Appendix E - Geotechnical Report

                             PROPOSED RECONFIGURATION OF A LOT
                             216 BLACK MOUNTAIN ROAD, BLACK MOUNTAIN

7.1.4        Filling
Filling of up to 1 m height has been allowed to create level building platforms, from a slope stability point of
view. Fill of greater height shall be supported by an engineer designed retaining wall. Any imported fill must
have a minimum CBR value of 10%, and maximum ‘fines’ content (percent passing 0.075 mm sieve) of 15%.

Future fill must be compacted at moisture contents within the range of ±2% of optimum moisture content for
Standard Compaction. Fill particles greater than 100 mm must be excluded. Fill should be placed in
maximum 250 mm thick (loose thickness) layers and be compacted by repeated rolling to achieve a dry
density ratio of at least 95% of the maximum Dry Density Ratio (Standard Compaction method), or 70% of
the Dry Density Index for cohesionless fills (e.g. sands).

Compaction should be carried out using a minimum 6 tonne smooth drum roller with vibration generally
turned on.

Confirmatory compaction testing must be carried out at regular intervals. Details for inspection and testing of
fill are given in Australian Standard AS 3798-2007 Guidelines on Earthworks for Commercial and Residential
Developments.

7.1.5        Material Suitability for Re-Use
Excavated material from the development area is expected to comprise mostly silty clays. These materials,
where free of deleterious material (e.g. vegetation, cobbles greater than 150 mm), should be suitable for
placement as structural fill subject to appropriate moisture control.



7.2      Building Foundations
7.2.1        Site Classification
Based on the existing natural soil profile encountered, and laboratory test results, footing design may be
based upon a site classification of Class M according to AS2870:2011, with estimated characteristic surface
movements (‘ys’) of 20 mm to 40 mm. Final site classification and footing design will be dependent on
earthworks, type of fill material placed and degree of fill placement supervision.

It should be noted that the predicted order of movement is based on natural soil profile and moisture content
changes due to normal seasonal moisture variations only. Should high plasticity clay be placed as fill across
the building envelope, a more sever site classification may result.

7.2.2        Footing Design
The future residence on proposed Lot 2 is likely to be one to two storey, and either slab-on-ground or
suspended floor (or a combination). Footing design will depend on earthworks undertaken and building type
(loads). It is recommended that footings are founded at least 0.3 m into the highly weathered phyllite (rock).

Conventional footings beams founded directly on phyllite may be suitable in cut areas, however, where fill is
placed or where excavations do not expose rock close to the surface, ‘bucket piers’ or bored piers would be
required to extend footings to rock.

Footings founded in weathered phyllite rock may be designed using an allowable bearing capacity of
350 kPa. Based on the test pits, founding depths are estimated to range up to about 3 m BGL.

If any subsurface conditions encountered during construction are found to differ from those noted in the
geotechnical investigation, Tectonic should be notified immediately and an inspection carried out to
determine if changes to footing design are required.

Subject to design and construction in accordance with the above recommendations, settlements are
expected to be within building serviceability limits (i.e. less than 25 mm).

All footings should found such that they are not adversely affected by any adjacent excavations, batter
slopes, trenches, or retaining walls that are not designed to support loads. To minimise the potential for any
adverse interaction effects, footings should found at least below a plane extending 1 m horizontally from the

19 June 2018
Report No. 17427-001-Rev0                              10