S25-107-Stormwater Report

Best Practice Erosion And Sediment Control                   Erosion Hazard Assessment Form


[3]   If the soils have not been tested for Emerson Class, then adopt a score of 4.

      REQUIREMENTS:
      Works proposed on sites containing Emerson Class 1 or 2 soils have a very high
      pollution potential and must submit a conceptual ESCP to the regulatory authority
      for review and/or approval (as required by the authority) during planning
      negotiations.

      WARNINGS:
      Class 3 and 5 soils disturbed by cut and fill operations or construction traffic are
      highly likely to discolour stormwater (i.e. cause turbid runoff). Chemical
      stabilisation will likely be required if these soils are placed immediately adjacent
      to a retaining wall. Any disturbed Class 1, 2, 3 and 5 soils that are to be
      revegetated must be covered with a non-dispersive topsoil as soon as possible
      (unless otherwise agreed by the regulatory authority).

      Class 1 and 2 soils are highly likely to discolour (pollute) stormwater if exposed to
      rainfall or flowing water. Treatment of these soils with gypsum (or other suitable
      substance) will most likely be required. These soils should not be placed directly
      behind a retaining wall unless it has been adequately treated (stabilised) or
      covered with a non-dispersible soil.

[4]   The duration of disturbance refers to the total duration of soil exposure to rainfall
      up until a time when there is at least 70% coverage of all areas of soil.

      REQUIREMENTS:
      All land developments with an expected soil disturbance period greater than 6
      months must submit a conceptual ESCP to the regulatory authority for review
      and/or approval (as required by the authority) during planning negotiations.

      COMMENTS:
      Construction periods greater than 3 months will generally experience at least
      some significant storm events, independent of the time of year that the
      construction (soil disturbance) occurs.

[5]   REQUIREMENTS:
      Development proposals with an expected soil disturbance in excess of 1ha must
      submit a conceptual ESCP to the regulatory authority for review and/or approval
      (as required by the regulatory authority) during planning negotiations.

      The area of disturbance refers to the total area of soil exposed to rainfall or dust-
      producing winds either as a result of:
        (a) the removal of ground cover vegetation, mulch or sealed surfaces;
        (b) past land management practices;
        (c) natural conditions.

      WARNINGS:
      A Sediment Basin will usually be required if the disturbed area exceeds 0.25ha
      (2500m2) within any sub-catchment (i.e. land flowing to one outlet point).

      COMMENTS:
      For soil disturbances greater than 0.25ha, the revegetation phase should be
      staged to minimise the duration for which soils are exposed to wind, rain and
      concentrated runoff.



IECA (Australasia)                           November 2008                          Page 5