Attachment K - HSTP Design

4.1 Limitations.

Our site and soil evaluation noted the following limitations which may have an
adverse effect on the performance, serviceability, and sustainability of
environmentally acceptable on-site domestic wastewater management

e allotment size, configuration and topographic idiosyncrasies,

e — separation distance requirements,

e areas previously used or required for construction or landscaping

In formulating our recommendations we have noted, considered and made allowance
for the effect these limitations will have on the performance, serviceability, and
sustainability of on-site domestic wastewater management. We consider that in line
with the recommendations set out within this report, and with appropriate control
measures in position, sustainable on-site domestic wastewater treatment and disposal
will be achieved.

In consideration of these limitations and with reference to the Queensland Plumbing
and Wastewater Code and AS/NZS1547-2012 On-site Domestic Wastewater
Management, we recommend advanced secondary treatment of all domestic
wastewater flows for the efficient, sustainable and environmentally acceptable
disposal of treated effluent on this allotment. The use of such approved systems
consequentially enables the 30m horizontal separation distance from the intermittent
watercourses/dams to be reduced to 10m, and the vertical separation distance to be
reduced to 300mm.

Although we recorded no existing evidence of eutrification, we believe there is the
potential for eutrification of any associated dam or watercourse if there is nutrient
leakage from any disposal site. However, with our recommended, and appropriate
vegetation planting, with the incorporation of a wastewater treatment system with
nutrient stripping capabilities and with the encouraged use of phosphate free cleaning
products, we believe the reduced potential will be contained.

 

Unearthed Geotechnical P/L. 5 Design Report 023-038