Appendix D - Geotechnical Report

1.           Introduction
This report details the results of a geotechnical investigation undertaken for a proposed five lot
subdivision at 220 Black Mountain Range Road, Black Mountain. The investigation was carried out by
Tectonic for Threedom Nominees Pty Ltd, generally in accordance with our proposal P25610-Rev0, dated
9 December 2025.
The site investigation comprised a walk-over by an experienced engineering geologist and geotechnical
engineer from Tectonic; and the excavation of eight test pits, together with in situ soil strength and
laboratory testing. This report summarises the results of the investigation and includes a slope stability
assessment, together with recommendations regarding geotechnical matters for the development
pertaining to earthworks, retaining structures, footings, and drainage. Quantitative and qualitative slope
stability assessments are included.



2.           Proposed Development
Proposed development layout plans by Max Watterson & Associates (MWA, Ref. 25-6775AG, dated
20 April 2026) were provided to Tectonic.
These indicate that it is proposed to subdivide an existing single rural allotment in to five future
allotments. Proposed Lot 3 towards the centre of the development would retain an existing residence,
with new building envelopes to be established on Lots 1 & 2 and 4 & 5, mostly focussed around the
crests of spurs or broad flank slopes. The proposed lots would range in size from about 2.931 ha to
7.699 ha.
All lots have direct frontage to Black Mountain Range Road, so it is expected that separate accesses will
be feasible for each of the lots. Therefore, to effect the subdivision, no significant earthworks should be
required, although concrete crossovers established outside of the site boundaries are expected.
For future building works, lots focussed towards the crest of rounded spurs may have more flexibility in
terms of earthworks and building construction, with those on slightly steeper flanking spurs (e.g. Lots 2
and 4) limited to about 1 m depth/height of cut/fill, to create localised building pads and drainage
diversion etc.
Mains water and sewerage connections are not available, and therefore collection of rainwater in tanks
and on-site disposal of effluent will be required.
Text Figure 1 on the following page provides an extract of the layout drawing provided.




Geotechnical Investigation
10 June 2026 | 26073-001-Rev0                                                                                 1