Attachment 7B - Site Based Stormwater Manamgment Plan by ADG

Ul UF2O9p p.4

Centra( Facilities Building. Noosa Sanctuary

Geotechnical Report

Site Classification

The site has been classified in accordance with AS 2870 -1996. Site classifications for this
development is Class H. The footing design should be undertaken using engineering principles based
on the parameters sct out below.

Groundwater

Groundwater was noted at depths within 1.3 metres of the surfacein boreholes on the site. As the
subsurface profile is predominantly sands, the watertable is likely to fluctuate with tides, floods and
rainfall events. Higher watertable levels than those recorded may thus occur under certain conditions.
The design of the basement and the design and planning of basement excavations should allow for the
likely variations in ground water levels.

Excavations

Soils on the site to depths in excess of 4 metres may be excavated with conventional heavy
carthmoving equipment. Temporary open excavations should be battered back at a slope not steeper
than 1.5 horizontal to 1 vertical where the excavation is above the water table and 3 horizontal to 1
vertical for excavations below the water table. Alternatively, the sides of the excavation may be
retained.

Footing System

Itis understood that a piled raft footing system will be designed to withstand likely uplift forces
associated with the tanked basement.

Pile design is a function of pile load, type and geometry. Your piling contractor Should be able to design
the system based on Coffey borehole logs BH35 and BH36. If the piles are to rely on end bearing in
residual soils, your contractor should note the depth to residual in BH30 suggests some variability in the
depth of alluvial materials over the residual basement.

{t should also be noted that a substantial very dense indurated layer was noted in BH36 at a depth of
about 3 metres. Itis likely that driven piles will not penetrate this stratum and allowance for the need to

predrill should be made.
Allowable Bearing Capacity

The allowable bearing capacity is a function of depth and location on the site. An allowable bearing
capacity of 100 kPa may be adopted for the design of any high level footings at depths between 0.5
metres and 1.5 metres.

Coffey Geotechnics
GEOTKPARII73ANA
8 June 2007