wastewater design · MCU22/0192

hydraulic load to each of the trench/beds. The invert level of the distribution box
outlets must be sufficiently higher than the highest trench to ensure adequate drainage
from, and to prevent backflow/flooding into distribution box.

The treatment plant/ tanks traps and associated fittings shall be

e constructed of durable materials with expandable and/or flexible connections,

e positioned correctly in relation to boundaries, buildings etc to provide an angle of
repose of at least 45 degrees between the bottom of the footing system/excavation
and the base of any associated excavation,

e watertight and capable of withstanding loads imposed on the roof and walls,

e — installed so that flotation will not occur when the tank/s is empty,

e — installed on a stable base and to prevent surface water infiltration,

e located with good clear access for servicing and desludging operations,

e located within a designated area to enhance its amenity,

e be protected from roof water/tank discharge, surface water flow and/or seepage,

e — installed and operated in accordance with regulatory guidelines.

The supply lines to the septic tank must be adequately vented with mosquito proof
cowls fitted to all vents.

The Land Application Area shall

e not be located on land prone to water logging or subject to floodwater inundation,
e _ be sited to be open to prevailing winds and not totally shaded from sunlight,

e be protected from roof water discharge, surface water flow and/or seepage,

e have no runoff or seepage of the applied effluent beyond the designated area,

e be regularly inspected and maintained,

e have the mandatory signage prominently displayed,

e have boundaries (fence) to deter grazing animals and casual pedestrian traffic.

As the slope configuration was recorded to be linear planar the Land Application Area
shall be protected from surface water infiltration by the installation of an excavated
surface water diversion drain (suggested minimum 1000mm wide and 150mm deep)
and from runoff by the installation of a vegetated track rolled retention
mound/transpiration buffer zone (suggested minimum 1000mm wide and 150mm
high).

In this instance the topographical location of the proposed Land Application Area (i.e.
adjacent to, and downslope of the hill top) may be deemed to offer some, or sufficient
protection from surface water infiltration. It is essential that all associated stormwater
flows from this and neighbouring allotments, driveways, roads, tanks and roofs are
diverted away and well clear of the proposed Land Application Area.

We recommend ripping the base of the entire excavation to a depth 200mm before
backfilling with aggregate. We recommend the application of dolomite/gypsum at a
nominal rate (say, 0.25 kg/sqm) when preparing the existing soil. This will assist with
both plant growth and/or pH control (further applications may be required during the
serviceable life of the Land Application Area).

 

Unearthed Geotechnical P/L. 14 Design Report 022-164