Appendix E - Wastewater Report

                             PROPOSED RESIDENTIAL SUBDIVISION
                             9A JIRRIMA CRESCENT, COOROIBAH

7.3       Recommendations
7.3.1       System Type

It is recommended that wastewater from the future residence on Lot 1 be directed to a suitably sized
Household Sewage Treatment Plant (HSTP) connected to a shallow subsurface or surface irrigation system.
The HSTP must be licensed to produce at least Secondary standard effluent, with Chief Executive approval
from the Department of Housing and Public Works. To maximise available residential space, by limiting
setback requirements, it may also be desirable to use an Advanced Secondary treatment system on the new
allotment.

The HSTP and land application area currently servicing the existing residence located within proposed Lot 2
would be adequate to continue to service the existing dwelling. Relocation or retrofitting of the existing
system is not expected to be necessary, but if required, should be completed by a suitably qualified and
licensed plumber, experienced with on-site effluent systems.

Table M1 of AS1547:2012 recommends a Design Irrigation Rate (DIR) of 2 mm/day for Category 6 soil.
Therefore, a minimum irrigation area of about 360 m² (720 L/day / 2 mm/day) will be required for each lot.
Sufficient wastewater irrigation areas for both proposed lots are available and are shown in Figure 1, where it
can be seen that there is sufficient room to site the wastewater irrigation areas with the necessary setbacks.

7.3.2       System Positioning

Positioning (‘setbacks’) of the land application systems must be in accordance with the horizontal and
vertical setback distances recommended in Tables T2, T3 and T5 of the Queensland Plumbing and
Wastewater Code 2019, as summarised in Tables 1, 2 and 3 below and over page.

Table 1: Setbacks for subsurface land application area for on-site sewage treatment plant

                                                                             Horizontal separation distance
  Site Feature
                                                                             Upslope      Downslope      Level

 Property boundaries, pedestrian paths, walkways, recreation areas,
                                                                               2m            4m           2m
 retaining wall, and footings for buildings and other structures.

 Inground swimming pools.                                                                   6m

 Inground potable water tank.
                                                                                            6m
 (Secondary standard effluent or better)


Note:   Distances measured from the edge of trench/bed excavation or subsurface irrigation distribution
        pipework to the nearest point of the feature.




4 November 2020
Report No. 20333-001-Rev0                               7