Nandroya Planning Report

leddy sergiacomi &
associates pty. itd.

LSA Ref: 45-021

 

2.3.2

2.3.3

2.3.4

> Dam wall stability assessment; and

> Site classification in accordance with AS2870.
The Morrison Geotechnic Investigation has been included as Appendix A of this report.

Soil Classification
Nineteen (19) boreholes were advanced on the site using a light 4+WD mounted auger rig and
classified to AS1726 Geotechnical Site Investigations. Soils encountered comprised

predominately natural material with some fill (as shown on Figure 1 of the Morrison Report).

Generally, the boreholes advanced on the subject site found medium to high plasticity, stiff to
very stiff, brown to brown-reds and brown-orange silty clay and sandy clays at shallow depths,
becoming darker brown, grey and mottled at increasing depth (>1.0m). The soil was generally
moist with some laterite gravels found at depths of >1.0m also. The presence of shallow fill (<1
metre depth) on the site was found in Boreholes 1, 6, 7, 8, 9, 11, 12, 13, 16, 17 and 18, with
greater depths encountered on the edges of the cut and fill platforms previously established and
used for timber storage (refer Boreholes 10 (>1.7 metres), 14 (2.1 metres), 15 (1.35 metres)) and
associated with excavation of the dams (refer Boreholes 2 (2.1 metres)). Where greater depths of
fill were encountered, the material was considered relatively synonymous in composition to the
natural sub-soil profile, apart from the material found in BH10 and BH15 which consisted of

timber waste and sawdust, covered by a thin layer of clay material.

Groundwater
Groundwater was encountered in BH2 at a depth of 2.7m. This borehole was situated in close
proximity to the dam and is likely to represent seepage from the dam itself. No evidence of

groundwater in any other boreholes was found.

Field Permeability

Five (5) permeability tests were carried out using a constant head permeameter at the locations
shown on the site plan of the Morrison Geotechnic Report. Results for the field permeability
results ranged from 1.7x10% to 3.9x10*. These results are consistent with Table 4.2A4 of

 

14 November 2005 Department of State Development, Trade and Innovation Page: 5

Planning Report