Response to Info Request - Attachment 5 - Geotechnical Report MCU18-0015 & RAL18-0001 · MCU18/0015

J000635-002-R-Rev1                                                                               November 2018




Photograph 2: Site conditions at the time of our investigation, looking approximately south across the concrete
footpath on the western portion of proposed Lot 1.

4.0     METHOD OF INVESTIGATION
The investigation included the following:

     A review of geological and landslide hazard overlay plans

     A walk-over survey

     Subsurface investigation and sampling at nine borehole locations

     Seismic (MASW) testing along two lines (one 180 m line and two 30 m lines).
More detail on the investigation is provided in Sections 4.1 to 4.2 below.

4.1   Fieldwork – Boreholes
The subsurface investigation and walk-over survey was conducted on 11 and 12 April 2018. Prior to carrying
out the borehole drilling, a Dial Before You Dig (DBYD) search was carried out.
Nine boreholes (designated BH1 to BH9) were drilled using hand auger techniques to depths of between
0.7 m to 4 m below ground level (BGL). Dynamic cone penetrometer (DCP) testing was carried out adjacent
to the boreholes to help make an assessment of soil density/consistency.
The boreholes were drilled by a geotechnical engineer and engineering geologist from Core, who logged the
subsurface conditions in accordance with AS1726-2017 Geotechnical Site Investigations. Borehole locations
were recorded using a handheld GPS unit with a reported horizontal accuracy of ± 5 m.
The test locations are shown on the attached Figure 1. Reports of Boreholes are presented in Appendix A,
together with explanatory notes. The ground conditions are discussed in Section 5.2.

4.2 Fieldwork - MASW Seismic Testing
Seismic testing in the form of multi-channel analysis of surface waves (MASW) was undertaken along three
lines: Line 1 (180 m), Line 2 (30 m) and Line 3 (30 m) to an investigation depth of about 20 m BGL. The
alignments are shown on the attached Figure 1. The seismic survey equipment and data acquisition
parameters are summarised in Table 1.
The SurfSeis 2 software by Kansas Geological Survey (MASW) was used to process the field data.
Dispersion curves were obtained by selecting the peak amplitudes from the frequency-wavelength spectrum
in the fundamental mode. Inversion of the dispersion curves was then undertaken to estimate the strata vs
values.



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