Appendix E - Geotechnical Report

                              PROPOSED RECONFIGURATION OF A LOT
                              216 BLACK MOUNTAIN ROAD, BLACK MOUNTAIN

Table 4.2A4 of AS1547:2000 recommends a Design Irrigation Rate (DIR) of 15 mm/week for Category 6 soil.
Therefore, the following land application area is recommended for the drip irrigation system:
       4,900 L/week / (15 mm/week) = 322 m2

An indicative 322 m2 wastewater irrigation area is shown in Figure 1, where it can be seen that there is
sufficient room to site the wastewater irrigation area on Lot 2 with sufficient setbacks (including a 30 m setback
from the natural watercourse) and leaving enough space for a 100% reserve area.

8.3.2         System Positioning
Positioning (‘setbacks’) of the irrigation systems must be in accordance with the horizontal and vertical
setback distances recommended in Tables T5 and T7 of the Queensland Plumbing and Wastewater Code
2013, as summarised in Table 5.
Table 5: Horizontal and Vertical Setback/Separation Distances for Irrigation Areas
 Site Feature                            Secondary Effluent               Advanced Secondary
                                                                               Effluent

                                   Horizontal Setback Distances

 Property boundary                           2 m (up slope or level) and 4 m (down slope)

 Buildings                                       10 m                              10 m

 Surface Water                                   30 m                              10 m

 Bore, well                                      30 m                              10 m

 Recreation areas (children’s
 play areas, swimming pools,                     10 m                              10 m
 etc.)

 In-ground water tank                             6m                                6m

 Retaining wall and
 embankments, escarpments,                   2 m (up slope or level) and 4 m (down slope)
 cuttings

                                   Vertical Separation Distances

 Hardpan or bedrock                              0.6 m                            0.3 m


An unsaturated soil depth of 0.6 m (i.e. depth to rock or wet soil) is recommended for Secondary effluent.
Test pits indicate adequate soil depths are available across the proposed effluent disposal areas.

8.3.3         System Construction
Construction of the wastewater land application areas should be carried out in accordance with Appendix
4.2A of AS1547:2000 and NC requirements. In order to minimise potential undesirable environmental
impacts associated with wastewater application at the site, the following practices should be employed:

       Any sandy topsoil material won from stripping works associated with the main construction works
        may be used to supplement the soil within the disposal field.
       Install surface diversion drainage on the up slope side of the possible effluent disposal area in order
        to divert stormwater flows away.
       Maintain vegetation on the possible effluent disposal area.



19 June 2018
Report No. 17427-001-Rev0                                13