Site and Soil Evaluation

The size of the Land Application Area is calculated as follows:

  Minimum requirement       q        120           litres per person per day   AS 1547 –2012 Appendix H1

      Water Supply                Tank Water

  Number of persons =                 8                                            AS 1547 Table J1


      Total Volume          Q=       6720      L/week

      Soil Category                   5                                            AS 1547 Table M1

  Indicative permeability          0.06-0.12                                       AS 1547 Table M1

              DIR                     21       mm/week                             AS 1547 Table M1

                                                 2
      Disposal Area         A=       320       m


WE RECOMMEND THAT A MINIMUM LAND APPLICATION AREA OF 320m 2 BE PROVIDED.

A check of Water Balance requirements in accordance with the Code has been undertaken and have
been found to comply.

The Irrigation System should be designed in accordance with AS 1547–2012 and comply with all relevant statutory
requirements.


Construction Guidelines for Land Application Areas:

Sub-Surface Drip Irrigation

Consists of a reticulated pressurised irrigation system that uses an arrangement of equally spaced shallow sub-
surface drains to equally distribute the treated effluent across the Land Application Area. This system allows
vegetation within the area to directly benefit from such watering which also assists in disposal of the effluent via
evapo-transpiration. The drains can consist of small diameter poly piping that has pre-drilled holes for drainage of
the effluent. These pipe must be contained within another Agg drain with a geofabric wrapping that inhibits root
growth which could block the system. Other types of drains include pressure compensated dripper lines. A
number of different manufactured systems exist. Points to consider in the construction of the area include the
following:

      (i)      To avoid runoff from the area it should be as level as possible. Any sloping areas should be terraced
               or retained and filled.
      (ii)     The pump and irrigation system must have a separate effluent storage chamber that matches the
               electrical starting requirements of the pump. A volume 200 L is recommended as a minimum. The
               pump is to have a minimum capacity of 1.5 times the maximum 30 minute flow rate.
      (iii)    Rainwater shall be diverted around the area by use of open catch drains or similar from the irrigation
               area. Similarly a retention bund should be constructed around the low side of the area to retain any
               effluent overflow.
      (iv)     The pipework is to be spaced to ensure an even distribution of the effluent over the application area.
               A maximum spacing of 1000mm in clay soils and 600mm in sand should be adopted. Greater rates of
               evapo-transpiration is achieved through closer spacing of the dripper lines and or reducing the spacing
               between the drip emitters.
      (v)      The dripper lines should have a stop cock downstream from their connection to the supply line
               (manifold) and be brought to the surface at their ends. This will enable flushing of the individual lines
               and enable easy identification of blocked lines.
      (vi)     The treated effluent must not be used for the irrigation of fruit or vegetables.
      (vii)    Siting of the irrigation area shall be in a location away from regular pedestrian traffic and recreational
               areas, so there is no risk of direct spray or wind driven spray onto such areas.


   AUSTRALIAN SOIL INVESTIGATIONS                                   4                             ASI Ref: 250385 (A)