Attachment 3 - Revised Slope Stability Assessment

Brett Hage                                                                                   22328-001-Rev1
                                                                                           17 November 2022

       Surface diversion drainage shall be installed on the up-slope sides of the land application areas to
        divert surface water and shallow subsurface seepage flows away. Such drainage should penetrate
        to a minimum depth of 0.3 m BGL.
       A low earthen bund shall be constructed, down slope of the effluent disposal areas up to 0.3 m high
        to retain run-off and promote sheet flow.
       Plant and maintain grasses, reeds and/or small shrubs within the land application areas. Preference
        should be given to native plant species endemic to the local area, which are suitable for mostly wet
        soils and are tolerant of nutrient loads (e.g. native riparian vegetation)
       Erect signage at the boundaries of the area in at least two places in accordance with Council
        requirements to warn people regarding the presence of wastewater pipes (e.g. “Sewage Effluent
        Pipework Installed Below – DO NOT DIG” or “Recycled Water – Avoid Contact - DO NOT DRINK”).
       Erect barriers where necessary to restrict access to public which may interfere or damage the
        irrigation system.

Detailed design of the effluent disposal systems must be carried out by a NC registered evaluator to
accompany the plumbing application at the building stage, once the building designs are finalised.
5.3.4 Maintenance and Inspection
Operation and maintenance of a HSTP is the responsibility of the property owner. A licensed service agent
must be appointed to undertake routine servicing works in line with regulatory authority approval conditions.
To comply with NC requirements, the following management and inspection shall be implemented once the
effluent disposal systems are established:

       Continuous monitoring by the property owner for any signs of system failure such as septic odour,
        seepage, soil and/or plant discoloration.

       Should any signs of system failure be observed by the property owner, including the in-built HSTP
        failure alarm, the manufacturer shall be contacted immediately to arrange for the necessary repairs.

       Quarterly inspection, testing and repair (if necessary) to the HSTP and irrigation area by a Licensed
        Inspector (normally a service provided by the HSTP manufacturer).


6.0     SUMMARY & CONCLUSIONS
Based on the findings of our assessment we consider that there would be a Low Risk of slope instability
impacting the proposed development. This advice is subject to implementation of the recommendations
given in this report.
This assessment relates only to the proposed subdivision for the development application
process. Existing structures, batter slopes and road connections may be subject to risk of slope
instability but assessment of those matters was beyond the scope of our commission. Also excluded
from this assessment are any future building works, which would be subject to site specific assessment
and review by a geotechnical RPEQ prior to construction.




                                                     18/19