S25-107-Stormwater Report

Best Practice Erosion And Sediment Control                        Erosion Hazard Assessment Form


Explanatory notes
Requirements:        Specific issues or actions required by the proponent.
Warnings:            Issues that should be considered by the proponent.
Comments:            General information relating to the topic.


[1]   REQUIREMENTS:
      For sites with an average slope of proposed land disturbance greater than 10%, a
      preliminary ESCP must be submitted to the regulatory authority for approval
      during planning negotiations.

      Proponents must demonstrate that adequate erosion and sediment control
      measures can be implemented on-site to effectively protect downstream
      environmental values.

      If site or financial constraints suggest that it is not reasonable or practicable for
      the prescribed water quality objectives to be achieved for the proposal, then the
      proponent must demonstrate that alternative designs or construction techniques
      (e.g. pole homes, suspended slab) cannot reasonably be implemented on the
      site.

      WARNINGS:
      Steep sites usually require more stringent drainage and erosion controls than
      flatter grade sites.

      COMMENTS:
      The steeper the land, the greater the need for adequate drainage controls to
      prevent soil and mulch from being washed from the site.

[2]   REQUIREMENTS:
      If the actual soil K-factor is known from soil testing, then the Score shall be
      determined from Table 1.

      If a preliminary ESCP is required during planning negotiations, then it must be
      demonstrated that adequate space is available for the construction and operation
      of any major sediment traps, including the provision for any sediment basins and
      their associated embankments and spillways. It must also be demonstrated that
      all reasonable and practicable measures can be taken to divert the maximum
      quantity of sediment-laden runoff (up to the specified design storm) to these
      sediment traps throughout the construction phase and until the contributing
      catchment is adequately stabilised against erosion.

      WARNINGS:
      The higher the point score, the greater the need to protect the soil from raindrop
      impact and thus the greater the need for effective erosion control measures. A
      point score of 2 or greater will require a greater emphasis to be placed on
      revegetation techniques that do not expose the soil to direct rainfall contact
      during vegetation establishment, e.g. turfing and Hydromulching.

      COMMENTS:
      Table 2 provides an indication of soil conditions likely to be associated with a
      particular Soil group based on a statistical analysis of soil testing across NSW.
      This table provides only an initial estimate of the likely soil conditions.



IECA (Australasia)                           November 2008                               Page 2