Slope Stability Assessment Existing Earthworks - OPW21-0279

Anthony Kelly                                                                                        21354-001-Rev0
                                                                                                  17 September 2021

A search of historical aerial photos (Ref. www.qimagery.information.qld.gov.au) indicates that the alignment
of the track formalised as part of the recent earthworks may have been present from about 1989, and
possibly earlier, although the older available aerial images (1954 onwards) are not of sufficient resolution to
provide certainty on this.

It is understood that the recent earthworks have formalised the existing alignment, including formation of a
drainage swale on the upslope side. Recent earthworks have been minimal, with the historic earthworks
being mostly in cut (up to about 1 m), with shallow fill on the downslope (eastern) side being spread out on
the natural slope, mostly outwith the track corridor. The fill material was graded to the same approximate
gradient as the natural ground (≤ 25°).
This is shown below in Text Figure 7.




Text Figure 7: Looking south along northern (LHS) and southern (RHS) portions of the formalised existing track

The cleared northern area had exploited a very gently rounded, and relatively wide, natural crest of the
ridgeline running south-north through the site. Based on available contour information and observations on
site, it was estimated that the maximum depth of cut would be in the order of about 1.5 m to the south,
pinching out to the north-east and north-west. Material removed from the south of the cleared area had
been spread out in fill batters inclined at around 20° to 25° to the periphery. A slight fall to the north-eastern
corner was noted over the surface of the cleared area.

A view of this is shown below in Text Figure 8.




Text Figure 8: Looking south over northern cleared area

Across the four main areas forming the earthworks at the site, no irregular natural surface features were
noted in the ground adjacent, and no slumping or cracking of batters having been undertaken was noted at
the time of our assessment.




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