Attachment 3 - Revised Slope Stability Assessment

Brett Hage                                                                                              22328-001-Rev1
                                                                                                      17 November 2022

We have been supplied with a proposed layout plan for the subdivision by CadCon Surveying & Town
Planning (CadCon, Ref. Dwg. No. 218806-02-02, dated 25 May 2022), and site and roadwork layout plans
by Alta Projects (Ref. A6682/22/P01 to P04, dated July 2022) which indicated that it is proposed to retain an
existing residence on a slightly smaller lot to the north (proposed Lot 1) which would total 1.882 ha.
Proposed Lot 2 to the south would be of 4.754 ha, with a proposed building area along the western
boundary.

A separate driveway access would be expected for each lot, with a cross-over shown to the south-western
corner of proposed Lot 1, and north-western corner of proposed Lot 2.

The property does not have access to mains sewerage or a piped, potable water supply, and therefore
collection of rainwater in tanks and on-site disposal of effluent will be required.

An extract of the proposed layout plan is given below in Text Figure 2.




                                                                                   Proposed subdivision boundary




                                       Proposed Lot 2 building area




                                                                                                     Overall existing lot boundary
Text Figure 2: Extract of overall subdivision layout plans, including roadworks (courtesy Alta)

1.2       Method and Scope of Investigation
As part of our slope stability assessment, a desk-top study was carried out comprising a review of
published geological maps, stability studies and aerial photos.

Tectonic undertook a site investigation to inform this assessment, which comprised the following:

          Two boreholes drilled to depths of between 4.3 m and 4.5 m below ground level (BGL) using a
           4WD utility mounted, solid flight auger drill rig owned and operated by Tectonic. In situ testing
           included dynamic cone penetrometer (DCP) testing from surface adjacent to each location and at
           selected depths downhole. Pocket penetrometer tests were also carried out on suitable recovered
           cohesive materials.
          Laboratory testing at a NATA accredited geotechnical laboratory comprising one Atterberg Limits
           and one Particle Size Distribution test.
A walk-over survey was conducted in order to make an appraisal of the general condition of the site in
regard to topography, drainage, vegetation cover, geology, erosion and slope stability and existing
structures. The walk-over survey was carried out by an experienced engineering geologist from Tectonic
on 19 August 2022 concurrent with the borehole drilling. The results of the desk-top study and walk-over
survey are included in Section 2 below.

1.3       Qualifications of Responsible Engineer
This report has been reviewed by Ashley Davey, an RPEQ with more than 27 years’ experience in
geotechnical engineering, including a number of slope stability projects.




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