Compiled Reference Documents - MCU25/0091 (As Published)

            Wingara Hills Pty Ltd

            8.0         WASTEWATER TREATMENT AND DISPOSAL
            An assessment of the type and configuration of wastewater systems that may be suitable for a proposed
            development requires the following:

                    Assumptions to be made regarding the development configuration and probable wastewater flow; and

                    Evaluation of the terrain-soil combinations to identify distinct units.

            8.1 Wastewater Flow Design Allowance
            For the proposed development, comprising two single bedroom, single level eco-cabins we understand that
            the maximum occupancy will be 4 Equivalent Persons (EP) total. For each EP, a typical wastewater flow
            allowance has been taken from Table H4 of Australian Standard AS1547:2012 On-site domestic wastewater
            management (Table H4 refers to New Zealand conditions, and AS1547 allows for a reduction of about 30%
            of wastewater to allow for differences between Australian and NZ climatic conditions), as follows:

                 •      Guests of cabins (4 EP)                     150 L/person/day (roof water supply)
            We therefore estimate a typical total wastewater flow rate of 600 L/day during the maximum occupancy of
            the cabins.
            Wastewater flow rates may be reduced by the adoption of water reduction fixtures. Conversely, the use of
            extra wastewater producing fixtures (e.g. spa baths) and/or additional cabins etc. with more people has the
            potential to increase the wastewater flow rate.
            It should be noted that sewage treatment works discharged through an irrigation scheme with a total daily
            peak design capacity of 21 to 100 EP are deemed to be an environmental relevant activity and must comply
            with the obligations of the Environmental Protection Act 1994, and the regulations made under that Act. The
            proposed development does not meet this threshold of assessment; however, the addition of more cabins
            could result in exceeding the threshold and require further assessment.

            8.2 Terrain-Soil Assessment
            The terrain-soil combination(s) at a site are assessed so that an expected available area can be delineated
            for suitable methods of wastewater treatment and land application.
            The terrain across the site has been categorised in accordance with the slope configurations described in
            Figure C2 of AS1547:2012, which also describes the relationship between the shape of the slope and
            surface drainage. The topography across the site varies but could generally be described as Linear Planar
            to Linear Divergent in the area where effluent disposal is proposed (Ref. Figure No. 1).
            At the location of the potential effluent disposal area(s) (ref. Figure 1), subsurface conditions comprised silty
            clay of low to medium plasticity, broadly corresponding to Soil Category 5 (Light Clay; Strongly Structured)
            which has an indicative permeability of 0.12 m/day to 0.5 m/day (Table 5.1 of AS 1547:2012) and could be
            described as “poorly to moderately drained”.
            Results of insitu permeability testing, indicated permeability values in the range 0.6 m/day adjacent toTP4 (in
            clay soils).
            A second test was performed at TP5 due to that area possessing a flatter gradient and potentially being an
            effluent disposal site. The test indicated a permeability of about 1.2 m/d in sandy soil. However, it was
            reassessed that location is potentially a catchment of surface runoff and, actually possessed standing water
            (in parts), and as such that area was not further considered.

            8.3 Recommendations
            Having consideration for the terrain-soil assessment and environmental constraints of the site, it is
            recommended that treated wastewater be directed to a surface or shallow subsurface drip irrigation system.
            The wastewater treatment system(s) must be licensed to produce minimum Secondary standard effluent in
            accordance with the Queensland Plumbing and Wastewater Code (QPW Code). Treated greywater may be



            J002915-001-R-Rev0                                      12


Document Set ID: 24031832
Version: 1, Version Date: 14/08/2025