Appendix C - Effluent Disposal Report · MCU26/0099

REFER TO AES CALCULATOR FOR AES BED SIZING.

Recommendations and construction guidelines for AES beds:

Ensure all manufacturers installation guidelines and requirements are strictly adhered to.(Copy of installation
requirements included in appendix).

Installers must use specified filter material.

            Avoid excavation when the soil is damp;
            Where smearing has occurred, rake the smeared soil to reinstate a more natural soil surface,
             taking care to use fine tines and effect surface penetration only;
            Plan excavation work only when the weather is fine, if rain is forecast then cover trenches, if open,
             protect them from rain damage;
            In permanently wet areas or when construction cannot be delayed until fine weather conditions are
             achieved, smearing of soil surfaces may be alleviated via the use of gypsum (an application of
             1kg/m2 may be utilised);
            Avoid compaction by not having people stand on the finished trench or bed floor, and when
             excavating by machine, having the bucket fitted with ‘raker teeth’ and excavate in small ‘bites’ to
             minimise compaction;
            When sited on sloping ground, beds should be excavated perpendicular to the line of fall or surface
             contours;
            Trench and bed inverts should be level;
            Diversion drain to be excavated above slope of land application area.

Septic Tanks:

The septic tank size shall be in accordance with the local authorities requirements. The tank must be de-
sludged at regular intervals to ensure its performance is maintained.

Backfilling:

The filter media should be placed in the trench by excavator or bucket or a shoot, and not dumped in.
Dumping is likely to cause soil damage to both the trench base and the side walls. Such damage is also likely
when backfilling is placed over in-situ filter media during or after period of heavy rainfall. The filter media for
AES system should be clean washed material suitable to manufacturers specifications. Note: ASTM Standard C-
33(Concrete sand) meets requirements. Trenches and beds will be covered with soil which should not be more
permeable than the surrounding natural soil. A protective barrier should be laid over the filter media to prevent
ingress by cover material.

Where the trench is being covered by cast in-situ concrete or other paving, plastic film or a suitable synthetic
fabric should cover the trenches to prevent concrete infiltration or ingress or bedding fines.


Preparation of irrigation area:

When a proposed irrigation area has a low permeability, it is particularly important to ensure that the
permeability of the soil in the irrigation area is improved and maintained and that there is an adequate cover of
porous and fertile topsoil to act as immediate storage of effluent applied to it, and to support rapid growth of
vegetation on the area to maximise evapo-transpiration.

It is recommended that topsoil be imported to improve rapid growth of vegetation and improve the evapo-
transpiration process.




AUSTRALIAN SOIL INVESTIGATIONS                      Page 4 of 6                           ASI Ref: 260176 (A)Rev-A