SUPERSEDED Decision Notice OPW25 0042 · OPW25/0042

               38.    A construction hold point with a council delegate shall be established once the bioretention
                      device underdrainage pipe work is installed. At the time of inspection, a sample of the
                      drainage layer, transition layer, and filtration media materials must be stockpiled onsite.
                      Laboratory results must be provided for the filter media which demonstrate that the media
                      complies with the specifications contained in the latest version of the “Guidelines for Soil
                      Filter Media in Bioretention Systems” (produced by the Facility for Advancing Water
                      Biofiltration) and that the minimum hydraulic conductivity specified on the approved
                      engineering plans will be achieved. In addition, laboratory results must be provided
                      demonstrating that the transition layer and drainage layer meet the following bridging criteria:
                      a.      D15 (drainage layer) ≤ 5 × D85 (transition layer)
                      b.      D15 (transition layer) ≤ 5 × D85 (filter media).
               c.     The drainage layer, transition layer, and filtration media materials must not be installed until
                      the catchment draining to the bioretention device has 70% groundcover as determined by
                      Council’s delegate.
                      Erosion and Sediment Control
               39.    Prescribed Water Contaminants (as defined in Schedule 10 of Environmental Protection
                      Regulation 2019) 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
                              i.       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.



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Document Set ID: 24023937
Version: 2, Version Date: 12/08/2025