Reference Document - OPW25 0085 (AS Published)

7.3.3        System Construction
Construction of wastewater land application areas must be carried out in accordance with Appendix M of
AS1547:2012 and SCC requirements. In order to prevent any adverse impacts on the water quality from
effluent disposal, the following shall be implemented:
    For shallow subsurface drip irrigation, systems must be installed at 100 mm to 150 mm depth into
     150 mm to 250 mm of good quality topsoil, in grassed of other suitably vegetated areas. Any sandy
     topsoil material won from site works may be used to supplement the soil within the respective
     disposal fields or alternatively may be imported to the site.
    Where stiff or hard clays are encountered, receiving soils should be prepared by undertaking deep
     ripping / shallow cultivation combined with the addition of organic matter (10 kg/m² raw mulch) and
     gypsum (1 kg/m²) to ‘break up’ any relatively hard clay subsoils and improve overall drainage
     characteristics.
    Shallow subsurface irrigation lines will run parallel to slope contours. To evenly distribute
     wastewater throughout the irrigation area, a pressure equalisation system (i.e. pressure
     compensating drip emitters) should be installed.
    Surface diversion drainage shall be installed on the up-slope sides of the land application area(s) in
     order to divert surface water and shallow subsurface seepage flows away. Such drainage should
     penetrate to a minimum depth of 0.3 m BGL, to capture and divert any seepage which may develop
     between the topsoil and underlying soils.
    Plant and maintain grasses, reeds and/or small shrubs within the land application areas. Preference
     should be given to native plant species endemic to the local area, which are suitable for mostly wet
     soils and are tolerant of nutrient loads (e.g. native riparian vegetation)
    Erect signage at the boundaries of the area in at least two places in accordance with Council
     requirements to warn people regarding the presence of wastewater pipes (e.g. “Sewage Effluent
     Pipework Installed Below – DO NOT DIG” or “Recycled Water – Avoid Contact - DO NOT DRINK”).
Detailed design of the effluent disposal systems must be carried out by a qualified wastewater designer
to accompany the plumbing application at the Building Works stage, once the building designs are
finalised.

7.3.4        Maintenance and Inspection
Operation and maintenance of an STP is the responsibility of the property owner. A licensed service
agent must be appointed to undertake routine servicing works in line with regulatory authority approval
conditions. To comply with NC requirements, the following management and inspection shall be
implemented once the effluent disposal systems are established:
    Continuous monitoring by the property owner for any signs of system failure such as septic odour,
     seepage, soil and/or plant discoloration.
    Should any signs of system failure be observed by the property owner, including the in-built STP
     failure alarm, the manufacturer shall be contacted immediately to arrange for the necessary repairs.
    Yearly inspection, testing and repair (if necessary) to the STP and irrigation area by a Licensed
     Inspector (normally a service provided by the STP manufacturer).




Geo-Environmental Investigation for Proposed Subdivision
7 February 2025 | 24386-001-Rev0                                                                         26