220328 - Edwards Street - Slope Stability Assessment

Bev Jenner Const.                                                                                    22073-001-Rev0
C/- Westera Partners                                                                                  25 March 2022

Architectural drawings supplied to us (Gockel Architects, Ref. Dwg. No. 100.01 to 400.02, Rev A, dated 1
February 2021) indicate that the proposed development would consist of an offset, two storey dual
occupancy building, with a semi-basement, daylightling to the site frontage and being completely in ground
to the rear (north).

The basement would consist of a concrete ground slab and walls, with a suspended concrete slab then
forming the base level for the initial habitable floor above. Lightweight cladding would be used on the exterior
to the two upper storeys, with relatively lightweight sheetmetal roofing above. A masonry blockwork party
wall is anticipated through the centre of the structure. Some relatively small outstands from the first floor form
small cantilevered sections to the front, with a verandah covered by an extended and suspended upper
storey on each of the properties.

A small swimming pool would be located to the rear boundary of each of the properties within the dual
occupancy, being dug in to the upslope side, and left above ground to the front (facing the residences).

No specific earthworks details were available at the time of reporting; however, based on existing site
conditions and the proposed development it is anticipated that bulk cutting of up to about 3 m depth would be
required to reach the design floor level for the basement. The swimming pool would require cut of about
1.5 m depth. Isolated deeper excavations may be required for the pool and underground services/footings.
Filling is expected to the corners of the block either side of the entrance, of about 1 m to
2 m height, to form landscaped gardens and stairs up to the level of the first habitable floor of the buildings.

The property has existing connections to town water and sewerage. A proposed layout plan is provided in
Text Figure 2 below.




Text Figure 2: Proposed site layout plan and section through northernmost unit (courtesy Gockel Architects)

1.2    Method and Scope of Investigation
As part of our assessment, a desk-top study was carried out comprising a review of published geological
maps, Noosa Council (NC) planning overlays and a site classification ‘soil test’ report by Unearthed
Geotechnical (Unearthed Ref. 022-020, dated February 2022).

An experienced engineering geologist from Tectonic undertook a site walk-over on 24 February 2022 to
visually assess any indicators of past slope instability. The walk-over included assessment of soil
exposures, surface drainage conditions, topography, evidence of erosion or past instability, vegetation
coverage and existing structures.

The Unearthed ‘soil test’ included three hand auger boreholes to a depth of 2 m below ground level (BGL),
which did not meet with the maximum excavation depth for the semi basement, or deeper information
sufficient to provide advice on footings and stability. Concurrent with the walk-over, Tectonic undertook
additional in situ testing using the dynamic cone penetrometer (DCP) method to depths of 3.9 m at the
maximum excavation depth, and a second test towards the front of the block to correlate the Unearthed
results with.

The results of the desk-top study, walk-over survey and subsurface investigation are included in Section 2
below.




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