Information response - GEOTECH REPORT

Report: 15960, May 11

4.7

Septic & Sullage Disposal

Performance Criteria: -

Page 9

¢ Usually requires pump-out or mains sewer systems; absorption trenches may be possible in

some areas if risk is acceptable.

¢ Storage tanks should be watertight and adequately founded.
Acceptable measures: ~

Selecting the land-application system to fit the site and the soil:

 

 

Site or Soil System Selection Possible Installation System
Constraint Modifications to Practice Management
mitigate constraint’ ~
® Disinfection and | © Needs special © Install when soils | © Minimise

Soils with very
low
permeability
(Category 5 and
6 soils)

nutrient removal.

© Large application
area.

® Reduce flow of
wastewater using
water saving
devices, or
composting
toilets.

© Mounds, ETA
beds or trenches
or inigation
systems,
designed using
water-balance
analysis.

design.

© Prepare receiving
soil by deep
tipping, shallow
cultivation, and
applying gypsum.

* Promote formation
of biological pores
by growing
vigorous
vegetation.

© Dose effluent so as
to wet the soil
more than once per
day.

@ Place soil of good
permeability
around absorption
trenches, or around
ETA beds and
trenches.

are dry or slightly
moist.

© Avoid heavy
equipment on
application area
when soils are
moist or wet.

e Avoid smearing
sides and
bottoms of
trenches and
beds.

© Prepare surface
of soil if using
irrigation.

domestic water
use,

« Minimise
discharge of
sodium salts to
application area.

« Alternate
between
different parts of
the land
application area.

© Monitor level of
groundwater.

 

 

Steep slope

 

® Surface irrigation
unsuitable for
slopes >6%.

© The primary
criterion for
selection may be
coast {eg.
Mounds will need
much soil on
downhill side).

 

*Benching may be
feasible if soil is
reasonable stable.

®Pay special attention
lo reducing surface
infiltration (eg.
Interception drains
uphill and
tainwater-shredding
designs).

® If mound is used,
design toe to
encourage
infiltration.

 

*Trenches more
difficult to dig,
particularly for
slopes above 25%.

© Pay extra
attention to the
tisk of erosion
during
construction.

 

* Needs monitoring
of erosion and
seepage.

*Access is best
discouraged.

 

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]