DECISION
23 In my opinion, there was an inference open that AGL had dug a pit under the slab to a depth of around 700 millimetres, and certainly no greater than about 850 millimetres; and that there was another pit or trench to a depth of two metres immediately to the north of the slab. The primary judge drew that inference, and in my opinion made no error in doing so.
24 The expert opinions supported the view that it was deficiency in backfilling and ingress of water that caused the subsidence. However, the opinions did not differentiate between deficiencies associated with an AGL pit of around 700 millimetres and the two metre pit or trench; and did not identify the source of the water. On that basis, in my opinion it was open to the primary judge not to be satisfied that the problem was due to AGL's inadequate backfilling and compacting.
25 It is true that the primary judge might have inferred that the two metre pit or trench was dug about twenty years ago, when the stormwater pipe was installed; that there was no indication of subsidence problems until the AGL work was done; and that accordingly, AGL caused the subsidence by its own inadequate backfilling and compaction, or by introducing a source of water to the two metre pit, or both. It does seem clear that water could have been introduced to the area by opening up the old gas pipes and inserting the smaller new gas pipes inside them, leaving a space along which water could run. However, this basis of liability in AGL was not specifically addressed or supported by any of the experts, so in my opinion one cannot find appealable error of the primary judge in not reasoning along those lines.
26 The problem for the appellant of evidence of a two metre deep pit or trench was raised in cross-examination, and there is no evidence that it was not raised in submissions; so in my opinion there is no substance in any suggestion that the primary judge decided the case on a basis that was not fairly before him.
27 For all these reasons, in my opinion there is no appealable error in the primary judge reaching the conclusion that there was deficiency in proof by the appellant as to whether the subsidence was the fault of AGL or was due to other causes associated with the two metre pit or trench for which AGL had no responsibility.
28 As regards the Council, in my opinion the finding in relation to AGL is fatal to any liability of the Council based on the backfilling by AGL and the installation of the pavement by the Council. No basis was suggested on which the Council could be held liable for problems associated with the two metre deep pit or trench.
29 As regards liability in the Council for failure to detect and rectify the problem, it is my opinion that the evidence does not suggest that the problem was of such a magnitude or persisted for such a time as to justify a finding of negligence in the Council for failure to detect and rectify it. The primary judge's conclusion to this effect was justified by Ghantous pars.[5]-[7], [163]-[168], [245]-[248], and [355].
30 Dr. Morrison relied on my judgment in Watkins. That case concerned a sharp 50 millimetre change of level from the surface of a road to a manhole cover, where the Council had re-surfaced the road and achieved a gradual transition for one such cover but not for this one; and where this manhole cover was in a position where it could be partially obscured by parked vehicles. In those circumstances, I was not satisfied that the District Court judge who found negligence in the Council was wrong. I made the following comments at par.[27]:
[27] I am inclined to think that sudden variations in level of this magnitude may generally be expected at the edge of footpaths, at transitions between different paths or surfaces, and even between footpath slabs in the vicinity of trees; and also between paved and unpaved areas of road. However, the same may not be true within the paved surface of an apparently well-maintained road, particularly where the change of level is not obvious; and the circumstance that the change in level in this case was in a designated parking area, where it could be partially obscured by a parked car, would add to the risk. While the matter is not free from doubt, I am not satisfied that the primary judge was wrong to hold that the change in level was an unreasonable hazard in this case.
31 In the present case, there was evidence from the engineer Mr. Burn that "under normal circumstances the average pedestrian raises their foot approximately ten millimetres when walking", there was the risk management document classifying a footpath "trip size" of 20-30 millimetres as high risk, even in good lighting; and there was the concession by Mr. Franca from the Council that the 25 millimetre step in this case was an unacceptable tripping risk.
32 However, I do not entirely accept Mr. Burn's evidence as to the extent to which an average pedestrian raises his or her foot; and even if one accepts that the lowest part of the foot is often only about ten millimetres above the ground as it passes the other foot, the front of the foot is higher at this point, and the foot rises further as it moves forward. I do not accept that a plainly visible step of 25 millimetres in a footpath is correctly regarded as high risk or unacceptable risk. It is desirable that even obvious steps of 25 millimetres in footpaths be avoided and eliminated if possible; but that is not to say that the failure of a Council to detect and eliminate all such risk is negligent. As a general rule, in my opinion it is not.