Attachment 7B - Site Based Stormwater Manamgment Plan by ADG

Jun Of O7 O4:52p p.3

Central Facilities Budding, Noosa Sanctuary

Geotuchnical Report

3.0 GEOTECHNICAL INVESTIGATIONS

Three boreholes were drilled to depths between 12.4 and 13 metres on or adjacent to the building site
on 16 and 17 May 2007 and 2 June 2007, Boreholes BH35 and BH36 are within the building envelope.
Borehole BH30 is located off the southeast corner of the building. The location of the borcholes is
shown in Figure 1-A. Borehole logs together with explanation sheets defining the terms and symbols
used are attached.

Field investigations were directed by a Principal Engineer from Coffey's Maroochydore office.

4.0 SUBSURFACE PROFILE

5.1 Fill

The building site has been filled to depths between 1.0 and 1.2 metres. The fill soils consist of stiff
sandy clays. In borehole BH30 adjacent to the building site. fill depths to about 2.8 metres were
encounlered. The fill soils were medium dense silty sands. {t may be that some variability in fill depth
will occur across thé site. The fill was placed under a Level 1 Overview undertaken by Bowler
Geotechnical. Copies of the carthworks overview report and compaction test certificates were provided
to Coffey. Borehole investigations indicate that the fill soils are clean and sound. Below the surface
strata, the fill soils were indicated to be at least medium dense in consistency.

§.2 Natural Soils

The fill is underlain on this site by interbedded alluvial sands and clays overlying residual soils at depths
of about 10 m. Soft marine clays were not present in boreholes BH35 and BH36. In borehole BH30
adjacent to the building site, the alluvial soils included a soft marine clay stratum some 1.5 metres thick
The depth to residual was also deeper at 12.2 metres in BH30. These results indicate some
inconsistency in the natural subsurface profile across the site.

6.0 DESIGN CONSIDERATIONS
Shrink Swell Movements

The near surface soils within the zone of influence of moisture content include a layer of sandy clay fill
up to 1.2 metres thick. Experience with similar soils indicate a likely shrink/swell index of about 3%.
Characteristic surface movements as per AS2870 were assessed to be about 6D mm for the site.

Scttlements

Due to the proposed basement and swimming pool excavations, there will be no net increase in
confining pressures on the clay soils at depth below the site. There will be some differential elastic
settlements where variations in the subsurface profile and loads occur and where the upper structure
protrudes beyond the basement foot print. There may also be some settlement associated with the fill
on the site. Maximum differential settlements of less than 40 mm have been assessed.

Coffey Geotucnnies
GLOTKPARI178AAVA
5 June 2007