensure stormwater is diverted
                                             or managed either:
                                             i.    around the site or through the site without causing erosion and
                                                   without contaminating the flow; or
                                             ii.   if it is impractical to convey the flows around or through the site,
                                                   convey the flows into appropriately sized sediment basins without
                                                   causing erosion
                                       (b)   From all disturbed areas of the site to sediment basin(s) without causing
                                             erosion
                      c.      Minimise sediment released from the site
                              i.       Install and maintain sediment basins for each disturbed catchment area of the
                                       site and including undisturbed catchments which cannot be diverted, such that:
                                       (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).
                                       (b)   Each basin is to be provided with an automated system of flocculent dosing
                                             and a suitable supply of flocculent/coagulant, with the type of
                                             flocculent/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.


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Document Set ID: 24395463
Version: 4, Version Date: 03/02/2026