Response to Information Request - MCU12/0184

Geotechnical and Slope Stability Investigation




4           SURFACE CONDITIONS

The site consists of a series of interconnected ridge lines across the site. The ridges are separated by

steeply incised valleys.

Additional site observations include:


      .   The site consists of numerous steep ridges;


      .   The ridges contain planted to avocado trees about 5 metres high. Other native trees are
          located sporadically over the area. A dense groundcover of grasses, weeds and shrubs was

          present on the site at the time of inspection.

      .   The side slopes of the ridges are generally terraced to provide access to the avocado trees;


      .   The average side slope gradient is estimated to be between 25 and 30 percent with some
          localised sections being slightly steeper;


      .   The slopes along the top of ridge lines is about 5%;


      .   Gravel roads have been constructed along the tops of the ridges;


      .   Mudstone is exposed under the gravel roads within the proposed building envelopes;

      .   Some quartz seams were observed across the site;


      .   Some scour was noted in some exposed cut batters;


      .   The large trees on site were noted to have no inclination off vertical and showed no sign of
          distress.



5           SUBSURFACE CONDITIONS


5.1         Geology
The 1:100000 Geological Series Maps, Sheet 9445, indicates the site is underlain by Early to Middle
Triassic aged Murock from the Kin Kin Beds formation (mapping unit Rk) which is describes as a

arenite, argillite and phyllite.

Site geology has been projected over a Google Earth image of the site and is shown within Figure 2.


5.2         Subsurface Profile

Field observations indicate that the site generally comprised highly to moderately weathered mudstone.
Mudstone was overlain by residual clayey gravel in test pits TP2, TP4 and TP5. Excavator refusal
occurred between 0.9 and 2.8 metres below ground surface. Dynamic cone penetrometer (DCP)

testing was undertaken adjacent to three test pits where a significant depth of overburden soils was
encountered.

Borehole logs together with explanation sheets defining the terms and symbols used are attached in

Appendix B. The location of the boreholes is shown within Figure 1. DCP test results are also attached
in Appendix B.




Coffey Geotechnics                                                                                         2
GEOTKPAR01945AAfA
23rd April 2013