20220109 - Geotech · OPW23/0182

                              PROPOSED RESIDENCE
                              21 MAHER TERRACE, SUNSHINE BEACH

Should excessive column loads preclude the use high level footings, or in areas where unsuitable materials
are exposed at the design level, deeper piled footings would be required. Piles could be designed on the
following ABPs:
       0.5 m into stiff/medium dense residual soils – ABP 150 kPa.
       0.5 m into very stiff/dense residual soils – ABP 300 kPa.
       0.3 m into XW materials or very low strength sandstone – ABP 600 kPa.

Please note that as outlined in Section 6.1 an additional borehole is required to be drilled following removal
of the existing residence to confirm the required foundation design parameters.

Due to close proximity to the surrounding properties driven piles are not considered to be suitable for this
site. Based on the ground conditions encountered, steel reinforced concrete bored piles or steel screw piles
could be utilised. Should loose sands or groundwater seepage be encountered during piling sacrificial liners
(e.g. formatube etc.) and dewatering equipment may be required for bored piles. The advice of a specialist
piling contractor must be sought regarding feasibility, design and installation of the piling system for this site,
including an assessment of potential vibration effects on nearby structures, and monitoring requirements.
Any foundation subgrades and footing excavations must be inspected by a suitably qualified and
experienced Geotechnical Engineer to confirm the foundation materials and allowable bearing capacity, and
to advise on treatment of any unsuitable zones if encountered.

Resultant settlements from footings founded as described above should be within serviceability limits,
estimated to be less than 25 mm or 1% of footing width. Settlement estimations will need to be confirmed
once working wall and column loads are available.

Footing design should also account for potential soil reactivity to be equivalent to Class M. It should be noted
that placement of reactive clay may result in a more severe equivalent site classification, such as H1 or
greater.

All footings should found such that they are not adversely affected by any adjacent excavations, batter
slopes, trenches, retaining walls, or in ground structures that are not designed to support building loads.
Footings should found at least below a plane extending 1 m horizontally from the base of
trenches/excavations/retaining walls/swimming pool, then rising up at 1V:1H, as illustrated in Text Figure 12
overleaf.




                        Text Figure 12: Footing depth required to prevent undermining

Site drainage should be designed to readily remove surface water and to prevent ponding of water on
subgrade areas during construction and also adjacent to foundations and perimeter slabs once construction
is completed. It is recommended that footings be inspected by a suitably qualified and experienced engineer



16 July 2021
Report No. 21236-001-Rev0                               14