Attachment K - HSTP Design

4.0 FINDINGS

All the field information and test results collected during our site investigation and
detailed in this report, including any site plans, log and data sheets together form the
basis of our recommendations for this Land Application Facility.

The soil profile encountered during our investigations, and as reported, was
reasonably and acceptably consistent across the proposed development, and within
our expectations from regional experience and correlation with The Qld Dept of
Mines/Energy Geology Sheet 9445/1999 (Gympie), which describes the geology as
Late Triassic-Jurassic, Duckinwilla Group, Myrtle Creek Sandstone.

Our site investigation confirms the existing Land Application Facility incorporates a
Taylex treatment plant and moveable spray irrigation. Our site investigation confirms
the Land Application Facility has reached the end of its serviceable life, may have
failed, or is otherwise non-compliant, for one or a combination of the following
reasons;

e inadequate siting

e inadequate sizing

e inappropriate sprinkler placement and effluent distribution

e non-compliant pipework to and within disposal areas.

The proposed Land Application Area is on a partially exposed 3-5% southwestern
slope with neighbouring vegetation consisting of grasses and trees.

The landform was recorded as natural and partially disturbed.

Slope configuration across the proposed site is determined to be linear planar. Slope
stability problems were not evident during our investigations and expert evaluation
deemed unnecessary.

The susceptibility to flooding from groundwater is low and the indicative drainage
was recorded as moderate. No water table was encountered on the day of our site
investigation.

To comply with Queensland Plumbing Laws and Code it is now a requirement on
certain sites to be accompanied by a Sanitary Articulation Design (SAD). A SAD is
now required when the underlying soils of a site may be subject to excessive
settlement or surface movement due to a volumetric change of the soil caused by
changes in the ground moisture condition. The range of soil movement dictates the
Site classification and as such where it is expected some natural soil movement will
occur, articulated joints at key points on a drainage system is required. The
articulated joints are required to carry the differential movement between adjacent
structures (i.e. a house or retaining wall) and the natural ground around it in order to
prevent pipework from shearing and becoming displaced (potential spilling sewage
into the ground). On such sites a Sanitary Articulation Designs is now mandatory
across Queensland and requires a suitably qualified RPEQ Civil Engineer (or
Drainage Designer) to undertake the design.

 

Unearthed Geotechnical P/L. 4 Design Report 023-038