Appendix D - On-site domestic wastewater evaluation report · MCU25/0022

PROJECT NO. 23/8894                                                            24th JULY 2023


4.0    HYDRAULIC FLOWS AND RECOMMENDED DISPOSAL SYSTEMS:
       Calculations in accordance with Appendix 4.2D of A.S.1547:2012, using the
       proposed 4-bedroom residence, supplied by on site storage tank water supply as
       having 6 equivalent person occupancy rating. A typical wastewater flow design
       allowance from Table H1 of AS1547 of 120 litres/person per day was used to
       calculate a daily effluent sullage flow figure of 720 litres per day or 5,040 litres per
       week using standard water fixtures.
       We recommend the use of Standard Water Reduction Fixtures. These fixtures should
       include: -     a) Dual Flush 11 litre/5.5 litre WC's.
                      b) Shower Flow Restrictors.
                      c) Aerator Faucets.
                      d) Water Conserving Washing Machines.


       Due to the poorly-draining Category 5 silty soils and the presence of a shallow
       weathered siltstone, the steep slope and the close proximity of nearby gully
       (watercourse),, we recommend all domestic effluent be treated to a minimum
       Secondary Quality as described in Clause 11.8.4 of the “On-Site Sewerage Code”
       and discharged into a shallow sub-surface irrigation area, utilizing the
       evapotranspiration effects of the surface soils, plants, the sun and wind. Treatment
       shall be by On-Site Treatment Plant with model or type specification approval,
       installed, operated and maintained in accordance with the conditions of model or type
       specification approval. Many approved Secondary treatment wastewater systems are
       available these days and their particular irrigation methods may vary slightly.


       We recommend a suitable wastewater land application area could be a Shallow Sub-
       Surface Irrigation area consisting of rows of shallow buried geofabric wrapped
       seepage pipes along the contour surrounded by 10-15mm gravel connected by
       manifold and turf valves from the treatment tank. Each shallow pipe should have its
       own isolation valve and cleanout end capping.




8894-193 SANKEYS RD-FEDERAL             Page 3 of 13                             24/07/2023