wastewater design report

As the slope configuration was recorded to be linear planar the Land Application
Areas 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 drainage characteristics of the consistent soil profile, and the
topographical location of the proposed Land Application Areas (i.e. adjacent to, and
downslope of the well-formed pad) may be deemed to offer some, or sufficient
protection from surface water infiltration.

‘Similarly, the existing endemic vegetation, extending more than 30 m downslope of
the proposed Land Application Areas may be deemed to be satisfactory as the
recommended transpiration buffer zone.

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 Areas by proper final grade of the finished surface.

We recommend the base of the entire excavations and the existing ground
immediately downslope of the AES trench (approximately 1m) shall be ripped, along
the contour and parallel to the lay of pipes, to a depth of 200mm prior to the
construction of the AES installation, whilst adding dolomite/gypsum at nominal rate
(say 0.5 kg/sqm).

During the excavation processes we recommend separation of the brown topsoil (to
be spread over the top of the entire installation to facilitate grass growth) from the
orange/red/brown subsoil which is used to backfill the sand bed.

We further recommend a minimum depth of cover at the low side of the sand bed
extension of 300mm.

 

Unearthed Geotechnical P/L. 10 Design Report 022-003