Seven signs of possible sinkhole formation

Following recent media reports about the threat posed by two sinkholes in Harris Park, Sydney, where occupants of three neighbouring strata buildings were evacuated, Wayne Costin, one of the experts called upon during the Harris Park sinkholes crisis, suggested there are seven potential indicators of subsidence or subterranean sinkhole formation which strata residents and property managers could watch for.

“Observing the presence of any one of these seven indicators could provide a compelling reason to call for a diagnostic engineering report to be carried out as soon as possible,” Wayne said. “To presume that any minor-looking anomaly is benign could mean exposure to unnecessary risk.”

The seven signs:
  1. Water penetration of retaining walls or shoring walls, particularly in basement carparks, around any excavations, and as used in landscaping between different ground levels.
  2. Water accumulation in basement carparks, around swimming pools, and in low-lying areas of common grounds or neighbouring properties, even when attributable to heavy rain.
  3. Cracks in footpaths or driveways which appear suddenly, or old cracks which are gradually widening or extending.
  4. Non-superficial cracks in concrete slabs, walls or brickwork, plastered finishes, ceilings or cornices, skirting boards, or architraves around windows or doors.
  5. Noticeable changes in flooring levels or the alignment of windows or doors.
  6. Depressions or dips starting to appear in lawns or paved areas, even if only slight.
  7. Any faults in guttering and rainwater downpipes, and any broken pipes which leak water directly into the ground.

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